Surface Plasmon Resonance Spectra Research Articles

Single-Particle Spectroelectrochemistry: Revealing the Electrochemical Tuning Mechanism of Chemical Interface Damping in 1,2-Benzenedithiol-Adsorbed Single Gold Nanorods.

Chemical interface damping (CID) is a newly proposed plasmon damping pathway based on interfacial hot-electron transfer from metal to adsorbate molecules. However, achieving in situ tunability of CID in single gold nanorods (AuNRs) remains a considerable challenge. Here, we present the CID effect induced by benzene 1,2-dithiol (BDT) molecule adsorption on single AuNRs and the effective electrochemical tunability of CID in BDT-adsorbed AuNRs immobilized on an indium tin oxide (ITO) surface. Manipulations of the electrochemical potential alter the electron density of AuNRs, thereby influencing and tuning the localized surface plasmon resonance (LSPR) spectrum, with cathodic potential blueshifting and anodic potential redshifting. The strong adsorption of BDT on Au induced CID in single AuNRs. The potential-induced LSPR scattering spectra of BDT-adsorbed AuNRs for linear potential sweep showed a stable LSPR spectral response, irrespective of the concentrations of BDT molecules. Due to the involvement of two Au-S bonds, BDT molecules have a higher free adsorption energy and a lower desorption rate on the Au surface. This resulted in a stable LSPR spectral response for a linear electrochemical potential sweep. Furthermore, a constant anodic and cathodic potential application showed the tunability of the CID at the BDT-Au interface.

Dual-Mode Sensing of Fe(III) Based on Etching Induced Modulation of Localized Surface Plasmon Resonance and Surface Enhanced Raman Spectroscopy.

Convenient, rapid, highly sensitive and on-site iron determination is important for environmental safety and human health. We developed a sensing system for the detection of Fe(III) in water based on 7-mercapto-4-methylcoumarine (MMC)-stabilized silver-coated gold nanostars (GNS@Ag@MMC), exploiting a redox reaction between the Fe(III) cation and the silver shell of the nanoparticles, which causes a severe transformation of the nanomaterial structure, reverting it to pristine GNSs. This system works by simultaneously monitoring changes in the Localized Surface Plasmon Resonance (LSPR) and Surface-Enhanced Raman Spectroscopy (SERS) spectra as a function of added Fe(III). The proposed sensing system is able to detect the Fe(III) cation in the 1.0 × 10-5-1.5 × 10-4 M range, and its selectivity of the GNS@Ag@MMC sensor toward iron has been verified monitoring the LSPR and the SERS response to other cations with a clear selectivity toward Fe(III).

Optical fiber sensor based on magneto-optical surface plasmon resonance with ultra-high figure of merit

Compared to surface plasmon resonance (SPR), the sensors based on the magneto-optical SPR (MOSPR) technique have much higher figure-of-merit (FOM). However, there are no reports about applying MOSPR in the optical fiber structure now. In this work, a novel D-shaped optical fiber sensor based on the MOSPR technique is proposed. The D-shaped optical fiber is coated with a thin silver film and a magneto-optical (MO) material film of Cerium-doped Yttrium-Iron garnet (CeYIG). By applying a magnetic field on the sensing region, the magneto-optical Kerr effect (MOKE) of the CeYIG layer and the related MOSPR phenomenon could be excited when appropriate light is transmitted in the proposed optical fiber sensor. The influence of the structural parameters including the residual cladding thickness, silver and MO material film thicknesses are analyzed theoretically by the finite element method (FEM). With the optimal parameters, the sensor achieves the sensitivity of 5304 nm RIU−1. Since the peak width of MOSPR spectra is much narrower than that of the SPR spectra, the FOM of the sensor is largely enhanced to 3864 RIU−1 on average and 13260 RIU−1 in maximum, which surpasses the optical fiber SPR sensors vastly. The miniaturized and simple design of the D-shaped optical fiber MOSPR sensor, coupled with the ultra-high FOM, offers itself great potential in biochemical sensing applications.

Real-Time Plasmonic Strain Sensors Based on Surface Relief Diffraction Gratings.

Large-scale diffraction gratings were fabricated in surface relief on azobenzene thin films and transferred to flexible PDMS substrates using soft lift-off lithography. The PDMS gratings were strained along the grating vector axis and the resulting surface topography was analyzed using diffraction angle measurements, AFM imagery and surface plasmon resonance (SPR) spectra. All measurement methods exhibited a linear response in strain indicating the useability of these sensors in real-world applications. For SPR-based strain sensing, an increasing pitch and a decreasing modulation depth were observed with increasing strain. The SPR peak shifted by ~1.0 nm wavelength and the SPR intensity decreased by ~0.3 a.u. per percentage of applied strain. The tested PDMS samples retained their integrity even after multiple cycles of stretching and relaxation, making them a suitable strain sensor.

Phytochemical Investigation and Characterization of Azadirachta Indica-Mediated Silver Nanoparticles and Their Potential as Antibacterial and Antidiabetic Agents

In this study, we report the synthesis of silver nanoparticles (AgNP’s) by reducing silver ions from a solution of silver nitrate with an aqueous extract from Azadirachta indica. Using silver ions as the catalyst, nanoparticles were formed in 8[Formula: see text]min without the use of toxic chemicals. As evidenced by UV-vis spectroscopy, a broad surface plasmon resonance spectrum at 225[Formula: see text]nm was detected, which indicates the colloidal solution of silver nanoparticles is stable and produces silver nanoparticles. As revealed by the fourier transform-infrared spectrometer (FTIR) analysis, the flower extract contained a variety of biomolecules that acted as capping and reducing agents for the synthesis of AgNPs. As determined by X-ray diffraction (XRD), silver nanoparticles displayed a crystalline structure and ranged in size from 18 to 39[Formula: see text]nm. In addition to these findings, transmission electron microscopy (TEM) images showed that the silver nanoparticles were spherical and rod-shaped, as confirmed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDAX). A variety of pathogenic bacteria, such as Klebsiella pneumoniae, Escherichia coli, Bacillus subtilis and Staphylococcus aureus, were tested against AgNP’s antibacterial properties. A significant inhibition zone was observed for Escherichia coli when AgNPs were applied at different concentrations. Silver nanoparticles were shown to have antidiabetic effects through a diphtheria assay with inhibition rates ranging from 31.09% to 83.33% for concentrations of 50–250[Formula: see text][Formula: see text]g/mL. As researchers seek natural sources of compounds with potential health benefits, silver nanoparticles were also investigated for their antioxidant properties.

In situ monitoring of thin alumina passive film growth by surface plasmon resonance (SPR) during an electrochemical process

This article presents a sensing technique to characterize the growth of an alumina passive film on an aluminum micro structured layer in situ. The technique uses surface plasmon resonance (SPR) on aluminum coated gratings with spectroscopic measurements during electrochemical polarization in 0.02M Na2SO4. The structure of the sensor was first simulated and then fabricated by photolithography. The grating was then replicated by nanoimprint (NIL) in Sol–Gel before pure aluminum layer was deposited by RF magnetron sputtering to produce the samples used in this study. Coupled plasmonic and electrochemical measurements confirmed the feasibility of in situ characterization (thickness) of alumina passive film on aluminum-based gratings in neutral aqueous media. Combining both measurements with an appropriated SPR spectrum fitting lead to alumina thickness monitoring within a few nanometers’ accuracy. The objectives and challenges of this study are to better characterize the alumina growth during electrochemical process combining in situ electrochemical process and SPR spectra in order to determine thin passive layer characteristics.

Temperature self-compensated fiber-optic Pb(II) sensor with improved selectivity by Resorcylaldehyde post-modified organic metal framework

Post-modification of metal-organic framework (MOF) materials is an effective means to enhance their efficient and selective adsorption for heavy metal ions. In this article, we presented a reflection-type optical fiber surface plasmon resonance (SPR) sensor based on dual core fiber (DCF) coated with UiO-66-RSA (UiO-66-NH2 post-modified with resorcinol aldehyde) film for the specific detection of Pb(II) in aqueous media. The composite material UiO-66-RSA exhibits stronger affinity and specificity for Pb(II) than UiO-66-NH2. The adsorption of Pb(II) can change the equivalent refractive index (RI) of UiO-66-RSA film, causing a regular shift in SPR spectra. Experiments have shown that the limit of detection (LOD) of the SPR Pb(II) sensor can reach 0.1 nM. Meanwhile, research has found that the SPR sensor is accompanied by temperature crosstalk of 0.356 nm/°C. Therefore, we constructed a Michelson temperature interferometer using polymer micro tips on the end face of the fiber core to achieve temperature compensation. Based on the above two sensing channels, dual parameter demodulation of Pb(II) concentration and temperature can be achieved with an error rate of less than 0.5 %. This article has potential research value in exploring the application of post modification techniques of MOF in fiber optic lead ion detection.

Reflective optical fiber SPR sensor with DNA modification for high-sensitive Hg2+ concentration measurement

A reflective optical fiber surface plasmon resonance (SPR) sensor was proposed to measure the concentration of mercury ions (Hg2+). The specific single-stranded DNA was modified on the optical fiber sensing surface coated with Au film by the combination of covalent bond and charge adsorption. The Hg2+ can mismatch with T-T (thymine-thymine) base pairs in single-stranded DNA to form T-Hg2+-T structure, which led to the change of refractive index in sensing area and the wavelength shift of SPR spectrum. The measurement results showed that when the concentration of Hg2+ increased from 0 μM to 13 μM, the resonance spectrum shifted by 14.26 nm. In the linear range between 1–8 μM, the measurement sensitivity of the sensor could reach 1.51 nm/μM. The limit of detection (LOD) was found to be 0.28 μM. Besides, the sensor showed good stability, selectivity and reusability.

Ammonia-trapping multilayer polymer urease film amplifier coated surface plasmon resonance sensor for ultra-sensitive urea detection

In this paper, we have developed a new urea signal amplification technology based on a multilayer urease polymer film self-assembly structure for the first time, enabling the realization of ultra-accurate urea optical detection. We demonstrate the effectiveness of this technique based on surface plasmon resonance (SPR) platform. When the urea signal amplifier is combined with SPR sensors, multilayer urease polymer film contacts with urea molecules, the urea molecules are oxidated into NH3 and CO2, causing the pH increase, which weakens the electrostatic interaction between different polymer layers and induces the RI reduction of the multilayer urease film, thereby causing the shift of the SPR spectrum. Experiment results confirm that urea sensitivity has been improved 12-fold, and the limit of detection (LOD) has been optimized to less than 10−3 mmol/L. Furthermore, the anti-interference has been improved 22.8-fold and is kept even the interference signal strength increases by 100 times. Moreover, multilayered urease polymer leads to the increase of urease on the sensor surface, thus expanding the detection range of urea by 3.5 times. This provides a new way to solve the contradiction between high sensitivity and large measurement range of optical fiber biosensor. Importantly, the concept of using enzyme-loaded polymer films for signal amplification can be adapted for the detection of various other biomolecules by replacing the enzyme with a specific recognition element for the target molecule. This opens doors for developing highly sensitive and specific biosensors for diverse applications in healthcare, environmental monitoring, and food safety.

Synthesis of carbon quantum dots from waste Phaseolus vulgaris for the development of a fluorescence sensing probe to detect plasticizer in cookies

Dibutyl phthalate (DBP) is a commonly used plasticizer in the fabrication of various packaging materials, however upon exposure, it poses significant health and environmental hazards. These plasticizers consist of low-molecular-weight components, which permeate easily into the food matrix. Hence, the development of a cost-effective detection technique is necessary for the detection and monitoring of DBP. Therefore, this research focuses on the utilization of broken Phaseolus vulgaris-derived carbon quantum dots (PV-CQDs) as a fluorescent probe for the detection of DBP in cookies. Herein, PV-CQDs were synthesized through a hydrothermal reaction, which exhibited a blue color under UV-luminescence and localized surface plasmon resonance spectrum at 238 and 270 nm. The highest fluorescence emission intensity was recorded at 428 nm. The resulting PV-CQDs exhibited an average particle size of 1.22 ± 0.05 nm and prominent peaks obtained during infrared spectroscopy were found to be of carboxylic and hydroxyl functional groups, respectively. Transmission electron microscopy and energy dispersive spectroscopy analyses confirmed the spherical morphology and elemental composition, which include C (58.05% by weight) and O (41.92% by weight), respectively. The topographical height profile of the PV-CQDs was observed by atomic force microscopy and it was found to be approximately 100 µm with a thickness of 2.9 µm . The inherent fluorescence of CQDs demonstrated notable quenching efficiency when exposed to varying concentrations of 0.1, 0.2, 0.3, 0.4, 0.5, 1, 5, and 10 µM of DBP residue, resulting in a linear relationship with a high detection sensitivity of 3.19634 µM. Furthermore, the developed method was successfully implemented to determine DBP in cookies, achieving recovery rates within the range of 97–99%. Thus, the rapid sensing capabilities of CQDs could be highlighted as their promising potential for the detection of DBP in food products.

Penicillium oxalicum-mediated the green synthesis of silica nanoparticles: characterization and environmental applications

AbstractIn terms of biocompatibility, environmental friendliness, scalability, and cost-effectiveness, green nanoparticle (NP) synthesis is a modern area of nanotechnology that performs better than physical and chemical methods. The utilization of endophytic Penicillium oxalicum for the biogenesis of silica nanoparticles is the goal of the current work. The structural and optical properties of the fungal produced silica nanoparticles were investigated utilizing transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FTIR), x ray diffraction (XRD) and dynamic light scattering (DLS). All of the investigated parameters and their interactions were found to have a significant effect on the crystallite size, according to the results. The average diameter size of the biosynthesized SiO2-NPs was ranged between 20 -50 nm. The size of the biosynthesized SiO2-NPs was 28.7 nm, and their crystalline nature was confirmed by XRD, according to characterization results. A surface plasmon resonance spectrum of silica nanoparticles was obtained at 280 nm. Under UV light, Ribazol black b and Crystal violet dyes were photocatalytically degraded utilizing biosynthesized SiO2 nanoparticles. The highest decolorization percentage of Crystal violet and Ribazol black b was 94.1% ± 1.2% and 85.1% ± 0.93%, respectively after 90 and 120 min, for both crystal violet and Ribazol black b of incubation at 50.0 mg mL─1 of SiO2 nanoparticles. Furthermore, SiO2-NPs were successfully used more than once for biodegradation and that was regarded as its efficacy. Silica nanoparticles were used to remove Co, Pb, Cd, and Zn with percentages of 99.9% ± 1.2%, 99.9% ± 1.3%, 99.9% ± 1.3%, and 99.4% ± 1.4%, respectively. The phytotoxicity test was investigated by using Zea mays L seed which the root length increases to (28 ± 0.35) and (21 ± 0.51) cm, respectively when subjected tothe treated CV and Ribazole black b effluent... In conclusion, endophytic Penicillium oxalicum was used to successfully biosynthesize SiO2-NPs, which showed, phytotoxicity, heavy metal bioremediation, and photocatalytic activity against CV and Ribazol black b dye.

Study the Optical Properties of Noble Metal (Au, Ag, and Cu) Thin Film Biosensors Based on Surface Plasmon Resonance Performance by a Simulation Program

In this work, we studied the effect noble metal thicknesses, namely gold (Au), silver (Ag), and copper (Cu) on the surface plasmon resonance (SPR) characteristics for sensitive optical sensor and biosensor applications. SPR spectra for Au, Ag and Cu were widely studied in the Fresnel equation to calculate the total reflection, the wavelength ([Formula: see text] range from 500 nm to 700 nm with the angle of incidence ([Formula: see text] ranging from 0∘ to 90∘ and thickness of the film ([Formula: see text] reaching from 30 nm to 70 nm. Analysis simulation (in MATLAB) has been made for SPR of three metals placed on the N_LASF9 glass prism and the sensing medium is the air. The properties of the angle of resonance [Formula: see text] have been calculated from plotted reflectance via incident angle [Formula: see text]. The results give efficient detection in a change of reflection ([Formula: see text] and full half width maximum FWHM. The minimum reflection was obtained (0.003 a.u.) at wavelength 700 nm and thickness [Formula: see text]= 50 nm for gold Au at [Formula: see text] = 0.0. The best FWHM was recorded at the wavelength (500 nm) at thickness (70 nm) for silver at [Formula: see text] = 0.0, which was equal (0.1 nm).

Single-Particle Spectroelectrochemistry: Promoting the Electrocatalytic Activity of Gold Nanorods via Oxygen Plasma Treatment without Structural Deformation.

Understanding of the electrocatalytic activity enhancement in gold nanoparticles is still limited. Herein, we present the effect of the oxygen plasma treatment on the electrochemical activity of gold nanorods (AuNRs). Oxygen plasma treatment resulted in the blueshift and line width narrowing of the localized surface plasmon resonance (LSPR) spectra obtained from individual AuNRs immobilized on an indium tin oxide (ITO) surface. These changes can be attributed to increases in the surface charges of the AuNRs. The formation of a Au-ITO heterojunction provided structural stability to the immobilized AuNRs regardless of the duration of oxygen plasma exposure. The electrocatalytic oxidation of hydrogen peroxide (H2O2) was induced by increases in the free-electron densities on the surfaces of these AuNRs owing to oxygen plasma treatment, and Au did not dissolve under the experimental conditions. However, the potential-dependent LSPR spectra of the individual AuNRs showed similar patterns of LSPR behavior, irrespective of the duration of oxygen plasma treatment and the concentration of H2O2. Therefore, this study based on single-particle spectroelectrochemistry and cyclic voltammetry improves the understanding of the role of oxygen plasma treatment in promoting the catalytic activity of structurally stable AuNRs immobilized on an ITO surface.

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.

Biofabrication of Nanosilver From Punica granatum Peel Extract and Their Anticoagulant Applications.

For utilizing biodegradable waste as a natural source for nanofabrication, this study was designed to highlight a simple, sustainable, safe, environmentally friendly, and energy consumption reduction waste management approach using hot aqueous extract of Punica granatum (pomegranate) peel waste (PPE) to biosynthesize silver nanoparticles (PPE-AgNPs). The fabrication of biosynthesized nanosilver was confirmed by UV-visible spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and atomic force microscope (AFM). The initial pale brown color change upon adding silver nitrate to PPE confirmed bioreduction. For PPE, the absorption spectrum for UV-vis spectroscopy in the visible light region was 230-290 nm, while for PPE-AgNPs, the graph shows that surface plasmon resonance (SPR) spectrum for nanosilver at 360-460 nm. The XRD analysis proved that the PPE-AgNPs were crystalline in nature. The SEM micrograph revealed that silver nanoparticles were sphere-shaped, homogenous accumulations with particle size in the range of 21.63-30.97 ± 0.4 nm. The EDX data analysis also proved the presence of a sharp peak of silver element with 8.83% weight at 3 keV. The 3D AFM images of Ag nanoparticles illustrated that the diameter is around 7.20-14.80 nm with a median of 7.16 ± 1.3 nm and the root mean square (RMS) value corresponds to 1.40 ± 0.4 nm. The PPE-AgNPs efficiently exhibited a potent antioxidant and dose-dependent DPPH inhibition action. Visual and microscopic observations of fresh human blood when treated with 25, 50, 75, and 100 μg/mL of PPE-AgNPs were proven to be biocompatible with no morphological changes and no coagulation. This study predicts that PPE can be utilized to synthesize biocompatible nanosilver.

Optical enhancement of perovskite solar cells by metallic nano-patterns

The integration of metallic nanoparticles (MNPs) with plasmonic effects is an alternate approach for managing photons and charge carriers, and is considered a promising method for advancing solar cell technologies. Plasmonic-enhanced solar energy harvesting involves three mechanisms: hot-electron injection, light trapping, and modulation of energy flow direction through dipole-dipole coupling. These phenomena have been observed to significantly enhance the performance of silicon, gallium arsenide, dye-sensitized, and organic solar cells. However, for emerging perovskite solar cells, the light trapping effect, specifically, the far-field scattering via MNPs, has been seldom reported. The anomalous phenomenon is primarily attributed to the size constraints imposed on MNPs by the thickness of the functional layers in cell devices. According to the theory of localized surface plasmon resonance (SPR), the characteristic size of the MNPs needs to be larger than 90 nm to achieve optimal photon scattering. Conversely, charge transport layers like NiO<sub>x</sub> and SnO<sub>2</sub> in perovskite solar cells are typically thin, ranging from a few to several tens of nanometers in thickness. Therefore, the community of perovskite solar cells still faces a great challenge in harvesting light through plasmonic scattering.<br>Compared to MNPs, the shape, size, periodicity, and other characteristic parameters of two-dimensional metal patterns within the horizontal plane are not limited by the thickness of the device's functional layer, thus enabling a more flexible regulation of the SPR response band, vibration intensity, and dissipation method of plasmonic energy. In this study, based on the finite-difference time-domain (FDTD) method and rigorous coupled-wave analysis (RCWA), we systematically investigated the SPR spectra of different metal patterns. The results demonstrate that by optimizing characteristic parameters such as pattern shape, thickness, and periodicity, a significant SPR phenomenon can be observed in the near-infrared region, with scattering dominating over extinction. For the optimal metal ring pattern, the SPR peak corresponds to a wavelength of 772 nm, with relative absorption, scattering, and extinction cross-sections of 0.54, 1.39, and 1.93, respectively. The weighted average absorption of the perovskite response layer in the range of 700-850 nm increased from 53.61% to 65.36%. Correspondingly, the photocurrent density of the device increased from 20.39 to 22.72 mA/cm<sup>2</sup>, and the photoelectric conversion efficiency was relatively improved by 11.45%. This research provides a novel path for light trapping design in perovskite solar cells in the near-infrared region, and serves as a "spectrum-based" reference for SPR regulation in other similar devices.

Air-silica core microstructured optical fiber-based SPR sensor for temperature and refractive index measurement

We propose an air-silica core microstructured optical fiber-based surface plasmon resonance (SPR) sensor to simultaneously measure temperature and refractive index (RI). The sensing channel is formed by coating the outside of the fiber with a gold film and a polydimethylsiloxane (PDMS) layer as a temperature sensing medium, and then being immersed into the liquid analyte. The plasmon mode can penetrate through the PDMS layer and then into the analyte, therefore both the temperature and the analyte RI changings can lead to the variations of SPR spectra that will be measured. Our numerical results demonstrate that the proposed sensor can support two resonance peaks in the x-polarized core mode and one resonance peak in the y-polarized core mode, therefore providing two detection approaches, peak-based and polarization-based approaches. By measuring the two peaks in the x-polarized core mode, for the peak-based approach, the temperature coefficients are −2.077 nm/°C and −2.723 nm/°C, and the RI coefficients are 1252 nm/RIU and 1931 nm/RIU, respectively. While by measuring the second peak in x-polarized core mode and the peak in y-polarized core mode, for the polarization-based approach, the temperature coefficients are −2.723 nm/°C and −3.401 nm/°C, and the RI coefficients are 1931 nm/RIU and 2973 nm/RIU, respectively.

Click reaction-based single-particle dark-field microscopy: A visual platform for the highly sensitive and selective detection of pyrophosphatase

Inorganic pyrophosphatase (PPase) plays significant roles in diverse pathophysiological processes, therefore, developing a reliable method to measure PPase activity is crucial for the early diagnosis of the related diseases. In this work, a novel platform with single-particle dark-field microscopy (DFM), consisting of core gold nanoparticles (AuNPs), satellite AuNPs, pyrophosphate ions (PPi), copper ions (Cu2+), and sodium ascorbate (NaAsc), is designed for the selective and sensitive analysis of PPase according to a click reaction. After the introduction of PPase, the coordination between PPi and Cu2+ can be destroyed by catalyzing the hydrolysis of PPi to release free Cu2+ which can be reduced by NaAsc to produce cuprous ions (Cu+). Then the formed Cu+ promotes the click reaction between azide-modified core AuNPs and alkynyl-modified satellite AuNPs to cause the significant redshift of the localized surface plasmon resonance (LSPR) spectra of core AuNPs. Thus, PPase can be ultra-sensitively detected with a low detection limit of 0.003 U/L in a wide linear range from 0.01 to 1 U/L. This click reaction-based DFM technique can also be used to assess PPase inhibition, which suggests that it has a lot of potential for both the screening of PPase inhibitors and the diagnosis of PPase-related disorders.

Elucidating Surface Plasmon Damping and Fano Resonance Induced by Epitaxial Growth of Palladium on Single Gold Nanorods.

Plasmon damping and Fano resonance induced in the growth of palladium (Pd) on gold nanorods (AuNRs) have been poorly understood. Herein, we investigated the optical properties and morphologies of single AuNRs@Pd (core@shell) synthesized using epitaxial Pd growth at different Pd concentrations. The localized surface plasmon resonance (LSPR) spectra of single AuNRs@Pd showed characteristic subradiant and superradiant peaks as well as Fano resonance as a spectral dip, which was highly influenced by the Pd shell thickness. The occurrence of the Fano resonance during the Pd growth was further verified by in situ real-time observation experiments. We then elucidated time-dependent, real-time variations in LSPR peak wavelength, metal-induced surface damping, and Fano resonance mode of single AuNRs@Pd during Pd shell formation in three successive phases: Pd reduction, nucleation, and growth. Therefore, this study provides new insights into metal interface damping, the Fano resonance, and optical tunability by engineering the Fano resonance energy and Pd shell thickness.

The Effects of Thermal Annealing and Postirradiation on Silver Nanoparticle Films Fabricated by Pulsed Laser Deposition in the Flowless Open Air

Herein, Ag nanoparticle (NP) films are fabricated by pulsed laser deposition technique in the flowless atmospheric air. A Q‐switched Nd:YAG pulsed laser beam is used for the ablation process. The fabricated NP films are postirradiated by the pulsed laser beam. In addition, as‐deposited NP films are annealed in argon gas flow ambient for 45 min at different temperatures (250, 350, and 450 °C), and also annealed at 450 °C for 15, 30, and 45 min. The characteristics of fabricated NP films are investigated after postirradiating by pulsed laser beam, and thermal annealing in Ar gas flow. UV–vis absorption spectroscopy is utilized to provide surface plasmon resonance (SPR) characteristics of films. The results show that thermal annealing can lead to strong enhancement, and also narrowing of the SPR spectrum. The results of field emission scanning electron microscopy and atomic force microscopy show that the annealing and postirradiation processes can influence the NPs size and film structure. As an application, the fabricated film is utilized for surface‐enhanced Raman spectroscopy (SERS) using a 10−6 molar aqueous solution of Rhodamine 6G. The SERS results indicate that the annealed NP films become more sensitive than the as‐deposited films.