Plasmonic Au Nanoparticles Research Articles

Au Cluster-Nanoparticle Dual Coupling for Photocatalytic CO2 Conversion.

CO2-selective photoreduction to value-added products is ideal, but its practical application suffers from weak photogenerated carrier separation and insufficient multielectron transport. Herein, we constructed the tricomponent AuNPs@SnO2-AuNCs hybrid by decorating Au nanoclusters (AuNCs) on the Au nanoparticle (AuNPs)@SnO2 core-shell structure. AuNC-NP dual coupling endowed AuNPs@SnO2-AuNCs with an excellent CO yield of 64.8 μmol g-1 h-1 during CO2 photoreduction, which was higher than the role of separate application of AuNCs (25.3 μmol g-1 h-1) and AuNPs (16.0 μmol g-1 h-1). It was mainly attributed that the coaction of AuNPs and AuNCs not only enhanced the visible light absorption capacity but also improved the photogenerated carrier separation/migration. As a result, the electron-rich AuNCs induced from plasmonic AuNPs and photoexcited SnO2 promoted the photocatalytic CO2-to-CO performance. This work provides a new perspective to design multicomponent photocatalysts for highly efficient CO2 conversion.

All‐in‐One: Plasmonic Janus Heterostructures for Efficient Cooperative Photoredox Catalysis

AbstractJanus heterostructures consisting of multiple jointed components with distinct properties have gained growing interest in the photoredox catalytic field. Herein, we have developed a facile low‐temperature method to gain anisotropic one‐dimensional Au‐tipped CdS (Au−CdS) nanorods (NRs), followed by assembling Ru molecular co‐catalyst (RuN5) onto the surface of the NRs. The CdS NRs decorated with plasmonic Au nanoparticles (NPs) and RuN5 complex harness the virtues of metal‐semiconductor and inorganic‐organic interface, giving directional charge transfer channels, spatially separated reaction sites, and enhanced local electric field distribution. As a result, the Au−CdS−RuN5 can act as an efficient dual‐function photocatalyst for simultaneous H2 evolution and valorization of biomass‐derived alcohols. Benefiting from the interfacial charge decoupling and selective chemical bond activation, the optimal all‐in‐one Au−CdS−RuN5 heterostructure shows greatly enhanced photoactivity and selectivity as compared to bare CdS NRs, along with a remarkable apparent quantum yield of 40.2 % at 400 nm. The structural evolution and working mechanism of the heterostructures are systematically analyzed based on experimental and computational results.

All-in-One: Plasmonic Janus Heterostructures for Efficient Cooperative Photoredox Catalysis.

Janus heterostructures consisting of multiple jointed components with distinct properties have gained growing interest in the photoredox catalytic field. Herein, we have developed a facile low-temperature method to gain anisotropic one-dimensional Au-tipped CdS (Au-CdS) nanorods (NRs), followed by assembling Ru molecular co-catalyst (RuN5) onto the surface of the NRs. The CdS NRs decorated with plasmonic Au nanoparticles and RuN5 complex harness the virtues of metal-semiconductor and inorganic-organic interface, giving directional charge transfer channels, spatially separated reaction sites, and enhanced local electric field distribution. As a result, the Au-CdS-RuN5 can act as an efficient dual-function photocatalyst for simultaneous H2 evolution and valorization of biomass-derived alcohols. Benefiting from the interfacial charge decoupling and selective chemical bond activation, the optimal all-in-one Au-CdS-RuN5 heterostructure shows greatly enhanced photoactivity and selectivity as compared to bare CdS NRs, along with a remarkable apparent quantum yield of 40.2 % at 400 nm. The structural evolution and working mechanism of the heterostructures are systematically analyzed based on experimental and computational results.

Investigation of Cu-Oxidation and Its Roles in Unassisted CO2 Reduction and Electrochemical Oxygen Evolution

Sunlight-driven photocatalytic CO2 reduction to CO under unassisted (unbiased) conditions was recently demonstrated using heterostructured catalysts that combine p-type GaN with plasmonic Au nanoparticles and Cu nanoparticle co-catalysts (p-GaN/Al2O3/Au/Cu) [1]. However, the exact oxidation state of Cu and the hole transfer directionality between Au and Cu remain under debate. Here, we combine computational and experimental efforts to investigate the different oxidation states of Cu under unassisted photocatalytic operating conditions. Experimentally we found that the Cu nanoparticles are primarily composed of Cu2O and CuO, CuCO3.Cu(OH)2 species, with no detectable metallic Cu present. The calculated bulk thermodynamics confirmed the high stability of CuCO3.Cu(OH)2 which is also validated by its largest contribution in the Pourbaix diagram, consistent with experimental observations. To gain insights into the origin of charge transfer, we simulate material interfaces namely, Au/CuO, Au/Cu2O, and Au/CuCO3.Cu(OH)2. Our theoretical analysis supports experimentally observed light-driven hole transfer from Au to Cu.More recently significant progress has been made in understanding copper oxide (CuO) behavior at oxidizing electrochemical conditions (> 1.5 V) [2]. In our study, we show CuO transforms into the OER active phase CuOOH, as evident in the bulk Pourbaix diagram presented here. Our calculations show a novel square planar, non-magnetic CuOOH phase. This discovery is supported by calculated Raman spectroscopic analysis, revealing distinct features corresponding to Cu3+ species at 567 and 585 cm-1, closely matching experimental peaks at 587 cm-1. These findings provide insights into the electrochemical properties of copper oxide phases and their relevance towards electrocatalytic OER. Acknowledgments:This material is based on work performed by the Liquid Sunlight Alliance, which is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Fuels from Sunlight Hub under Award Number DE-SC0021266. Reference:[1] H. A. Atwater et al. ACS Energy Lett, 6, 1849 (2021)[2] M J. Janik et al. ACS Appl. Mater. Interfaces, 15, 27878 (2023)

(Invited) Plasmon-Driven Nitrogen Photofixation

Ammonia is one of the most important chemicals as well as an efficient energy carrier. The nitrogen element is indispensable for nearly all living species on the earth. However, dinitrogen molecules that are abundant in the atmosphere cannot be used directly by living species. They need to be converted into ammonia or nitrate for use. Such conversion is known as nitrogen fixation. Because natural nitrogen fixation is insufficient for sustaining all population on the earth, the industrial Haber-Bosch process has been developed for producing ammonia from dinitrogen and dihydrogen. The process consumes a large amount of energy and generates a large amount of carbon dioxide. Photocatalytic nitrogen fixation can operate under mild conditions and uses solar energy and water. It offers an intriguing alternative approach for the conversion of atmospheric dinitrogen into ammonia.Plasmonic metal nanocrystals can effectively absorb light and efficiently generate hot charge carriers. Compared to traditional interband excitation in semiconductors, plasmon excitation offers a new approach for generating hot charge carriers, which can thereafter be utilized for various physical and chemical processes. The use of plasmonic hot charge carriers for photocatalysis has become a hot research topic in the recent years. Plasmonic hot charge carriers can not only enhance the reaction yield and selectivity, but also introduce new reaction pathways. Moreover, the plasmon resonance wavelengths of various nanoparticles can be synthetically adjusted over a broad range that surpasses the solar spectrum.We have demonstrated the powerfulness of localized plasmon resonance on driving photocatalytic reduction of atmospheric nitrogen, where plasmonic hot electrons play an essential role. First, Au nanoparticles are anchored on ultrathin titania nanosheets with oxygen vacancies. The oxygen vacancies chemisorb and activate nitrogen molecules, which are subsequently reduced to ammonia by plasmonic hot electrons generated from the Au nanoparticles. Our synthesized all-inorganic hybrid structures mimic the function of biological nitrogenase enzymes, where the plasmonic Au nanoparticles play the role of the Fe proteins and the titania nanosheets play the role of the MoFe proteins. Second, we have extended the biomimetic idea into another popular semiconductor. A plasmonic hybrid catalyst is produced by uniformly embedding Au nanoparticles in the mesopores of nitrogen-deficient hollow carbon nitride spheres. The carbon nitride spheres possess abundant nitrogen vacancies, which serve as the sites for nitrogen chemisorption and activation, and capture photoexcited electrons stemmed from the carbon nitride spheres and the plasmon resonance of the embedded Au nanoparticles for the efficient reduction of the adsorbed nitrogen molecules to ammonia. Third, when metal-semiconductor hybrid nanostructures are designed as photocatalysts for nitrogen fixation, the introduction of a Schottky barrier at the junction is unavoidable. This Schottky barrier will undoubtedly lower the utilization efficiency of plasmonic charge carriers because only plasmonic hot charge carriers with sufficient energies and appropriate momenta can overcome the barrier and inject into the semiconductor. In addition, noble metals are well-known to be expensive. We have synthesized different metal oxide nanoparticles that are degenerately doped and thus exhibit strong plasmon resonance and demonstrated Schottky-barrier-free plasmonic photocatalysts for nitrogen fixation. The excitation of the plasmon resonance in these metal oxide nanoparticles can efficiently generate hot charge carriers. Because of the abundance of defects in these degenerately doped semiconductor nanoparticles, the photogenerated hot charge carriers can rapidly migrate to the defect sites and get trapped there. In this way, the lifetime of the plasmonic hot charge carriers is Moreover, these metal oxide nanoparticles possess active sites for adsorbing and activating dinitrogen molecules. Therefore, they function in a “one-stone-two-birds” manner. As a result, a record-high solar-to-chemical energy conversion efficiency has been achieved.

Filamentous bacterial nanocelluloses decorated with dense Au nanoparticles for developing ultrasensitive SERS biosensors

Based on hydrogen peroxide (H2O2)-modified bacterial nanocelluloses (BNCs(M)), we report in-situ overgrowth of highly dense plasmonic Au nanoparticles (NPs) on these filamentous three-dimensional (3D) supports by an ingenious “green” photochemical strategy. The measured relative atomic ratio of Au element in the resultant BNCs(M)@Au NPs is ∼ 13 times higher than that formed on pristine BNCs. The BNCs(M)@Au NPs exhibit a higher surface-enhanced Raman scattering spectroscopy (SERS) activity than the reference BNCs@Au NPs. The flexible SERS biosensors enable the label-free detection limit of glucose molecules to be achieved as low as 10−10 M, surpassing many reports in previous works and then facilitating the ultrasensitive evaluation of glucose metallic diseases.

Oxidizing Role of Cu Cocatalysts in Unassisted Photocatalytic CO2 Reduction Using p-GaN/Al2O3/Au/Cu Heterostructures.

Photocatalytic CO2 reduction to CO under unassisted (unbiased) conditions was recently demonstrated using heterostructure catalysts that combine p-type GaN with plasmonic Au nanoparticles and Cu nanoparticles as cocatalysts (p-GaN/Al2O3/Au/Cu). Here, we investigate the mechanistic role of Cu in p-GaN/Al2O3/Au/Cu under unassisted photocatalytic operating conditions using Cu K-edge X-ray absorption spectroscopy and first-principles calculations. Upon exposure to gas-phase CO2 and H2O vapor reaction conditions, the composition of the Cu nanoparticles is identified as a mixture of CuI and CuII oxide, hydroxide, and carbonate compounds without metallic Cu. These composition changes, indicating oxidative conditions, are rationalized by bulk Pourbaix thermodynamics. Under photocatalytic operating conditions with visible light excitation of the plasmonic Au nanoparticles, further oxidation of CuI to CuII is observed, indicating light-driven hole transfer from Au-to-Cu. This observation is supported by the calculated band alignments of the oxidized Cu compositions with plasmonic Au particles, where light-driven hole transfer from Au-to-Cu is found to be thermodynamically favored. These findings demonstrate that under unassisted (unbiased) gas-phase reaction conditions, Cu is found in carbonate-rich oxidized compositions rather than metallic Cu. These species then act as the active cocatalyst and play an oxidative rather than a reductive role in catalysis when coupled with plasmonic Au particles for light absorption, possibly opening an additional channel for water oxidation in this system.

Plasmon-induced electron transportation in heterostructure N-rGO/NiFe-LDH@Au with enhanced photoelectrochemical water oxidation

Facile design and fabrication of an ideal heterointerface model is considered as a significant advancement towards photoelectrochemical (PEC) water splitting efficiency. Here, we detail the incorporation of plasmonic Au nanoparticles into N-doped reduced graphene oxide/NiFe-layered double hydroxide (N-rGO/NiFe-LDH) interface by cost-effective coprecipitation-photoreduction method and photoelectrode assemblage via drop casted technique for enhanced PEC water oxidation. Au nanoparticles efficiently harvest the light energy upon plasmonic excitation and transfer the energy towards contacted NiFe-LDH and N-rGO, thereby promoting PEC performances. In comparison to N-rGO/NiFe-LDH, the as-obtained N-rGO/NiFe-LDH@Au composite exhibits 1.46 fold times enhancement in photocurrent density (5.7 mA/cm2 at 1.23 V vs RHE) and considerable cathodic shift of 20 mV at onset potential of 0.18 V for PEC water oxidation. Additionally, N-rGO/NiFe-LDH@Au exhibits incident photon to current conversion efficiency (IPCE) of 10 % and better photostability of more than 6 h for boosted water splitting. The incorporation of Au nanoparticles significantly augmented the photoactivity as apparent from the photocurrent density assessment. The improved PEC performance of N-rGO/NiFe-LDH@Au photoelectrode is accredited to the surface plasmon resonance (SPR) induced electron transfer process and heterostructure configuration holding numerous defect sites for smooth charge transportation. This fabrication approach is quite a simplistic method to enlarge the optical behavior and effective performance of the PEC system and also provide guidance to assemble other sophisticated materials suitable for the energy conversion process.

In situ Raman reveals the critical role of Pd in electrocatalytic CO2 reduction to CH4 on Cu-based catalysts.

Electrocatalytic CO2 reduction reaction (CO2RR) for CH4 production presents a promising strategy to address carbon neutrality, and the incorporation of a second metal has been proven effective in enhancing catalyst performance. Nevertheless, there remains limited comprehension regarding the fundamental factors responsible for the improved performance. Herein, the critical role of Pd in electrocatalytic CO2 reduction to CH4 on Cu-based catalysts has been revealed at a molecular level using in situ surface-enhanced Raman spectroscopy (SERS). A "borrowing" SERS strategy has been developed by depositing Cu-Pd overlayers on plasmonic Au nanoparticles to achieve the in situ monitoring of the dynamic change of the intermediate during CO2RR. Electrochemical tests demonstrate that Pd incorporation significantly enhances selectivity toward CH4 production, and the Faradaic efficiency (FE) of CH4 is more than two times higher than that for the catalysts without Pd. The key intermediates, including *CO2-, *CO, and *OH, have been directly identified under CO2RR conditions, and their evolution with the electrochemical environments has been determined. It is found that Pd incorporation promotes the activation of both CO2 and H2O molecules and accelerates the formation of abundant active *CO and hydrogen species, thus enhancing the CH4 selectivity. This work offers fundamental insights into the understanding of the molecular mechanism of CO2RR and opens up possibilities for designing more efficient electrocatalysts.

Effect of crystal facets in plasmonic catalysis

While the role of crystal facets is well known in traditional heterogeneous catalysis, this effect has not yet been thoroughly studied in plasmon-assisted catalysis, where attention has primarily focused on plasmon-derived mechanisms. Here, we investigate plasmon-assisted electrocatalytic CO2 reduction using different shapes of plasmonic Au nanoparticles - nanocube (NC), rhombic dodecahedron (RD), and octahedron (OC) - exposing {100}, {110}, and {111} facets, respectively. Upon plasmon excitation, Au OCs doubled CO Faradaic efficiency (FECO) and tripled CO partial current density (jCO) compared to a dark condition, with NCs also improving under illumination. In contrast, Au RDs maintained consistent performance irrespective of light exposure, suggesting minimal influence of light on the reaction. Temperature experiments ruled out heat as the main factor to explain such differences. Atomistic simulations and electromagnetic modeling revealed higher hot carrier abundance and electric field enhancement on Au OCs and NCs than RDs. These effects now dominate the reaction landscape over the crystal facets, thus shifting the reaction sites when comparing dark and plasmon-activated processes. Plasmon-assisted H2 evolution reaction experiments also support these findings. The dominance of low-coordinated sites over facets in plasmonic catalysis suggests key insights for designing efficient photocatalysts for energy conversion and carbon neutralization.

Heterojunction-Based Photocatalytic Degradation of Rose Bengal Dye via Gold-Decorated α-Fe2O3-CeO2 Nanocomposites under Visible-Light Irradiation

Developing photocatalytic nanomaterials with unique physical and chemical features using low-cost and eco-friendly synthetic methods is highly desirable in wastewater treatment. In this work, the magnetically separable α-Fe2O3-CeO2 nanocomposite (NC), with its respective metal oxides of α-Fe2O3 and CeO2 nanoparticles, was synthesized using a combination of hexadecyltrimethylammonium bromide (CATB) and ascorbic acid via the hydrothermal method. To tune the band gap, the heterojunction nanocomposite of α-Fe2O3-CeO2 was decorated with plasmonic Au nanoparticles (Au NPs). The various characterization methods, such as FTIR, UV-vis DRS, XRD, XPS, TEM, EDX, SEM, and PL, were used to determine the properties of the materials, including their morphology, elemental composition, optical properties, band gap energy, and crystalline phase. The nanocomposite of α-Fe2O3-CeO2@Au was utilized to remove Rose Bengal (RB) dye from wastewater using a photocatalytic technique when exposed to visible light. A comprehensive investigation of the impact of the catalyst concentration and initial dye concentration was conducted to establish the optimal photodegradation conditions. The maximum photocatalytic efficiency of α-Fe2O3-CeO2@Au (50 mg L−1) for RB (20 ppm) dye removal was found to be 88.9% in 120 min under visible-light irradiation at a neutral pH of 7 and 30 °C. Various scavengers, such as benzoquinone (BQ; 0.5 mM), tert-butyl alcohol (TBA; 0.5 mM), and ethylenediaminetetraacetic acid (EDTA; 0.5 mM), were used to investigate the effects of different free radicals on the photocatalytic process. Furthermore, the reusability of the α-Fe2O3-CeO2@Au photocatalyst has also been explored. Furthermore, the investigation of the potential mechanism demonstrated that the heterojunction formed between α-Fe2O3 and CeO2, in combination with the presence of deposited Au NPs, led to an enhanced photocatalytic efficiency by effectively separating the photogenerated electron (e−)–hole (h+) pairs.

Surface plasmonic hot hole driven Ag2S/Au/Al2O3 photocathode for enhanced photoelectrochemical water splitting performance

Herein, Ag2S/Au/Al2O3 photoelectrode was fabricated for superior photoelectrochemical (PEC) water splitting response. The working electrodes were deposited using the glancing angle deposition (GLAD) method followed by RF sputtering and atomic layer deposition (ALD). The as-prepared Ag2S/Au/Al2O3 samples revealed a higher photocurrent density of 2.50 mA/cm2 (at 0.95 V Ag/AgCl) as compared to bare Ag2S (1.70 mA/cm2) with a corresponding less charge transfer resistance at the semiconducting interface. The superior PEC response may be ascribed to the synergic effect of plasmonic Au nanoparticles and the tilted Ag2S nanorods. The plasmonic effect of Au nanoparticles increases the visible-light response of Ag2S as well as provides the hot holes to enhance the photocurrent density. In addition, the increased trapping of light due to the tilted architecture of Ag2S nanorods resulted in an effective absorption of light. The theoretical simulations based on finite difference time domain (FDTD) were also performed to explore the distribution of the electric-field intensity and optical trapping of light between the nanorods of Ag2S and Ag2S/Au. The experimental and theoretical results show a deeper insight into the role of plasmonic nanostructures decorated Ag2S nanorods and shed light on designing hybrid hot hole harvesting semiconductor nanostructures for the next generation photoelectrodes.

Facile fabrication of Au nanoparticles loaded Ce doped ZnO nanorods for efficient catalytic and photocatalytic decomposition of toxic pollutants in water

Plasmonic Au nanoparticles (NPs) have been deposited onto Ce doped ZnO nanorods prepared through wet chemical route to enhance their photodecomposition performance. The catalytic and photocatalytic performances were evaluated using a series of model pollutants such as 4-nitrophenol, antibiotic levofloxacin, cationic and anionic dyes under sunlight illumination. Various characterization tools such as XRD, Raman, FESEM, TEM, SAED, EDX, XPS, PL and UV–vis spectroscopy were used to examine the structure and physico-chemical properties of the fabricated photocatalysts. XRD, TEM, SAED, EDX, XPS and Raman analyses confirmed the existence of Ce doped ZnO and Au nanostructures while UV–visible absorption studies revealed the presence of SPR of Au NPs in the visible region. The results illustrated that decoration of Au NPs on Ce doped ZnO nanorods makes them outstanding catalyst as well as photocatalyst compared to pure Ce doped ZnO nanorods. The plasmonic nanohybrids with higher Au concentration exhibited superior degradation capability towards reduction and detoxification of 4-NP, decomposition of antibiotic levofloxacin and synthetic dyes, respectively. In addition, detailed study of possible mechanisms behind 4-NP reduction and photodegradation process have been explored. Furthermore, the quenching experiments elucidating ·O2- radicals as the main active species in the degradation mechanism have also been discussed. Moreover, the prepared Ce doped ZnO-Au hybrid plasmonic nanorods maintained high stability and stunning photoactivity even after four cycles which highlights it as a promising material for wastewater treatment.

Adsorption-catalysis synergy in the visible-light-driven removal of 17β-estradiol by (Au)TiO2 nanotubes-graphene composites

Visible light-mediated photodegradation offers a sustainable and environmentally friendly solution for removing emerging contaminants from water sources. Herein, we report on the synergy effect between adsorption and visible-light-driven photo-degradation of 17β-estradiol using (Au)TiO2 nanotubes-graphene composites. The graphene structures (graphene oxide - GO or thermally reduced graphene oxide - trGO) provide a platform for strong adsorption of 17β-estradiol molecules and facilitate the charge transfer between plasmonic Au nanoparticles and TiO2, leading to an improvement of the overall degradation process. To better understand the effect of Au nanoparticles and TiO2 separately, three different concentrations of Au (1 %, 2.5 %, and 5 %) were prepared and characterized. The estrogenic molecules preferred GO over trGO, suggesting that hydrogen bonds govern the interaction between GO and 17β-estradiol. Consequently, a higher photocatalytic efficiency of GO-containing composites was observed when removing estrogenic molecules. The role of adsorption proved crucial for capturing and retaining more contaminant molecules on the composite surface, thus increasing the odds of surface reactions with the photogenerated carriers. A total removal of 17β-estradiol has been obtained for Au (1 %, 2.5 %, and 5 %) TiO2 nanotubes-GO. The mechanism behind the adsorption and photo-degradation processes has been discussed.

Construction of piezoelectric photocatalyst Au/BiVO4 for efficient degradation of tetracycline and studied at single-particle level

Piezopotential-assisted catalysis has been proven to be a low-cost and high-efficiency environmental purification process. Herein, Au/bismuth vanadate (BiVO4) piezoelectric photocatalysts are prepared by modifying highly dispersed Au nanoparticles (AuNPs) on piezoelectric BiVO4 microcrystal by a deposition-precipitation approach. Under visible light irradiation and assisted ultrasound excitation, the removal rate of tetracycline was 95% within 60 min, demonstrating the optimum photocatalytic performance over 3Au/BiVO4. The significantly enhanced photocatalytic performance is due to the synergistic coupling of plasmonic and piezotronic effect based on facet engineering. Single-particle spectroscopy technology can provide photoluminescence (PL) lifetime and PL spectra information in the micro-/nano regions, thereby exploring the charge transfer behavior of heterostructures. Single-particle PL images revealed a significant attenuation of PL emission and shortened PL lifetime of 3Au/BiVO4, compared with BiVO4, indicating that high-density dispersed AuNPs promote charge transfer. In situ monitoring of individual BiVO4 and 3Au/BiVO4 particles before and after polarization treatment confirms that the piezoelectric field of the BiVO4 decahedron further promotes separation of photogenerated carriers induced by plasmonic effect. Driven by the piezoelectric potential induced by ultrasonic vibration near the heterostructures, high-energy hot electrons excited on plasmonic AuNPs can be effectively extracted to BiVO4. This work provides new choices for designing high-performance pollutant treatment catalysts.

Dual-Photosensitizer Synergy Empowers Ambient Light Photoactivation of Indium Oxide for High-Performance NO2 Sensing.

Light-activated chemiresistors offer a powerful approach to achieving lower-temperature gas sensing with unprecedented sensitivities. However, an incomplete understanding of how photoexcited charge carriers enhance sensitivity obstructs the rational design of high-performance sensors, impeding the practical utilization under commonly accessible light sources instead of ultravioletor higher-energy sources. Here, a rational approach is presented to modulate the electronic properties of the parent metal oxide phase, exemplified by this model system of Bi-doped In2O3 nanofibers decorated with Au nanoparticles (NPs) that exhibit superior NO2 sensing performance. Bi doping introduces mid-gap energy levels into In2O3, promoting photoactivation even under visible blue light. Additionally, green-absorbing plasmonic Au NPs facilitate electron transfer across the heterojunction, extending the photoactive region toward the green light. It is revealed that the direct involvement of photogenerated charge carriers in gas adsorption and desorption processes is pivotal for enhancing gas sensing performance. Owing to the synergistic interplay between the Bi dopants and the Au NPs, the Au-BixIn2-xO3 (x=0.04) sensing layers attain impressive response values (Rg/Ra=104 at 0.6ppm NO2) under green light illumination and demonstrate practical viability through evaluation under simulated mixed-light conditions, all of which significantly outperforms previously reported visible light-activated NO2 sensors.

Photosensitization of TiO2 electrodes immobilized with chiral plasmonic Au nanocolloids by circularly polarized light irradiation.

Photosensitization of semiconductors by excitation of chiral plasmonic metallic nanostructures has attracted much attention, not only for the analysis and detection of circularly polarized light but also for its potential applications in chiral photosynthesis. Although there have been reports on the detection of semiconductor-sensitized current in chiral nanostructures precisely fabricated by physical vapor deposition and/or lithography techniques, there have been no studies using plasmonic metal nanocolloids synthesized by chemical processes. In this study, we report the establishment of a fabrication method for large-area chiral photoelectrodes and the semiconductor photosensitization phenomenon realized using chiral plasmonic nanoparticles. Chiral plasmonic Au nanoparticles prepared by previously reported colloidal methods were immobilized onto a TiO2 thin film electrode by electrophoresis. When TiO2 electrodes loaded with chiral Au nanoparticles synthesized using L-cysteine were irradiated with circularly polarized light, left circularly polarized light irradiation at a wavelength of 500-600nm generated a larger anodic photocurrent than right circularly polarized light irradiation at the same wavelength. This trend was reversed for TiO2 electrodes immobilized with colloidal Au nanoparticles synthesized with D-cysteine. From these results, we conclude that the efficiency of photocurrent generation by chiral plasmon excitation can be controlled by the polarization direction of the incident light.

Optical, thermal, and electrical analysis of perovskite solar cell with grated cds and embedded plasmonic Au nanoparticles

We propose a novel approach to enhance the performance of perovskite solar cells (PSCs) by incorporating grated Cadmium Sulfide (CdS) and plasmonic gold nanoparticles (Au NPs) into the absorber layer. The CdS grating acts as the electron transport layer and penetrates into the perovskite absorber layer, increasing the absorption of the active layer and reducing the electron–hole recombination rate. The plasmonic Au NPs enhance the absorption in the infrared region by scattering and trapping the incident light. We perform a coupled optical and electrical study that shows a significant improvement in the short circuit current density ( JSC ) and power conversion efficiency (PCE) of the PSC after introducing the CdS grating and plasmonic Au NPs. Specifically, we observe a 48% increase in average optical absorption from 800 nm to 1400 nm and a 7.42 mA cm−2 increase in J SC . We also find that the PCE of the PSC is increased by 7.91% when comparing the planar reference structure (without the CdS grating and the plasmonic Au NP). However, metal nanoparticles introduce ohmic losses and temperature rise in the solar cell. We analyze the non-radiative heat profile, electric field distribution, and temperature distribution across the PSC. We observe a temperature increase of approximately 14 K above the ambient temperature for the grated CdS layer with incorporated Au NPs, which is comparable to the temperature increase observed in the planar reference structure. Our results have the potential to pave the way for the development of highly efficient and stable PSCs in the future.

Advancing Breath‐Based Diagnostics: 3D Mesh SERS Sensor Via Dielectrophoretic Alignment of Solution‐Processed Au Nanoparticle‐Decorated TiO2 Nanowires

AbstractSurface enhanced Raman spectroscopy (SERS) is becoming an attractive analytical technique for the next generation of breath diagnostics. However, current SERS substrates present challenges related to fabrication cost, complexity, signal uniformity, and reproducibility. Here, a low‐cost, label‐free SERS sensor based on fully solution‐processed decoration of TiO2 nanowires is demonstrated (NW) with plasmonic Au nanoparticles (NP) followed by the dielectrophoretic self‐assembly into a 3D mesh with high signal to noise ratio. The sensor performance is tested using 4‐aminothiophenol (4‐ATP) as a model analyte in gas phase, at concentrations down to 10 ppbv, and in solution, with limit of detection ≈2.4 pM. Finally, to explore the sensor capability for breath‐based diagnostics, a proof‐of‐concept experiment is performed with exhaled breath condensates (EBCs). The possibility to discriminate EBCs of individuals with upper respiratory tract infection (URTI) from healthy ones is demonstrated. Multiple SERS spectra (n≈50) from each sample are analyzed using orthogonal partial least squares discriminant analysis (OPLS‐DA), which identifies spectral features representative of URTI in up to 80% of the infection‐related spectra. These results demonstrate the applicability and potential of 1D nanomaterials together with state‐of‐the‐art solution‐processed techniques for the development of low‐cost and compact SERS breath‐based diagnostic platforms for clinical point‐of‐care applications.

High-detectivity silver telluride nanoparticle-based near-infrared photodetectors functionalized with surface-plasmonic gold nanoparticles

Herein, the performance of near-infrared (NIR) photodetectors fabricated through a combination of AgxTe films comprising colloidal AgxTe nanoparticles (NPs) with plasmonic Au NPs was investigated. The surface-plasmonic Au NPs on low-bandgap AgxTe considerably enhanced the detectivity of NIR photodetectors. The Au NPs formed on the AgxTe surface triggered localized surface-plasmon resonance and increased light absorption, hot-carrier injection, and silver telluride crystallinity during an additional annealing process, which was required to form Au NPs from thermally deposited thin Au layers. Under illumination using an 808-nm laser, the detectivity of the as-fabricated Au NP–decorated AgxTe photodetectors was 7.17 × 1011 cmHz1/2 W−1. Compared with that of pristine AgxTe photodetectors, the detectivity of the prepared photodetectors was seven-fold higher; this detectivity was superior to those of devices based on MoS2, arsenic phosphorus, and SnTe nanoplates and commercial photosensors at room temperature. Thus, the proposed strategy of combining AgxTe films with surface-plasmonic Au NPs for enhanced performance of NIR photodetectors provides a new approach for realizing next-generation optoelectronic devices for detection in the NIR region.