Silver Nanoprisms Research Articles

Rapid and simple colorimetric detection of hydrogen sulfide using an etching-resistant effect on silver nanoprisms.

A fast and sensitive colorimetric paper sensorhas been developed using silver nanoprisms (Ag NPRs) with an edge length of ~50nm for the detection of free H2S gas. We prepared two types of Ag NPRs-coated H2S sensing papers: a multi-zone patterned paper for passive (diffusion mode), and a single-zone patterned paper for pumped mode of H2S gas. The change in color intensity wasquantitatively analyzed of Ag NPRs-coated paper after KCl treatment depending on the concentration of H2S gas, from yellow to purplish brown. As a result, Ag NPRs-coated H2S sensing paper showed good sensitivity with a linear range of 1.03 to 32.9 μM H2S, high selectivity, and good reproducibility and stability, together with a fast response time of 1min. The developed H2S sensing paper was applied to detect the free H2S gas released from three types of garlic including crushed, peeled, and fresh garlic. Therefore, it can be utilized as a simple, fast, and reliable tool for on-site colorimetric detection of free H2S gas for quality control of dietary supplements and exhaled breath analysis.Graphical abstract.

Influence of optical radiation on the silver nanoparticles formation

In this work, the synthesis of spherical silver nanoparticles in aqueous solution was performed by photostimulated reduction. A research of the laser exposure time effect of silver colloids on the optical response and nanoparticles concentration in the studied solution was carried out. The influence of long time exposure (up to 6 days) of silver colloid by LEDs with radiation wavelengths of 525 and 633 nm on their geometric, spatial and optical parameters was studied. It has been shown that prolonged irradiation of silver colloid leads to changes in the nanoparticles morphology, which is confirmed by a change in the colloidal color and appearance of additional plasmon absorption peaks on the spectral scale. The formation of silver nanoparticles and nanoprisms in aqueous solution was confirmed by spectrophotometry and transmission electron microscopy. Modelling of absorption spectra of triangular silver nanoparticles by the discrete dipole approximation approach, implemented in DDSCAT software, was carried out.. The electromagnetic radiation of the optical range is a promising tool that can be effectively used for both synthesis and modification of optical and spatial parameters of silver nanoparticles.

Improvement of organic solar cell performance by multiple plasmonic excitations using mixed-silver nanoprisms

Three different silver nanoprisms (AgNPrs) were combined and used as light-trapping materials in organic solar cells (OSCs). These mixed AgNPrs (M-AgNPrs) increased the photocarrier generation in the OSCs due to the broadband absorption, which was attributed to mutual multiple plasmonic excitations covering the entire visible light region. The M-AgNPrs were incorporated into a poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) hole-transport layer in the OSCs. The UV–vis spectra, atomic force microscope images and current density versus voltage curves of the fabricated devices were recorded at different loading concentrations of the M-AgNPrs. Finite-difference time-domain simulation, impedance spectroscopy, and measurement of incident photon-to-current efficiency of the devices confirmed the effect of the multiple plasmonic excitations. The results suggest that, in an optimum condition, the efficiency of the OSCs loaded with M-AgNPrs was 7.9% higher than the reference OSC.

Colorimetric detection of individual biothiols by tailor made reactions with silver nanoprisms

We herein described a rapid, sensitive, and selective colorimetric sensing platform for biothiols in human serum, which relies on the dual functions of biothiols as anti-etching and aggregating agent for silver nanoprisms (AgNPRs). In principle, the target biothiols that bind to the surface of AgNPRs through Ag–S covalent interactions protect the AgNPRs from being etched by chloride ion (Cl−) in human serum, thus exhibiting the blue/purple color that is indicative of AgNPRs. On the other hand, the color of AgNPRs turned to yellow in the absence of biothiols or the presence of non-sulfur-containing amino acids, indicating the formation of small silver nanoparticles (AgNPs). Importantly, we found that individual biothiols (Hcy, Cys, and GSH) exert not only the anti-etching effect, but also the aggregating effect on AgNPRs, which can be modulated by simply tuning the pH conditions, and this consequently allows for the discriminative detection of each biothiol. Based on this simple and cost-effective strategy, we successfully determined the Hcy, Cys, and GSH in human serum with high sensitivity and selectivity within 10 min, demonstrating the diagnostic capability and potential in practical applications.

Surface Plasmon Resonance Field-Enhanced Fluorescence Properties of Gold Quantum Dots on Polyelectrolyte Multilayers and Their H2O2 Sensor Application

In this work, we investigate surface plasmon field-enhanced fluorescence (SPF) emission from gold quantum dots (AuQDs) on a polyelectrolyte multilayer ultrathin film deposited onto an Al thin film. Polyelectrolyte layers of poly(diallyl dimethyl ammonium chloride) (PDADMAC) and poly(sodium 4-styrenesulfonate) (PSS) are deposited onto the Al surface using a layer-by-layer (LbL) adsorption technique. AuQDs are subsequently deposited onto the PDADMAC/PSS ultrathin films to study their fluorescence enhancement/quenching phenomenon, as monitored by SPF spectroscopy. The distance between the AuQDs and the Al thin film is controlled by the number of deposited PDADMAC/PSS LbL films. With increasing number of the PDADMAC/PSS bilayers, the fluorescence intensity of the AuQDs increases until the optimum distance between the AuQDs and Al layers is achieved. Moreover, silver nanoprisms (AgNPrs) are coated onto the AuQDs for H2O2 sensing. When the AgNPrs are present, a decrease in the fluorescence intensity of the AuQDs due to energy transfer from the AuQDs to the AgNPrs is observed. Recovery of the fluorescence intensity of the AuQDs is observed upon injection of a H2O2 solution, where the recovery of the intensity is proportional to the H2O2 concentration in the range from 1 pM to 100 nM and results from the oxidation reaction or etching of the AgNPrs. The fluorescence recovery is attributed to weakening of the quenching effect by a reduction in concentration of the AgNPrs. The proposed system exhibits strong potential for the development of H2O2 sensors.

Detection of multi-class pesticide residues with surface-enhanced Raman spectroscopy

The excessive use of pesticides disturbs the natural balance in the environment, creates resistance to pesticides and leads to water and food contamination. Therefore, the implementation of fast, robust and cost effective techniques for the monitoring of pesticides is required. In this work surface-enhanced Raman spectroscopy (SERS) was used for the detection of four common pesticides: atrazine, simazin, irgarol, and diuron. SERS is nowadays considered an effective technique for detection of various analytes in low concentration. Sensitivity of the SERS method depends on the type of substrate that can be either a colloidal solution of metal nanoparticles (NPs) or a metal surface with a suitable nanostructured topology. Here, we have investigated the application of silver nanospheres and silver nanoprisms as SERS substrates in pesticides detection. Colloids with spherical NPs were produced by chemical reduction while Ag nanoprisms were prepared by reducing silver nitrate with borohydride (with citrate as a stabilizing agent) and stirring under a UV lamp for 4 and 10 h. The SERS results have shown that, in the presence of synthesized NPs, it was possible to detect millimolar concentrations of aforementioned pesticides with the exception of diuron.

Ultrasensitive detection of disinfection byproduct trichloroacetamide in drinking water with Ag nanoprism@MoS2 heterostructure-based electrochemical sensor

The chlorination disinfection of drinking water generates disinfection byproducts (DBPs), which are toxic, carcinogenic, mutagenic, and teratogenic. Recently, trichloroacetamide (TCAM) has been proved to be highly genotoxic and cytotoxic. In this study, a sensitive and selective electrochemical sensor for TCAM detection is reported that is based on the triangular silver nanoprism (AgNPR) and MoS2 nanosheet (AgNPR@MoS2) heterostructure. The AgNPR can catalyze the dechlorination reaction of TCAM; and the abundant S sites on the edge of MoS2 nanosheet can absorb H+, thereby accelerating the dechlorination hydrogenation reaction. The AgNPR@MoS2 heterostructure exhibits a high charge transfer rate, high electrocatalytic activity, and good stability in TCAM detection. The sensor shows two linear sensing ranges of 0.5−10 μM and 10−80 μM, a detection limit of 0.17 μM, and high specificity to coexist DBPs. This study is one of the first reports of electrochemical detection of TCAM, and has successfully demonstrated the significant potential of electrochemical sensor for the real-time analysis and monitoring of trace TCAM in drinking water.

Salicylazine activated plasmonic silver nanoprisms for identification of Fe(ii) and Fe(iii) from aqueous solutions

Silver nanoprisms were synthesized using salicylazine as a reducing and capping agent and were used to identify Fe2+/Fe3+ from a few real samples.

Microfluidic nanopaper based analytical device for colorimetric and naked eye determination of cholesterol using the color change of triangular silver nanoprisms

A microfluidic nanopaper-based analytical device (μNPAD) has been prepared for the determination of cholesterol by using triangular silver nanoprisms (T-AgNPrs).

Structural Study of the Photo-Mediated Growth of Silver Nanoprisms.

We present a small-angle X-ray scattering (SAXS) study of the anisotropic photoinduced growth of silver (Ag) nanoprisms in aqueous dispersions. The growth of nearly spherical (<10 nm) Ag particles into large (>40 nm) and thin (<10 nm) triangular nanoprisms induced by 550 nm laser is followed in terms of particle size using indirect and direct methods for irradiation times up to 150 min. During the process, the surface-to-volume ratio of the particles decreased. The SAXS data of the initial solution fit well to the model of polydisperse spheres with pronounced average diameters around 7.4 nm and 10 nm. The data after 45 min irradiation fit well to the model containing approximately the same amount of the initial particles and the end product, the nanoprisms.

Enhanced bactericidal activity of azithromycin‐coated silver nanoprisms in comparison to their spherical‐shaped counterparts

Human beings have been bearing great medical, social, and economic losses due to the ever-increasing rate of microbial infections and the development of resistance; hence, there is a dire need to develop novel strategic alternate tools to circumvent these infections. In this regard, metallic nanomaterials (NMs) have been reported to exhibit promising bactericidal properties. In the present study, two different shaped silver NMs, i.e. silver nanoparticles (AgNPs) and silver nanoprisms (AgNPrs) and their conjugates with azithromycin were synthesised, characterised, and tested for their bactericidal activity. The average particle sizes analysed for spherical nanoparticles were 30–47.5 nm, and for prismatic-nanoparticles was 35–60 nm, respectively. The distinct ultraviolet–visible peaks were obtained for NMs and their nanoconjugates. The results of Fourier transform infrared spectroscopy indicated the interaction of various functional groups from Azy with metallic NMs. The nanoprisms and their conjugates showed enhanced bactericidal potential as compared to AgNPs and their corresponding control. The efficiency of Azy–AgNPrs was statistically higher (P <0.05) than AgNPs, Azy–AgNPs, and AgNPrs against the growth of Escherichia coli and Staphylococcus aureus. These results can be used as an innovative tool for further in-depth optimisation of shape-dependent nanoconjugates for their bactericidal activity.

Plasmonic random laser from dye-doped cholesteric liquid crystals incorporating silver nanoprisms.

Plasmonic random lasers have been demonstrated in combining dye-doped cholesteric liquid crystals (DD-CLCs) and silver nanoparticles (AgNPs). The DD-CLC laser reveals the lowest threshold and highest slope efficiency through the localized surface plasmon resonance of AgNPs with the best coupling of the emission spectrum of lasing dye and resonance of electron oscillation on the metal surface. Thermal control of the DD-CLC lasers has been achieved to simultaneously shift the long- and short-edge lasing peaks. By the α-stable analysis, the DD-CLC random laser (RL) reveals heavy tail distribution with relatively low α∼1.06 to show the Lévy behavior. Owing to its low spatial coherence, the DD-CLC RL has been demonstrated to produce a speckle-reduced image with a lower contrast of about 0.04.

Photomodulated Spatially Confined Chemical Reactivity in a Single Silver Nanoprism

Single-atom and single-particle catalysis is an area of considerable topical interest due to their potential in explaining important fundamental processes and applications across several areas. An interesting avenue in single-particle catalysis is spatial control of chemical reactivity within the particle by employing light as an external stimulus. To demonstrate this concept, we report galvanic replacement reactions (GRRs) as a spatial marker of subparticle chemical reactivity of a silver nanoprism with AuCl4- ions under optical excitation. The location of a GRR within a single Ag nanoprism can be spatially controlled depending on the plasmon mode excited. This leads to chemomorphological transformation of Ag nanoprisms into interesting Ag-Au structures. This spatial biasing effect is attributed to localized hot electron injection from the tips and edges of the silver nanoprisms to the adjacent reactants that correlate with excitation of different surface plasmon modes. The study also employs low-energy-loss EELS mapping to additionally probe the spatially confined redox reaction within a silver nanoprism. The findings presented here allow the visualization of a plasmon-driven subparticle chemical transformation with high resolution. The selective optical excitation of surface plasmon eigenmodes of anisotropic nanoparticles offers opportunities to spatially modulate chemical transformations mediated by hot electron transfer.

Solid-phase colorimetric sensing probe for bromide based on a tough hydrogel embedded with silver nanoprisms

Sharp-tipped anisotropic silver (Ag) nanostructures are attracting increasing attention because of their unusual optical properties. However, the sharp tips make such nanostructures thermodynamically unstable; thus, they have been considered unsuitable for use in colorimetric sensing because of their tendency to aggregate or transform in a solution state. In the present study, a colorimetric sensing platform for detecting bromide (Br−) in an aqueous medium was developed. The platform is based on the localized surface plasmon resonance (LSPR) properties of Ag nanoprisms with sharp tips. The key to using such Ag nanocrystals with extreme anisotropic structures is to adopt a solid-phase sensing platform. A Ag-nanoprism-embedded tough hydrogel with interpenetrating polymer networks was synthesized via aqueous-phase polymerization and crosslinking processes. The Ag nanoprisms immobilized inside the hydrogel were stable and did not exhibit aggregation or degradation over time; specifically, when the hydrogel was dried, the nanoprisms retained their inherent LSPR properties for an extended period. By taking advantage of the rapid and spontaneous morphological transformation of Ag nanoprisms inside the hybrid hydrogel exposed to Br− and the corresponding changes in their LSPR properties, we designed a plasmonic sensing platform for the sensitive and selective detection of Br− in an aqueous medium. The proposed colorimetric sensing platform was found to exhibit a wide sensing range and high selectivity, with a low limit of detection (LOD) of 10 μM, and offers substantial advantages over previously developed systems; specifically, it is portable, eco-friendly, safe to use and handle, stable for extended periods, and enables naked-eye detection. We believe that the as-proposed sensing platform can be used as a point-of-care analytical tool for detecting Br− in a broad range of samples.

Superior Resonant Nanocavities Engineering on the Photonic Crystal-Coupled Emission Platform for the Detection of Femtomolar Iodide and Zeptomolar Cortisol.

Although luminescence spectroscopy has been a promising sensing technology with widespread applications in point-of-care diagnostics and chem-bio detection, it fundamentally suffers from low signal collection efficiency, considerable background noise, poor photostability, and intrinsic omnidirectional emission properties. In this regard, surface plasmon-coupled emission, a versatile plasmon-enhanced detection platform with >50% signal collection efficiency, high directionality, and polarization has previously been explored to amplify the limit of detection of desired analytes. However, high Ohmic loss in metal-dependent plasmonic platforms has remained an inevitable challenge. Here, we develop a hybrid nanocavity interface on a template-free and loss-less photonic crystal-coupled emission (PCCE) platform by the quintessential integration of high refractive index dielectric Nd2O3 "Huygens sources" and sharp-edged silver nanoprisms (NPrs). While efficient forward light scattering characteristics of Nd2O3 nanorods (NRs) present 460-fold emission enhancements in PCCE, the tunable localized plasmon resonances of NPrs display high electromagnetic field confinement at sharp nanotips and protrusions, boosting the enhancements 947-fold. The judicious use of silver NPr (AgNPr) metal-Nd2O3 dielectric hybrid resonances in conjugation with surface-trapped Bloch surface waves of the one-dimensional photonic crystal (1DPhC) displayed unprecedented >1300-fold enhancements. The experimental results are validated by excellent correlations with numerical calculations. The multifold hotspots generated by zero and nonzero nanogaps between the coassembly of NPrs, NRs, and 1DPhCs are used for (i) determination of hyper and hypothyroidism levels through monitoring the concentration of iodide (I-) ions and (ii) single-molecule detection (zeptomolar) of the stress hormone, cortisol, through the synthesized cortisol-rhodamine B conjugate obtained using a simple esterification reaction.

Colorimetric sensing of barium ion in water based on polyelectrolyte-induced chemical etching of silver nanoprisms

Because water contamination by barium ion (Ba2+) is still common, the ability to detect Ba2+ in aqueous media is important. However, the development of an easy-to-use and point-of-care sensing method for detecting Ba2+ in aqueous media has proven challenging. In the present study, a colorimetric sensing platform for detecting Ba2+ in an aqueous medium was developed. The platform stands on the basis of the localized surface plasmon resonance (LSPR) properties of Ag nanoprisms, where a strong polyelectrolyte, poly(styrene-4-sulfonate) (PSS), is used as a powerful chemical etchant for the nanoprisms. Upon the addition of PSS to a solution of the Ag nanoprisms, the sharp tips of the Ag nanoprisms were immediately etched and the nanoprisms spontaneously transformed into spheroidal nanostructures, giving rise to dramatic changes in their LSPR properties. The chemical etching reaction of Ag nanoprisms exposed to PSS was retarded in the presence of Ba2+, which enabled the design of a new chemical sensing platform for the sensitive and selective detection of Ba2+ in aqueous media. The proposed Ba2+ sensing platform using highly anisotropic Ag nanostructures and a polyelectrolyte etchant offers numerous advantages over existing platforms, including naked-eye recognition and safe use and handling; hence, the developed platform can be used at the point of care.

Silver Nanoprism Enhanced Colorimetry for Precise Detection of Dissolved Oxygen.

Dissolved oxygen (DO) content is an essential indicator for evaluating the quality of the water body and the main parameter for water quality monitoring. The development of high-precision DO detection methods is of great significance. This paper reports an integrated optofluidic device for the high precision measurement of dissolved oxygen based on the characteristics of silver nanoprisms. Metal nanoparticles, especially silver nanoprisms, are extremely sensitive to their surroundings. In glucose and glucose oxidase systems, dissolved oxygen will be transformed into H2O2, which affects the oxidation and erosion process of nanoprisms, then influences the optical properties of nanoparticles. By detecting the shift in the plasma resonance peak of the silver nanoparticles, the dissolved oxygen (DO) content can be determined accurately. Great reconfigurability is one of the most significant advantages of the optofluidic device. By simply adjusting the flow rate ratio between the silver nanoprisms flow and the water sample flow, real-time continuous adjustment of the detection ranges of DO from 0 to 16 mg/L can be realized dynamically. The detection limit of this device is as low as 0.11 µM (3.52 µg/L) for DO measurement. Thus, the present optofluidic system has a wide range of potential applications in fields of biomedical analyses and water sensing.

Structural effects of silver-nanoprism-decorated Si nanowires on surface-enhanced Raman scattering

Surface enhanced Raman scattering (SERS) is an important analytical tool for the optochemical detection of molecules. The enhancement is commonly achieved by engineering (i) novel types and morphologies of plasmonic nanomaterials, and (ii) patterned or roughened supporting substrates of high surface area for increased light scattering and molecule adsorption. Si substrates can be easily and reproducibly textured for effective SERS applications. In this work, silver nanoprisms (AgNPr) coated silicon nanowire (SiNWs) of different morphologies have been prepared by metal-assisted chemical etching and tested for SERS detection of R6G dye. By varying the etching time from 5 to 30 min, the nanowires’ lengths increased from 2.4 to 10.5 µm and resulted in a variable topological morphology of the substrates in terms of bundles and valleys. We found that an optimum of 10 min etching time led to the highest SERS enhancement of R6G on AgNPr/SiNWs at 612 cm−1 Raman shift (30× compared to R6G/Si and 2× compared to R6G/AgNPr/Si), with a detection limit comparable to that of state-of-the-art performances (down to 5×10−10 M of R6G). Such an enhancement is attributed to a middle ground between increased overall surface area of SiNWs, and the available bundle tops trapping the AgNPr and R6G molecules.

Embedded plasmonic nanoprisms in polymer solar cells: Band-edge resonance for photocurrent enhancement

Introduction of metallic nanoparticles that can generate the surface plasmon resonance (SPR) has been considered as a prominent option for enhancing the performance of polymer solar cells (PSCs), as the radiative scattering and field confinement by the SPR can extend the effective photon traveling length and manipulate the spatial absorption profile. Despite many successful efforts to favorably exploit metallic nanoparticles, further studies of their effects on the PSC performance have been demanded to achieve the full benefit from them. Here, we systematically investigate the optical and photovoltaic performances of PSCs with disorderly distributed silver nanoprisms embedded in the photoactive material. Due to the superior properties of the plasmonic scattering of this class of nanoparticles, a significant improvement of photon absorption is gained from the devices with silver nanoprisms, particularly in the wavelength range of substandard absorption property including the band-edge wavelengths. While such absorption improvement can be obviously reinforced as an increase in the particle density, its level becomes saturated and decayed eventually because of the concurrently promoted photon loss by plasmonic absorption. At the optimal configurations of silver nanoprisms for the productive light trapping effect, the incorporated PSC devices present a photocurrent of ∼17.76 mA/cm2 and a power conversion efficiency of ∼9.68%, where their net increase ratios are ∼10% and ∼13% compared to the reference PSC devices, respectively. Details of numerical modeling and experiments for both metal nanoprisms and PSC devices offer an optimum route to tailoring metallic nanoparticles for high-performance PSC systems.

Ag/PVP/PAN nanocomposites with triangular nanoprisms of silver synthesized by UV-induced polymerization: Morphology manipulation and optical properties tuning

Solid nanocomposite films of “silver/polyvinylpyrrolidone/polyacrylonitrile” were synthesized for the first time by means of UV-induced polymerization. Structural characterization carried out by transmission electron microscopy revealed the presence of triangular silver nanoprisms with an edge length of ~40 nm and a thickness of ~15 nm in addition to spherical nanoparticles. The nanoparticles shape evolution process during synthesis and storage has been monitored in detail by UV-VIS-NIR spectroscopy and plasma resonance bands depending on the shape of the silver nanoparticles have been identified. Unlike spherical nanoparticles, which absorb light at 420–450 nm, the triangular nanoprisms demonstrate a clear absorption in the red range of the spectrum. The optical spectra of the composite films with incorporated silver nanoprisms manifest an intense in-plane dipole plasmon resonance band at 585–650 nm, as well as a weak out-of-plane quadrupole resonance band at 340 nm.