Symposium: Laser Ablation
Plenary lectures (45 minutes):
1.- Emmanuel Haro (haro@xanum.uam.mx)
Nanostructured surfaces and bulk systems synthesized by laser ablation: fabrication and subsequent experiments.
Emmanuel Haro.Laboratorio de Fisicoquímica de Sistemas Nanoestructurados, Departamento de Física Universidad Autónoma Metropolitana Iztapalapa
In this presentation we review some experimental and theoretical results obtained in our group related to laser ablation and laser patterning. The need of developing original solutions for obtaining nanostructured materials is raised. Furthermore, we report on a new method that combines the Laser Ablation and the Sol-Gel techniques in order to obtain nanostructured glasses. Au nanoparticles are generated by pulsed laser deposition using the corresponding target. The target is immersed in a transparent solution previously prepared made of tetraethyl orthosilicate, and water. The ablation process was performed subsequently using a NdYAG laser emitting at 532 nm. The pulse duration was 8 ns at a frequency of 10 HZ. Once the nanoparticles were dispersed in the solution the gels were stored for 24 hours at room temperature. After that the samples were thermally treated at 300°C for 10 hours in order to obtain the glasses. High resolution transmission electron microscopy images and UV-visible spectroscopy were used to characterize the Au nanoparticles.
2.- Citlali Sánchez (citlali.sanchez@icat.unam.mx)
Nanosecond laser nanostructuring of glass assisted by thin films, nanoparticles and nanoprism arrays.
Citlali Sánchez. Instituto de Ciencias Aplicadas y Tecnología, Universidad Nacional Autónoma de México, Circuito Exterior S/N, C. U., Delegación Coyoacán, C.P. 04510, Cd. Mx., México;University of Padova, Department of Physics and Astronomy, NanoStructures Group, via Marzolo 8, I-35131 Padova, Italy; Instituto de Física, Universidad Nacional Autónoma de México, Circuito de la Investigación Científica, Ciudad Universitaria, Delegación Coyoacán, C.P. 04510, Ciudad de México, México.
Nanostructures have an outstanding potential in several industrial applications, which has motivated to develop fast, easy and flexible methods for their fabrication. Laser irradiation of metal nanostructures such as thin films and nanoparticles induces melting and ablation, which allows the transformation of the nanostructures itself, and the structuration of the substrate below them. For instance, ns pulsed-laser irradiation converts metal films previously deposited on non-wetting substrates, into metal nanodroplets. Once the droplets have been produced, subsequent irradiation allows either the tailoring of the nanoparticles’ shape or the nano-drilling of the substrate at the position of the droplets. We study the effect of laser parameters (laser fluence, wavelength and pulse number) and the background pressure on the formation of these nanostructures. In addition, the irradiation of periodic arrays deposited by nanosphere lithography was performed, allowing the morphological manipulation of the nanospheres and the ordered structuration of the substrate.
3.- Sadasivan Shaji (sshajis@yahoo.com, sadasivan.shaji@uanl.edu.mx)
Pulsed laser ablation in liquid – Nanocolloids to thin films and devices.
Sadasivan Shaji. Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León; Centro de Innovación, Investigación y Desarrollo en Ingeniería y Tecnología (CIIDIT)- Universidad Autónoma de Nuevo León.
Pulsed laser ablation in liquid (PLAL) is an interesting green technique to synthesize nanoparticles of metals, semiconductors, polymers and ceramics. We have synthesized nanoparticles of metals, semiconductors and ceramics using PLAL. Also explored the effects ablation wavelength, fluence and post irradiation effects on the morphology and properties of nanomaterials fabricated. From these nanocolloids, we have prepared and characterized thin films and coatings using different techniques. Also, these thin films were used to fabricate devices like photodetector and solar cells. Details of the characterization and properties nanomaterials by PLAL as well as their thin film device properties are included in this work.
4.- Santiago Camacho (camachol@cicese.mx; scamacholopez@gmail.com)
Short and ultrashort pulsed laser processing of materials at CICESE.
Santiago Camacho. Departamento de Óptica, CICESE, Carretera Ensenada-Tijuana 3018, Zona Playitas, Ensenada, Baja California, 22860. México; Cátedra CONACyT - Departamento de Óptica, CICESE, Carretera Ensenada-Tijuana 3018, Zona Playitas, Ensenada, Baja California, 22860. México.
CICESE was the first institution in México to build and operate (three decades ago) an ultrashort pulse laser system in México. In year 2003 we created the laboratory of ultrashort pulse lasers and processing of materials. Since then we have consolidated a research group that focuses on the following topics: fs laser-induced metallic oxides; fs laser-writing of photonics structures in transparent materials with special interest on polycrystalline ceramics; laser-induced periodic surface structures (LIPSS); synthesis of core-shell nanoparticles by laser ablation of solids in liquids; and laser-induced cavitation focused on medical applications. Some relevant results are the rapid formation of multiple phase nanostructured metallic oxides; laser-induced index shaping through oxygen vacancy suppression; transition from plasmonic to dielectric LIPSS; luminescent Bi@C nanoparticles; and the measurement of intraocular pressure through laser-induced cavitation. In this presentation, we will elaborate on the research group activities, our current infrastructure and potential collaborations we are open to.
5.- Sven Reichenberger (sven.reichenberger@uni-due.de)
Pulsed laser post-processing of colloidal metal and oxidic nanoparticles to tailor nanomaterials properties.
Sven Reichenberger. Technical Chemistry I and Center for Nanointegration Duisburg-Essen (CENIDE). University of Duisburg-Essen, Germany
In the field of catalysis research and catalyst development especially tailored catalyst design is only possible when structure-activity correlations are mechanistically understood.1To that end, catalyst materials with gradually tuned properties are required. A promising tool to deliver nanomaterials with increasingly altered properties (e.g. band gap or photo-luminescence) and consequently catalytic activities is given by Pulsed Laser Post Processing (PLPP) in liquids.2-5Functionalization of catalysts with surfactant-free laser generated co-catalysts (e.g. Au NP) prior to PLPP5enables further systematic studies of potential active sites present on the heterogenous catalyst during reaction. While a gradual tuning of materials properties is mainly achieved by controlling the number of laser pulses per particle (I. e. mass-specific energy dose, see Fig. 1), the transformation processes driven by each individual laser pulse will (considering constant laser pulse duration and wavelength) directly depend on the applied laser fluence being the main driving force. Consequently, fluence gradients known to occur in state of the art PLPP setups need to be avoided.4
Fig. 1: Effect of PLPP of P25-TiO2(without and loaded with 1 wt% and 3 wt% of laser-generated Au NPs) on the catalytic activity shown for a): Photocurrent density j in photocatalysis5and b): Turn-over number (TONS) of ethanol to acetic acid during selective oxidation reaction2. Data are shown with respect to the number of laser irradiation cycles (Ncycle) applied. Figure was taken from Ref. 2.
Within this presentation, a new flat-jet setup, minimizing the fluence gradient will be presented and subsequently evaluated regarding the homogeneity of the PLPP process at the example of well-established laser fragmentation of gold nanoparticles. Next, recent advances on laser-based processing of oxidic nanomaterials using nano- and picosecond lasers and its implication for the catalytic activity in different types of catalytic reactions will be presented and discussed.
Acknowledgments:
The authors gratefully acknowledge the Mercator Research Centre Ruhr (MERKCUR) for funding theproject Pr-2016-0044 and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – Projektnummer 388390466 – TRR 247
References
- A. J. Medford, A. Vojvodic, J. S. Hummelshøj, J. Voss, F. Abild-Pedersen, F. Studt, T. Bligaard, A. Nilsson, and J. K. Nørskov, Journal of Catalysis, vol. 328, pp. 36–42, (2015).
- S. Reichenberger, G. Marzun, M. Muhler, S. Barcikowski, ChemCatChem. 2019, 11 (18), 4489
- M. Lau, S. Barcikowski, Appl. Surf. Sci., 348, 22–29 (2015)
- F. Waag, B. Goekce, C. Kalapu, G. Bendt, S. Salamon, J. Landers, U. Hagemann, M. Heidelmann, S. Schulz, H. Wende, N Hartmann, M. Behrens, S. Barcikowski, Scientific Reports, 7, 1-13, (2017).
- 5. M. Lau, S. Reichenberger, I. Haxhiaj, S. Barcikowski, A. M. Müller, ACS Applied Energy Materials1, 5366−5385, (2018)
6.- Luis Escobar
Laser ablation of metals submerged in water as an alternative method for hydrogen production.
Luis Escobar. Departamento de Física, Instituto Nacional de Investigaciones Nucleares, Carretera México-Toluca S/N, la Marquesa, Ocoyoacac, Estado de México, C.P.52750, México; Departamento de Química, Instituto Nacional de Investigaciones Nucleares, Carretera México-Toluca S/N, la Marquesa, Ocoyoacac, Estado de México. C.P.52750 México; Universidad Autónoma del Estado de México, Facultad de Química, Paseo Colon esq. Paseo Tollocan S/N, Toluca, Estado de México, CP 50120, México; Departamento de Física, Universidad Autónoma Metropolitana Iztapalapa, Apdo. Postal 55-534, CDMX, México.
The laser ablation of solids in liquid medium has been actively used in the last two decades for the synthesis and processing of nanoparticles. An important effect of the plasma formation as a result of the laser-solid interaction is that some of the plasma surrounding liquid is vaporized producing a cavitation bubble. This bubble expands to its maximum size and then collapses, this process occurs at temperatures of thousands of Kelvin and pressures of several GPa. Under these extreme conditions if the liquid is water, splitting in hydrogen and oxygen occur, so that it can be considered as an alternative way to produce hydrogen. The generation of hydrogen upon ablation of different metals: Al, Mg, Ti and four different Al-Mg alloys with different Al contentis reported. A ns pulsed Nd: YAG laser emitting in the fundamental line (1064 nm) was used to ablateeach metal immersed in 20 mL of deionized water for 5 minutes,with and without the presence of an ultrasonic field. The laser beam was directed perpendicular to the surface of the metal target contained inside of a sealed glass flask. The flask was connected through a flexible hose to a glass beaker with water, in which an inverted graduated cylinder was placed; the volume of the produced gas (hydrogen) was determined directly by measuring the displacement of the liquid. Experiments varying the laser fluence at higher values from 27 to 77 J/cm2, as well as at lower fluences from 0.7 to 1.8 J/cm2were performed. The produced gas was characterized by gas chromatography and mass spectrometry. Molecular hydrogen was found suggesting that this procedure allows the production of H2of high purity. In general terms, all the studied metals under laser ablation produce H2and the volume rise as the laser fluence was increased following a no-linear monotonic behavior with similar tendencies. The present approach to generate hydrogen can be considered as a bifunctional procedure because at the same time it can be used to produce nanomaterials with different shape and size as by-products.
7.- Arturo Robledo (arm@azc.uam.mx)
Effect of the sample’s temperature on the line emission in laser ablation at cryogenic temperatures.
Arturo Robledo. Depto. Ciencias Básicas, Universidad Autónoma Metropolitana, Av. San Pablo 180, Azcapotzalco, 02200 Cd. de México; Instituto de Ciencias Aplicadas y Tecnología, UNAM, Circuito Exterior S/N, C.P. 04510, Cd. Universitaria, Cd. de México.
We report results obtained in a laser-ablation experiment using targets chilled down to 20 K. In a previous work, our co-workers found that by increasing the temperature of the target above room temperature the emission of the lines increased in proportion to the target’s temperature [1]. In the present work we applied the focused beam of a pulsed, nanosecond Nd:YAG laser on a metallic surface that is in contact with the cold finger of a He refrigerator. In this way the sample’s temperature could be varied in the interval 20-290 K. The sample and the cold finger were kept in a high vacuum in order to obtain good thermal insulation. In the present work we noticed a slight increment in the emissivity of the lines as the temperature increased. The most notable effect however, one that was unexpected, is that at low temperatures (~20K) the electron density of the plasma was found to be higher than at room temperature. The explanation for this behavior is attributed to a pre-heating of the target before plasma onset. This is a consequence of the sharp variation of the sample’s specific heat with temperature, according to Debye’s theory.
8.- Marco Antonio Camacho (macamacholo@uaemex.mx, mcl.fq.uaemex@gmail.com)
Laser-induced transformations in metal oxides and metals.
Marco Camacho. Laboratorio de Investigación y Desarrollo de Materiales Avanzados, Facultad de Química, Universidad Autónoma del Estado de México, Campus Rosedal, Km 14.5 Carretera Toluca-Atlacomulco, San Cayetano de Morelos, Toluca C.P. 50295, México
In the last few years our group have been focusing on three main research areas. The first one concerns the study of cw-laser induced transformations in metal oxides and metals as molybdenum oxide and bismuth thin films. The second one is the study of pulsed ns-laser induced effects on some metallic materials as titanium, molybdenum and bismuth thin films, the third one and more recent is the preparation of nanoparticles colloids by using the laser ablation of solids in liquids technique. As an example of our current research activities, in this talk I will present experimental results on the modification of bismuth thin films under nanosecond laser irradiation. Varying the per pulse laser fluence and the irradiation time, i. e. the number of pulses, bismuth can be significantly modified. We have found either the formation of Laser Induced Periodic Surface Structures (LIPSS) or oxidation effects depending on number of delivered laser pulses for a well determined per pulse laser fluence. This laser processing technique let us obtain, in a very simple form, micrometric sized regions with either LIPSS or metallic oxides patterning. Potential applications for this processed surfaces are for instance gas sensor and SERS substrates, among others.
9.- Gerardo Contreras (gscp1953@hotmail.com)
Thin film and device processing at the Pulse Laser Deposition (PLD) laboratories of the Superior School of Physics and Mathematics (ESFM) –IPN and the Chemistry Faculty (FQ)-UAQ.
Gerardo S. Contreras Puente Superior de Física y Matemáticas del Instituto Politécnico Nacional(IPN), Edificio 9, Unidad Profesional “A.L.M.”, Col. San Pedro Zacatenco, 07738 Ciudad de México, México.
In this talk we present the research studies at Escuela Superior de Física y Matemáticas-IPN and Facultad de Química-UAQ with the use of the Pulse Laser Deposition (PLD) technique. The research work is oriented to the following topics, namely: a) The thin film processing and characterization by PLD and applications as white light emitters of HfO2; b) Thin film processing and characterization of GaN and ternary compounds by PLD and their possible use as LED´s; c) The processing and characterization by PLD of Transparent Conducting Oxides of SrCuSeF and its employ in solar cells; d) The processing and photovoltaic-performance characterization of CdS/CdTe solar cells by the PLD technique.
10.- José Luis Hernández Pozos
Enhanced light transmission in disordered metallic nanoisland flims.
José Luis Hernández. Departamento de Física. Universidad Autónoma Metropolitana-Iztapalapa (UAM-I). Av. San Rafael Atlisxco No 186. Col Vicentina. C.P 09340. Ciudad de México. México.
This talk we will present a brief historical review about metallic films with arrays of ordered holes which present extraordinary optical transmission. Then, the transmission properties of thin gold, copper and silver films deposited on quartz by pulsed laser deposition are presented. Well before the deposited metal forms a continuous film, these metals form islands on the substrate, when these islands reach a critical distance, the light transmission near the surface plasmon resonance frequency is enhanced. These results remind of extraordinary optical transmission, however, instead of having relatively sharp peaks of transmission at characteristic frequencies, in our experiments broad peaks at are observed.
11.- Miguel Angel Camacho (macamachol@uaemex.mx; mikentoh@hotmail.com)
Short pulsed laser synthesis of nanomaterials and optical characterization of materials at UAEMex
Laboratorio de Fotomedicina, Biofotónica y Espectroscopía Láser de Pulsos Ultracortos, Facultad de Medicina, Universidad Autónoma del Estado de México, Jesús Carranza y Paseo Tollocan s/n, Toluca, 50120, México; Laboratorio de Investigación y Desarrollo de Materiales Avanzados, Facultad de Química, Universidad Autónoma del Estado de México, Campus Rosedal, Km 14.5 Carretera Toluca-Atlacomulco, Toluca, 50925, México; Departamento de Materiales Radiactivos, Instituto Nacional de Investigaciones Nucleares, Ocoyoacac, 52750, Estado de México, México.
In year 2004 we created the "Laboratorio de Fotomedicina, Biofotónica y Espectroscopía Láser de Pulsos Ultracortos".Since then we have consolidated the Laser Ablation of Solids in Liquids (LASL) technique through a 30 ps Nd:YAG laser system, UV-Vis spectroscopy and photoluminescence (PL) spectroscopy. Our research group focuses on the following topics: synthesis of colloidal nanoparticles by laser ablation of solids in liquids; optical characterization of materials and nanomaterials by using UV-Vis and PL, laser-induced photothermal effects in metallic nanoparticles, optical characterization of radiochromic films and the characterization of the optically stimulated luminescence of some crystals. In this presentation, we will elaborate on the research group activities, our current infrastructure and potential collaborations we are open to.
12.- José Quiñones (jose.quinones@academicos.udg.mx)
Control of plasma parameters for the pulsed laser deposition of alloys, compounds and composite thin films.
José Quiñones. Departamento de Física, Centro Universitario de Ciencias Exactas e Ingenierías, Universidad de Guadalajara, Boulevard Marcelino García Barragán 1421, C.P. 44430, Guadalajara, Jalisco, Mexico.
Pulsed laser deposition of thin films has proven to be a highly versatile technique for the growth of a number of different materials for almost any application. However, for the deposition of alloys, compounds or composite films, there are some drawbacks regarding targets preparation due to the deposited film is composed of two of more elements, making necessary the fabrication of targets with specific compositions depending of the material of interest.
On the other hand, the properties of the growing films are strongly dependent on both laser parameters and target physical properties, which makes the control of the deposition process and thus, the films properties in general, a difficult task. Plasma diagnostics in pulsed laser deposition experiments, has demonstrated to be a powerful tool for controlling experimental reproducibility and more important, to modify the deposited films properties. In this talk the influence of mean kinetic ion energy and density as measured by Langmuir planar probes on the deposition of alloys, compounds and composite thin films, will be discussed.
Invited Talks (30 minutes):
1.- Akshana Parameswaran Sreekala (akshana2770@gmail.com)
Nanostructured thin films of tin sulphide for photodetector applications from pulsed laser ablated nanocolloids.
Akshana Parameswaran. Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León
Photodetectors based on nanostructured semiconductor materials have been successfully used in advanced communications, flame detection, air purification, ozone sensing and leak detection, among others, in the past few decades. We present fabrication and characterization of photodetectors based on nanomaterials using their nanocolloids prepared by Liquid-phase Pulsed Laser Ablation technique which can lead to photodetection in enhanced wavelength ranges with improved efficiency. Tin sulfide (SnS) nanoparticles were synthesized by pulsed laser ablation of a SnS target in different liquid media using the 1064 nm output wavelengths from a pulsed (10 ns, 10 Hz) Nd:YAG laser. The nanocolloids obtained were spin coated on different substrates for the development of thin films and also the p-type SnS nanocolloids were deposited on an n-Si wafer for the p–n heterojunction fabrication. The fabricated films were characterized by techniques like UV-Visible spectroscopy, XPS, Raman, SEM, XRD etc. To investigate the photoresponse, the device was illuminated using varying light emitting diodes (LED) and bias voltages. The key parameters of a photodetector, the responsivity (R), sensitivity, detectivity, rise time and fall time were estimated.
2.- Tupak García-Fernández (tupak.garcia@uacm.edu.mx, tupacgarcia@yahoo.com)
Photoacoustic analysis during laser synthesis and processing of colloids.
Tupak García-Fernández. Universidad Autónoma de la Ciudad de México
Nanoparticles (NPs) of Au and Ag were obtained by laser synthesis and processing of colloids, including laser ablation, fragmentation and melting in liquids. Some parameters as the laser pulse energy (from few mJ to100 mJ) and repetition rate of the laser pulses (RRLP, in the range from 1– 10 Hz), as well as the lens to target distance (LTD) were varied, which produced changes in the concentrations and dimensions of synthesized NPs. The synthesis process and resulting Ag-NPs colloids were studied by a pulsed photoacoustic technique. Characteristic parameters of PA signals such as bubble collapse time, arrival time and root mean square were determined as functions of the number of laser pulses, RRLP and LTD. For comparison, other techniques as UV-Vis-IR analysis, atomic absorption spectroscopy, electron microscopy, as well as the measurement of the transmission of the laser pulses through the colloid were used. The results show that the photoacoustic analysis can be used in-situ and in real-time for obtaining useful information on both the synthesis process and the colloids themselves.
3.- Víctor Contreras (victor@icf.unam.mx)
Analysis of liquids impurities with LIBS assisted by acoustic levitation sampling.
Victor Contreras. Instituto de Ciencias Físicas, Universidad Nacional Autónoma de México, Cuernavaca, Morelos, 62210, México.
Real-time and multi-elemental analysis for online water monitoring is an important task towards environmental safety, public health, water purification control, the adequate reuse of wastewater, and for many processes in engineering and industrial fields. However, the online water monitoring cannot be performed by analytical conventional techniques (LA-ICP-MS, ICP-OES or XRF) because they demand long operation times and/or specialized handling. Laser induced breakdown spectroscopy (LIBS) represents one of the most appealing alternatives for multi-elemental analysis where rapid information is required. For liquids analyses, it has been demonstrated that LIBS improve its analytical performance when drops are trapped and partially dried by an acoustic levitation system, enabling multi-elemental trace detection on liquids with relatively simple instrumentation requirements.
In this talk I will introduce the methodology based on LIBS assisted by acoustic levitation sampling. The talk will focus on the generation of acoustic potentials for single-axis acoustic levitation systems and the most interesting spectroscopic results based in the analysis of trace heavy metal detection contained in liquid samples acoustically levitated. The approach is addressed to develop a methodology for online monitoring applications demanding limited volumes of liquid samples with simple instrumentation.
4.- Beatriz de la Mora
Strategies for functionalization of gold nanoparticles fabricated by laser ablation in liquids.
Beatriz de la Mora. CONACyT Fellow‐ICAT, Universidad Nacional Autónoma de México, Mexico City, Mexico;Instituto de Investigaciones en Materiales, UNAM, A.P. 70-360, Coyoacán, C.P. 04510 México, DF, Mexico; Instituto de Ciencias Aplicadas y Tecnología, Universidad Nacional Autónoma de México, Mexico City; Laboratorio de Hematobiología, Escuela Nacional de Medicina y Homeopatía, Instituto Politécnico Nacional, Mexico City, Mexico; Universidad Autonoma de la Ciudad de Mexico (UACM), Prolongacion San Isidro 151,Col. San Lorenzo Tezonco, Mexico D.F., C.P. 09790, Mexico.
In the last 20 years the field of nanotechnology has grown extensively due to its surface, optical and magnetic properties. Among the different types of nanoparticles gold nanoparticles (Au-NPs) outstand due its optical properties, chemical surface and biocompatibility. Laser ablation in liquids (LAL) is a synthesis method that allow to obtain high purity gold nanoparticles in a variety of solvents for different applications. In general, for the different applications gold nanoparticles require a functionalization. To functionalize gold nanoparticles obtain from ALL need different strategies than the ones used for colloidal solutions produced by chemical synthesis. The presence of the plasm during the formation of Au-NPs, thewide distribution sizes and the flocculation state of the colloidal solution changes the surface chemistry of the Au NPs. Here, a study of the physicochemical properties of Au-NPsobtained by ALLand functionalized with different thiolate compounds (AMP, Dodecanethiol and POSS thiol) is presented. Floculation, size distribution, stability and optical response were measured by TEM microscopy, 𝞷potential, DLS and UV-Vis spectroscopy. Some strategies to get a successful functionalization such as a post-treatment of the colloidal solution with laser treatment and centrifugation to diminish the size distribution of the particles, the optimization of concentration of the thiol compounds and the use of buffers to modify the pH of the solutions are discussed.
5.- Linda V. García (linda@cicese.mx)
Femtosecond laser-induced crystallization in Antimony Sulphide thin films (Sb2S3).
Linda V. García-Quiñonez. Cátedra CONACyT-Unidad Foranea Monterrey, CICESE, Alianza centro 504, Parque de Investigación e Innovación Tecnológica (PIIT), Apodaca, Nuevo León, C.P. 66629, México. Centro de Investigación en Materiales Avanzados, Cimav, Alianza Norte 202, Parque de Investigación e Innovación Tecnológica (PIIT), Apodaca, Nuevo León, C.P 66600, México.
In recent years, the use of thin films of metal chalcogenides has been increased in photovoltaic solar technology. Mainly, semiconductor materials such as Antimony Sulphide (Sb2S3) are used due to their high absorption coefficient and band gap (1.7-2.5 eV). However, Sb2S3thin films obtained by chemical bath, the most common method of manufacturing them, have an absence of crystallinity, making it necessary to use post-deposit or in situ treatments to improve their crystalline properties, important for the performance of the photovoltaic device. The main objective of this work is to promote, by laser irradiation with ultrashort pulses, the crystallization of thin films of Sb2S3obtained by a chemical bath. The laser irradiation will be carried out by using femtosecond laser pulses (1030 nm, 250 fs, 2 MHz), varying the irradiation parameters such as fluence, repetition rate, and scanning speed. Also, the characterization of Sb2S3films is contemplated, before and after laser irradiation. Therefore, it will be determined changes in the structure (X-Ray Diffraction); the thickness of the films (Reflection and Transmission Spectroscopy); the molecular structure (Raman Spectroscopy); its elementary composition (XPS); morphology of the films and their roughness (AFM); optical properties (UV-Vis-NIR Spectroscopy); and, electrical and photoconductivity measurements of the films.
6.- César Guarín (cesar.guarin@conacyt.mx)
Disentangling the different and ultrafast relaxation processes in aromatic molecules.
César Guarín. Universidad Autónoma Metropolitana.
The energy that carries an electromagnetic wave can be transferred to a chemical species via absorption. Once the molecule is in an excited state, it relaxes through various photophysical and photochemical channels [1]. Molecular dynamics is important because it involves the various deactivation channels through which the excitation energy dissipates. This study investigates the dynamics of relaxation of molecules of more than 25 atoms in condensed phase (polar and nonpolar solvents). We are working on the implementation of ultrafast spectroscopy techniques (pump-probe) and we also employ a computational approach (DFT and TDDFT) to study the ultrafast decay in aromatic molecules [2].
In this study, we show that the solvent-effect leads to a change in the relative energies of the singlet and triplet excited states. The presence of n-type orbitals in substituted aromatic molecules implies the existence of upper excited states, which substantially increase the coupling between the singlet and triplet manifolds. It should be noted that, along with the spectroscopic techniques that will allow us to accurately measure these processes, the current advances in computational methods allow us to clarify the details of the relaxation dynamics, including the geometries, the relative energies of the excited states, the conformational changes or intermediate species, all of which affect the efficiency of the decay processes [3]. Clarifying the relaxation dynamics of electronic states involved in ultrafast decay is vital for the development of the next generation of photo-materials.
7.- Ramón Carriles Jaimes (ramon@cio.mx)
Nano- and micro-machining of stainless steel for superhydrophobicity.
Ramón Carriles Jaimes. Centro de Investigaciones en Óptica A.C.
We will present a brief overview of CIO´s experimental work on ablation and micro-machining using an ultrafast amplified system (50 fs, 1 kHz). Specifically, we will cover surface nano- and micro-machining of stainless steel to achieve superhydrophobicity; also, we will present results on nanoparticle ablation from solid targets immersed in liquid.
8.- Osmary Depablos Rivera (osmarydep@yahoo.com)
Analysis of plasmas produced by pulsed laser ablation combined with magnetron sputtering
Osmary Depablos-Rivera. Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, 04510, Mexico City, Mexico.Instituto de Ciencias Aplicadas y Tecnología, Universidad Nacional Autónoma de México, Circuito Exterior s/n, Ciudad Universitaria, 04510, Mexico City, Mexico.
The plasma diagnostic is an in-situ method to monitor the deposition processes that involve the generation of plasmas. The pulsed laser ablation (PLA) and magnetron sputtering (MS) are plasma-assisted deposition techniques. Their combination is known as hybrid technique and denoted as MS-PLA. This hybrid technique has been employed to prepare coatings and films with specific applications such as solid lubrication, photocatalysis and biomedical materials. We implemented the hybrid technique MS-PLA to prepare films of ZnO-Au, an Au target was ablated and MS was used to deposit ZnO. The aim of this work was to diagnose the plasmas generated during the hybrid deposition by optical emission spectroscopy (OES). Additionally, the plasmas produced during the PLA of an Au target in high vacuum and under an Ar atmosphere (0.67 Pa) were studied. These PLA plasmas were studied as reference to understand the effects of the plasmas combination in the hybrid process MS-PLA. The processes with PLA were done varying the pulse laser fluence at 4.5, 13.6 and 20.9 J cm-2. The OES results allowed to identify and to analyze the emission evolution of neutral atoms of Au, Ar and Zn and single-ionized Au atoms. The loss of material from the growing films was evidenced during the PLA of Au under Ar atmosphere because the emission of Au neutral atoms increased in front of the substrates. However, the increase of Au emission near the substrates did not occur during the hybrid deposition, while the increase of the Zn emission was observed. The Zn excitation revealed the energy loss of the Au species by the collisions, and their final energy caused less removal of material from the films with respect to the PLA process in Ar. Consequently, the deposition rate improved in the hybrid process.
9.- Rosalba Castañeda (rosalba.castaneda@icat.unam.mx)
Synthesis of lead free electroceramics thin films by PLD.
Rosalba Castañeda. Photophysics Laboratory, Instituto de Ciencias Aplicadas y Tecnología, Universidad Nacional Autónoma de México, Circuito Exterior S/N, Ciudad Universitaria, 04510 Coyoacán, Ciudad de México, México.
Lead-free piezoelectric materials were developed during the second half of the past century, among them, the potassium sodium niobate (K0.5Na0.5)NbO3 (KNN), KNN-based ferroelectrics and based ferroelectrics in Titanates of Barium (BaTiO3), are considered a promising lead-free materials alternative to Pb(Zr,Ti)O3 (PZT,) particularly the KNN by its high Curie temperature (Tc). Using PLD (pulsed laser deposition) we grown thin films of (K0.5Na0.5)NbO3 (KNN) and Ba1-xCaxTi0.9Zr0.1O3 (BCTZ). KNN thin films were deposited on Pt/TiO2/SiO2/Si substrates at different deposition conditions (substrates temperature, oxygen pressure and laser fluence). BCTZ were deposited on Si and glass substrates at different conditions. The morphology of all the films were examined by scanning electronic microscope (SEM). The structural analysis of the films was performed by Pulsed Laser Photoacoustic (PLPA) technique, this method was employed to identify the structural phases and structural changes with the increase in temperature. Furthermore, X-ray Diffraction Spectroscopy (XRD), X-ray Photoelectron Spectroscopy (XPS) and Raman Spectroscopy were performed to prove the PLPA results. The PLPA analysis shows tetragonal structural phase in KNN thin films, and the orthorhombic and tetragonal structural phases in the BCTZ thin films.
10.-Paulina Segovia-Olvera (camachol@cicese.mx)
Laser induced periodic surface structures on Bi and Ti thin films under femtosecond irradiation.
Paulina Segovia-Olvera. Cátedra CONACyT-Departamento de Óptica, CICESE, Carretera Ensenada-Tijuana 3018, Zona Playitas, Ensenada, Baja California, 22860. México.
The laser induce periodic surface structures (LIPSS) have attracted considerable attention due to its potential to change, improve or provide new features to material surfaces. LIPSS appear as a quasi-periodic pattern of parallel lines on the surface after being irradiated with linearly polarized laser radiation. These structures can be generated in a single-step process and their characteristics are strongly correlated with the irradiation parameters, such as; wavelength, polarization, angle of incidence. Generally, LIPSS are classified in two groups depending on their periodicity referred as Low Spatial Frequency LIPSS (LSFL) and High Spatial Frequency LIPSS (HSFL). Particularly, the use of femtosecond laser pulses to generate LIPSS offers the advantage of minimizing the formation of the heat-affected zone (HAZ), improving the spatial resolution of the surface modification. In this context, the LIPSS formation with fs pulses offers a plethora of options to design and fabricate functional surfaces with complex morphologies in micro and nano scale. Nevertheless, considering that the formation of the structures also depends on material properties and surrounding media, controlling the morphology of the LIPSS is a very difficult task. In this sense, the most recent results in the study of the formation of LIPSS on metals obtained by our research group will be discussed in this presentation.
11.- Noé Zamora Romero (noe.zamora.r@gmail.com)
Synthesis of Molybdenum Oxide Nanoparticles by Laser Ablation of Solids in Liquids.
NoéZamora-Romero. University of California, Riverside, Department of Materials Science and Engineering, 900 University Avenue, Riverside, CA 92521, United States.
The synthesis of molybdenum oxide (MoOx) nanoparticles (NPs) by using the laser ablation of solids in liquids (LASL) technique and their oxidation process was investigated. S/TEM-EDX microscopy images were used to study the oxidation process of these type of NPs. We hypothesized that the NPs oxidation depends on size, particularly it was observed that the smaller the NP not only the more oxidizes but the faster. The formation of spherical core-shell type NPs was seen in most cases. Besides, micro-Raman spectroscopy shows the shell is composed of molybdenum trioxides hydrated (MoO3 · xH2O), x= 1/3, ½ and 1.
12.- Luis Felipe Devia-Cruz (ldevia@cicese.mx)
Ultrafast laser welding of ceramics.
Luis Felipe Devia-Cruz. Materials Science & Engineering Program and Mechanical & Aerospace Engineering Department, University of California, San Diego. Departamento de Óptica, CICESE, Carretera Ensenada-Tijuana 3018, Zona Playitas, Ensenada, Baja California, 22860. México.
Material welding techniques have been a key aspect in the last industrial era. In fact, still there are some welding challenging applications that involve ceramic characteristics i. e. joining pieces of components in which biocompatibility or extremely high temperatures are in play. High temperature resistance of ceramics makes its welding a complex and difficult process.
The present work describes an ultrafast pulsed laser welding approach that relies on focusing light on the interfaces to ensure an appropriate optical interaction volume in the ceramic pieces to stimulate nonlinear absorption processes, causing localized melting rather than ablation.
The methodology of this work considered the optical properties of the polycrystalline ceramics: linear and nonlinear absorption, and the laser parameters: exposure time, number of laser pulses, and pulse duration (femtosecond versus picosecond). Theinterplay between linear and nonlinear optical properties and laser energy–material coupling was studied. The resulting laser welding enable the ceramic pieces as integral components within devices for harsh environments as well as in optoelectronic and/or electronic packages needing visible-radio frequency transparency.
13.- René I. Rodríguez-Beltrán (rrodrigu@cicese.mx)
Femtosecond laser fabrication of periodic nanostructures on polymeric surfaces reinforced by carbon additives.
René I. Rodríguez-Beltrán. CONACyT-Unidad Foránea Monterrey, CICESE, Alianza centro 504, Parque de Investigación e Innovación Tecnológica (PIIT), Apodaca, Nuevo León, C.P. 66629, México.Grupo de Aplicaciones del Láser y Fotónica (ALF-USAL), Universidad de Salamanca, Pl. de la Merced s/n, Salamanca, E-37008 Spain. Instituto de Química Física Rocasolano (IQFR-CSIC), C/Serrano 119, Madrid 28006, Spain.
It has been demonstrated that carbon-based compounds, namely Expanded Graphite (EG), have become excellent fillers to reinforce polymers as Poly (ethylene terephthalate) (PET) to improve their mechanical resistance or electrical conductivity. Additionally, nanostructuring of polymers allows the modification of surface properties. A study about the generation of Laser Induced Periodic Surface Structures (LIPSS) in polymeric surfaces of PET and PET reinforced with expanded graphite is presented. Laser irradiation was carried out with the fundamental and the 3rdharmonic of a linearly polarized Ti:Sapphire laser (FWHM 120 fs for 795 nm and 260 fs for 265 nm; 1kHz)focused on thin films (~100 nm thick) of the aforementioned materials deposited in glass, silicon, and metal substrates and on self-standing films (~400 μm thick). Differences are observed for the films deposited on the different substrates in terms of irradiation parameters, i.e., fluence and number of pulses, needed for the onset of the formation of well-ordered nanostructures. Furthermore, the properties of the surfaces after irradiation were monitored. Atomic Force Microscopy (AFM) was used to analyze the topography and the adhesion force in the micrometer range. Contact angle measurements were carried out to evaluate the wettability of the samples and calculate the surface free energies. Finally, Raman spectroscopy was used to check possible chemical modifications in the materials. This study opens the possibility of extending the applicability of LIPSS to different combinations of deposited layers and substrates with properties on demand.
14.- Gabriel R. Castillo (gabriel.castillo@conacyt.mx)
Ultrafast laser inscription of photonic devices in transparent dielectrics.
Gabriel R. Castillo.Cátedras CONACyT - Centro de Investigaciones en Óptica, Parque de Investigación e Innovación Tecnológica (PIIT), Alianza Centro 504, Apodaca, Nuevo León, 66629, México.
Ultrafastlaserinscriptionisatechniquebywhichpulsesfromafemtosecondlaser,are usedtomicro-structurethesurfaceorthebulkofsolidmaterials.Oneofthemostinterestingfeaturesofthiskindoflasersisthehighpeakintensities thatcanbereachedwhenthe delivered pulses aretightlyfocused.The intensitiesaretypicallyintherangeof1012 – 1015W/cm2,whichcan easilyinducenonlinearabsorptionintransparentmaterials.Therefore,ifthelaser beam is focusedinsideatransparentmaterial, nonlinearabsorptioncanbeconfinedtoaregionnearthefocalvolumeallowingultrahighprecisionmodificationsand3Dmicroprocessingofthematerial.In particular,theinteractionoffemtosecondpulseswithtransparentdielectricshasattractedalotofinterestinthelasttwo decades,mainlyduetothepossibilitytoinducelocalizedrefractiveindexchangestocreatecomplexphotonicstructuresinsidethematerialkeepingthesurfaceintact.Nowadays,thistechniquehasbeenconsolidatedasa threedimensional(3D)photonicdevicefabricationtechnology.Inthis presentation, a brief review of the different techniques used for the fabrication of photonic devices using femtosecond laser pulses and some interesting results such as 3D photonic structures in different materials such as glasses, crystals, and ceramics will be presented.
Short Talks (15 minutes):
1.- Luis Guillermo Mendoza Luna (luisgml@xanum.uam.mx)
Ultrafast study of cyanine IR-780:efficiency of two photon absorption by control of molecule release.
Luis Guillermo Mendoza Luna. Departamento de Física. Universidad Autónoma Metropolitana-Iztapalapa.
Materials that have properties of two-photon absorption (2PA), such as cyanine dyes, have wide applications in emerging areas such as coherent laser control, optical limiting, photofarmacology or 3-dimensional imaging of biological tissue [1,2]. In this study, the efficiency of 2PA of cyanines was explored by the two-photon induced fluorescence (TPIF) technique with a femtosecond laser [3]. An Optical Parametric Amplifier (OPA) has been used to excite a sample at various wavelengths in regular intervals in the near-infrared (850-1050 nm); light-induced fluorescence has been produced by the sample and said light in the proper intensity regime has been chosen so as to trigger the 2PA phenomenon. Rhodamine B and 6G were used as standard and validation, respectively; relevant cross-sections were also measured. This work is ongoing, and we will discuss the experimental setup as well as the results obtained so far. These preliminaries results are complementary to other studies of femtochemistry for this type of molecules [4]. We are determining the best properties (efficiency of 2PA) with the aim of using these dyes as antennas that can release species with the advantages of enhanced spatial selectivity and deeper light penetration.
2.- Sharma Kanakkillam (sreed.sharmakn@uanl.edu.mx)
Pulsed laser fragmentation of nanostructured ZnO-Co2O3materials for solar photocatalysis.
Sreed Sharma Kanakkillam. Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León, San Nicolás de los Garza, Nuevo León, 66455, México.
Photocatalysis is an emerging field in which the solar energy/visible light is utilized for different types of catalytic applications including elimination of contaminants from water, air, soil, water splitting mechanisms, sterilization etc. Metal oxide nanoparticles and its different categories like modified metal oxides, nanocomposites, hybrids etc. were used commonly for photocatalytic applications. Here we modified zinc oxide nano powders with cobalt oxide by a simple unique synthesis technique called pulsed laser fragmentation in liquid. The modification was conducted by pulsed laser fragmentation of cobalt oxide powder in water to make a stable nanocolloid. Then zinc oxide powder was mixed to it and laser irradiation was carried out. All these processes finished within 45 minutes so that green powders were obtained. The synthesized powders were taken for characterization techniques like UV-Visible spectroscopy, XPS, Raman, SEM etc. Their photocatalytic properties were studied using degradation of dyes under visible light irradiation. Details of the characterization, properties and photocatalysis are included in this work.
3.- José Morales (jose_gmm@hotmail.com)
Commercial aluminum foil as a substrate for Surface-Enhanced Raman Spectroscopy: A study via atomic force microscopy (AFM) and scanning electron microscopy (SEM).
M.C. José Gpe. Morales Méndez. UAM Izt.Physics department San Rafael Atlixco No. 186, Col. Vicentina, Iztapalapa CDMX Mexico.
Three commercial brands of aluminum foil available in Mexico (Reinolds, Avilés, Great Value) are studied. In this work, we have obtained experimental results, which demonstrate that commercial aluminum foil enhances the Raman signal. The Raman signal enhancement of methylene blue at a concentration of 1x10-6M has been analyzed by placing a drop (6 ul) onto samples of the three commercial brands of aluminum foil and the reference. Preliminary results show that Raman enhancement has been observed in the Great Value samples. Microchannels on the surface of the three commercial brands of aluminum foil have been observed via SEM and AFM; their origin is possibly due to the aluminum foil manufacturing process. We hypothesize that these microchannels give rise to the Raman enhancement of methylene blue.
4.- V. Gámez Albo
Synthesis of silver nanoparticles in a liquid medium for application as bactericidal and fungicidal agents.
V. Gámez Albo. Instituto Politécnico Nacional, CICATA U. Altamira, 89600, Altamira, Tamaulipas, México; Universidade Federal de Pernambuco, DQF, Recife, 50670-901, Brazil.
In this work, a fast and efficient method for the synthesis of silver nanoparticles coated with silica by means of the laser ablation technique in combination with oxidation-reduction mechanisms in aqueous solution is presented. This method is a chemical synthesis where the reducer agent is introduced in nanometer form by laser ablation of a solid target submerged in an aqueous solution. In a first step a silicon target immersed in water was ablated for several minutes. After this, the material extracted and suspended in the solution was re-irradiated using a lower energy density to finish fractionating the larger particles. Subsequently, an aliquot of an AgNO3dissolution was added and the redox reaction produced between the silver ions and ablation products leads to a colloidal suspension of core-shell Ag@Silica NPs. For the stability of the colloids, Na2CO3was also added to the solution. Once synthesized, silica-coated silver nanoparticles can be used as bactericidal agents when irradiated with a low energy density in the absorption region, which causes resonance of surface plasmons, resulting in several scenarios that can cause death of nearby bacteria. However, for fungicidal applications where the specimens are larger, an AlCl3solution was used to promote the tendency of the nanoparticles towards agglomerations, which allows such application. On the other hand, the colloidal suspensions were studied by UV-VIS-NIR spectroscopy, dynamic light scattering(DLS) and electrophoretic light scattering(ELS). Also, pH measurements were carried out.
5.- Carlos Acosta (caz@xanum.uam.mx)
Modelling of single nanosecond laser pulse-induced modifications of Silicon surfaces.
Departamento de Física, Universidad Autónoma Metropolitana Iztapalapa, Av. San Rafael Atlixco No. 186, Col. Vicentina, C.P. 09340 México D. F., México.
Irradiation with a single nanosecond laser pulse in the melting regime can result in a characteristic change in the surface morphology of crystalline silicon. This has been verified experimentally in a variety of situations. In certain irradiation conditions dimple-shaped surface topographies are produced. In this work the dimple height, depth and width are modelled following the approach of Schwarz-Selinger and coworkers, upon varying the laser irradiation parameters like peak energy density, pulse duration and wavelength. This is achieved with numerical simulations of one-dimensional heat flow as input to the analytical fluid-flow equations. This model has been implemented in order to explain some results obtained in nanosecond laser-induced interference grating formation experiments on silicon.
6.- A.M. López (alvaro.lopez@icat.unam.mx)
Separation and size determination of silver nanoparticles synthesized by laser ablation in liquid.
A.M. López-Rodríguez.Programa de Maestría y Doctorado en Ingeniería, Universidad Nacional Autónoma de México,Edificio Bernardo Quntana Piso 1, C.U., 04510 Coyacán, CDMX, México. Instituto de Ciencias Aplicadas y Tecnología, Universidad Nacional Autónoma de México, Circuito Exterior S/N, Ciudad Universitaria, A.P. 70-186, Delegación Coyoacán, C.P. 04510 CDMX, México.
The unique properties of silver particles are strongly dependent on the size and shape of the nanoparticles, NPs [1]. Ablation synthesis in solution has some limitations in the size control of NPs. So, to have a uniform size distribution at the time of synthesizing the NPs in solution, either by chemical method [2]or by laser ablation [3], has been a problem that is difficult to solve. Among traditional separation methods, centrifugal separation technology has been successfully applied in the separation and purification of different types of NPs [4]. In this report, a simple method is shown to obtain size distribution-controlled spherical silver nanoparticles, Ag-NPs, by repeated centrifugation-dispersion steps, controlling the centrifugation speed. The morphology and surface plasmon resonance for Ag-NPs, were investigated by scanning-transmission electron microscopy, STEM, and UV-Vis absorption spectroscopy, respectively.Meanwhile, the statistics of the size distribution of the separated nanoparticles was takenfrom the microscopy images using software for particle measurement and data analysis. During this study, the results obtained for each centrifugation stage, their corresponding values for the central peak of the surface plasmon resonance and the percentage of the majority population of NPs report nanoparticles in the range of 11 to 20 nm of diameter. In conclusion, a viable procedure was found for the separation of spherical Ag-NPs by size and therefore a way to standardize nanoparticles size distribution.
7.- Áulide Martinez Tapia (aulide.13@gmail.com)
Bessel beam propagation in calcium vapor and conical emission.
Áulide Martinez Tapia. Departamento de Física. Universidad Autónoma Metropolitana - Iztapalapa.
We have observed anomalous conical emission from the first resonant transition of calcium (λca=422.67nm) using two types of laser beam, Gaussian and zeroth-order Bessel beams. We used the third harmonic of a Nd:YAG laser to pump a homemade tunable dye laser to excite the transition, and a 1° axicon to produce the Bessel beams. The conical emission featured different half-angles for the same wavelength as a function of the excitation beam. The results of our experiments support conical emission models based upon four-wave mixing, and we believe this is due to the fact we have modified the phase-matching condition with the zeroth-order Bessel beam wave vector.
8.- Enrique Esparza (espaleg@ciencias.unam.mx)
Monolayers of cholesterol deposited by Langmuir-Blodgett technique on nanostructured substrates.
Enrique Esparza-Alegría. Posgrado en Ciencias (Física), Universidad Autónoma Metropolitana Unidad Iztapalapa (UAMI), Av. San Rafael Atlixco 186, Leyes de Reforma 1ra Secc, México C.D.Mx., C.P. 09340.
Cholesterol monolayers were deposited by the Langmuir-Blodgett (LB) technique on silicon wafers, glass slides, nano structured silicon wafers and nanostructured glass slides. These latter substrates are known as nanostructured substrates (SN) since they have deposited a silver film by the pulsed laser ablation technique (ALP). The films were characterized by the Raman spectroscopy technique to study whether the SERS effect (Surface Enhanced Raman Spectroscopy) presented by nanostructured substrates aids in the detection of thin films synthesized by the LB technique.
9.- Noé Enríquez Sánchez (noeensa@hotmail.com)
Synthesis of manganese oxides by laser ablation of solids in liquids (LASL).
Noé Enríquez Sánchez. Posgrado en Ciencia de Materiales, Facultad de Química, Universidad Autónoma del Estado de México, Paseo Colón esquina Paseo Tollocan S/N, 50180 Toluca, México.
Currently there are a number of different methods for obtaining nanosized materials such as thermal oxidation, sol-gel method, solvothermal synthesis, among others. However, the laser ablation of solids in liquids (LASL) technique has acquired great importance due to its relatively low cost, also considered as a green technique because it does not generates by-products and extra chemicals are not required for the synthesis. In addition, a large variety of nanomaterials can be obtained with a simple variation of the laser irradiation parameters during the synthesis, which translates into the modification of sizes and morphologies of the created nanostructures. It is a fast technique since it allows to obtain nanomaterials in a short time as compared to the long synthesis times required by some chemical techniques.
In this work, colloidal suspensions of manganese oxide nanoparticles were synthesized, especially the Mn3O4phase, by using LASL. The experiments were carried out by ablating a manganese target immersed in deionized water as the liquid medium. In addition, the effect of ablation time on the formation of these oxides was studied, this being an important parameter for the final composition of the obtained products. The optical properties were characterized, as well as the structure and morphology of the obtained nanoparticles.
10.- Katia del Carmen (kcmartinezguzman@hotmail.com)
Synthesis and optoelectronic properties of nanocomposites of Sb2S3 with Si from laser ablated nanocolloids.
Katia del Carmen Martínez Guzmán. Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León. San Nicolás de los Garza Nuevo León, 66455, México.
Pulsed laser ablation in liquid technique is used frequently due to the advantage of obtention of stable, surfactant free nanomaterials in colloidal form. In this work, we synthesized semiconductor nanocolloids with laser ablation in liquid. The ablation process was carried out with pure Sb2S3target and with additions of polycrystalline-Si and monocrystalline-Si in ethyl alcohol solution and thin films were deposited by spin coating. Different morphology has been observed in synthesis by means of laser ablation and deposition by spin coating compared to the conventional one obtained by other synthesis technique like chemical bath deposition. Characterization on their structure, morphology, elemental composition, chemical states, optical and electrical properties are done. Results on these hybrid nanostructured thin films at optimized synthesis parameters and their optoelectronic properties will be presented.
11.- Fernando González Zavala (ferngoz@hotmail.com)
Pulsed laser deposition of silver vanadates thin films employing two non-conventional array plasmas.
F. González-Zavala. Facultad de Química, Universidad Nacional Autónoma de México, Av. Universidad No. 3000, CDMX, 04510, México.
Thin films of vanadium oxide compounded with silver were prepared by pulsed laser deposition using a two parallel plasmas and sequential plasmas configuration on glass and silicon substrates (100). These substrates were placed in front of the expansion line of the plasmas at a distance of 6 cm. For the array of parallel plasmas, a high purity vanadium and silver targets were placed geometrically parallel and ablated simultaneously. During experiments the plasma parameters, mean ion kinetic energy and plasma density, of vanadium remain approximately constant while the plasma parameters of silver were varied in order to obtain different silver content in the deposited thin film.
For the sequential plasmas configuration different number of silver pellets were attached to the vanadium target in order to incorporate in the thin film different content of silver by varying the Ag/V ablated area ratio, for this experiments the plasma parameters, mean ion kinetic energy and plasma density, of vanadium and silver remain approximately constant.
All of these experiments were executed in vacuum chamber at working pressures close to 4x10-6mbar and a Nd: YAG (1064nm) laser, pulse width 10 ns and a frequency of 10 Hz was employed. Afterwards, the thin films were subjected to thermal treatment at 450°C in order to obtain crystalline oxides. The obtained materials were characterized by Raman spectroscopy showing that the thin films were composed by mixtures of vanadium oxides, silver vanadates, and silver oxides in different proportions. XPS confirmed the existence of mixtures of V2O5, V2O3, VO2and AgVO3, as well as the presence of AgO and AgO2for films prepared at higher silver plasma densities.
12.- Patricia Maldonado-Altamirano (pma8410@gmail.com)
Optical and morphological characterization of CdSe nanoparticles processed by laser ablation in liquid.
Patricia Maldonado-Altamirano. Programa de Nanociencias y Nanotecnología, CINVESTAV- Instituto Politécnico Nacional, Av. Instituto Politécnico Nacional 2508, Gustavo A. Madero, San Pedro Zacatenco, 07360 Ciudad de México, CDMX.
In this work we present some results and analysis concerning the processing of semiconducting CdSe nanoparticles obtained by laser ablation of diluted CdSe powder in acetone. A Nd-YAG pulsed laser was used for ablation, tuned at the first and second harmonic, λ=1064 and 532 nm, 50 Hz frequency repetition during 30 minutes. The experiment was performed at different power intensities. An important difference in the size of the samples synthesized at 1064 nm and 532 nm is observed, being 12 nm for the samples processed with the infrared line and less than 5 nm for those processed with the green line. The emission and absorption of the samples runs from 1.8 to almost 2.4eV for the smallest particles. A deep analysis of the results is presented and discussed.
13.- Anahí Limas (little-ezqovr@hotmail.com)
Preparation of Graphite nanoparticles by laser ablation in distilled water with and without ultrasonic excitation.
AnahíLimas Escobar. UAM- Izt Physics Department, San Rafael Atlixco No. 186, Col. Vicentina, Iztapalapa, C.P. 09340, México D.F.,México.
In this work we report the synthesis of Graphite nanoparticles by laser ablation of a Graphite target immersed in distilled water. The laser used is a Nd: YAG emitting at 1064 nm with a pulsed length of 10 ns. The effect of an ultrasonic excitation and the laser energy density on the size and shape of the nanoparticles is investigated. The nanoparticles size and shape are determined from transmission electron microscopy (TEM) micrographs. The samples were characterized also by Raman spectroscopy. Photoluminescence measurements were also performed. The UV-Vis measurements show a typical plasmonic absorption at 265 nm approximately this band is characteristic of Graphite. In general samples fabricated under ultrasonic excitation are composed on nanoparticles and plane like structures. Without the presence of the ultrasonic field individual nanostructures having spherical shapes are observed. Furthermore, different experimental conditions were studied such as height of water above the target and the spot size effect.
14.- Alejandro Cruz (josephcruzmx@gmail.com)
Ag:Au bimetallic nanoparticles by pulsed laser ablation in liquid and their coatings.
Joseph Alejandro Cruz Turcios. Facultad de Ingeniería Mecánica y Eléctrica, Universidad Autónoma de Nuevo León, San Nicolás de los Garza, Nuevo León, 66455, México.
Bimetallic nanoparticles have interesting properties for optical, electronic, magnetic and chemical applications. Pulsed laser ablation in liquid is an effective synthesis method to develop nanoparticles of metals, semiconductors and ceramics. In this work, colloidal solutions of bimetallic nanoparticles of silver / gold (50/50) were obtained by ablation using a Nd:YAG laser of 532 nm wavelength, with 10 nanosecond pulse, frequency 10 Hz. Then electrophoretic deposition was used to fabricate their coatings from bimetallic nanocolloids. The coating is deposited on different substrates under various electrophoretic deposition parameters. The optical properties of the Ag:Au nanocolloids were analyzed by UV-visible spectroscopy. The elemental composition and chemical states analysis of bimetallic nanoparticles and coatings were done by X-ray photoelectron spectroscopy (XPS), The morphology of the coating was analyzed by scanning electron microscope (SEM) technique. The results show that electrophoretic deposition is effective for developing coatings of bimetallic nanoparticles from their laser-synthesized nanocolloids.
15.- A. Núñez Cristóbal (b_adry13@ciencias.unam.mx)
Effect of laser fluence in Si nanocrystals generatedby laser ablation.
A. Núñez-Cristóbal. Posgrado de Ingeniería Eléctrica, UNAM, Ciudad de México, México. Laboratorio de Fotónica de Microondas, Departamento de Óptica, Microondas y Acústica,UNAM, Ciudad de México, México.
Silicon nanocrystals are generated by physical and chemical techniques, with the change of the parameters in each of the techniques it is possible to modify its physical characteristics and its optical properties. Laser ablation is a technique that allows the production of silicon nanocrystals, which have photoluminescence by quantum confinement. In this work, nanocrystals of different sizes were obtained changing parameters such as; ablation time, type and quantity of liquid. The effect of laser fluence on the generation of nanocrystals was studied by analyzing the dimensions of the craters formed by the shock wave, to determine the optimal energy conditions for obtaining the desired nanocrystals.
16.- Delfino Reyes Contreras (dreyes.fc@gmail.com)
Laser ablated/fragmented carbon materials for the production of photoluminescent nanocolloids.
Delfino Reyes Contreras. Facultad de Ciencias, Campus el Cerrillo, Universidad Autónoma del Estado de México, Toluca, Estado de México, CP. 50200, México.
The laser ablation of solids in liquids (LASL) is a novel and growing route for the synthesis of nanomaterials. It is mainly based on two approximations: the laser ablation of solid targets and the laser fragmentation of suspended powders or micromaterials. In both, the laser, solvent and solid target and/or the suspended material can be tuned in order to reach the desired nanomaterials. In this talk, results concerning to the laser ablation of a graphite solid target for the production of carbon nanodots-based nanocolloids or the laser fragmentation of functionalized multiwall carbon nanotubes or carbon black microspheres to synthesize carbon nanocages and/or carbon dots-colloids will be presented and discussed. For all the obtained nanocolloids, the optical features were analyzed by absorbance and photoluminescent spectroscopies while its structural properties of the produced carbon nanomaterials were analyzed through TEM and Raman techniques. The physical mechanism for the formation of the nanomaterials is discussed and their optical and structural features are correlated with the experimental parameters of synthesis.
