Multiphotonic Ablation and Electro-Capacitive Effects Exhibited by Candida albicans Biofilms.

This work reports the modification in the homogeneity of ablation effects with the assistance of nonlinear optical phenomena exhibited by C. albicans ATCC 10231, forming a biofilm. Equivalent optical energies with different levels of intensity were irradiated in comparative samples, and significant changes were observed. Nanosecond pulses provided by an Nd:YAG laser system at a 532 nm wavelength in a single-beam experiment were employed to explore the photodamage and the nonlinear optical transmittance. A nonlinear optical absorption coefficient -2 × 10-6 cm/W was measured in the samples studied. It is reported that multiphotonic interactions can promote more symmetric optical damage derived by faster changes in the evolution of fractional photoenergy transference. The electrochemical response of the sample was studied to further investigate the electronic dynamics dependent on electrical frequency, and an electro-capacitive behavior in the sample was identified. Fractional differential calculations were proposed to describe the thermal transport induced by nanosecond pulses in the fungi media. These results highlight the nonlinear optical effects to be considered as a base for developing photothermally activated phototechnology and high-precision photodamage in biological systems.

Electrochemical conversion of CO2 using metal-organic framework catalysts.

Metal-organic frameworks (MOFs) have been an excellent platform for carbon dioxide reduction reactions (CO2RR). In this work, the feasibility of electrochemical reduction of CO2 to obtain C2-deep value-added products was investigated by the preparation of Mg-containing MOF-74 samples combined with transition metal cations (Ni2+, Co2+ and Zn2+). The prepared MOFs were used as electrocatalysts in CO2RR. Chronoamperometric analysis coupled to ATR-FTIR spectroscopy was employed to characterize the CO2 reduction products and subsequently via 1H NMR. Although an isostructural crystalline structure was observed in all synthesized MOFs, the pore diameter distribution was significantly affected due to the Mg coordination along with each transition metal nuclei with the organic ligand to form the MOF-74. Our results showed that Mg-containing MOF-74 electrocatalysts combined with Ni, Co and Zn ions successfully reduced CO2 to C2-deep products, while the monometallic Mg-MOF-74 showed only CO2 mineralization. An ester acetate, isopropyl alcohol, and formic acid were produced by Mg/Ni-MOF-74; isopropyl alcohol was provided by Mg/Co-MOF-74, and ethanol was generated by Mg/Zn-MOF-74. We observed that the change of the transition cation was a key factor in the selectivity of the obtained products, while the degree of Mg ions effectively incorporated into the MOF structure tuned the porosity and the electrocatalytic activity. Among them, Mg/Zn-MFOF-74 showed the highest Mg content loaded after synthesis and thus the most favorable electrocatalytic behavior towards CO2 reduction.

Synthesis and characterization of V2O5-Ga2O3 photocatalysts and their application on the photocatalytic reduction of CO2.

The photocatalytic reduction of carbon dioxide (CO2) to produce methanol (CH3OH) is a promising strategy for producing clean energy. The catalyst, the aqueous medium, and the UV light are key parameters for the formation of the most relevant pair (e-/h+) and the specific selectivity towards the desired product (methanol). The use of Ga2O3 and V2O5 in the photocatalytic reduction of CO2 to produce methanol has been little studied. However, the combination of these oxides is important to generate synergies and decrease the band energy, enhancing the photocatalytic activity in CO2 reduction. In this work, V2O5-Ga2O3 combined photocatalysts have been prepared and investigated for the photocatalytic reduction of CO2. These photocatalysts were characterized by spectroscopic and microscopic techniques. The results showed that textural properties such as surface area and morphology do not influence the photocatalytic activity. However, species such as Ga2p3/2 and Ga2p1/2 identified by XPS enhanced the photocatalytic activity, most likely due to the formation of vacancies and the reduction of the bandgap in the combined oxides, as compared to single oxides. The contribution of these factors in pair interactions (e-/h+) with CO2 to generate methanol is demonstrated.

Navigation of Silver/Carbon Nanoantennas in Organic Fluids Explored by a Two-Wave Mixing.

Within this work are analyzed third-order nonlinear optical properties with a potential influence on the dynamic mechanics exhibited by metal/carbon nanofluids. The nanofluids were integrated by multiwall carbon nanotubes decorated with Ag nanoparticles suspended in ethanol or in acetone. Optical third-order nonlinearities were experimentally explored by vectorial two-wave mixing experiments with a Nd-YAG laser system emitting nanosecond pulses at a 532 nm wavelength. An optically induced birefringence in the metal/organic samples seems to be responsible for a significant modification in density and compressibility modulus in the nanosystems. The measured nonlinear refractive index was associated with a thermal process together with changes in density, compressibility modulus and speed of sound in the samples. Nanofluid diffusivity was studied to characterize the dynamic concentration gradients related to the precipitation of nanostructures in the liquid solutions. The evolution of the nanoparticle density suspended in the nanofluids was considered as a temporal-resolved probabilistic system. It is stated that the incorporation of Ag nanoparticles in carbon nanotubes produces strong mechanical changes in carbon-based nanofluids. According to numerical simulations and optical evaluations, immediate applications for developing dynamic nanoantennas optical logic gates and quantum-controlled metal/carbon systems can be contemplated.

Dynamic compressibility and third-order optical nonlinearities in carbon/metal-based nanofluids.

The influence of the superposition of two high-irradiance optical beams on the mechanical properties exhibited by carbon nanotubes decorated with platinum nanoparticles was analyzed. The change in density, compressibility modulus and acoustic velocity in the samples suspended in acetone and ethanol was estimated by measuring the nonlinear refractive index tested by a two-wave mixing experiment. The nanotubes were prepared by a spray pyrolysis processing route and the metal decoration was carried by chemical vapor deposition. High-Resolution Transmission Electron Microscopy studies confirmed the multiwall nature of the carbon nanotubes; while energy-dispersive X-ray spectroscopy reveals the separated presence of platinum nanoparticles incorporated to the hybrid nanostructures. An Nd-YAG laser system emitting at 532 nm wavelength with 4 ns pulse duration was used for conducting the third-order nonlinear optical evaluations by a standard optical Kerr gate technique. Comparative experiments showed that the composition of the liquid solution plays an important role in the manipulation of the density exhibited by the nanofluids. Remarkably, the incorporation of Pt in the tubes originates stronger changes of the mechanical characteristics induced by optical nonlinearities in the nanofluids irradiated by nanosecond pulses. Within this work, it is highlighted that potential applications for developing multivalent logic operations by fuzzy mechano-optic effects exhibited by nanofluids can be contemplated.

Chaotic Signatures Exhibited by Plasmonic Effects in Au Nanoparticles with Cells.

The evolution of the optical absorptive effects exhibited by plasmonic nanoparticles was systematically analyzed by electronic signals modulated by a Rössler attractor system. A sol-gel approach was employed for the preparation of the studied Au nanoparticles embedded in a TiO2 thin solid film. The inclusion of the nanoparticles in an inhomogeneous biological sample integrated by human cells deposited in an ITO glass substrate was evaluated with a high level of sensitivity using an opto-electronic chaotic circuit. The optical response of the nanoparticles was determined using nanosecond laser pulses in order to guarantee the sensing performance of the system. It was shown that high-intensity irradiances at a wavelength of 532 nm could promote a change in the absorption band of the localized surface plasmon resonance associated with an increase in the nanoparticle density of the film. Moreover, it was revealed that interferometrically-controlled energy transfer mechanisms can be useful for thermo-plasmonic functions and sharp selective optical damage induced by the vectorial nature of light. Immediate applications of two-wave mixing techniques, together with chaotic effects, can be contemplated in the development of nanostructured sensors and laser-induced controlled explosions, with potential applications for biomedical photo-thermal processes.

Ultrasonic Influence on Plasmonic Effects Exhibited by Photoactive Bimetallic Au-Pt Nanoparticles Suspended in Ethanol.

The optical behavior exhibited by bimetallic nanoparticles was analyzed by the influence of ultrasonic and nonlinear optical waves in propagation through the samples contained in an ethanol suspension. The Au-Pt nanoparticles were prepared by a sol-gel method. Optical characterization recorded by UV-vis spectrophotometer shows two absorption peaks correlated to the synergistic effects of the bimetallic alloy. The structure and nanocrystalline nature of the samples were confirmed by Scanning Transmission Electron Microscopy with X-ray energy dispersive spectroscopy evaluations. The absorption of light associated with Surface Plasmon Resonance phenomena in the samples was modified by the dynamic influence of ultrasonic effects during the propagation of optical signals promoting nonlinear absorption and nonlinear refraction. The third-order nonlinear optical response of the nanoparticles dispersed in the ethanol-based fluid was explored by nanosecond pulses at 532 nm. The propagation of high-frequency sound waves through a nanofluid generates a destabilization in the distribution of the nanoparticles, avoiding possible agglomerations. Besides, the influence of mechanical perturbation, the container plays a major role in the resonance and attenuation effects. Ultrasound interactions together to nonlinear optical phenomena in nanofluids is a promising alternative field for a wide of applications for modulating quantum signals, sensors and acousto-optic devices.

Acousto-Plasmonic Sensing Assisted by Nonlinear Optical Interactions in Bimetallic Au-Pt Nanoparticles.

A strong influence of mechanical action in nonlinear optical transmittance experiments with bimetallic nanoparticles integrated by gold and platinum was observed. The nanostructured samples were synthesized by a sol-gel method and contained in an ethanol suspension. UV-VIS spectroscopy evaluations, Transmission electron microscopy studies and input-output laser experiments were characterized. A two-photon absorption effect was induced by nanosecond pulses at 532 nm wavelength with an important contribution from the plasmonic response of the nanomaterials. All-optical identification of acoustical waves was remarkably improved by optical nonlinearities. High sensitivity for instrumentation of mechano-optical signals sensing particular fluids was demonstrated by using a variable carbon dioxide incorporation to the system.