Two-thiols-regulated fabrication of plasmonic nanoparticles with co-enhanced Raman scattering and circular dichroism responses

Plasmonicnanoparticles(PNPs)with stable nanogaps are important to achieve strong,uniform and quantitative gap-enhanced Raman scattering(GERS)signals.Chiral PNPs with plasmonic circular dichroism(PCD)responses have been discovered to be suitable for applications in enantiomeric recognition,cancer therapy and activation of immune system.Herein,two-thiolsmodulated growth was demonstrated to result in the acquisition of PNPs with synergistically enhanced GERS and PCD signals.4-Aminothiophenol(4-ATP)and cysteine(Cys)played the role of Raman reporter and chiral stimulus,respectively.At a fixed 4-ATP concentration,the GERS signal of PNPs was significantly enhanced with the increase of the concentration of Cys.Simultaneously,at a fixed concentration of Cys,an increase in PCD response was observed by elevating the concentration of 4-ATP.Both aforementioned molecules acted as morphology controllers,leading to the formation of helical shell.It is suggested that the giant GERS and PCD response were contributed by the‘‘hot spots''within the PNPs and more perfect helical shells.Our research pointed out a novel synthetic guideline to obtain PNPs with multiple functionalities by incorporating multi-ligands into the growth stages.

The versatility of Fe(Ⅱ) in the synthesis of uniform citrate-stabilized plasmonic nanoparticles with tunable size at room temperature

A highly versatile seed-mediated approach for the synthesis of citrate-stabilized gold,silver and palladium nanoparticles(NPs)with size control is reported.The use of iron(Ⅱ)as a reducing agent enables the fabrication of monodisperse NPs in a wide range of sizes(from 15 nm to at least 120 nm(90 nm for Pd))at room temperature.The citrate as capping ligand on the NPs surface facilitates its further surface modification with proteins and thiolated molecules.

Surface-modified Ag@Ru-P25 for photocatalytic CO_(2) conversion with high selectivity over CH_(4) formation at the solid–gas interface

Systematic optimization of the photocatalyst and investigation of the role of each component is important to maximizing catalytic activity and comprehending the photocatalytic conversion of CO_(2) reduction to solar fuels.A surface-modified Ag@Ru-P25 photocatalyst with H_(2)O_(2) treatment was designed in this study to convert CO_(2) and H_(2)O vapor into highly selective CH4.Ru doping followed by Ag nanoparticles(NPs)cocatalyst deposition on P25(TiO_(2))enhances visible light absorption and charge separation,whereas H_(2)O_(2) treatment modifies the surface of the photocatalyst with hydroxyl(–OH)groups and promotes CO_(2) adsorption.High-resonance transmission electron microscopy,X-ray photoelectron spectroscopy,X-ray absorption near-edge structure,and extended X-ray absorption fine structure techniques were used to analyze the surface and chemical composition of the photocatalyst,while thermogravimetric analysis,CO_(2) adsorption isotherm,and temperature programmed desorption study were performed to examine the significance of H_(2)O_(2) treatment in increasing CO_(2) reduction activity.The optimized Ag1.0@Ru1.0-P25 photocatalyst performed excellent CO_(2) reduction activity into CO,CH4,and C2H6 with a~95%selectivity of CH4,where the activity was~135 times higher than that of pristine TiO_(2)(P25).For the first time,this work explored the effect of H_(2)O_(2) treatment on the photocatalyst that dramatically increases CO_(2) reduction activity.

Simultaneous Detection and Removal of Formaldehyde at Room Temperature: Janus Au@ZnO@ZIF-8 Nanoparticles

The detection and removal of volatile organic compounds(VOCs) are of great importance to reduce the risk of indoor air quality concerns. This study reports the rational synthesis of a dual-functional Janus nanostructure and its feasibility for simultaneous detection and removal of VOCs.The Janus nanostructure was synthesized via an anisotropic growth method, composed of plasmonic nanoparticles,semiconductors, and metal organic frameworks(e.g.,Au@ZnO@ZIF-8). It exhibits excellent selective detection to formaldehyde(HCHO, as a representative VOC) at room temperature over a wide range of concentrations(from 0.25 to100 ppm), even in the presence of water and toluene molecules as interferences. In addition, HCHO was also found to be partially oxidized into non-toxic formic acid simultaneously with detection. The mechanism underlying this technology was unraveled by both experimental measurements and theoretical calculations: ZnO maintains the conductivity, while ZIF-8 improves the selective gas adsorption; the plasmonic effect of Au nanorods enhances the visible-light-driven photocatalysis of ZnO at room temperature.

Gold/monolayer graphitic carbon nitride plasmonic photocatalyst for ultrafast electron transfer in solar-to-hydrogen energy conversion

Gold(Au)plasmonic nanoparticles were grown evenly on monolayer graphitic carbon nitride(g‐C3N4)nanosheets via a facile oil‐bath method.The photocatalytic activity of the Au/monolayer g‐C3N4 composites under visible light was evaluated by photocatalytic hydrogen evolution and environmental treatment.All of the Au/monolayer g‐C3N4 composites showed better photocatalytic performance than that of monolayer g‐C3N4 and the 1%Au/monolayer g‐C3N4 composite displayed the highest photocatalytic hydrogen evolution rate of the samples.The remarkable photocatalytic activity was attributed largely to the successful introduction of Au plasmonic nanoparticles,which led to the surface plasmon resonance(SPR)effect.The SPR effect enhanced the efficiency of light harvesting and induced an efficient hot electron transfer process.The hot electrons were injected from the Au plasmonic nanoparticles into the conduction band of monolayer g‐C3N4.Thus,the Au/monolayer g‐C3N4 composites possessed higher migration and separation efficiencies and lower recombination probability of photogenerated electron‐hole pairs than those of monolayer g‐C3N4.A photocatalytic mechanism for the composites was also proposed.

Interplay between out-of-plane magnetic plasmon and lattice resonance for modified resonance lineshape and near-field enhancement in double nanoparticles array

Two-dimensional double nanoparticle （DNP） arrays are demonstrated theoretically, supporting the interaction between out-of-plane magnetic plasmons and in-plane lattice resonances, which can be achieved by tuning the nanoparticle height or the array period due to the height-dependent magnetic resonance and the periodicity-dependent lattice resonance. The interplay between the two plasmon modes can lead to a remarkable change in resonance lineshape and an improvement on magnetic field enhancement. Simultaneous electric field and magnetic field enhancement can be obtained in the gap region between neighboring particles at two resonance frequencies as the interplay occurs, which presents “open” cavities as electromagnetic field hot spots for potential applications on detection and sensing. The results not only offer an attractive way to tune the optical responses of plasmonic nanostructure, but also provide further insight into the plasmon interactions in periodic nanostructure or metamaterials comprising multiple elements.

Bifunctional S-scheme g-C3N4/Bi/BiVO4 hybrid photocatalysts toward artificial carbon cycling

Although both the aerobic photocatalytic oxidation of organic pollutants into CO2 and the anaerobic photocatalytic reduction of CO2 into solar fuels have been intensively studied,few efforts have been devoted to combining these carbon-involved photocatalytic oxidation-reduction processes together,by which an artificial photocatalytic carbon cycling process can be established.The key challenge lies in the exploitation of efficient bifunctional photocatalysts,capable of triggering both aerobic oxidation and anaerobic reduction reactions.In this work,a bifunctional ternary g-C3N4/Bi/BiVO4 hybrid photocatalyst is successfully constructed,which not only demonstrates superior aerobic photocatalytic oxidation performance in degrading an organic pollutant(using the dye,Rhodamine B as a model),but also exhibits impressive photocatalytic CO2 reduction performance under anaerobic conditions.Moreover,a direct conversion of Rhodamine B to solar fuels in a one-pot anaerobic reactor can be achieved with the as-prepared ternary g-C3N4/Bi/BiVO4 hybrid photocatalyst.The excellent bifunctional photocatalytic performance of the g-C3N4/Bi/BiVO4 photocatalyst is associated with the formation of efficient S-scheme hybrid junctions,which contribute to promoting the appropriate charge dynamics,and sustaining favorable charge potentials.The formation of the S-scheme heterojunction is supported by scavenger studies and density functional theory calculations.Moreover,the in-situ formed plasmonic metallic Bi nanoparticles in the S-scheme hybrid g-C3N4/Bi/BiVO4 photocatalyst enhances vectorial interfacial electron transfer.This novel bifunctional S-scheme g-C3N4/Bi/BiVO4 hybrid photocatalyst system provides new insights for the further development of an integrated aerobic-anaerobic reaction system for photocatalytic carbon cycling.

Plasmonic Au nanoparticles supported on both sides of Ti02 hollow spheres for maximising photocatalytic activity under visible light

A strategy of intensifying the visible light harvesting ability of anatase Ti02 hollow spheres(HSs)was developed,in which both sides of Ti02 HSs were utilised for stabilising Au nanoparticles(NPs)through the sacrificial templating method and convex surface-induced confinement.The composite structure of single Au NP yolk-Ti02 shell-Au NPs,denoted as Au@Au(Ti02,was rendered and confirmed by the transmission electron microscopy analysis.Au@Au(Ti02 showed enhanced photocatalytic activity in the degradation of methylene blue and phenol in aqueous phase under visible light surpassing that of other reference materials such as Au(Ti02 by 77%and Au@P25 by 52%,respectively,in phenol degradation.

Enhanced plasmonic absorption of Pt cuboctahedra-WO_(3)nanohybrids used as visible light photocatalysts for overall water splitting

Localized surface plasmon resonance(LSPR)effects of nanoscale plasmonic metals/semiconductor composites have been extensively applied into visible light photocatalysis.However,Pt nanoparticles(NPs)with the visible LSPR absorption maxima have rarely been used as a photosensitizer to facilitate photocatalytic reactions,especially the photocatalytic overall water splitting(POWS)reaction,presumably because they feature weak light absorption.Herein,we present that the increased plasmonic absorption and local field enhancement can be achieved in the wide visible range by exploiting the simulated and experimental expressions of Pt nanocuboctahedra and Pt cuboctahedra-WO_(3)nanohybrids(Pt-WO3).First,monodisperse Pt cuboctahedra with different sizes,a hierarchical WO_(3)nanoarchitecture composed of radially patterned WO_(3)nanopillars,and Pt-WO_(3)were systematically synthesized.Subsequently,visible plasmonic Pt-WO_(3)photocatalysts were employed in the POWS tests and exhibited the significant activity enhancement in the visible light region.The apparent quantum efficiency(AQE)of greater than 7%within the range of visible light has been achieved for the optimal Pt-WO3.

A facile and sensitive colorimetric detection for RNase A activity based on target regulated protection effect on plasmonic gold nanoparticles aggregation

In this work,a facile and sensitive colorimetric detection method was firstly reported for RNase A activity detection based on target regulated protection effect of chimeric DNA probe on the salt-induced aggregation of plasmonic gold nanoparticles.Compared with previous works of RNase A activity detection,this colorimetric assay integrated the advantages of sensitive,low cost,facile operation,rapid response and low biological toxicity.

Ag nanoparticles preparation and their light trapping performance

Ag nanoparticles were fabricated on Si substrates by radio-frequency magnetron sputtering and thermal annealing treatments.It was found that Ag nanoparticles are ellipsoid at low annealing temperature,but the axis ratio decreases with the increase of annealing temperature,and a shape transformation from ellipsoid to sphere occurs when the temperature increases to a critical point.The experimental results showed that the surface plasmon resonances depend greatly on the nanoparticles'shape and size,which is in accordance with the theoretical calculation based on discrete dipole approximation.The results of forward-scattering efficiency(FSE) and light trapping spectrum(LTS) showed that Ag nanoparticles annealed at 400°C could strongly enhance the light harvest than those annealed at 300 and 500°C,and that the LTS peak intensity of the former is 1.7 and 1.5 times stronger than those of the later two samples,respectively.The conclusions obtained in this paper showed that Ag ellipsoid nanoparticles with appropriate size is more favorable for enhancing the light trapping.

Pd/Ag nanosheet as a plasmonic sensing platform for sensitive assessment of hydrogen evolution reaction in colloid solutions

A nanoplasmonic hydrogen-sensing system based on palladium/silver nanosheets （Pd/Ag NSs） was developed and used for sensitive assessment of the hydrogen evolution reaction （HER） in colloid solutions. As a model HER system, the semiconductor CdS/CdSe core/shell quantum dot （QD）-based hydrogen-producing colloidal system was used, and the HER performances of QDs with two different surface coatings were assessed in this study. In the sensing system, the photocatalytically generated hydrogen reacts with Pd/Ag NSs, resulting in a gradual red-shift of localized surface plasmon resonance, which to a certain degree is almost linearly proportional to the amount of hydrogen generated. Such a nanoplasmonic hydrogen sensing platform would be useful as an alternative for optical assessment and fast selection of a highly efficient and cost-effective solar hydrogen generation system for practical applications.

Plasmonic metal‐organic frameworks

Plasmonic metal‐organic frameworks are composite nanoparticles comprising plasmonic metal nanoparticles(NPs)embedded within a metalorganic framework(MOF)matrix.As a result,not only the functionalities of the individual components are retained,but synergistic effects additionally provide improved chemical and physical properties.Recent progress in plasmonic MOFs has demonstrated the potential for nanofabrication and various nanotechnology applications.Synthetic challenges toward plasmonic MOFs have been recently addressed,resulting in new opportunities toward practical applications,such as surface‐enhanced Raman scattering,therapy,and catalysis.The impact of key parameters(thermodynamic vs.kinetic)on the synthetic pathways of plasmonic MOFs is reviewed,while providing insight into related progress toward structure‐derived applications.

Highly sensitive and selective two-photon sensing of cartap using Au@Ag core-shell nanoparticles

A highly sensitive and selective two-photon sensing scheme for detection of cartap was developed by using Au@Ag bimetallic core-shell nanoparticles.Cartap was found to induce the aggregation of Au@Ag nanoparticles and up to 700-fold enhancement in two-photon photoluminescence.Huge enhancement in two-photon photoluminescence allows achieving a detection limit of as low as 0.0062 mg/kg,which is better than the conventional colorimetric methods.This two-photon sensing scheme has a broad dynamic range and displays excellent selectivity in detection of cartap against over other ten kinds of commonly used insecticides.

Adjustable surface plasmon resonance with Au,Ag,and Ag@Au core-shell nanoparticles

We report an experimental study on the synthesis of metal nanoparticles （NPs） with adjustable optical density based on surface plasmon resonance （SPR）. Metal NPs prepared by laser ablation in liquid method and the effect of laser parameters on the size, distribution, wavelength of SPR of Ag, Au, and mixture of Ag-Au, and Ag core/Au shell NPs are investigated. Our results show that the adjustable SPR band can be achieved in each class of NPs which is suitable for adjustable optical window applications.

DNA Nanostructure-Guided Plasmon Coupling Architectures

Plasmon coupling architectures with specific spatial and orientational arrangement configurations possess unique and tailored plasmonic properties and hold promise for advancements in nano-optics,nanoantennas,and biosensors.Numerous research has focused on the construction of plasmonic assemblies with predetermined configurations.DNA nanostructures with arbitrary geometry,high compatibility with metal nanoparticles,and spatial addressability meet the requirement for precise spatial and orientation arrangement.Currently,DNA nanostructures are widely exploited as structural materials to generate plasmonic structures with well-defined topologies.We review the evolution of DNA nanostructureguided plasmon coupling architectures,including the introduction of DNA nanostructures,DNA modification on the surface of plasmonic nanoparticles,and three strategies for constructing complex plasmonic nanostructures.Then we focus on the emerging applications of DNA nanostructure-guided architectures with engineered local electromagnetic enhancement for modulating plasmon coupling,amplifying emitter signals,and serving as biosensors.Finally,we will critically discuss the challenges and opportunities in this field.

Dual-step hybrid SERS scheme through the blending of CV and MoS_(2) NPs on the AuPt core-shell hybrid NPs

Along with a wide range of applications,the surface-enhanced Raman spectroscopy(SERS)is a promi-nent analytical technique to recognize and detect molecules and materials even at an extremely low mo-lar concentration.In this work,a unique hybrid SERS platform is demonstrated by the incorporation of molybdenum disulfate(MoS_(2))nanoparticles(NPs)onto the core-shell AuPt hybrid NPs(HNPs)for the en-hanced molecular Raman vibration of crystal violet(CV).The hybrid platform takes the advantage of both the electromagnetic mechanism(EM)offered by the AuPt HNPs and chemical mechanism(CM)owing to the MoS_(2)NPs.The distinctive core-shell morphology of AuPt HNPs with the high-density background Au NPs is attained by a unique two-step solid-state dewetting method,which can offer a high concentration of electromagnetic hot spots.At the same time,the MoS_(2)NPs can provide an ample charge transfer with abundant active sites.Through the hybrid SERS approach,a dramatic SERS enhancement of CV Raman vibration is demonstrated,and the SERS capability is thoroughly studied.In addition,the finite-difference time-domain(FDTD)simulations provide a deeper understanding of the electromagnetic field distributions for various configurations of nanostructures and their hybrid combinations:i.e.,HNPs,alloy NPs,MoS_(2)/HNPs configurations.

Fast Surface Restructuring within the Gap of Au Nanocube Dimer for the Enhancement of Catalytic Efficiency

Identification of the catalytic dynamics and plasmonic effects plays a critical role in the design of heterogeneous catalysts.However,the knowledge of plasmonic effect on catalytic dynamics remains limited at the single-particle level.Using the non-fluorescent amplex red to fluorescent resorufin as a model reaction,significant enhancement in catalytic efficiency from the coupled Au nanocube dimer(AuCD)was clearly revealed with the single-molecule fluorescence microscopy.AuCD exhibits noticeably higher catalytic efficiency than the monomer,which is attributed to the spontaneous dynamic surface restructuring.Spatiotemporally resolved dynamics suggest that the active catalytic sites essentially originate from the plasmonic nanogap where an electromagnetic(EM)hot spot exists.The enhanced EM field accelerates the generation of hot carriers and promotes the spontaneous surface restructuring by enhancing the lattice vibrations,which ultimately improves the catalytic activity.These microscopic views provide new insights into the effect of EM fields on surface restructuring dynamics of nanocatalysts.

Self-powered photoelectrochemical biosensing platform based on Au NPs@ZnO nanorods array

Photoanodes, which are used in photoelectrochemical （PEC） water splitting, have been shown to be applicable in the construction of a PEC biosensing platform. This was realized by replacing water oxidization with oxidation of an appropriate test molecule. Here, we have demonstrated the feasibility of adopting photoanodes consisting of zinc oxide nanorods arrays decorated with plasmonic gold nanoparticles （Au NPs@ZnO NRs） for the self-powered PEC bioanalysis of glutathione （GSH） in phosphate-buffered saline （PBS） at an applied bias potential of 0 V vs. Ag/AgCl. This heterostructure exhibited enhanced PEC properties because of the introduction of the Au/ZnO interface. Under visible light illumination, hot electrons from surface-plasmon resonance （SPR） at the Au NP surface were injected into the adjacent ZnO and subsequently driven to the photocathode. Under ultraviolet （UV） light illumination, the photogenerated electrons in ZnO tended to transfer to the fluorine-doped tin oxide due to the step-wise energy band structure and the upward energy band bending at the ZnO/ electrolyte interface. These results indicate that plasmonic metal/semiconductor heterostructure photoanodes have great potential for self-powered PEC bioanalysis applications and extended field of other photovoltaic beacons.

CdS nanocrystallites sensitized ZnO nanorods with plasmon enhanced photoelectrochemical performance

A novel architecture of CdS/ZnO nanorods with plasmonic silver(Ag) nanoparticles deposited at the interface of ZnO nanorods and CdS nanocrystallites,was designed as a photoanode for solar hydrogen generation,with photocurrent density achieving 4.7 mA/cm^2 at 1.6 V(vs.RHE),which is 8 and 1.7 times as high as those of pure ZnO and CdS/ZnO nanorod films,respectively.Additionally,with optical absorption onset extended to^660 nm,CdS/Ag/ZnO nanorod film exhibits significantly increased incident photo-tocurrent efficiency(IPCE) in the whole optical absorption region,reaching 23.1% and 9.8% at 400 nm and500 nm,respectively.The PEC enhancement can be attributed to the one-dimensional ZnO nanorod structure maintained for superior charge transfer,and the extended visible-light absorption of CdS nanocrystallites.Moreover,the incorporated plasmonic Ag nanoparticles could further promote the interfacial charge carrier transfer process and enhance the optical absorption ability,due to its excellent plasmon resonance effect.