Silver Nanoprisms Research Articles

Influence of Sodium Borohydride Content on Triangular Silver Nanoprisms Dropped on Copper Hydroxide Nanowire-Based SERS Substrates

Influence of Sodium Borohydride Content on Triangular Silver Nanoprisms Dropped on Copper Hydroxide Nanowire-Based SERS Substrates

Colorimetric detection of platinum (IV) ions based on triangular silver nanoprism particles in aqueous environmental sample

Colorimetric detection of platinum (IV) ions based on triangular silver nanoprism particles in aqueous environmental sample

Plasmon-Exciton Interaction at the Nanoscale: Silver Is More "Precious" than Gold!

Predictive understanding of factors affecting plasmon-exciton coupling is crucial for the successful realization of the exciting potentials of plexcitonic nanostructures. Here, we systematically investigate the role of plasmonic metals in controlling the plasmon-exciton coupling strength. We use gold and silver nanoprisms, having identical LSPR maxima, as the plasmonic components and form two plexciton hybrids with the J-aggregates of a cyanine dye. Single-particle spectroscopy is employed to study and compare the abilities of gold and silver in influencing plasmon-exciton interaction at the nanoscale. Despite much faster plasmon dephasing than its gold counterpart, the silver nanoprism exhibits greater Rabi splitting. We reveal that the smaller plasmon mode-volume despite having larger physical volume, superior local electric-field enhancement, and smaller Ohmic losses compared to gold, enables the silver nanoprism to defy the pronounced plasmon decoherence effects and to show stronger plasmon-exciton coupling. These findings suggest that silver nanostructures should be the unequivocal choice over gold when "strong coupling" is desired for any application.

Unlocking Single Particle Anisotropy in Real‐Time for Photoelectrochemistry Processes at the Nanoscale

AbstractThe key to rationally and rapidly designing high‐performance materials is the monitoring and comprehension of dynamic processes within individual particles in real‐time, particularly to gain insight into the anisotropy of nanoparticles. The intrinsic property of nanoparticles typically varies from one crystal facet to the next under realistic working conditions. Here, we introduce the operando collision electrochemistry to resolve the single silver nanoprisms (Ag NPs) anisotropy in photoelectrochemistry. We directly identify the effect of anisotropy on the plasmonic‐assisted electrochemistry at the single NP/electrolyte interface. The statistical collision frequency shows that heterogeneous diffusion coefficients among crystal facets facilitate Ag NPs to undergo direction‐dependent mass transfer toward the gold ultramicroelectrode. Subsequently, the current amplitudes of transient events indicate that the anisotropy enables variations in dynamic interfacial electron transfer behaviors during photothermal processes. The results presented here demonstrate that the measurement precision of collision electrochemistry can be extended to the sub‐nanoparticle level, highlighting the potential for high‐throughput material screening with comprehensive kinetics information at the nanoscale.

Unlocking Single Particle Anisotropy in Real-Time for Photoelectrochemistry Processes at the Nanoscale.

The key to rationally and rapidly designing high-performance materials is the monitoring and comprehension of dynamic processes within individual particles in real-time, particularly to gain insight into the anisotropy of nanoparticles. The intrinsic property of nanoparticles typically varies from one crystal facet to the next under realistic working conditions. Here, we introduce the operando collision electrochemistry to resolve the single silver nanoprisms (Ag NPs) anisotropy in photoelectrochemistry. We directly identify the effect of anisotropy on the plasmonic-assisted electrochemistry at the single NP/electrolyte interface. The statistical collision frequency shows that heterogeneous diffusion coefficients among crystal facets facilitate Ag NPs to undergo direction-dependent mass transfer toward the gold ultramicroelectrode. Subsequently, the current amplitudes of transient events indicate that the anisotropy enables variations in dynamic interfacial electron transfer behaviors during photothermal processes. The results presented here demonstrate that the measurement precision of collision electrochemistry can be extended to the sub-nanoparticle level, highlighting the potential for high-throughput material screening with comprehensive kinetics information at the nanoscale.

Smartphone-based ratiometric fluorescence sensor for sensitive visual detection of H2O2 and glucose based on B-CDs-Ag NPRs-OPD ternary system

A straightforward and highly sensitive ratiometric fluorescence sensor comprising blue emissive carbon dots, silver nanoprisms, and o-phenylenediamine (B-CDs-Ag NPRs-OPD) was developed for the detection of H2O2 and glucose. Ag NPRs were etched into Ag+ ions upon exposure to H2O2, which caused non-fluorescent OPD to be oxidized and produce 2,3-diaminophenazine (DAP), resulting in intense yellow fluorescence emission at 555 nm. DAP can quench the B-CDs based on inner filter effect (IFE), leading to a decrease in their fluorescence intensity at 435 nm. Because glucose oxidase may catalyze the oxidation of glucose to produce H2O2, this approach can also be used to detect glucose. The unique triangular structure leads to the easy etching of the edge and tip of Ag NPRs by H2O2 into Ag+ ions, allowing for the high sensitivity of detection of H2O2 and glucose with limit of detection (LOD) of 0.12 μM and 0.6 μM, respectively. Furthermore, with the increase of the concentrations of H2O2 and glucose, a visible color shift from blue to yellow-green occurs, which can be detected using a smartphone's color recognition application that captures the RGB channel values of the image. Real-time and on-spot detection of H2O2 and glucose were achieved based on smartphone sensing platform, presenting vast potential for applications in various fields.

Site-Selective Plasmonic and Photonic Modulation of Galvanic Replacement Reaction between Silver Nanoprisms and Aqueous Chloroplatinate Ions

Site-Selective Plasmonic and Photonic Modulation of Galvanic Replacement Reaction between Silver Nanoprisms and Aqueous Chloroplatinate Ions

Photomediated synthesis of stabilizer-free silver nanoprisms with a tunable plasmon wavelength for enhanced catalytic activity

Herein, we introduce a simplified photomediated method for fabricating silver nanoprisms (AgNPrs) with controllable surface plasmon resonance. The Ag nanoparticles (Ag seeds), Ag+, and citrate ions were used to control AgNPrs growth. Citrate ions served as a reducing agent and a stabilizer. The optimized [citrate]/[Ag+] ratio of 10 was sufficient to stabilize the final AgNPrs. Sodium borohydride (NaBH4) was used as a strong reducing agent to generate the initial Ag seed amount, then controlled by the [BH4−]/[Ag+] ratio. A ratio of 0.0005–0.005 ([BH4−]/[Ag+]) yielded a 545–702 nm plasmon band of AgNPrs. AgNPrs displayed an irregular plate shape in their morphological structure, featuring lateral dimensions spanning from 30.7 ± 4.3 to 51.0 ± 10.8 nm and a thickness ranging from 7.2 ± 0.8 to 10.7 ± 1.3 nm. The synthesized AgNPrs exhibited excellent stability in the dark at 4 °C without any additional polymeric stabilizer and presented negligible variations in their absorbance UV–visible spectra for at least 1 month. They demonstrated an enormous (111) facet potentially serving as an active catalytic site for reducing 4-nitrophenol to 4-aminophenol. With synthesized AgNPrs, the rate constant of the reduction reaction increased to 0.2440 min−1, which was 120 times greater than that without the catalyst or with spherical Ag nanoparticles. These AgNPrs can be reutilized for at least five catalytic cycles without losing their catalytic efficiency.

Photoinduced Stitching of Self-Assembled Triangular Silver Nanoprisms at the Air-Water Interface.

This study investigates the influence of optical excitation on the self-assembly of triangular nanoprisms of silver into a continuous monolayer at the air-water interface. Langmuir monolayers of octadecylamine (ODA) have been used to electrostatically assemble citrate-capped silver triangular nanoprisms (AgTNPs) in the presence and absence of light. Under optical excitation, the nanoprisms were observed to assemble into a well-ordered monolayer through plasmon-mediated stitching, whereas the particles were merely in close contact during assembly in the dark. These findings suggest new avenues for tailoring particle properties through light-mediated assembly in two dimensions.

Elastic scattering of gold and silver colloids: Difference between spherical and nonspherical nanoparticles

Light scattering of noble metal nanoparticles was widely used in solar cells, sensing and spectroscopy, so the research on the light scattering itself will be beneficial for their increasing applications. In this paper, gold and silver nanoparticles with different sizes and shapes were synthesized and their elastic scattering was investigated. The results demonstrate that the elastic scattering of metal nanoparticles is influenced by their size and shape, and the scattering behavior has a specific correlation with the surface plasmon resonance. The elastic scattering spectra of gold and silver nanospheres basically cover the extinction spectra, indicating plasmon resonance enhanced scattering of spherical nanoparticles. The elastic scattering spectra of nonspherical gold nanorods and silver nanoprisms only overlap the extinction peaks at short wavelengths. The elastic scattering is considered to be enhanced by the transverse resonance bands at short wavelengths for nonspherical gold or silver nanoparticles, but it cannot be contributed by the longitudinal resonance bands at the corresponding long wavelengths. This result will be helpful in selecting size and shape in the scattering application of plasmonic metal nanoparticles.

One-drop micro-array towards accelerated optical quantification of dopamine in human biofluids using triangular silver nanoparticles: Smartphone-assisted biomedical analysis by colorimetric sensing and Lab-on-paper technology

Trace-level detection of Dopamine (DA) in human body fluids is crucial for diagnosing neurological disorders, understanding mental health, and advancing drug discovery, but found challenging with rapid and low-cost detection technologies. Herein, an innovative paper-based photochemical method has been developed for the detection of DA using triangular silver nanoprism (AgNPrs), as an optical nanoprobe, in human blood plasma and urine samples. The redox reaction between DA and AgNPrs was evaluated through a color change at two pHs (5.35and 6.14), which can be analyzed by UV–Vis spectrophotometry and microfluidic paper-based colorimetric device (µPCD) with low limit of quantification of 0.01 µM. This study presents pioneering work with the potential to inspire the development of simple and effective on-site semi quantifying recognition devices for other neurotransmitters, requiring only a lightweight piece of paper and a single drop of the necessary reagent.

Application of hyperspectral imaging and colorimetric sensor array coupled with multivariate analysis for quality detection during salted duck eggs processing

AbstractIn order to realize the evaluation of salted duck eggs quality, this study constructed salts‐sensitive colorimetric sensor array (CSA) based on silver nanoprisms (AgNPRs) etching principle and utilized hyperspectral imaging (HSI) system to capture the reflectance spectral of CSA and section of salted duck eggs. To minimize the noise in spectral signals, three preprocessing methods including Savitzky–Golay Smoothing (SG), standard normal variate (SNV) transformation, and multiplicative scatter correction were used. The competitive adaptive reweighted sampling and uninformative variables elimination were used to select the optimal wavelengths, and then partial least squares regression was used to predict moisture, lipid, and salt content (SC). Results demonstrated coefficients of determination of 0.8200, 0.8969, 0.8709, and 0.9239 for protein moisture, yolk moisture, yolk lipid, and protein SC. Visualization distribution maps successfully display the distribution of moisture and lipid content during salting periods. The results indicated that the CSA based on AgNPRs etching principle can be an effective tool in quantitative measurement of salt and HSI combining CSA can be applied to evaluate the quality of salted duck eggs comprehensively. The study offers a rapid detection method for the production and processing of salted duck eggs in the industry.Practical applicationA novel salts‐sensitive CSA was constructed to evaluate quality of salted duck eggs based on AgNPRs etching. This study designed and developed a portable sample collection device using 3D printing technology to acquire the information of samples and CSA at the same time. This study combined with HSI system and colorimetric sensor technology to evaluate the quality of salted duck eggs during the salting process.

Optimization of the Bulk Refractive Index Sensitivity of Silver NanoPrisms

AbstractThe sensitivity and optical properties of silver nanoprisms (triangular plates with round‐truncated corners) are investigated in this paper. Results of boundary element method simulations are compared with experimental results and literature data. Based on electron microscopy images of the synthesized nanoprisms, a single‐particle model is set up for simulations with three running parameters: edge length, thickness, and roundness (defined as the radius of the circumscribed circle divided by the edge length). These geometric parameters can be optimized during chemical synthesis to create sensors with improved sensitivity. The effect of biomolecular layers is also investigated. As a novel approach to improve the agreement between the simulated and experimentally measured extinction spectra, the single‐particle model is extended to consider the variation of the prisms' parameters in the form of distributions. The resulting extinction cross‐section spectra correspond well with the experimental data. The calculated bulk refractive index sensitivity is 670 nm/RIU (RIU stands for refractive index unit) for the single particle model (length = 150 nm, thickness = 10 nm, and roundness = 0.1), while (690 ± 5) nm/RIU for the extended model. The presented model and obtained relations between sensitivity and geometry can be effectively used to design and optimize the fabrication technologies for silver nanoprism‐based sensing applications.

One-pot synthesis of near-infrared absorbing silver nanoprisms via a simple photochemical method using an ultraviolet-C light source

This study describes a simple one-pot photochemical method to synthesize triangular silver nanoprisms (T-AgNPs), for which a mixture of silver nitrate (AgNO3) and citrate was irradiated with an ultraviolet-C (UVC) lamp reactor. We successfully synthesized T-AgNPs with edge lengths ranging from 50 to 150 nm, showing a significant localized surface plasmon resonance (LSPR) band over a wavelength of 1200 nm. This photochemical reaction appears to be unrestricted by plasmon resonance conditions, allowing for the formation of colloidal T-AgNPs with an LSPR band in the near-IR region. In addition, this new method does not require any highly reactive reducing agents or initially prepared silver seed solution. The reduction of Ag+ ions by citrate is induced by UVC light, and the nascent Ag first undergoes nucleation to form spherical or quasi-spherical silver nanoparticles (S-AgNPs). Subsequently, continuous irradiation with UVC light facilitates the transformation of these S-AgNPs into T-AgNPs. The growth kinetics of the nanoparticles with different reaction conditions were examined using ultraviolet–visible–near-infrared spectroscopy and transmission electron microscopy. This new method offers a simple, efficient, and cost-effective means to synthesize T-AgNPs with near-IR LSPR, contributing to wider applications in the fields of optoelectronics, spectroscopics, photovoltaics, etc.

Core-shell structured lignin-stabilized silver nanoprisms for colorimetric detection of sulfur ions

Widespread occurrence of sulfides in domestic and industrial wastewater contributes to environmental pollution and poses risks to human health. Therefore, the development of highly selective, sensitive, and rapid sulfur ion (S2−) detection probes in aquatic ecosystems is of paramount importance. In this study, lignin-stabilized silver nanoprisms (EHL@AgNPRs) were prepared using the seed growth and self-assembly methods. Based on this, a novel, high-performance, and environmentally friendly S2− colorimetric detection method was proposed. Lignin is believed to coat the surface of AgNPRs through cation-π and electrostatic interactions, acting as an excellent dispersant and stabilizer to prevent aggregation and shape deformation. This allows AgNPRs to maintain localized surface plasmon resonance (LSPR) characteristics and superior colorimetric sensing sensitivity towards S2− even after 30 d. The EHL@AgNPRs exhibited remarkable selectivity towards S2− with a minimum detection limit of 41.3 nM. The conjugation of lignin with AgNPRs offers a highly promising approach for the rapid detection of S2− in natural aquatic environments and for the valorization of lignin.

Dual light-responsive shape transformations of a nanocomposite hydrogel sheet enabled by in situ etching shaped plasmonic nanoparticles.

We report here on dual shape transformations of the same thermo-responsive hybrid hydrogel sheet under irradiation of a laser with two different wavelengths (808 nm and 450 nm). By in situ etching the silver nanoprisms in the sheet to silver nanodiscs by using chloride ions (Cl-), two areas with distinct light extinction properties are integrated in a single sheet. The conversion of photon energy to thermal energy in local areas by the silver nanoprisms or nanodiscs under laser irradiation with an appropriate wavelength heats up the sheet locally and causes a local volumetric shrinkage, and hence a volumetric mismatch in different areas in the sheet. The sheet then transforms in a specific way to accommodate this volumetric mismatch. Different patterns of silver nanoprisms and nanodiscs in the sheet are achieved by controlling the delivery patterns of the etchant Cl-. We demonstrate that by designing the distribution pattern of silver nanoprisms and nanodiscs in the sheet, the same hybrid sheet transforms either to a saddle or to a helical twisted shape, while with another type of distribution pattern, it transforms either to a hoof-like or to a boat-like shape under the irradiation of a laser with a wavelength of either 808 nm or 450 nm. We point out that to program arbitrary curvature of the transformed shape of our sheet, the pattern size of silver nanoprisms and nanodiscs (i.e. actuation area) in the sheet needs to be largely reduced, which however limits the heat generated and hence the shape transformations. Factors that affect the sheet's shape transformations are discussed and solutions are suggested to enhance its performance. The hybrid sheet may find applications in soft robotics, for example, as a robotic finger.

Triangular silver nanoprism-based chemosensor for recognition of hyaluronic acid in human biofluids: a new platform for monitoring osteoarthritis treatment using smartphone-assisted digital image analysis.

Hyaluronic acid (HA) possesses unique viscoelastic properties and low immunogenicity, making it suitable for various biomedical purposes such as viscosupplementation in osteoarthritis treatment, assistance in eye surgery, and wound regeneration. The need for its quantification in human biofluids is crucial in clinical studies. This research work presents a novel approach using paper-based and parafilm-based photochemical techniques, employing triangular silver nanoprisms (TA-AgNPrs) as optical nanoprobes for HA detection in human biofluids. The interaction between HA and TA-AgNPrs leads to a notable change in the absorption spectrum, facilitating rapid and reliable measurement with a detection limit of less than 0.5 μM to 30 mM. The developed colorimetric setups, along with the single-drop parafilm colorimetric substrate, enable fast and on-site HA analysis. This research marks the maiden use of TA-AgNPrs for direct, rapid and sensitive HA detection in real samples, without the need for sample pre-preparation. The use of a digital image analysis strategy enhances the simplicity, affordability, and portability of this sensor, presenting promising potential for monitoring HA levels. This new technique is poised to enable early diagnosis of diseases associated with abnormal HA levels in human biofluids, thanks to its high sensitivity and selectivity in detecting HA.

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.

Optimizing the Distance between Upconversion Thin Films and Silver Nanoprisms for the Design of a High-Performance Plasmonic Triplet-Triplet Annihilation Upconversion System.

While the distance dependence of metal-enhanced fluorescence has been extensively studied for composite systems comprising fluorophores and metal nanoparticles, the corresponding distance dependence of triplet-triplet annihilation upconversion (TTA-UC) systems remains unexplored. Herein, we investigated the influence of the spatial distance between Ag nanoprisms (AgPRs) and TTA-UC thin films consisting of a palladium octaethylporphyrin (PdOEP) sensitizer and a 9,10-diphenylanthracene (DPA) emitter, aiming at enhancing the upconverted (UC) emission as efficiently as possible. Results indicated that the optimal distance for the examined system was significantly longer (12.6 nm) than those of typical metal-enhanced fluorescence systems (about 2 nm). We demonstrated that the UC emission enhancement factor can be expressed as a product including factors of the PdOEP photoexcitation rate, triplet-triplet energy transfer (TTET) efficiency from PdOEP to DPA, triplet excited DPA lifetime, and fluorescence efficiency of singlet excited DPA. We discovered that the AgPRs play a beneficial role in enhancing the PdOEP photoexcitation, whereas they exert detrimental effects on the other three factors. Among these three factors, quenching contributions by the decrease of the triplet excited DPA lifetime and DPA fluorescence efficiency were significant, making these the primary and secondary factors, respectively, for the UC emission quenching, particularly at short distances. These results demonstrate that the characteristic distance dependence of the UC emission enhancement is determined by the competing effects of beneficial PdOEP photoexcitation enhancement and the detrimental localized surface plasmon (and/or AgPR)-induced nonradiative decay of the triplet- and singlet excited DPA molecules. The findings offer valuable guidelines for the design of high-performance plasmonic TTA-UC systems.

Confined assembly of size-tunable silver nanoprisms on flexible Teflon tapes as highly active SERS hotspots for ultralow-level sensing of DNA and glucose

The design of smart and advanced sensors facilitates highly sensitive optical detection platforms for biomolecules. Herein, we attempted the confined assembly of silver nanoprisms (SNPs) on hydrophobic Teflon tapes to design a highly flexible and ultrasensitive biosensing platform for DNA and glucose. We investigated the sensor characteristics including morphological, optical, and SERS activities as a function of nanoparticle size. Pyramidal SNPs were synthesized, whose size was tuned by varying the bromide ion concentrations. The size of SNPs was decreased with an increase in bromide ion concentrations, where quasi-spherical nanoparticles were formed at higher bromide content. The hydrophobic Teflon surface caused considerable constrain during the evaporation of nanoparticle suspension, leading to highly confined SNPs. SERS activities of Teflon/SNP sensors were tuned by varying the size of SNPs, where a size of ∼34 nm exhibited the highest signal enhancement. The optimum Teflon/SNP sensor showed an enhancement factor of 1.3 × 109 with high stability and excellent reproducibility. Teflon/SNP sensor was further exploited to detect DNA and glucose in a label-free method, exhibiting sensitivities of approximately 13.6 fg/µL and 5 µM, respectively. Real-time monitoring of DNA and glucose from saliva was also investigated. Teflon/SNP substrates were found to be excellent biosensing platforms for ultralow-level sensing of biomolecules in a rapid and cost-effective manner.