Localized Surface Plasmon Resonance Peak Research Articles

A paper-based colorimetric sensor using Au/Ag nanocages for sensitive detection of hydrazine in water samples by smartphone

In this work, Au/Ag nanocages have been used as an effective platform for sensitive colorimetric detection of hydrazine. By adding hydrazine together with silver ions to the hollow Au/Ag nanocages, they undergo a morphological transformation to closed nanoboxes. This leads to a noticeable blue shift in the localized surface plasmon resonance (LSPR) peak position and a distinct color change from blue to purple in the solution. The extent of shift in the LSPR peak of the Au/Ag nanocages exhibited a direct correlation with the concentration of hydrazine within the range of 0.1 to 10.0 µM. The limit of detection (LOD) achieved was 0.03 µM, with a relative standard deviation (RSD) of 1.7% at a concentration of 0.5 µM. Furthermore, we developed a paper-based sensor with smartphone readout for hydrazine detection within the range of 0.5 to 10.0 µM, with an LOD of 0.3 µM and an RSD of 3.3% at a concentration of 2.0 µM. The effectiveness of the sensor was successfully demonstrated in the analysis of hydrazine in environmental samples. This is the first time that Au/Ag nanocages are used for simple paper-based assay. With its high sensitivity, low cost, and rapid analysis time, this method offers a promising solution for the quantitative measurement of hydrazine in environmental samples by portable paper-based test strips.

Enhanced cysteine sensor based on modified gold nanoparticles with synergistic role of pH-responsive poly (N,N-dimethylaminoethyl methacrylate)

The development of a highly sensitive and easy-to-prepare sensor for the detection of cysteine (Cys) is of great importance. Gold nanoparticles (AuNPs) have been frequently utilized as a Cys sensor owing to high affinity of the thiol group to gold. However, the presence of additional materials, such as stabilizers, can impact the sensitivity of this sensor. Herein, pH-sensitive gold nanoparticles (Au-PDA) were synthesized using poly (N,N-dimethylaminoethyl methacrylate) (PDMAEMA) for the purpose of Cys detection based on the aggregation size-dependent optical property of gold nanoparticles. Detection of cysteine was also followed by UV–Vis analysis, showing a decrease in intensity of localized surface plasmon resonance (LSPR) peak, a red shift from 525 to 550 nm as well as the appearance of a new peek at 650 nm. To enhance sensor performance, systematic investigations were conducted to optimize sensing conditions, focusing on pH, gold concentration, and ionic strength of the medium. Remarkably, the proposed sensor exhibited excellent selectivity towards Cys compared to other amino acids. The sensitivity of the sensor was evaluated using two methods: changes in the absorption intensity and the LSPR shift. The pH-sensitivity of PDMAEME led to a significant improvement in sensing parameters through a synergistic effect on the Au-Cys interaction, leading to a remarkably low LOD of 0.0004 nM, which is the lowest ever reported LOD for detection of Cys. Finally, practical application of the proposed sensor was validated in human blood serum.

Seedless synthesis of Au nanoplates with tunable plasmonic peaks

Au nanoplates with tunable in-plane dipolar localized surface plasmon resonance peaks in a broad range from the visible to near-infrared region were obtained in high yield using a seedless wet chemical growth method after purification. Cetyltrimethylammonium chloride was used as a surfactant, while hydrogen peroxide and sodium borohydride were used as the weak and strong reducing agents, respectively. The edge length and in-plane dipolar localized surface plasmon resonance peak of the Au nanoplates could be adjusted by varying the amounts of hydrogen peroxide and sodium borohydride. The Au nanoplates were further used as the saturable absorber to generate pulsed laser output in a passively Q-switched solid-state laser at approximately 2 µm. Our study offers a new method for obtaining Au nanoplates with tunable plasmonic peaks over a broad range.

Precision Loading and Delivery of Molecular Cargo by Size-Controlled Coacervation of Gold Nanoparticles Functionalized with Elastin-like Peptides.

Thermoresponsive elastin-like peptides (ELPs) have been extensively investigated in biotechnology and medicine, but little attention has been paid to the process by which coacervation causes ELP-decorated particles to aggregate. Using gold nanoparticles (AuNPs) functionalized with a cysteine-terminated 96-repeat of the VPGVG sequence (V96-Cys), we show that the size of the clusters that reversibly form above the ELP transition temperature can be finely controlled in the 250 to 930 nm range by specifying the concentration of free V96-Cys in solution and using AuNPs of different sizes. We further find that the localized surface plasmon resonance peak of the embedded AuNPs progressively red-shifts with cluster size, likely due to an increase in particle-particle contacts. We exploit this fine control over size to homogeneously load precise amounts of the dye Nile Red and the antibiotic Tetracycline into clusters of different hydrodynamic diameters and deliver cargos near-quantitatively by deconstructing the aggregates below the ELP transition temperature. Beyond establishing a key role for free ELPs in the agglomeration of ELP-functionalized particles, our results provide a path for the thermally controlled delivery of precise quantities of molecular cargo. This capability might prove useful in combination photothermal therapies and theranostic applications, and to trigger spatially and temporally uniform responses from biological, electronic, or optical systems.

Near-Infrared Dual-Band LSPR Coupling in Oriented Assembly of Doped Metal Oxide Nanocrystal Platelets.

Coupling effects of localized surface plasmon resonance (LSPR) represent an efficient means to tune the plasmonic modes and to enhance the near-field. While LSPR coupling in metal nanoparticles has been extensively explored, limited attention has been given to heavily doped semiconductor nanocrystals. Here, we investigate the LSPR coupling behavior of Cs-doped tungsten oxide (CsxWO3-δ) nanocrystal platelets as they undergo an oriented assembly into parallel stacks. The oriented assembly was achieved by lowering the dispersion stability of the colloidal nanoplatelets, of which the basal surface was selectively ligand-functionalized. This assembly induces simultaneous blue-shifts and red-shifts of dual-mode LSPR peaks without compromising the intensity and quality factor. This stands in contrast to the significant damping, broadening, and overall red-shift of the LSPR observed in random assemblies. Computational simulations successfully replicate the experimental observations, affirming the potential of this coupling phenomenon of near-infrared dual-mode LSPR in diverse applications including solar energy, bio-optics, imaging, and telecommunications.

Localized surface plasmon resonance sensing of Trenbolone acetate dopant using silver nanoparticles

In this work, localized surface plasmon resonance (LSPR) sensing as applicable in the detection of Trenbolone acetate dopant is demonstrated. We show that the LSPR of the Trenbolone acetate/silver nanoparticle (Tren Ac/AgNPs) complex is sensitive to changes in the adsorbent concentration. The results show an average redshift of + 18 nm in the LSPR peak with variations in intensity and broadening behavior of the LSPR band of the Tren Ac/AgNPs complex. AgNPs were synthesized using laser ablation in liquid (LAL) technique with water as the solvent. UV–Vis spectroscopy was used for absorbance measurements and particle size and morphology were monitored using scanning electron microscopy (SEM). The aggregation behavior of the Tren Ac/AgNPs complex was monitored using energy-dispersive X-ray spectroscopy (EDS). Molecular Electrostatic Potential (MEP) and the HOMO–LUMO orbitals of the optimized Trenbolone acetate structure were obtained using Density Function Theory (DFT). The molecule was optimized at the B3LYP level of theory using the 6–311 basis set carried out using the Gaussian 09 software package. The results showed that O2− is Trenbolone acetate’s active site that would interact with Ag+ to form a complex that would influence the plasmon behavior. The results presented in this work demonstrate the feasibility of LSPR for anabolic androgenic steroid detection.

Remarkable emission enhancement of CsPbBr3 quantum dots based on an Ag nanoparticle-Ag film plasmonic coupling structure.

All-inorganic halide perovskite quantum dots (QDs) have recently received much attention due to their excellent optoelectronic properties. And their emission properties still need to be improved for further applications. Here, we demonstrated a remarkable emission enhancement of the CsPbBr3 QDs based on an Ag nanoparticle-Ag film plasmonic coupling structure. Through precise control of the gap distance between Ag nanoparticle and Ag film, the localized surface plasmon resonance (LSPR) peak was tuned to match the emission wavelength of the CsPbBr3 QDs. We achieved a 30-fold fluorescence intensity enhancement and a lower lasing threshold, which is 25% of that of the CsPbBr3 QDs without plasmonic coupling structure. It is attributed to that the plasmonic coupling structure exhibits an extremely strong local electric field owing to the coupling between LSPR of Ag nanoparticle and surface plasmon polariton of Ag film. This work provides an effective way to enhance the optical emission of perovskite QDs and promotes the further exploration of on-chip light source.

Localize surface plasmon resonance of gold nanoparticles and their effect on the polyethylene oxide nanocomposite films

Colloidal Gold nanoparticles (AuNPs) with sodium citrate coating were successfully synthesized using a chemical reduction method with an average spherical size of about 20 nm dispersed in the water with high stability. The localized surface plasmon resonance (LSPR) peak was studied by experimental measurement and Mie theory. The absorbance spectrum of AuNPs exhibits a fingerprint peak in the 500–600 nm range, corresponding to the LSPR of AuNPs. Moreover, PEO/AuNPs nanocomposite films with different concentrations of AuNPs were also prepared to evaluate the effect of LSPR of AuNPs on the electrical conductivity and photoconductivity of nanocomposite films. The degree of crystallinity (Xcrys) and melting enthalpy (ΔHm) increase as the AuNPs content in the polymer matrix increases up to 0.5 wt% due to the enhanced nucleation points. The electrical conductivity of pure PEO film is 1.93×10−6 S.cm−1. Increasing the AuNPs concentration to 0.5 wt% in the PEO matrix leads to an increase in the electrical conductivity to 2.28×10−3 S.cm−1 as AuNPs.

A portable intelligent hydrogel platform for multicolor visual detection of HAase.

Hyaluronidase (HAase) is an important endoglycosidase involved in numerous physiological and pathological processes, such as apoptosis, senescence, and cancer progression. Simple, convenient, and sensitive detection of HAase is important for clinical diagnosis. Herein, an easy-to-operate multicolor visual sensing strategy was developed for HAase determination. The proposed sensor was composed of an enzyme-responsive hydrogel and a nanochromogenic system (gold nanobipyramids (AuNBPs)). The enzyme-responsive hydrogel, formed by polyethyleneimine-hyaluronic acid (PEI-HA), was specifically hydrolyzed with HAase, leading to the release of platinum nanoparticles (PtNPs). Subsequently, PtNPs catalyzed the mixed system of 3,3',5,5'-tetramethylbenzidine (TMB) and H2O2 to produce TMB2+ under acidic conditions. Then, TMB2+ effectively etched the AuNBPs and resulted in morphological changes in the AuNBPs, accompanied by a blueshift in the localized surface plasmon resonance peak and vibrant colors. Therefore, HAase can be semiquantitatively determined by directly observing the color change of AuNBPs with the naked eye. On the basis of this, the method has a linear detection range of HAase concentrations between 0.6 and 40 U/mL, with a detection limit of 0.3 U/mL. In addition, our designed multicolor biosensor successfully detected the concentration of HAase in human serum samples. The results showed no obvious difference between this method and enzyme-linked immunosorbent assay, indicating the good accuracy and usability of the suggested method.

Plasmonic sensing: FDTD calculations to interpret experimental LSPR water adsorption isotherms

Finite-Difference Time-Domain (FDTD) calculations are widely used to interpret experimental Localized Surface Plasmon Resonance (LSPR) spectra. With FDTD it is possible to predict the physical parameters of the nanostructures that will theoretically give the best experimental LSPR signals. This information is crucial for optimizing sample fabrication and saving significant time. FDTD is also essential to control and calibrate various parameters of the nanostructures and to understand effects such as a Cr adhesion layer and LSPR sensor size distribution. Finally, for water adsorption sensing, FDTD confirms that the LSPR peak shift strictly follows Campbell’s model, even at submonolayer coverage.

Microstrain effects of laser-ablated Au nanoparticles in enhancing CZTS-based 1 Sun photodetector devices.

Copper zinc tin sulfide (CZTS) thin films were synthesized on soda lime glass using pulsed laser deposition (PLD) at room temperature. Introducing gold nanoparticles (AuNPs) in a sandwich structure led to increased CZTS particle size and a shift in the localized surface plasmon resonance (LSPR) peak of the AuNPs, influenced by different laser energy levels. The absorption measurements revealed intriguing behavior across the visible and near-infrared (NIR) regions, making these films appealing for 1 Sun photodetectors. Furthermore, the presence of AuNPs in the sandwich structure reduced microstrain effects, measuring 1.94 × 10-3 compared to 3.38 × 10-3 in their absence. This reduction directly enhances carrier transport, which is particularly beneficial for accelerating the performance of photodetector devices. This effect of AuNPs also contributed to higher dielectric coefficients, further improving the photodetector performance. Under 1 Sun illumination conditions, this enhancement resulted in a rapid rising time of 95.4 ms, showcasing the potential for faster photodetection.

Experimental and Theoretical Screening of Core Gold Nanoparticles and Their Binding Mechanism to an Anticancer Drug, 2-Thiouracil.

This study demonstrated the capability of two readily available optical spectroscopy tools, namely UV-Vis absorption spectrophotometry and Raman/surface-enhanced Raman spectroscopy, to select in a rapid and noninvasive manner the most homogenous gold nanoparticle (AuNP) models and to identify their chemical binding mechanism to 2-thiouracil (2-TU). 2-TU is an anticancer drug of great promise in the antiproliferative and photothermal therapies of cancer. The citrate-capped AuNPs emerged as the most stable as well as time- and cost-effective AuNP model out of the three widely used colloidal nanocores (citrate-, borohydride-citrate-, and sodium dodecyl sulfate (SDS)-capped AuNPs) that were examined. 2-TU chemically attached to the relatively monodispersed AuNPs via a chemisorption mechanism. The 2-TU-AuNPs complex formed through the covalent bonding of the S atom of 2-TU to the nanosurface in a vertical orientation. The spectroscopic results were then confirmed with the help of density functional theory (DFT) calculations and other physicochemical characterization tools for nanomaterials such as transmission electron microscopy (TEM), dynamic light scattering (DLS), and zeta potential. Overall, the purified 2-TU-AuNPs were found to be spherical, had an average diameter of 25 ± 2 nm, a narrow size distribution (1-30 nm), a sharp localized surface plasmon resonance (LSPR) peak at 525 nm, and a negative surface charge (-14 mV).

A dual-signal output plasmonic sensor based on glucose oxidase-triggered etching of triangular silver nanoprism for sensitive detection of fumonisins

A dual-signal output plasmonic sensor based on glucose oxidase (GOx)-triggered etching of triangular silver nanoprisms (TAgNPRs) was developed for detecting fumonisins (FBs). In the sensor, glucose oxidase (GOx)-FB1 conjugation was used as competitive antigens that compete with FBs to bind with anti-FBs monoclonal antibody (McAb) coated in microplate well. GOx catalyzed glucose to produce hydrogen peroxide (H2O2) which acted as an oxidant to etch TAgNPRs. As a result, the wavelength of localized surface plasmon resonance (LSPR) peak blue shifted along with a color change of the solution. The amount of FBs was correlated to the wavelength shift of LSPR peak and the color change of the solution from light blue to violet in a linear range of 0.1–500 ng/mL. The colorimetric and LSPR detection limits were 0.1 ng/mL and 0.06 ng/mL respectively. The sensitivity of the dual-signal output sensor is better than those of aggregation plasmonic sensor and magnetoimmunosensor.

Construction of the fiber optic LSPR sensor for highly sensitive detection of miR-103 by a dual signal enhancement strategy based on the hot-spot effect and HexSG4 catalysis

MicroRNAs are important tumor biomarkers. How to effectively detect them by sensors is a challenge because of their extremely low concentrations. We proposed a dual signal enhancement strategy to develop the fiber optic (FO) localized surface plasmon resonance (LSPR) sensor for the highly sensitive detection of miR-103. It included two stages, one was to obtain the hot-spot by constructing the multimer structure, AuNP-spacer- AuNPs, and another was the combination of capturing miR-103 by the probe and catalytic amplification by Hexagonal star G-quadruplex catalyzing 4-chloro-1-naphthol to generate benzo-4-chlorohexadienone, which deposited on the AuNPs, resulting in the generation of LSPR peak redshift. The parameters of the preparation and detection application were systematically optimized. The redshift values had a good linear relationship with the logarithms of miR-103 concentrations, with high R2 0.9973, wide detection range 102 - 107 fM, and low LOD 6.4 fM. The method had high specificity, repeatability, and reproducibility, and was also successfully validated with real samples. Therefore, the dual signal strategy for constructing FO LSPR sensors can achieve the high sensitivity detection of extremely low concentration of MicroRNAs, which will have great application prospects in medicine and life science.

Tuning Chemical Interface Damping: Competition between Surface Damping Pathways in Amalgamated Gold Nanorods Coated with Mesoporous Silica Shells.

The mechanism of mercury (Hg) amalgamation in gold nanorods coated with a mesoporous silica shell (AuNRs@mSiO2) and the effect of chemical treatments on the localized surface plasmon resonance (LSPR) spectral changes in single amalgamated AuNRs@mSiO2 remains unclear. In this study, we investigated Hg amalgamation and inward Hg diffusion in single AuNRs@mSiO2 without structural deformation via dark-field scattering spectroscopy and X-ray photoelectron spectroscopy. Then, we investigated the chemisorption of thiol molecules on single amalgamated AuNRs@Hg-mSiO2. Unlike previous studies on single AuNRs, the thiolation on single AuNRs@Hg-mSiO2 resulted in a redshift and line width narrowing of the LSPR peak within 1 h. To determine the chemical effect, we investigated the competition between two surface damping pathways: metal interface damping (MID) and chemical interface damping (CID). When we exposed amalgamated AuNRs@Hg-mSiO2 to 1-alkanethiols with three different carbon chain lengths for 1 h, we observed an increase in the line width broadening with longer chain lengths owing to enhanced CID, demonstrating the tunability of CID and LSPR properties upon chemical treatments. We also investigated the competition between the two surface damping pathways as a function of the time-dependent Au-Hg surface properties in AuNRs@Hg-mSiO2. The 24-h Hg treatment resulted in increased line width broadening compared to the 1-h treatment for the same thiols, which was attributed to the predominance of CID. This was in contrast to the predominance of MID under the 1-h treatment, which formed a core-shell structure. Therefore, this study provides new insights into the Hg amalgamation process, the effect of chemical treatments, competition between surface decay pathways, and LSPR control in AuNRs@mSiO2.

Green synthesis of silver nanoparticles (AgNPs) by Lallemantia royleana leaf Extract: Their Bio-Pharmaceutical and catalytic properties

The study of the silver nanoparticles (AgNPs) synthesis based-green methods become more interesting recently due to their low-cost preparation, eco-friendly and non-toxic precursors. The present study approved the ability of the Lallemantia royleana (Benth. in Wall.) Benth. leaf extract for the synthesis of AgNPs for the first time. The synthesized AgNPs were physico-chemical characterized using ultraviolet–visible spectroscopy (UV–Vis), X-ray diffraction (XRD), Fourier Transform-Infrared Spectroscopy (FT-IR), zeta potential and transmission electron microscopy (TEM) analysis. The total phenols, flavonoids, anthocyanin, tannin contents, antioxidant, antimicrobial, anti-inflammatory, anti-arthritic and cytotoxic activities of L. royleana leaf extract and the synthesized AgNPs were investigated. The biocatalytic activity of prepared AgNPs was assessed on methylene blue as a pollutant organic dye. The TEM examination showed that the synthesized AgNPs were predominantly spherical with some mixed shapes and crystalline with average size 34.47 ± 1.6 nm, and showed a localized surface plasmon resonance (LSPR) peak at 425 nm. The zeta potential value was −24.1 mV indicating the stability of produced AgNPs. The new prepared AgNPs have lower total phenols, flavonoids, anthocyanin, tannin contents than L. royleana leaf extract. In addition, the new prepared AgNPs demonstrated the higher DPPH radical scavenging activity (87 %) and the ABTS radical scavenging activity (77 %) at the maximum prepared concentration of 250 μg mL−1 as compared to the L. royleana leaf extract (62 % and 58 %, respectively). The produced AgNPs also exhibited the higher antimicrobial activity against both the Gram-positive (Staphylococcus aureus and Bacillus cereus) and the Gram-negative (Escherichia coli and Shigella flexneri) bacteria and the Candida strains (Candida glabrata and Candida albicans) as compared to the L. royleana leaf extract. The resulting AgNPs indicated a dose-dependent anti-inflammatory effect on human red-blood cell (RBC) membrane stabilization assay and had more activity (72 %) compared to the L. royleana leaf extract (61 %) at 250 µg mL−1. The prepared AgNPs showed promising in vitro anti-arthritic activity evaluated by 73 % compared to 58 % in case of L. royleana leaf extract. The new produced AgNPs showed the higher cytotoxic effect against the human hepatoma (Hep-G2) and the human breast (MCF-7) cancer cells compared to the L. royleana leaf extract with 79.3 % and 77.2 % at 250 µg/mL, respectively. The obtained results revealed also that the green synthesized AgNPs were capable to catalyze MB dye. Therefore, the obtained results provide a promising route of the green synthesis of AgNPs using L. royleana leaf extract with considerable biopharmaceuticals and catalytic applications.

Dual signal AA detection based on fluorescence and local surface plasmon resonance absorption technology

The core/shell Au@MnO2 nanoparticles (Au@MnO2 NPs) were prepared and characterized by UV–vis spectrum, transmission electron microscopy (TEM) and X-ray photoelectron spectrum (XPS). It was found that MnO2 in the shell of Au@MnO2 NPs could oxidize thiamine (VB1) into blue fluorescent thiochrome (TC). The reduction of MnO2 in the shell layer could lead to a decrease of Au@MnO2 NPs size along with a blue shift of the localized surface plasmon resonance (LSPR) peak. Once ascorbic acid (AA) was introduced, MnO2 in the shell was rapidly reduced to Mn2+ ions. Accordingly, the oxidation of VB1 was inhibited and the fluorescence of TC was weakened. Based on these phenomena, we have established a dual signal method for AA determination with the help of UV–vis and fluorescence spectrophotometer. Under the optimum conditions, the LSPR absorption peak shift (Δλ) of Au@MnO2 NPs and the decrease in fluorescence of TC correlated well with AA concentration ranging from 0.75 to 17.5 μM. The detection limits of LSPR absorption assay and fluorescence assay were 0.18 and 0.47 μM, respectively. More importantly, this dual-signal detection method has been used for the determination of AA in vitamin C tablets with high accuracy and precision, indicating its promising potential applications.

Tightly focused linearly and radially polarized beam effect on the LSPR peak with varying particle size

Interactions of gold and silver spherical nanoparticles (NPs) of a wide range of radius size with tightly focused beams are investigated for a wide range of wavelengths. The scattering of tightly focused beams with a single NP of varying size is examined using a generalized Mie theory and average intensity enhancement in the near-field due to localized surface plasmons is examined for different tightly focused beams. A multipole expansion approach is used to observe the contribution of modes in shaping the scattered light intensity. Influence of particle size and tightly focused beam on intensity enhancement factor is investigated and a shift in localized surface plasmon resonance (LSPR) peak towards higher wavelength is observed with increasing particle size. Maximum intensity enhancement factor due to scattering of different incident beams by a metallic NP is theoretically examined and reported. Gold and silver NP having radius size ranging from 30–60 nm and 1–15 nm respectively showed a maximum intensity enhancement factor in different media. A significant enhancement for the tightly focused radially polarized beam is observed for gold and silver NPs of radius size between 50 nm and 100 nm. Variation towards higher wavelength in LSPR peak due to involvement of higher order of multipoles, and the surrounding medium are also examined in detail.

Elevating Second Near-Infrared Photothermal Conversion Efficiency of Hollow Gold Nanorod for a Precise Theranostic of Orthotopic Bladder Cancer.

The second near-infrared (NIR-II) window laser-activated agents have attracted broad interest in an orthotopic cancer theranostic. However, developing NIR-II photothermal agents (PTAs) with advanced photothermal conversion efficiency (PTCE) and tumor-specific response elevation remains a crucial challenge. Herein, a hollow gold nanorod (AuHNR) with a strong localized surface plasmon resonance (LSPR) peak in the NIR-II window was coated with MnO2 and chitosan to obtain AuHNR@MnO2@CS (termed AuMC) by a one-step method. Upon exposure to the tumor microenvironment (TME), the overexpressed GSH triggered degradation of the MnO2 layer to release Mn2+ and resulted in the PTCE elevation owing to exposure of the AuHNR. Consequently, photoacoustic and magnetic resonance imaging for accurate diagnosis, Mn2+-mediated chemodynamic therapy, and AuHNR elevating PT therapy for precise treatment could be achieved. Both in vitro and in vivo experiments confirmed the good performance of the AuMC on an orthotopic bladder cancer precise theranostic. This study provided NIR-II activated, TME-response PT conversion efficiency enhanced PTAs and offered a tumor-selective theranostic agent for orthotopic bladder cancer in clinical application.

Surface acoustic wave-tuned plasmonic resonances in liquid crystal-covered gold nanostructures

In this work, we propose an acoustically tunable plasmonic device based on liquid crystal (LC)-covered gold nanostructures. By utilizing the standing surface acoustic waves (SSAWs) to realign LC molecules, one can effectively tune the effective refractive index of LCs, and subsequently tune localized surface plasmon resonances (LSPRs) of the gold nanostructures. A 15 nm blue shift of the LSPR peak with the driving voltage of 400 mVpp is experimentally observed. Upon removal of the applied SSAWs, the LC molecules can return to their original orientation, and so does the LSPR peak. Besides the excellent reversibility, this active plasmonic device also features low power consumption and easy integration, which could find many potential applications including switches, modulators, and couplers.