Au Nanosheets Research Articles

Research on 2D/2D Au/g-C3N4 electron donor/acceptor strategy for highly efficient CO2 photoreduction

Utilizing CO2 photoreduction technology to convert CO2 into carbon-based gaseous fuels represented an effective strategy for maintaining sustainable development on Earth. Addressing the issue of poor electron separation efficiency in pure g-C3N4, an innovative approach was taken to construct a two-dimensional/two-dimensional (2D/2D) structure using Au nanosheets (Au NSs) combined with g-C3N4 nanosheets (CN NSs) for CO2 photoreduction. The CO and CH4 yields converted by CO2 photoreduction over Au/CN composite (15AC) with optimized proportion were about 44.76 and 32.12 μmol g−1 h−1 under UV–Vis light irradiation, respectively. Photoelectrochemical experiments revealed that the modification of CN NSs with Au NSs significantly improved the separation efficiency of photogenerated carriers at the 2D/2D interface, while enhancing the CO2 adsorption ability of pure CN NSs. Density Functional Theory (DFT) calculations were employed to analyze the electron transfer pathways at the 15AC interface and the formation of a built-in electric field, which concurrently confirmed that the electron donor–acceptor relationship accelerated the transfer of photogenerated electrons from CN NSs to Au NSs. In-situ FTIR and 13CO2 isotope calibration experiment were utilized to probe the CO2 photoreduction process. Finally, the possible electron donor–acceptor enhanced mechanism at the 2D/2D Au/CN interface for enhancing the CO2 photoreduction reaction were discussed.

Synergistic antibacterial effects of selenium-doped gold nanosheets with notable near infrared-II photothermal conversion against multidrug-resistant bacteria

Non-metallic nanoparticles are increasingly acknowledged for their broad-spectrum antibacterial properties, which often face limitations due to structural instability and potential biotoxicity. To address these challenges, integrating non-metallic nanoparticles with plasmonic metal nanostructures offers a promising solution. This fusion not only enhances structural stability but also reduces the required dosage. The synergistic coupling of the inherent antibacterial properties of non-metallic nanoparticles with the plasmonic absorption and photothermal conversion capabilities of metal nanostructures significantly amplifies antibacterial efficacy. In this study, we validate this concept by presenting the successful synthesis of selenium-doped gold nanosheets (AuSe NSs) that demonstrate robust absorption in the second near-infrared (NIR-II) window and exhibit efficient photothermal conversion, followed by testing their antibacterial activity. Notably, Au NSs were synthesized with high shape purity, followed by the introduction of SeO2 and ascorbic acid to facilitate Se doping. The resulting products displayed a uniform distribution of both Au and Se elements, while maintaining the NIR-II absorbance characteristic of Au nanosheets unaffected by the Se doping as evidenced by both experimental and FDTD simulation results. Subsequent assessments of the AuSe NSs demonstrated their potent synergistic antibacterial effects against multidrug-resistant bacteria at minimal inhibitory concentrations (MICs), which suggests that lower dosages can be employed and benefit minimizing potential side effects and optimizing treatment efficiency. Our findings indicate a synergistic boost between the photothermal attributes originating from Au's NIR absorption and Se's inherent antibacterial properties—an aspect minimally explored in prior research and offering a novel solution to tackling antibiotic-resistant bacterial strains.

2H‐Au Nanosheet‐Templated Growth of PdFe for Electrocatalytic Methanol Oxidation

AbstractPd‐based alloy nanomaterials normally crystallize in the conventional face‐centered cubic (fcc) crystal phase. Here, 2H‐Au nanosheets (NSs), possessing 2H crystal phase (2H: hexagonal close‐packed with a stacking sequence of “AB”), are used as templates for the growth of PdFe, during which the 2H‐to‐fcc phase transformation in Au NSs happens, leading to the formation of 2H/fcc Au@PdFe core–shell NSs. By changing the Pd/Fe atomic ratio, the 2H/fcc phase ratio in 2H/fcc Au@PdFe NSs can be tuned accordingly. As a proof‐of‐concept application, the as‐synthesized 2H/fcc Au@Pd0.66Fe0.34 NSs are used as an electrocatalyst for methanol oxidation reaction (MOR) in alkaline media, exhibiting a remarkable mass activity of 4.39 A mg−1Pd, which is 1.7, 5.4 and 12.9 times that of 2H/fcc Au@Pd0.56Fe0.44 NSs (2.57 A mg−1Pd), 2H/fcc Au@Pd0.40Fe0.60 NSs (0.81 A mg−1Pd), and Pd black (0.34 A mg−1Pd), respectively, placing it among the best of reported Pd‐based MOR electrocatalysts. This strategy, based on phase engineering of nanomaterials (PEN), paves an efficient way to the rational design and controlled synthesis of noble multimetallic nanostructures with unconventional phases for exploring the phase‐dependent properties and applications.

Au/Nb2O5 terahertz-gigahertz electro-optical filters designed for high frequency applications

Herein enhanced broad band filters are fabricated by deposing thin films of Nb2O5 onto glass and semitransparent Au nanosheets using the ion coating technique. Remarkable enhancement in the surface roughness of the films and in the visible and infrared light absorption by more than 270% and 750%, respectively, is achieved by coating the films onto Au nanosheets. Au nanosheets redshifted the energy band gap and initiated the free carrier absorption in the Nb2O5 films. As terahertz band filters, Au/Nb2O5 interfaces exhibited higher dielectric constant, higher optical conductivity and higher terahertz cutoff frequency values. Au/Nb2O5 optical filters showed terahertz resonator characteristics displaying six resonance modes two, three and one of which are dominant in the infrared, visible and ultraviolet ranges, respectively. On the other hand the impedance spectroscopy analyses for Au/Nb2O5/Au (ANA) filter showed microwave resonator characteristics with cutoff frequency values reaching 700 GHz for signal carriers of driving frequency of 1.65 GHz. ANA devices exhibited negative capacitance effect in a wide range of driving frequency domain. The features of the Au/Nb2O5 films demonstrate their potential for use as gigahertz-terahertz broad band electro-optical resonators suitable for high frequency applications.

Crystal-Phase-Selective Etching of Heterophase Au Nanostructures.

Selective oxidative etching is one of the most effective ways to prepare hollow nanostructures and nanocrystals with specific exposed facets. The mechanism of selective etching in noble metal nanostructures mainly relies on the different reactivity of metal components and the distinct surface energy of multimetallic nanostructures. Recently, phase engineering of nanomaterials (PEN) offers new opportunities for the preparation of unique heterostructures, including heterophase nanostructures. However, the synthesis of hollow multimetallic nanostructures based on crystal-phase-selective etching has been rarely studied. Here, a crystal-phase-selective etching method is reported to selectively etch the unconventional 4H and 2H phases in the heterophase Au nanostructures. Due to the coating of Pt-based alloy and the crystal-phase-selective etching of 4H-Au in 4H/face-centered cubic (fcc) Au nanowires, the well-defined ladder-like Au@PtAg nanoframes are prepared. In addition, the 2H-Au in the fcc-2H-fcc Au nanorods and 2H/fcc Au nanosheets can also be selectively etched using the same method. As a proof-of-concept application, the ladder-like Au@PtAg nanoframes are used for the electrocatalytic hydrogen evolution reaction (HER) in acidic media, showing excellent performance that is comparable to the commercial Pt/C catalyst.

Thermal-aware device design of low-power H2S sensors using Joule-heated Au nanosheet

We demonstrated Joule-heated Au nanosheet H2S sensors for low-power operation. We confirmed that low temperature regions in the Joule-heated Au nanosheet caused lower response and recovery characteristics than uniformly heated Au nanosheets. By using Pt electrodes, which has lower thermal conductivity than Au, heat dissipation to the electrodes could be suppressed, resulting in lower power consumption and faster recovery characteristics. We then discussed the optimal sensor structure by developing an analytical model of electrical and thermal resistances. We introduced semi-elliptical intermediate electrodes between the channel and pad electrodes to efficiently suppress the heat dissipation, demonstrating that the optimal channel length and thermal conductivity of the intermediate electrode κ int exist depending on the channel width. Finally, we proposed the sensor design strategy of considering the κ int dependences of the electrical and thermal resistances. This strategy is useful for all metal nanosheet sensors because it gives an estimation of their optimal structures.

A Fully Self‐Healing Patch of Integrated Bio‐Signal Monitoring Sensors with Self‐Healing Microporous Foam and Au Nanosheet Electrodes

AbstractA fully self‐healing sensor patch consisting of an in‐plane integrated dual‐mode sensor and a pressure sensor with a vertically integrated electrocardiogram (ECG) electrode is reported. For a full‐device self‐healing, interlayer self‐bonding by using self‐healing oxime‐carbamate bond‐based polyurethane and room temperature self‐healing TUEG3 capped Au nanosheet (T‐Au NS) electrodes are devised. Via the use of a self‐healing sensor foam prepared by a coating of a self‐healing composite of polyurethane and polyaniline onto a microporous graphene foam, a self‐healing dual‐mode sensor is fabricated to detect the pressure and temperature simultaneously without interference. Furthermore, the interdigitated self‐healing electrode of T‐Au NS is applied to the pressure sensor to enhance the sensitivity up to 208.62 kPa−1 (<1 kPa), enabling the detection of small pulse signals even after multiple self‐healing events. By using the common self‐healing T‐Au NS electrode vertically integrated onto the sensor patch, ECG signals are also detected. With this sensor patch, skin temperature, wrist pulse, and ECG signals are successfully detected after a simultaneous full‐device self‐healing from complete bisection. This study demonstrates the facile fabrication of a high‐performance, fully self‐healing patch of multi‐sensors via the deliberate selection of sensor design and the associated functional materials, confirming its high potential applicability to highly durable health monitoring systems.

Design of hybrid Ag–Au nanostructure based fully elastomeric nanocomposite electrodes for soft integrated electronics

Recent advancements in stretchable devices have opened new avenues for constructing soft electronics for use in applications such as health-monitoring wearables, advanced integrated circuits, and soft robotics. Meeting the increasing demand for enhanced functionality in soft electronics requires the development of soft conductors with high electrical conductivity, mechanical durability, and cost-effectiveness. Researchers have addressed this challenge by creating percolated networks within the elastomer as a nanocomposite using low-dimensional conducting nanomaterials to endow non-stretchable metallic materials with mechanical stretchability. For example, silver nanowires (AgNWs) have found wide application as essential fillers in soft conductor nanocomposites owing to their remarkable aspect ratio and cost-efficiency. However, their application is limited by their susceptibility to environmental degradation and poor compatibility with semiconducting materials. In this work, the hybrid Ag–Au based nanomaterials as a filler nanomaterial within an elastomer in a nanocomposite format was generated, as it exploits the strengths of each material while mitigating their respective weaknesses. Specifically, the work introduces the merit of the hybrid elastomeric electrodes that consist of AgNWs decorated with Au nanoparticles (AANWs), and Au nanosheets (AuNSs) embedded in a polydimethylsiloxane (PDMS) elastomer. These electrodes exhibit remarkable mechanical resilience and electrical conductivity, making them suitable for application in transistors, logic gates, integrated electronics, and soft displays. The work explores the synthesis and properties of hybrid materials comprising AgNWs and AuNSs, highlighting the promising potential of these materials for future research and development.

ZnPc based multifunctional devices designed as fast capacitors, rectifiers, infrared detectors and microwave resonators adequate for 6 G technology applications

Herein Zinc phthalocyanine (ZnPc) based multifunctional devices are fabricated and characterized. The device fabrication included formation of an Au nanosheets onto n-Si wafers and coating these nanosheets with 500 nm thick ZnPc layer. Silver and platinum were used to form a Schottky and an ohmic contacts with n-Si and ZnPc, respectively. The device hybrid structure (Ag/n-Si/Au/p-ZnPc/Pt; abbreviated as ASZ) is composed of Ag/n-Si Schottky arm and p- and n- layers forming pn junction separated by Au nanosheets. Electrical and photoelectrical measurements on the ASZ devices have shown their ability to perform as conventional metal-oxide-semiconductor capacitors (CMOS). These CMOS devices showed light and frequency controlled charge accumulation, depletion and inversion mechanisms within the range of 1.0–50 MHz. The flat band and threshold voltages of the ASZ capacitors are engineered by the imposed ac signal frequency and by infrared (IR) light. In addition, ASZ devices performed as biasing controlled IR photosensors and as current rectifiers. A rectification ratio of 103, IR light sensitivity of 39, specific detectivity of .96 ×109 Jones and current responsivity exceeding 9.0 mA W−1 are recorded at biasing voltage of 4.5 V. Moreover ASZ devices displayed microwave resonator characteristics presented by negative capacitance effect, resonance –antiresonance phenomena and high microwave cutoff frequency. The latter is larger than 10 GHz nominating the device for 6 G technology applications.

A stretchable, fully self-healable, temperature-tolerant, and water-proof supercapacitor using TUEG3 capped gold nanosheets on oxime-carbamate bonded polyurethane film and organohydrogel

In this study, we demonstrate a stretchable, fully self-healable, temperature-tolerant, and water-proof supercapacitor with high electrochemical performance via a deliberate selection of materials and device architecture. Distinct from previous works, our whole supercapacitor is stretchable and self-healable, owing to the application of specially devised stretchable and self-healing oxime-carbamate based polyurethane (OC-PU) substrate film, self-healing polymer (poly(ether-thioureas) triethylene glycol) capped Au nanosheet current collector (TUEG3-Au NS) and newly synthesized organohydrogel electrolyte. The fabricated supercapacitor exhibits a high electrochemical performances (specific capacitance of 165.5F g−1, energy density of 14.58 Wh kg−1, power density of 2181.75 W kg−1, and capacitance retention of 89 % after 10,000 cycles) with a capacitance retention of 81 % over stretching by 40 % even after repetitive healing from damages, the self-healing of all components (full self-healing) over repetitive damages with a capacitance recovery by over 83 %, a wide operational temperature range from −20 to 60 °C with retaining over 91 % of capacitance at RT. Furthermore, a μ-LED is stably operated with the supercapacitor immersed in water regardless of the mechanical deformation and self-healing from damage due to self-bonded encapsulation layer of hydrophobic OC-PU film. With a vertically integrated patch device consisting of the fabricated supercapacitor and a strain sensor, bio-signals are detected using the stored energy of the supercapacitor even after self-healing from damages over the temperature range from −20 to 60 °C. This work suggests the high application potential of our high performance multi-functional supercapacitor as an integrated energy storage device for wearable electronics featuring longevity and stability under harsh environments.

Conductive Nanosheets Fabricated from Au Nanoparticles on Aqueous Metal Solutions under UV Irradiation.

Highly transparent, conductive nanosheets are extremely attractive for advanced opto-electronic applications. Previously, we have demonstrated that transparent, conductive Au nanosheets can be prepared by UV irradiation of Au nanoparticle (AuNP) monolayers spread on water, which serves as the subphase. However, thick Au nanosheets cannot be fabricated because the method is not applicable to large Au NPs. Further, in order to fabricate nanosheets with different thicknesses and compositions, it is necessary to prepare the appropriate NPs. A strategy is needed to produce nanosheets with different thicknesses and compositions from a single type of metal NP monolayer. In this study, we show that this UV irradiation technique can easily be extended as a nanosheet modification method by using subphases containing metal ions. UV irradiation of 4.7 nm AuNP monolayers on 480 µM HAuCl4 solution increased the thickness of Au nanosheets from 3.5 nm to 36.5 nm, which improved conductivity, but reduced transparency. On the other hand, the use of aqueous AgNO3 and CH3COOAg solutions yielded Au-Ag hybrid nanosheets; however, their morphologies depended on the electrolytes used. In Au-Ag nanosheets prepared on aqueous 500 µM AgNO3, Au and Ag metals are homogeneously distributed throughout the nanosheet. On the other hand, in Au-Ag nanosheets prepared on aqueous 500 µM CH3COOAg, AuNPs still remained and these AuNPs were covered with a Ag nanosheet. Further, these Au-Ag hybrid nanosheets had high conductivity without reduced transparency. Therefore, this UV irradiation method, modified by adding metal ions, is quite effective at improving and diversifying properties of Au nanosheets.

Detection of PPB-Level H2S Concentrations in Exhaled Breath Using Au Nanosheet Sensors with Small Variability, High Selectivity, and Long-Term Stability.

The continuous monitoring of hydrogen sulfide (H2S) in exhaled breath enables the detection of health issues such as halitosis and gastrointestinal problems. However, H2S sensors with high selectivity and parts per billion-level detection capability, which are essential for breath analysis, and facile fabrication processes for their integration with other devices are lacking. In this study, we demonstrated Au nanosheet H2S sensors with high selectivity, ppb-level detection capability, and high uniformity by optimizing their fabrication processes: (1) insertion of titanium nitride (TiN) as an adhesion layer to prevent Au agglomeration on the oxide substrate and (2) N2 annealing to improve nanosheet crystallinity. The fabricated Au nanosheets successfully detected H2S at concentrations as low as 5.6 ppb, and the estimated limit of detection was 0.5 ppb, which is superior to that of the human nose (8-13 ppb). In addition, the sensors detected H2S in the exhaled breath of simulated patients at concentrations as low as 175 ppb while showing high selectivity against interfering molecules, such as H2, alcohols, and humidity. Since Au nanosheets with uniform sensor characteristics enable easy device integration, the proposed sensor will be useful for facile health checkups based on breath analysis upon its integration into mobile devices.

Macrocyclic Diacetylene / Sulfonate Fluorophore Hierarchical Multifunctional Nanotoroids.

Functional supramolecular materials exhibit important features including structural versatility and versatile applications. Here, this study reports the construction of unique hierarchically organized nanotoroids exhibiting fluorescence, photocatalytic, and sensing properties. The nanotoroids comprise of macrocyclic diacetylenes (MCDA) and 8-anilino-1-naphthalene sulfonate (ANS), a negatively charged aromatic fluorescent dye. This study shows that the hierarchical structure of the nanotoroids consist of MCDA nanofibers formed by stacked diacetylene monomers as the basic units, which are further bent and aligned into toroidal organization by electrostatic and hydrophobic interactions with the ANS molecules. The amine moieties on the nanotoroids surface are employed for deposition of gold nanostructures - Au nanoparticles or Au nanosheets - which constitute effective platforms for photocatalysis and surface enhanced Raman scattering (SERS)-based sensing.

Atomically dispersed Au confined by oxygen vacancies in Au-θ-Al2O3/Au/PCN hybrid for boosting photocatalytic CO2 reduction driven by multiple built-in electric fields

A new Au-θ-Al2O3/Au/PCN hybrid is fabricated by the collaborative design strategy of active site and assembled structure, which achieves highly efficient photocatalytic CO2 reduction (CO2R) performance. The energy band structure of PCN is adjusted significantly owing to the strong coupling effect of Au-θ-Al2O3/Au nanosheets intercalated in PCN nanosheets. The result brings about up-shift of CB, VB and Fermi energy level overall and decrease of bandgap, which is in favor of harvesting visible light, exciting VB electrons and increasing reduction ability. In addition, the multiple built-in electric fields are induced by electron diffusion effect between structural units, due to the tight interface contact in the Au-θ-Al2O3/Au/PCN hybrid, which can effectively promote the separation of photoinduced charge carriers. Furthermore, the atomically dispersed Au atoms confined by the oxygen vacancies in Au-θ-Al2O3/Au can provide the plenty of effective active sites for CO2R reaction, and meanwhile, the localized surface plasmon resonance (LSPR) effect induced by Au nanoparticles on Au-θ-Al2O3/Au can improve the visible light response and produce abundant hot electrons to contribute to CO2R reaction. As a consequence, the average CO evolution rate of over the optimizing 10 %-Au-θ-Al2O3/Au/PCN hybrid (7.76 μmol g-1h−1) reaches up to 3.53 times than that of PCN (2.20 μmol g-1h−1) in the CO2R reaction, and maintains basically stable operation within 7 cycles of running, suggesting the superior activity and recyclability.

Au/CrSe stacked layers designed as optical absorbers, tunneling barriers and negative capacitance sources

Herein thin films of CrSe (500 nm) are deposited onto glass and semitransparent gold nanosheets (100 nm) under a vacuum pressure of 10−5 mbar. Au nanosheets substrates induced the formation of CrSe instead of CrSe2 which grows onto glass substrates. The Au/CrSe stacked layers exhibited enhanced light absorption reaching 25% in the ultraviolet, visible and infrared ranges of light. In addition Au nanosheets successfully redshifted the direct allowed transitions energy band gap from 2.60 eV to 2.40 eV. On the other hand electrical investigations have shown that CrSe2 thin films exhibit a work function of 5.064 eV. The Au/CrSe interfaces displayed tunneling type Schottky barriers of height of 0.56 eV and barrier width of 8 nm. When an ac signal was imposed between the terminals of the Au/CrSe Schottky barriers a negative capacitance (NC) effects was observed in the spectral range of 0.02–1.80 GHz. The NC reached value of − 100 pF at 0.32 GHz. Fitting of the ac conductivity assuming tunneling type of transport indicated a high degree of localization near the Fermi level reaching a density of 2.4×1020 cm−3 eV−1. The enhanced light absorption and moderate value of work function in addition to the tunneling type of Schottky formation performing as NC source make the Au/CrSe interfaces promising for use in the design of electro-optic system.

Enhancement of the electrical properties of Au/MgSe/Au microwave resonators via pulsed laser welding of MgSe and Au nanosheets

Enhancement of the electrical properties of Au/MgSe/Au microwave resonators via pulsed laser welding of MgSe and Au nanosheets

Precise Photothermal Treatment of Methicillin-Resistant S. aureus Infection via Phage Lysin-Cell Binding Domain-Modified Gold Nanosheets.

The increasing spread of antibiotic resistance in bacterial pathogens poses a huge threat to global human health. Precise targeting of bacterial pathogens while avoiding collateral damage to healthy tissues has become the overriding goal for bacterial infection treatment. Inspired by the host specificity of bacteriophages, a biomimetic intelligent platform was designed for highly precise photothermal treatment herein. As proof-of-concept, the lysin cell-binding domain (CBD) from a newly discovered virulent methicillin-resistant S. aureus (MRSA) phage Z was applied to the functionalization of gold nanosheets. Our results demonstrated that the bionanocomposite gold particles (Au@PEG-CBDz) could be effectively delivered directly to MRSA and kill them effectively under near infrared irradiation in vitro, while displaying good in vivo biocompatibility. This work is the first to report the combination of phage lysin navigatory function with photothermal effect-induced bactericidal activity from Au nanosheets, providing a novel therapeutic mode for the precision treatment of antibiotic-resistant bacterial infections.

Dermal Toxicity Influence of Gold Nanomaterials after Embedment in Cosmetics.

Gold nanomaterials (Au NMs) have been widely used in cosmetic products for improving the brightening, and reducing the wrinkling of, skin, etc.; however, the dermal safety of Au NMs is rarely concerned. A previous study found that cosmetics could enhance the toxicity of Au nanosheets, but different physicochemical properties of Au NMs will induce different interaction modes with ingredients of cosmetics, potentially leading to different toxicity profiles. In the present study, spherical and rodlike Au NMs were first found in commercial cosmetics, and then Au nanospheres (NSs) with different sizes and Au nanorods (NRs) with different aspect ratios were prepared to simulate these Au NMs in cosmetics and further investigate their toxicity before and after embedment in cosmetics. It was found that the primary sizes, morphologies, and optical absorptions of these Au NSs and NRs before and after embedment were similar; however, their hydrodynamic sizes and zeta potentials were noticeably different. Then, these Au NSs and NRs presented weak or no cytotoxicity against HaCaT keratinocytes, while cosmetic cream could alleviate their cytotoxicity. Moreover, the cream could enhance the accumulation of Au NSs and NRs in the skin of hairless mice, but it also alleviated the toxicological responses of Au NSs and NRs in terms of superoxide dismutase (SOD) elevation and malondialdehyde (MDA) reduction. Therefore, the embedment of Au NSs and NRs into cosmetics can alleviate the in vitro and in vivo dermal toxicities of Au NSs and NRs.

Surface engineering of Au nanostructures for plasmon-enhanced electrochemical reduction of N2 and CO2 into urea in the visible-NIR region

The photoelectrochemical reduction of CO2 and N2 (N2CO2RR) is a promising method of producing urea under ambient conditions since highly active and stable electrocatalysts are desired. Plasmonic metals have attracted considerable attention due to their enhanced electrochemical activity at visible and near-infrared wavelengths (NIR). Herein, the morphology of Au was tuned to spherical nanoparticles, nanorods, and nanosheets by utilizing a variety of structure-directing agents. Among them, Au nanosheets (Au NSs) can absorb a broad spectrum of NIR wavelengths, enabling electrochemical reduction of N2 into NH3, with high yield rates and higher Faradic efficiency (FE) than most of the N2RR results reported. In addition, a distal associative pathway for N2RR into NH3 has been established over Au NSs. Additionally, the Au NSs photocathode demonstrates high stability over a period of 10 consecutive runs. In addition, this work provides a guide to fabricating highly stable photocathodes that convert N2 and CO2 into urea. Au NSs photocathode achieves a maximum urea yield rate of 98.5 µgureamgcat-1h−1 and FE of 22.7% at −0.7 V vs. RHE. Results show that the N2 and CO2 is the primary factor for urea production, whereas reducing NO3– and HCO3– contributes significantly to the total urea yield rate. Density functional theory calculations (DFT) reveal that Au NSs play a crucial role in promoting N2 and CO2 adsorption, activation, and stimulating the coupling reaction between C-N to form urea by the distal mechanism. As a result, this work opens up the possibility of developing hybrid catalytic systems for simultaneously reducing nitrate-containing wastewater and CO2, thus producing urea-rich treated water for agricultural use and achieving carbon neutrality.

Au Nanosheets‐Assisted Structural Phase Transitions, In Situ Monitoring of the Enhanced Crystallinity, and Their Effect on the Optical and Dielectric Properties of CuSe/Au/CuSe Thin Films

AbstractHerein, stacked layers of copper selenide thin films comprising Au nanosheets in its structure are fabricated and characterized. The CuSe/Au/CuSe (CAC) thin films are prepared by the thermal evaporation technique under a vacuum pressure of 10−5 mbar. It is shown that Au nanosheets improve the stoichiometric growth of the CuSe thin films and induce the structural phase transitions from cubic to hexagonal. In addition, the in situ monitoring of the structural modifications in the CAC in the temperature range of 293–473 K proves the permanent enhanced crystallinity of the films. Optically, while the Au nanosheets increase the light absorbability and redshifts the energy band gap of CuSe, the in situ heating blueshifts the energy band gap. Moreover, insertion of Au nanosheets between layers of CuSe and heating them at 473 K significantly increase the dielectric constant and the optical conductivity by more than five times. Moreover, the drift mobility of charged carriers, the scattering time at femtosecond level, and the plasmon frequency are remarkably enhanced. Values of plasmon frequency exceed 6.0 GHz nominating the CAC films as signal receivers suitable for 5G technology.