Utilizing solar energy for chemical transformations has attracted a growing interest in promoting the clean and modular chemical synthesis approach and addressing the limitations of conventional thermocatalytic systems. Under light irradiation, noble metal nanoparticles, particularly those characterized by localized surface plasmon resonance, commonly known as plasmonic nanoparticles, generate a strong electromagnetic field, excited hot carriers, and photothermal heating. Plasmonic nanoparticles enabling efficient absorption of light in the visible range have moderate catalytic activities. However, the catalytic performance of a plasmonic nanoparticle can be significantly enhanced by incorporating a highly catalytically active metal domain onto its surface. In this study, we demonstrate that femtosecond laser-induced atomic redistribution of metal domains in bimetallic Au-Pd nanorods (NRs) can enhance its photocurrent response by 2-fold compared to parent Au-Pd NRs. We induce structure changes on Au-Pd NRs by irradiating them with a femtosecond pulsed laser at 808 nm to precisely redistribute Pd atoms on AuNR surfaces, resulting in modified electronic and optical properties and, thereby, enhanced catalytic activity. We also investigate the trade-off between the effect of light absorption and catalytic activity by optimizing the structure and composition of bimetallic Au-Pd nanoparticles. This work provides insight into the design of hybrid plasmonic-catalytic nanostructures with well-tailored geometry, composition, and structure for solar-fuel-based applications.

The present study is the first attempt towards establishing computational insights into the structural, electronic, mechanical, dynamical and thermal properties of the tetragonal phases of potassium chalcoargentates (KAgX). We find that the lattice thermal conductivity of KAgX is anisotropic, with values of 0.553 (0.279), 0.509 (0.369) and 0.221 (0.125) Wm−1K−1 at room temperature (300 K) along the a-axis (c-axis) for KAgS, KAgSe and KAgTe, respectively. The calculated values of the lattice thermal conductivity are very small, especially along the c-axis. This highlights the potential of using KAgX in designing thermoelectric materials, since low lattice thermal conductivity is a requisite for maximizing the dimensionless figure of merit which defines the efficiency of a system in converting thermal to electrical energy and vice versa.

While Li-ion battery cathode-electrolyte interfaces (CEIs) have been extensively investigated in recent decades, accurately identifying the chemical nature and tracking the dynamics of the CEIs during electrochemical cycling still remain a grand challenge. Here we report our findings in the investigation into the dynamic evolution of the interface between a LiNi0.33Co0.33Mn0.33O2 (LNMC) cathode and an ethylene carbonate/dimethyl carbonate (EC/DMC)-based electrolyte using surface-enhanced Raman spectroscopy (SERS) performed on a model cell under typical battery operating conditions. In particular, the strong SERS activity provided by a monolayer of Au nanocubes deposited on a model LNMC electrode (additive-free) enables quasi-quantitative assessment of the CEI evolution during cycling, proving information vital to revealing the dynamics of the species adsorbed on the LNMC surface as a function of cell potential. Furthermore, our theoretical calculation, which is based on the interaction between a model interface-bound molecule and a model LNMC surface, agrees with our experimental observation. The carefully designed operando SERS platform has demonstrated high sensitivity, good surface specificity, and excellent compatibility with extensive electrochemical measurements; it is also applicable to fundamental studies of dynamic interfaces in other electrochemical energy storage and conversion systems.

This study is the first attempt towards establishing computational insight into the structural, electronic, mechanical, dynamical and thermoelectric properties of the monoclinic phases of NaSbS2 and NaSbSe2. The mechanical properties are predicted using the Hill approximation. Dynamical stability was investigated by computing the phonon frequency to check for the absence of imaginary modes. Lattice thermal conductivity was calculated by using a single-mode relaxation-time approximation in the linearized phonon Boltzmann equation from first-principles an-harmonic lattice dynamics calculations. We found that the lattice thermal conductivity of NaSbS2 and NaSbSe2 are anisotropic, with values ranging between 0.753 and 1.173 Wm−1 K−1 at room temperature (300 K). The calculated values of the lattice thermal conductivity are small, especially along the x-axis. The charge transport properties are predicted using Boltzmann transport equations. The highest values attained for the figure of merit are high as 4.22 and 2.88 when the electron concentration is 1018 cm−3 at 600 K for NaSbS2 and NaSbSe2, respectively. This highlights the potential of using NaSbS2 and NaSbSe2 in designing thermoelectric materials since low lattice thermal conductivity and high figure of merit are a requisite for maximizing the efficiency of thermoelectric materials.

Thermoelectric devices can convert heat into an electric current and have immense potential for efficient use of the available energy. This includes converting heat energy from internal combustion engines, conventional power plants and solar cells into usable energy. Research into finding efficient thermoelectric materials has intensified over the past decade. One of the desired features of efficient thermoelectric materials is a low lattice thermal conductivity. In other words, the thermal energy transported by the motion of the atoms in thermoelectric materials should be small. Recent research suggests that some layered materials may possess this property. In this study we used first-principles calculations to investigate the structural, mechanical, and vibrational properties of bulk ReSe2, a layered material. The lattice thermal conductivity was calculated by using a single-mode relaxation-time approximation in the linearized phonon Boltzmann equation from first-principles an-harmonic lattice dynamics calculations. We find that the lattice thermal conductivity of ReSe2 is non-isotropic, with the highest value of 18.58W(mK)-1 along the a-axis and lowest one of 0.69W(mK)-1 along the c-axis at room temperature. These values make this an interesting material as a potential active component in a thermoelectric device.

Research into finding efficient thermoelectric materials has intensified over the past decade. One of the desired features of efficient thermoelectric materials is a low lattice thermal conductivity. In other words, the thermal energy transported by the motion of the atoms in a thermoelectric materials should be small. Recent research suggests that some layered materials may have this property. In this study we used first principles calculations to investigate the structural, electronic, mechanical and vibrational properties of bulk WSe2, a layered material. The lattice thermal conductivity was calculated by using a single-mode relaxation-time approximation in the linearized phonon Boltzmann equation from first-principles an-harmonic lattice dynamics calculations (Phono3py) as well as an iterative self-consistent method to solve the lattice Boltzmann equation(ShengBTE). We find that the lattice thermal conductivity of WSe2 is non-isotropic, with a value of 63.789 and 49.092 Wm −1K−1 in the direction of the plane and 2.088 and 1.563 Wm−1K−1 perpendicular to the plane for Phono3py and ShengBTE respectively at room temperature. The calculated cross-plane thermal conductivity is close to the experimental value at room temperature, and is in a range which makes this an interesting material as a potential active component in a thermoelectric device.

We demonstrate that cellulose nanofiber (CNF) biomaterials with high transparency and mechanical robustness can be combined with gold nanorods to form a multifunctional porous membrane for dual-mode surface-enhanced Raman scattering (SERS) detection of both small molecules and cells. The nanoporous nature of the nanofiber membranes allows for effective molecular filtration and preconcentration of the analytes, further boosting the SERS performance. Specifically, because of the low fluorescence and Raman background of the CNF matrix, extremely low loading density of gold nanorods can be used. The nanorod assemblies within the CNF network can be resonantly driven by a 532 nm laser (transverse plasmonic mode) and near resonantly driven at by a 785 nm laser (longitudinal mode), facilitating dual operational modes at two excitation wavelengths. The shorter wavelength excitation mode yields better Raman scattering efficiency and has been demonstrated to be capable of detecting rhodamine 6G (R6G) dyes down to picomolar concentrations. On the other hand, the longer wavelength excitation mode provides autofluorescence suppression for the better detection of microorganisms such as Escherichia coli, shortening the required integration time from hours to minutes. Upon drastically lowering the spectral background noise and utilizing nanofiltration, the plasmonic CNF membranes reported here show significantly improved SERS sensitivity and detection fidelity as compared to traditional metal, metal oxide, synthetic polymer, and paper SERS substrates.

An electrochemically tunable plasmonic system with narrow visible-NIR absorption bands was designed by synthesizing poly[(3,4-propylenedioxy)pyrrole] nanoshells onto a AuNR core.

Silver nanotetrahedron (AgNT) two-dimensional arrays on a glass substrate generate nonthermal hot electrons, which induced photocatalytic oxidation of 4,4-dimercaptoazobenzene (DMAB) adsorbed onto its surface. The rate of the photocatalytic oxidation of DMAB is found to decrease upon increasing the intensity of the excitation light, unlike traditional photocatalysis reactions. The amount of 4-nitrothiophenol (4-NTP) resulting from the photocatalytic oxidation of DMAB is lower than expected, suggesting the partial desorption of DMAB or 4-NTP molecules from the surface of the AgNTs. However, the hot electrons remaining from the photocatalysis reaction thermalize and transfer their energy to the nanoparticle lattices, generating heat. The photothermal heat is sufficient to dissociate the Ag-S bond causing desorption of both DMAB and 4-NTP.

We demonstrate the electrically controlled and reversible plasmonic signature of hybrid polymer metal nanostructures composed of core/shell nanostructures: gold nanocubes (AuNCs) coated with electrochromic polyaniline (PANI) shells. A reversible tuning of the localized surface plasmon resonance (LSPR) peak of the AuNC core was obtained by applying an electrical potential that caused a reversible oxidation state change in the electroactive PANI nanoshell. A significant shift of the main LSPR peak was achieved with high reversibility and electrochemical stability due to the interplay of the local decay of the electromagnetic field and the controlled thickness of the surrounding polymer shell. Here, the PANI shell acts as an electroactive medium as well as a physical spacer to prevent uncontrollable plasmonic coupling. The most efficient LSPR shift can be induced by the refractive index change of nanoscale PANI shell thickness lower than the electromagnetic field decay length of the given gold nanoparticles. Single particle studies showed that coupling of plasmon resonances of densely packed nanocubes with thicker PANI shells was prevented and the extinction signature of individual core/shell nanocubes remained mostly unchanged after their assembly into densely packed aggregates. Therefore, these core/shell structures could preserve the original plasmonic signature of individual nanostructure by damping plasmonic coupling between AuNC cores.

Vertically aligned and well-separated 1D silver nanopillars (AgNPLs) are prepared on a large-area quartz surface using a robust colloidal,chemical techinque. Silver nanodisk (AgND) monolayers were first deposited on quartz using the Langmuir-Blodgett technique, and the presence of the substrate induced asymmetric chemical overgrowth, Of the AgNDs into AgNPLs. The height and diameter, of the prepared AgNPLs were controlled-by changing the rate of the overgrowth reaction. Chloride ions were used during overgrowth to etch the silver atoms that formed sharp features on the sides of the AgNDs and to limit growth in the lateral direction. The grown AgNPLs displayed two surface plasmon resonance modes corresponding to the transverse and longitudinal electron oscillations. The intensity of the longitudinal mode increased by a factor of 9 while the intensity of the transverse mode decreased by a factor of 2.5 upon. increasing the angle of incidence of the exciting light from 0 degrees to 60 degrees. This interesting property makes these AgNPL arrays on quartz useful as chromatic light polarizers.

We present a rational approach to fabricating plasmonically active hybrid polymer-metal nanomaterials with electrochemical tunability of the localized surface plasmon resonances (LSPRs) of noble metal nanostructures embedded in an electroactive polymer matrix. The key requirement for being able to significantly modulate the LSPR band position is a close overlap between the refractive index change [Δn(λ)] of a stimuli-responsive polymeric matrix and the intrinsic LSPR bands. For this purpose, gold nanorods with a controlled aspect ratio, synthesized to provide high refractive index sensitivity while maintaining good oxidative stability, were combined with a solution-processable electroactive and electrochromic polymer (ECP): alkoxy-substituted poly(3,4-propylenedioxythiophene) [PProDOT(CH2OEtHx)2]. Spectral characteristics of the ECP, in particular the Δn(λ) variation, were evaluated as the material was switched between oxidized and reduced states. We fabricated ultrathin plasmonic electrochromic hybrid films consisting of gold nanorods and ECP that exhibited a large, stable, and reversible LSPR modulation of up to 25-30 nm with an applied electrical potential. Finite-difference time-domain (FDTD) simulations confirm a good match between the experimentally measured refractive index change in the ECP and the plasmonic response during electrochemical modulations.

Colloidal silver nanodisks (AgNDs) are assembled into a monolayer with a coverage density gradient (CDG) on the surface of flat and cylindrical substrates using the Langmuir-Blodgett (LB) technique. Compressing the LB monolayers during transfer to the substrates causes the CDG assembly of the AgNDs. By functionalizing the AgNDs with poly(ethylene glycol), it is possible to control their order inside the LB monolayer assembly by changing the deposition surface pressure. Well-separated AgNDs, 2D aggregates with different numbers of particles, and highly packed 2D arrays are formed as the deposition surface pressure is increased. Localized surface plasmon resonance (LSPR) spectra collected at different separation distances from the highest coverage spot (HCS) of the CDG AgND arrays on a flat substrate are blue-shifted, and the shift increases systematically upon increasing the distance. The relationship among the LSPR peak position, the peak intensity at a fixed wavelength, and the corresponding separation distance from the HCS is fitted exponentially. A similar systematic blue shift in the LSPR spectrum of the CDG AgND monolayer on a cylindrical substrate is obtained when the substrate is rotated at different angles relative to the HCS. The fabricated CDG AgND monolayers can potentially be used for optically measuring distances and angles.

In operando resonance Raman spectroscopy suggests quantitative correlation between phonon band properties and the amount of charge storage of high-energy density NiO2H x battery/pseudocapacitive material. Comparing the spectroscopic evolution using different electrolytes reveals the contributions of breaking/formation of O-H bonds and insertion/extraction of cations to electrochemical charge storage of NiO2H x .

Gold nanocages (AuNCs) are comparatively novel nanostructures, as many of their characteristics are still to be exploited. The purpose of present study was to systematically investigate the toxicological effects of AuNCs on human keratinocyte cell line (HaCaT) utilizing Dark Field (DF)/Bright Field (BF) imaging and flow cytometry cell cycle techniques. We have applied surface modification, concentration, and incubation time of AuNCs as variables to investigate their effect on the cellular imaging and cell cycle response of HaCaT cells. The results indicate that the AuNCs interact with HaCaT cells in accordance to their surface charge and concentration. Cellular uptake is evident from DF images which lead to the cell cycle perturbations and apoptosis in HaCaT cells. AuNCs cause a prominent G2/M phase arrest after 24 h of incubation. To the best of our knowledge toxicological effects of AuNCs on cell cycle of HaCaT cell line in vitro are not reported previously.

The correlation of the Langmuir Blodgett deposition phase with the reversible LSPR modulation of P3HT-coated silver nanodisk monolayers.

Highly packed gold nanocube (AuNC) 2D arrays sandwiched between two layers of polydimethylsiloxane (PDMS) substrates act as an optical neutral density filter (NDFs) and a chromatic polarizer. Upon mechanical stretching, the intensity of the absorption spectrum of the AuNC 2D arrays-PDMS is found to decrease evenly in the UV, visible, and NIR regions of the electromagnetic spectrum. The color of the polarized light transmitted through the filter is dependent on its angle of polarization. The localized surface plasmon resonance (LSPR) extinction spectrum of the AuNC arrays arises mainly from scattering rather than absorption, unlike standard NDFs where their function is based on light absorption. Absorption of light causes heat generation that has a negative impact on the function of the NDFs. The ordering of the AuNCs inside the array after stretching was examined by dark field imaging, polarization-dependent optical measurements, and surface-enhanced Raman scattering spectroscopy.

We report novel dual-responsive plasmonic core shell anisotropic nanostructures composed of gold nanorod (AuNR) and responsive polyaniline (PANT) shells with plasmonic mode appearance reversibly modulated through orthogonal stimuli (i.e., electrical potential and pH change). In this system, the PANT shells provide AuNR cores with three different refractive index environments depending on stimuli (pH and electrical potential). Therefore, no additional secondary responsive component is necessary to induce the dual-responsive properties of AuNR cores. Furthermore, in this study, dual-responsive properties can be realized for nanostructures fixed on substrates, whereas previously reported dual-responsive plasmonic systems can only be controlled in solution. Here, the highest localized surface plasmonic resonance (LSPR) shift of the AuNR cores can be induced by changing both local pH and applying electric potential. Notably, a significant plasmon band shift by 107 nm is realized with only 8 nm thick PANI shell due to the large refractive index change at the gold polymer interface. A maximum shift of the longitudinal plasmon mode of 149 nm is obtained by applying a modest electrical potential (below +/- 1 V), a large shift rarely reported in the literature for metal nanostructures. Moreover, our anisotropic core/shell nanostructures exhibit stable and reversible dual-responsive LSPR behavior over 100 cycles without degradation.