Plasmon Coupling Effect Research Articles

CuS@Ag Heterostructure-based Surface Plasmonic Coupling Electrochemiluminescence Sensor for Glioma miRNA-124-3p Detection.

As an emerging class of extended crystalline organic materials, covalent organic framework (COF)-based aggregation-induced emission luminogen (AIE-gen) exhibited encouraging emissive properties. In this work, 4',4'',4‴,4‴'-(1,1,2,2-Ethenetetrayl)tetra(4-biphenylcarbaldehyde) (ETBC) as AIEgen was used to prepare AIE-COF (ET-COF-COOH) luminescent nanoprobe. ETBC and 1,3,5-Tris(4-aminophenyl)benzene (TAPB) had an extended π electronic system that allowed electron delocalization and overlapping transport. Because AIEgen-ETBC served as the luminescence center of ET-COF-COOH, the ET-COF-COOH possessed an ideal anodic electrochemiluminescence (ECL) performance. Moreover, due to the surface plasmonic coupling (SPC) effect of the CuS@Ag square-cavity array, the ECL signal of ET-COF-COOH was amplified as 2.8 times. The AIE-COF/CuS@Ag SCH array-based SPC-ECL sensor was used to detect miRNA-124-3p with a wide range of 1fM-10 nM and LOD of 0.49fM. Furthermore, the proposed biosensor can effectively distinguish between tumor tissue and adjacent tissue and offer significant potential for advancing glioma diagnosis.

Unveiling Spatial and Temporal Dynamics of Plasmon-Enhanced Localized Fields in Metallic Nanoframes through Ultrafast Electron Microscopy.

Plasmonic nanomaterials, particularly noble metal nanoframes (NFs), are important for applications such as catalysis, biosensing, and energy harvesting due to their ability to enhance localized electric fields and atomic efficiency via localized surface plasmon resonance (LSPR). Yet the fundamental structure-function relationships and plasmonic dynamics of the NFS are difficult to study experimentally and thus far rely predominately on computational methodologies, limiting their utilization. This study leverages the capabilities of ultrafast electron microscopy (UEM), specifically photon-induced near-field electron microscopy (PINEM), to probe the light-matter interactions within plasmonic NF structures. The effects of shape, size, and plasmonic coupling of Pt@Au core-shell NFs on spatial and temporal characteristics of plasmon-enhanced localized electric fields are explored. Importantly, time-resolved PINEM analysis reveals that the plasmonic fields around hexagonal NF prisms exhibit a spatially dependent excitation and decay rate, indicating a nuanced interplay between the spatial geometry of the NF and the temporal evolution of the localized electric field. These results and observations uncover nanophotonic energy transfer dynamics in NFs and highlight their potential for applications in biosensing and photocatalysis.

Construction of aptamers-modified plasmonic GO/urchin-like Au nanoparticles with enhanced photothermal performance and their efficient capture and elimination of Staphylococcus aureus

Here, aptamers-modified graphene oxide/urchin-like Au nanoparticles (Apt-GUANPs) were developed for efficient capture and photothermal therapy (PTT) of Staphylococcus aureus (S. aureus). Specifically, anisotropic UANPs were first prepared, and the excellent photothermal property was related to the localized surface plasmon resonance (LSPR) in the near infrared (NIR) region caused by sharp branching. Then GO, which was used to enhance the photothermal effect, was added and assembled into GUANPs by electrostatic action. Infrared images showed that GUANPs exhibited a stronger photothermal effect than UANPs. Under the irradiation of 808 nm laser, the photothermal conversion efficiency (η) of GUANPs was as high as 40.5 %, which was attributed to the enhanced optical response of GUANPs at 808 nm and the strong plasmonic coupling effect between tightly packed UANPs loaded on GO surfaces. Aptamers were modified on the surfaces of GUANPs for specific capture of S. aureus, with the capture efficiency of up to 72 %. Utilizing the specific capture ability of aptamers and the excellent photothermal property of GUANPs, Apt-GUANPs exhibited the strong photothermal killing ability against S. aureus. Therefore, Apt-GUANPs will be a promising and efficient photothermal agent, and will have a great application prospect in the treatment of bacterial infections in the future.

Dependent scattering and plasmon coupling in concentrated suspensions of optically hard nanoparticles

This study establishes the accuracy and efficacy of the recently developed radiative transfer with reciprocal transactions (R2T2) method for quickly simulating radiation transfer through concentrated thick suspensions of optically hard nanoparticles featuring a large mismatch in refractive and/or absorption indices compared with their surrounding medium. Concentrated suspensions of optically hard nanoparticles exhibit strong light scattering and dependent scattering effects including both near-field interactions among particles and interferences of scattered waves in the far-field. Concentrated suspensions of metallic nanoparticles also exhibit plasmon coupling effect that leads to widening of absorption peak and red-shift in the peak surface plasmon resonance wavelength. However, predicting these complex interactions between EM waves and particles in thick and concentrated suspensions by explicitly solving Maxwell's equations is computationally intensive, if not impossible. Conventional solutions like Lorenz–Mie theory combined with independent scattering approximation do not account for dependent scattering and plasmon coupling. Furthermore, the dense medium radiative transfer theory is a far-field approximation that does not account for near-field effects, leading to significant errors in predictions, as illustrated in this study. By contrast, the R2T2 method's predictions showed excellent agreement with the solutions of Maxwell's equations obtained using the superposition T-matrix method for thin films containing optically hard particles. The method also rigorously accounted for multiple scattering as well as plasmon coupling in thick concentrated suspensions. These results could facilitate the design of plasmonic suspensions used in various energy and environmental applications.

Electron–ion collision and polarization of X-ray fluorescence radiation under hot quantum plasma conditions

In the current article, the spectral properties and electron collision (total and magnetic) excitation cross sections of ions taking placed in quantum plasmas are investigated. These cross sections are further used to study the polarization and angular distribution characteristics of the de-excitation radiation X-ray spectra, which play an important role in basic theoretical research, the diagnosis of the plasma environment, and the design of optical devices. To do so, a distorted wave method within the relativistic Dirac–Coulomb atomic structure scheme is suggested. The effective interaction potential between electrons and particles in hot quantum plasmas in the method is determined using a quantum approach that incorporates the influence of effective plasma screening effects caused by collective plasma oscillations. This potential replaces the traditional Coulomb interaction potential and is used in solving the modified Dirac equation to obtain the bound and continuum electron wave functions. Higher-order relativistic effects, such as the Breit interaction and the dominant quantum electrodynamics corrections, are added to enhance the accuracy of the method. Detailed calculations for the relativistic atomic structure and collision excitation dynamics process are carried out, taking the highly stripped H-like O7+ ion of astrophysical importance as an illustrative example. Detailed investigations are also conducted on the variation of energies, collision cross sections, and fluorescence polarizations as functions of the plasma parameters. Our results suggest that the joint effects of shielding and plasma coupling lead the energies, cross sections and fluorescence polarizations decrease (compared with the isolated case). The angular distribution of the X-ray fluorescence emission shows large change, suggesting their sensitivity to these effects. This study not only offers a valuable approach to investigating the plasma shielding and plasmon coupling effects in quantum plasmas but also holds significant relevance for applications in controlled nuclear fusion, astrophysical plasmas and so on.

Large-area Ag “sesame cake-like” arrays with high-density hotspots for efficient SERS analysis

Nanogap-rich plasmonic metal nanostructures have attracted great attention in surface enhanced Raman scattering (SERS) applications due to their prominent performances. Herein, utilizing enhanced surface diffusion of Ag atoms on a low energy surface, a facile fabrication strategy is developed to construct a large-area Ag “sesame cake-like” (ASCL) array by combining the ultra-thin alumina mask (UTAM) and vapor deposition technique. Owing to the multiple plasmonic coupling effects, the proposed ASCL array possesses enormous hotspots responsible for remarkable sensitivity with an enhancement factor of 4.9 × 106, excellent reproducibility with a relative standard deviation (RSD) smaller than 7.12 % and obvious polarization independent in SERS analysis, which are confirmed by numerical simulations. In addition, the possibility to be fabricated on the flexible substrate makes the ASCL array substrate well meet the increasing demands for practical applications in the fields of food safety, health and environment monitoring.

A Platinum-Protein hybrid nanostructure enables both targeted cancer theragnosis and platinum clearance

Considering the fundamental advantages of photothermal therapy (PTT) and photoacoustic imaging (PAI) of cancer such as precise spatiotemporal control-based, non-invasive therapy with negligible drug resistance and side effects and sensitive, specific diagnosis with high spatial resolution at substantial depth, an advanced, or clinically feasible material that enables both PTT and PAI surely needs to be developed but remains a major challenge yet. Here we developed a hybrid nanostructure (PtNC@ABP-HBVC) between plasmonic platinum nanocluster (PtNC) comprised of many tiny Pt nanoparticles (PtNPs, ∼ 3 nm that is small enough to pass through glomerular filtration in kidney) and a specially designed protein scaffold (ABP-HBVC) capable of binding to human serum albumin (HSA). PtNC is beneficial for efficient light-to-heat conversion and acoustic wave generation due to plasmonic coupling effect among the small PtNPs, and the HSA binding to ABP-HBVC significantly lowers immunogenicity and enables PtNC to be effectively delivered to tumor. Using human breast cancer-bearing xenograft mice, we demostrated that PtNC@ABP-HBVC has the superior efficacy in targeted cancer theragnosis (PTT + PAI) and is rapidly cleared from the body through urinary excretion, which shows its great potential as a promising, clinically attractive agent for cancer theragnosis.

Highly Stable Silver Nanowire Plasmonic Electrodes for Flexible Polymer Light-Emitting Devices.

Silver nanowire (AgNW) transparent electrodes are considered as a promising candidate for applications in flexible optoelectronic devices. However, it remains a great challenge to obtain flexible AgNW electrodes with excellent optoelectrical properties and mechanical flexibility. Here, highly stable Ag nanoparticle (AgNP)-enhanced plasmonic AgNW electrodes are demonstrated via the controllable in situ growth of AgNPs at the AgNW junctions and introduction of an l-histidine (l-His) wrapping layer. The flexible transparent electrodes of AgNW-AgNP/l-His possess a low sheet resistance (Rsh) of ∼17.5 Ω sq-1, a high transmittance of ∼92.5% (550 nm), and a robust mechanical stability (100,000 bending cycles). Benefiting from plasmon-coupling effects, flexible polymer light-emitting devices (FPLEDs) with AgNW-AgNP/l-His electrodes present a current efficiency (CE) of ∼14.8 cd A-1 and an external quantum efficiency (EQE) of ∼5.6%, constituting ∼80% and ∼75% increases compared to those of the reference devices with AgNW electrodes, respectively. Additionally, the laminated flexible transparent PLEDs (FT-PLEDs) are demonstrated by integrating polydimethylsiloxane/AgNW-AgNP anodes by a soft lamination process. The FT-PLEDs present a CE of ∼7.1 cd A-1 (cathode side: ∼3.9 cd A-1; anode side: ∼3.2 cd A-1) and an EQE of ∼2.7% (cathode side: ∼1.5%; anode side: ∼1.2%). Furthermore, the FPLEDs and FT-PLEDs exhibit robust mechanical durability, maintaining ∼89% and ∼86% of their initial luminance after 1000 bending cycles at a bending radius of 2 mm, respectively. This work opens up a new avenue for the development of high performance and stable flexible optoelectronic devices.

Cu NCs@MXene-luminescent Faraday cage and Cu Nanocone/Bi NPs array-based saliva exosome assay for asthma evaluation

In this work, a novel nano-sensing system with luminescent Faraday cage mode has been developed to detect miRNA-221-5p in clinic saliva exosomes to evaluate asthma. Firstly, copper nanoclusters (Cu NCs) were synthesized in situ on the defects in Ti3CN nanosheets based on the nanoconfinement effect. Due to the Electronic metal-support interactions (EMSI) between MXene and the anchored Cu NCs, Cu NCs@MXene displayed the strong luminescence performance, high electrochemical activity and good stability properties. Furthermore, MXene nanosheets with good conductivity and flexibility was used to expand the outer Helmholtz plane and improve the sensing ability. Meanwhile, Cu nanocone/Bi nanoparticles (NPs) arrays were constructed by step-by-step electrodeposition. Due to the surface plasmon coupling effect, the Cu nanocone/Bi NPs arrays can convert the electrochemiluminescence (ECL) signal of Cu NCs@MXene-Faraday cage into the directional emission with 13.4-fold enhancement. Finally, a thin phospholipid film and capture DNA were modified on the surface of the Cu nanocone/Bi NPs array as the sensing interface to detect miRNA-221-5p in saliva exosomes. The designed nano-sensing system had a detection range was 1.0 × 10-16 ∼ 1.0 × 10-8 mol/L with the detection limit of 34 aM. Finally, the biosensor has been successfully employed to evaluate asthma in the clinical analysis.

Plasmonic Imaging of Multivalent NTD-Nucleic Acid Interactions for Broad-Spectrum Antiviral Drug Analysis.

The discovery and identification of broad-spectrum antiviral drugs are of great significance for blocking the spread of pathogenic viruses and corresponding variants of concern. Herein, we proposed a plasmonic imaging-based strategy for assessing the efficacy of potential broad-spectrum antiviral drugs targeting the N-terminal domain of a nucleocapsid protein (NTD) and nucleic acid (NA) interactions. With NTD and NA conjugated gold nanoparticles as core and satellite nanoprobes, respectively, we found that the multivalent binding interactions could drive the formation of core-satellite nanostructures with enhanced scattering brightness due to the plasmonic coupling effect. The core-satellite assembly can be suppressed in the presence of antiviral drugs targeting the NTD-NA interactions, allowing the drug efficacy analysis by detecting the dose-dependent changes in the scattering brightness by plasmonic imaging. By quantifying the changes in the scattering brightness of plasmonic nanoprobes, we uncovered that the constructed multivalent weak interactions displayed a 500-fold enhancement in affinity as compared with the monovalent NTD-NA interactions. We demonstrated the plasmonic imaging-based strategy for evaluating the efficacy of a potential broad-spectrum drug, PJ34, that can target the NTD-NA interactions, with the IC50 as 24.35 and 14.64 μM for SARS-CoV-2 and SARS-CoV, respectively. Moreover, we discovered that ceftazidime holds the potential as a candidate drug to inhibit the NTD-NA interactions with an IC50 of 22.08 μM from molecular docking and plasmonic imaging-based drug analysis. Finally, we validated that the potential antiviral drug, 5-benzyloxygramine, which can induce the abnormal dimerization of nucleocapsid proteins, is effective for SARS-CoV-2, but not effective against SARS-CoV. All these demonstrations indicated that the plasmonic imaging-based strategy is robust and can be used as a powerful strategy for the discovery and identification of broad-spectrum drugs targeting the evolutionarily conserved viral proteins.

Programmable Colloids with Analogous Hypercoordination Complex Architectures.

Colloidal molecule clusters (CMCs) are promising building blocks with molecule-like symmetry, offering exceptional synergistic properties for applications in plasmonics and catalysis. Traditional CMC fabrication has been limited to simple molecule-like structures utilizing isotropic particles. Here, we employ molecular dynamics simulation to investigate the co-assembly of anisotropic nanorods (NRs) and the stimulus-responsive polymer (SRP) via reversible adsorption. The results of the simulation show that it is possible to fabricate hypercoordination complex structures with high symmetry from the co-assembly of NRs and the SRP, even in analogy to the Th(BH4)4 structure. The coordination number of these CMCs can be precisely programmed by adjusting the shape and size of the ends of the NRs and the SRP cohesion energy. Furthermore, a finite-difference time-domain simulation indicates these hypercoordination structures exhibit significantly enhanced optical activity and plasmonic coupling effects. These findings introduce a new design approach for complex molecule-like structures utilizing anisotropic nanoparticles and may expand the applications of CMCs in photonics.

Ultra-Broadband Plasmon Resonance in Gold Nanoparticles Precipitated in ZnO-Al2O3-SiO2 Glass

Optical materials with a tunable localized surface plasmon resonance (LSPR) are of great interest for applications in photonics and optoelectronics. In the present study, we explored the potential of generating an LSPR band with an ultra-broad range of over 1000 nm in gold nanoparticles (NPs), precipitated through a thermal treatment in ZnO-Al2O3-SiO2 glass. Using optical absorption spectroscopy, we demonstrated that the LSPR band’s position and shape can be finely controlled by varying the thermal treatment route. Comprehensive methods including Raman spectroscopy, X-ray diffraction, and high-resolution transmission electron microscopy were used to study the glass structure, while computational approaches were used for the theoretical description of the absorption spectra. The obtained results allowed us to suggest a scenario responsible for an abnormal LSPR band broadening that includes a possible interparticle plasmonic coupling effect taking place during the liquid–liquid phase separation of the heat-treated glass. The formation of gold NPs with an ultra-broad LSPR band in glasses holds promise for sensitizing rare earth ion luminescence for new photonics devices.

Large-scale SU-8 Micro-Pole-Arrays decorated with Hierarchical Metal-Dielectric-Metal nanostructures as sensitive 3D SERS substrates

Dielectric layer-mediated surface-enhanced Raman scattering (SERS) substrates are currently explored for ultrasensitive detection and expected to provide uniform SERS response by the virtue of three-dimensional micro-nanostructures, dielectric layer, and plasmonic metal nanostructures. For this purpose, the present work reports on the development of the metal-dielectric-metal (MDM) three-dimensional (3D) micro-pole-arrays structure based on SU-8 colloid lithography. By utilizing the large-scale periodic arrangement characteristics of SU-8 colloidal lithography, along with the hot spot effect created by the nano-gap between MDM, we successfully prepared an array of SERS substrates that exhibit both periodicity and multi-dimensional plasmonic coupling effect. Compared to a single metal nanoparticle substrate, the SERS activity of the substrate is significantly enhanced, and the substrate has trace detection ability (LOD of detection of 10−12 mol/L for R6G). The enhancement factor (EF) is 5.72 × 107. Periodicity ensures that the prepared substrate has good reproducibility (RSD < 8 %) and stability. Furthermore, the substrate modified with HS-β-CD demonstrated potential for rapid trace SERS detection of polychlorinated biphenyls (PCB-77) (LOD of 10−8 mol/L for PCB-77). The results indicate that the proposed substrate has the potential for application in the preparation of SERS sensors with high sensitivity and uniformity.

Magnetoplasmonic Metasurface-Modulated Electrochemiluminescence Strategy for Extracellular Vesicle Detection.

Due to the ideal optical manipulation ability, the metasurface has broad prospects in the development of novel optical research. In particular, an active metasurface can control optical response through external stimulus, which has attracted great research interest. However, achieving effective modulation of the optical response is a significant challenge. In this work, we have developed a novel electrochemiluminescence (ECL) signal modulation strategy by an active magnetoplasmonic metasurface under an external magnetic field. The magnetoplasmonic metasurface was assembled based on yolk-shell Fe3O4@Au nanoparticles (Fe3O4@Au YS-NPs). On the one hand, the yolk-shell structure of Fe3O4@Au YS-NPs possessed the surface plasmon coupling effect and cavity-based Purcell effect, which provided high-intensity electromagnetic hot spots in the magnetoplasmonic metasurface. On the other hand, due to the strong magnetic response of the Fe3O4 core, the local magnetic field was induced by the external magnetic field, which further generated Lorentz force acting on the free electrons of Au nanoshells with strong optical anisotropy. The plasmon frequency of the metasurface can be effectively modulated by the Lorentz force effect. As a result, the ECL signal of nitrogen dots (N dots) was dynamically modulated and significantly enhanced at a specific polarization angle by the magnetoplasmonic metasurface under the variable external magnetic field. Based on the luminescence modulation ability and structure feature, the magnetoplasmonic metasurface was further established successfully as a sensing interface for gastric cancer (GC) extracellular vesicle (EV) detection. This study illustrated that the electromagnetic response of the active metasurface can effectively improve the optical modulation ability and luminescence sensing performance.

Dual plasmonic coupling effect in Bi/vacancy-rich Bi2WO6 heterojunction for selective CO2 photoreduction to CH4

Low-cost plasmonic semiconductors with high density of free carriers have attracted increasing attention in photocatalytic CO2 reduction (PCR), since they display the localized surface plasmon resonance (LSPR) to improve the light-harvesting and produce hot electrons to boost the PCR activity. However, the produced hot electrons in plasmonic semiconductors are easily suppressed to limit the enhancement of the PCR performance. Herein, the dual plasmonic coupling system of Bi nanoparticles/vacancy-rich Bi2WO6 nanosheets (BWO-Vo-Bi) is designed and constructed. An intense plasmonic coupling induced by metal Bi and plasmonic semiconductor of vacancy-rich Bi2WO6 is formed, thus contributing to a strong full-spectrum solar absorption and fast charge transfer in BWO-Vo-Bi heterojunction. The significant enhancement of light absorption and charge movement further accelerates the generation of high-energy hot electrons and extends the lifetime of photogenerated electrons, thereby yielding a high CH4 evolution rate of 20.36 μmol g-1 h−1 with a selectivity of 93.0 % in BWO-Vo-Bi under light irradiation without sacrificial agents, which is 55 times higher than that of Bi2WO6. This work provides a new strategy for the development of high-performance photocatalysts for CO2 reduction through dual plasmonic coupling.

Facile construction of polycation/Au@CuS nanohybrids for synergistic gene/photothermal therapy

The integration of Au and CuS into a nanostructure holds promise for tumor photothermal therapy (PTT) due to the unique plasmonic coupling effect in the second near infrared (NIR-II) region. However, the therapeutic efficacy of monotherapy is limited, while the facile preparation of Au-CuS-based nanohybrids for enhanced tumor therapy remains challenging. Herein, a facile method is proposed to fabricate polycation/Au@CuS nanohybrids (ASC-PGEA) comprising Au nanorods, CuS nanoparticles and polycationic cloak for gene/photothermal combination therapy. ASC-PGEA nanohybrids possess favorable cellular uptake and gene transfection efficiency, which could effectively deliver antioncogene p53 to achieve gene therapy (GT). Taking advantage of the enhanced photothermal effect, ASC-PGEA-mediated therapy shows promising therapeutic effect both in vitro and in vivo, and the growth of tumors is substantially inhibited. In particular, synergistic therapy is realized due to PTT-enhanced GT. Additionally, the feasibility of ASC-PGEA to visualize and monitor the therapeutic process by computed tomography imaging is demonstrated. This work presents a facile strategy to construct polycation/Au@CuS nanohybrids to achieve synergistic gene/photothermal tumor therapy.

Effect of thin MoS2 film with different layer numbers on tip-enhanced photoluminescence spectroscopy

As a novel semiconductor material, Molybdenum disulfide (MoS2) has great application potential in sensors, catalysts and optoelectronic devices. In this study, we aim to investigate the unique optical properties of MoS2 by theoretically exploring the impact of thin MoS2 films with varying layer numbers on the tip-enhanced fluorescence of a single molecule confined within the nanocavity formed by an Au tip over a substrate. The influence of incidence angle, layer numbers, tip radius and tip-MoS2 film distance on the excitation field, quantum yield and fluorescence enhancement are quantitatively analyzed in detail. The results show that the presence of multilayer MoS2 film can significantly improve tip-enhanced fluorescence spectroscopy. In the strong gap-mode plasmon coupling effect, the maximum fluorescence enhancement reaches approximately five orders of magnitude when it consists of six layers under excitation wavelength of 660 nm. Furthermore, the spatial resolution of Raman and fluorescence increases with decreasing tip radius and gap distance, reaching a maximum of 2.6 nm and 3.8 nm, respectively. Our results provide a theoretical guidance for further understanding and application of the two-dimensional material in optical experiments.

One-pot synthesized Au@Pt nanostars-based lateral flow immunoassay for colorimetric and photothermal dual-mode detection of SARS-CoV-2 nucleocapsid antibody

In addition to confirming virus infection, quantitative identification of the antibodies to severe acute respiratory syndrome coronavirus 2(SARS-CoV-2) also evaluates persons immunity to guide personal protection. However, portable assays for fast and accurate quantification of SARS-CoV-2 antibodies remain challenging. In this work, we synthesized Au@Pt star-like nanoparticles (NPs) quickly and easily by a one-pot wet-chemical approach, allowing the stellate Au core to be partially decorated by Pt nanoshells. The nanoparticles were used as probe in a lateral flow immunoassay (LFIA) that operated in both colorimetric and photothermal dual modes, which could detect the antibodies to the SARS-CoV-2 nucleocapsid (N) protein with high sensitivity. Due to the sharp tips on the external region of nanostars and surface plasmon coupling effect between the Au core and Pt shell, the NIR absorption capacity and photothermal performance of these NPs were exceptional. Under optimal conditions, the colorimetric mode's detection limit for SARS-CoV-2 N protein antibody was 1 ng mL−1, which is significantly lower by 2-order of magnitude compared to commercially available colloidal gold strips. And the detection limit for the photothermal mode was as low as 24.91 pg mL−1, which was approximately 40-fold more sensitive than colorimetric detection. Moreover, the method demonstrated favorable specificity, reproducibility and stability. Finally, the approach was employed for the successful identification of actual serum samples. Therefore, the dual-mode LFIA can be applied for screening and tracking the early immunological reaction to SARS-CoV-2, and it has great promise for clinical application.

Acid-Responsive Aggregation of Gold Nanoparticles for the Photothermal Treatment of Bacterial Infections.

Photothermal therapy (PTT) is considered to be one of the promising methods to combat pathogenic bacteria. However, traditional PTT is prone to generate undesired temperature increase to surrounding normal tissues, which limits the application of PTT. Herein, an acid-responsive PTT system (Au nanoparticles system: AuNPs-S) was constructed based on the photothermal feature of spherical gold nanoparticles (AuNPs) and the low pH of the bacterial infected site. AuNPs-S is composed of two kinds of AuNPs: AuNPs modified with Asp-Asp-Asp-Asp-Asp-Cys (peptide A) were denoted as AuNPs-A; AuNPs modified with 2,3-dimethylmaleic anhydride (DA) grafted Lys-Gly-Gly-Lys-Gly-Gly-Lys-Cys (peptide B) were denoted as AuNPs-B/DA. AuNPs-B/DA with an acid-responsive moiety showed a charge-convertible feature. The negatively charged AuNPs-B/DA became positively charged AuNPs-B at low pH, aggregating with the negatively charged AuNPs-A via an electrostatic interaction, reaching the threshold to the interparticle plasmonic coupling effect among AuNPs, thereby killing bacteria precisely under the irradiation of near-infrared (NIR) light through the elevated temperature at the targeted area. This acid-responsive PTT strategy supplies an excellent mode for combating bacterial infections with no vital damage to normal tissues.

Graphene nanospacer layer modulated multilayer composite structures of precious metals and their SERS performance.

Graphene(G)-noble metal-ZnO hybrid systems were developed as highly sensitive and recyclable surface enhanced Raman scattering (SERS) platforms, in which ultrathin graphene of varying thickness was embedded between two metallic layers on top of a ZnO layer. Due to the multi-dimensional plasmonic coupling effect, the Au/G/Ag@ZnO multilayer structure possessed ultrahigh sensitivity with the detection limit of Rhodamine 6 G (R6G) as low as 1.0×10-13 mol/L and a high enhancement factor of 5.68×107. Both experimental and simulation results showed that graphene films could significantly regulate the interlayer plasmon resonance coupling strength, and single-layer graphene had the best interlayer regulation effect. Additionally, the SERS substrate structure prepared through physical methods exhibited high uniformity, the graphene component of the substrate possessed excellent molecular enrichment ability and silver oxidation inhibition characteristics, resulting in a substrate with high stability and exceptional reproducibility. The signal change was less than 15%. Simultaneously, due to the excellent photocatalytic performance of the low-cost and wide-band-gap semiconductor material ZnO, the SERS substrate exhibited exceptional reusability. Even after five cycles of adsorption-desorption, the SERS performance remained stable and maintained a reliable detection limit. The study introduced a novel approach to creating multilayer composite SERS substrates that exhibited exceptional performance, offering a new analytical tool with high sensitivity, stability, and reusability.