Triangular Ag Research Articles

Ultrasensitive Dual-Mode Visual/Photoelectrochemical Bioassay for Antibiotic Resistance Genes through Incorporating Rolling Circle Amplicons into a Tailored Nanoassembly.

As emerging contaminants in the environment, antibiotic resistance genes (ARGs) have aroused a global health crisis and posed a serious threat to ecological safety and human health. Thus, efficient and accurate onsite detection of ARGs is crucial for environmental surveillance. Here, we presented a colorimetric-photoelectrochemical (PEC) dual-mode bioassay for simultaneous detection of multiple ARGs by smartly incorporating rolling circle amplification (RCA) into a stimuli-responsive DNA nanoassembly, using the tetracycline resistance genes tetA and tetC as models. The tailored DNA nanoassembly containing RCA amplicons hybridized with specific signal probes: CuO nanoflowers-anchored signal DNA1 and HgO nanoparticles-anchored signal DNA2, respectively. Upon exposure to an acidic stimulus, numerous Cu2+ and Hg2+ were released, serving as the reporting agent of colorimetric/PEC dual-mode assay. The released Cu2+ and Hg2+ induced localized surface plasmon resonance shifts in Au nanorods and triangular Ag nanoplates through an etching process, respectively, enabling visual analysis of ARGs with distinguishing color changes. Meanwhile, numerous Cu2+ and Hg2+ triggered the amplified PEC variations via reacting with the photoactive layers of CuS/CdS and ZnS, respectively. Thus, a rapid and ultrasensitive colorimetric/PEC dual-mode detection of multiple ARGs was achieved with the detection limit down to 17.2 aM. Furthermore, such dual-mode bioassay could discriminate single-base mismatch and successfully determine ARGs in E. coli plasmids and sludge samples, holding great promise for point-of-care genetic diagnostics.

Solar energy utilization with double-layer cascaded grating metamaterial

In order to produce clean energy, a double-layer cascaded grating light-trapping structure and a triangular back-reflecting Ag layer were used to improve the light-capturing ability of amorphous silicon solar cells. And the structure was compared with a planar thin-film solar cell without grating by finite element method. The average absorption of the device is improved and the tolerance of the angle is also enhanced. Besides, the physical mechanism of solar energy can be well explained by studying the electric field distribution of solar cells. The absorption of cascaded grating cells has been enhanced by 12.19%, and the average absorption efficiency at 300–800 nm is 87.91%. The performance has been significantly improved by the cascaded grating solar cells. In addition, the structure has maintained its superiority in angle analysis. This provides guidance for the preparation of wide-spectrum, wide-angle thin-film solar cells in the future.

MoS2 embedded triangular silver nanosheets modified MOF-808 as electrochemical sensing platform for highly sensitive simultaneous detection of ACOP and 4-AP

The detection of acetaminophen (ACOP) and its toxic hydrolyzed product p-aminophenol (4-AP) is very significant for clinical diagnosis and quality control of drug formulation. In this study, a novel electrochemical sensor based on MoS2 embedding triangular Ag nanoplates (Tri-AgNPs) coated MOF-808 was developed for simultaneous and sensitive detection of ACOP and 4-AP. The morphology and structure MOF-808@MoS2/Tri-AgNPs nanocomposite were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and so on. The electrochemical and electrocatalytic properties of the composite electrode were evaluated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The experimental results demonstrated that the constructed sensor had excellent electrochemical performance for ACOP and 4-AP detection due to the synergistic interaction among MOF-808, MoS2 and Tri-AgNPs. The proposed sensor exhibited a wide linear range (1–450 μM) and low limits of detection for detection of ACOP (0.054 μM) and 4-AP (0.046 μM). At the same time, the sensor also showed outstanding repeatability, reproducibility, stability and selectivity. In addition, MOF-808@MoS2/Tri-AgNPs/GCE was also employed to determine ACOP and 4-AP in acetaminophen tablets and Yellow River water samples with satisfactory recovery rates, which indicated the feasibility of the developed electrochemical sensor in the actual sample analysis.

Ultrasensitive levofloxacin electrochemical biosensor based on semiconducting covalent organic framework/poly-L-cysteine/triangular Ag nanoplates modified glassy carbon electrode.

Anovel electrochemical biosensor with excellent performance was fabricated for levofloxacin (LEV) detection, which adopted triangular Ag nanoplates (Tri-AgNP) confined in a poly-L-cysteine (poly-L-Cys) film and a semiconducting covalent organic framework (COF) as the electrochemical sensing material. The developed electrochemical sensor revealed excellent analytical properties because of its good electrical conductivity, fast electron transfer, and abundant bioactive site. Based on this, a linear relationship between the LEV concentration and the peak current response at 0.92 V was obtained under the optimal experimental conditions by differential pulse voltammetry (DPV), with a wide linear range of 0.05 to 600 μM and a low limit of detection (LOD) of 0.0061 μM. The prepared sensor also realized sensitive and accurate determination of LEV in human serum and urine samples by standard addition method, with satisfactory recoveries (97.1 to 104%) and a low relative standard deviation of less than 4.6%. These results indicated that the novel ternary system has a promising application in the development of electrochemical signal probe and electrochemical biosensing platform.

Etching triangular silver nanoparticles to initiate the fluorescent response of Ru@SiO2 for sensitive detection of glutathione

Fluorescent probes usually face the issue of photobleaching and premature leakage when they are directly exposed to exterior environment, causing poor photostability and low sensitivity. In this paper, Ru(bpy)32+ encapsulated fluorescent SiO2 nanoparticles (Ru@SiO2 NPs) were synthesized and used as fluorescent probe. The SiO2 nanoparticles were used as carriers to prevent the leakage of the probe. Triangular Ag nanoparticles (T-Ag NPs) were prepared as quenchers to construct a quenching system (Ru@SiO2-T-Ag NPs) with Ru@SiO2 NPs through inner filter effect (IFE). In this quenching system, T-Ag NPs were also designed as recognize units for glutathione (GSH) detection. When GSH existed, the GSH bond with T-Ag NPs to form Ag-S bonds, making the T-Ag NPs etched. In this case, the fluorescent signal of Ru@SiO2 NPs quenched by T-Ag NPs restored. The fluorescence recovery of the Ru@SiO2 NPs depended on GSH concentrations and thus it could realize the quantitative analysis of GSH. Under optimized conditions, the proposed assay had good analytical performance for the detection of GSH in the concentration range of 0.01–1 µM with a limit of detection (LOD) as low as 2.8 nM. This assay was also used to measure GSH levels in human serum samples. This work provides a new way for the fluorescent analysis of thiol biomolecules.

Colorimetric sensing of Cu(II) ions in water on the basis of selective chemical etching of EDA-capped Ag nanoplates

Cu(II) ions are one of the essential mineral elements in the human body, but can pose a substantial health risk to people exposed to high concentrations of Cu(II) ions over a long period. Therefore, the ability to detect Cu(II) ions in drinking water is important. In this study, a novel colorimetric sensing probe for the easy and onsite detection of Cu(II) ions in drinking water was developed. The probe was constructed through selective chemical etching of triangular Ag nanoplates with tunable localized surface plasmon resonance (LSPR) properties. Ethylenediamine (EDA) was used as an organic capping agent to improve the chemical stability of triangular Ag nanoplates. Selective chemical etching of the EDA-capped Ag nanoplates in the presence of Cu(II) ions as a result of the formation of a coordination complex between the EDA and Cu(II) ions caused remarkable changes in the nanoplates’ LSPR characteristics. On the basis of this phenomenon, a novel colorimetric sensing probe capable of detecting Cu(II) ions in drinking water at concentrations above the safety limit was developed. Our findings were also extended to develop a portable and paper-based sensing probe with good long-term stability to overcome the shortcomings of liquid-phase colorimetric sensors without requiring a spectrometer. The proposed colorimetric sensing probes provide accurate results even with a real sample and offer numerous advantages over conventional sensing platforms, including clearly distinguishable color changes that can be observed by the naked eye; thus, the proposed probes can be used for the selective, reliable, and low-cost point-of-care detection of Cu(II) ions in water.

One-step surfactant-free photoreduction synthesis of single-crystal silver triangular nanoprisms by surface modified chemically patterned ferroelectric crystals for SERS application

Anisotropic metal nanoparticles with plasmonic and photocatalytic action exhibit significant applications for SERS detection and green transformation. Current synthetic approaches using multiple chemicals cause substantial resource consumption and surface chemical residues that hinder analyte adsorption and thus prevent efficient action. Herein, we present a green production process using surface modified ferroelectric templates to grow triangular Ag nanoprisms for surface enhanced Raman spectroscopy (SERS). Surface modification of ferroelectric templates with positively charged ions suppresses the Ag nucleation on template surface and enables the reaction-controlled process to promote anisotropic photoreduction for the growth of Ag nanoprisms. Under optimal experimental conditions, numerous Ag nanoprisms with the (111) plane can be photoreduced with sharp tips and edges and greatly strengthen the excited electric field for Raman signal enhancement. The synthesized Ag nanoprism array presents superior SERS performance, including enhancement factor of 3.78 × 108, limit of detection as low as 4.95 × 10-9 M, and Raman signal enhancement by 8.63 times. The practical application of Ag nanoprisms is effectively demonstrated by the SERS detection of antibiotics. The reaction control by utilization of surface-modified ferroelectric templates provides a promising prospect for the green synthesis of anisotropic metal nanomaterials and the technical development of green applications.

Plasmon-Mediated Reconfiguration of Twin Defect Structures in Silver Nanoparticles

Defects in metal nanoparticles can play a critical role in directing interfacial processes, such as catalytic reactions, at the surface of these materials. Interest in understanding the fundamental role of crystalline defects in controlling nanoparticle properties has inspired exploration of synthetic methods for tuning the twin defect structure of metal nanoparticles. However, controlling this structural parameter is a challenge due to the subtle reaction kinetics that dictate defect formation. For plasmonic silver (Ag) nanomaterials, the potential for light-induced growth provides a unique opportunity for driving structural reconfiguration between nanoparticle morphologies with different twin defect structures. We report a plasmon-mediated reconfiguration pathway in which {111}-faceted Ag nanoparticles are sequentially converted: first from planar twinned triangular Ag prisms to multiply twinned icosahedra (along with a smaller subpopulation of other twinned shapes), subsequently to multiply twinned Ag nanospheres, and finally back to planar twinned triangular Ag prisms. These consecutive reconfiguration processes occur as a result of the precise manipulation of reaction kinetics using a combination of illumination wavelength and pH. This method provides a valuable tool for reconfiguring, recycling, and regenerating Ag nanoparticles.

New electrode material integrates silver nanoprisms with phosphorus-doped carbon nanotubes for forensic detection of nitrite

A screen-printed carbon electrode (SPCE) was modified with a nanohybrid of silver (Ag) nanoprisms and phosphorus (P)-doped carbon nanotubes (AgNPr@P-CNT). The modified SPCE was coupled with a simple, portable flow system to produce an efficient amperometric sensor for the detection of nitrite ion (NO2−). P-doped CNTs were prepared via a one-pot solvothermal method and the P-CNTs were decorated with Ag nanoprisms synthesized by a one-pot chemical reduction method. The as-prepared AgNPr@P-CNT nanohybrid was thoroughly characterized. Energy-dispersive x-ray (EDX) analysis, Fourier transform infra‐red (FTIR), and Raman spectroscopy results confirmed the successful doping of CNTs with P atoms. Transmission electron microscopy (TEM) revealed the decoration of P-CNTs with triangular Ag nanoprisms measuring 25 ± 7 nm. In the optimal condition, the flow injection-amperometric sensor based on the developed AgNPr@P-CNT/SPCE exhibited suitable electrocatalytic activity toward NO2− oxidation. As a result, NO2− was detected with high sensitivity (0.73 µA µM−1 cm−2), a wide linear range (0.010–4000 µM), and a low limit of detection (0.0032 µM). The proposed sensing system was successfully applied to detect NO2− in gunshot residue samples, achieving good recoveries. The advantages of the proposed AgNPr@P-CNT nanohybrid can be applied in other electrochemical sensing applications.

Localized Surface Plasmon Resonance Decorated with Carbon Quantum Dots and Triangular Ag Nanoparticles for Chlorophyll Detection

This paper demonstrates carbon quantum dots (CQDs) with triangular silver nanoparticles (AgNPs) as the sensing materials of localized surface plasmon resonance (LSPR) sensors for chlorophyll detection. The CQDs and AgNPs were prepared by a one-step hydrothermal process and a direct chemical reduction process, respectively. FTIR analysis shows that a CQD consists of NH2, OH, and COOH functional groups. The appearance of C=O and NH2 at 399.5 eV and 529.6 eV in XPS analysis indicates that functional groups are available for adsorption sites for chlorophyll interaction. A AgNP–CQD composite was coated on the glass slide surface using (3-aminopropyl) triethoxysilane (APTES) as a coupling agent and acted as the active sensing layer for chlorophyll detection. In LSPR sensing, the linear response detection for AgNP–CQD demonstrates R2 = 0.9581 and a sensitivity of 0.80 nm ppm−1, with a detection limit of 4.71 ppm ranging from 0.2 to 10.0 ppm. Meanwhile, a AgNP shows a linear response of R2 = 0.1541 and a sensitivity of 0.25 nm ppm−1, with the detection limit of 52.76 ppm upon exposure to chlorophyll. Based on these results, the AgNP–CQD composite shows a better linearity response and a higher sensitivity than bare AgNPs when exposed to chlorophyll, highlighting the potential of AgNP–CQD as a sensing material in this study.

Efficient adsorptive removal of dibenzothiophenes from liquid fuel over a novel triangular Ag(I) complex

The use of a π-acidic triangular silver(I) pyrazolate (Ag3pz3) as an adsorbent for adsorptive desulfurization (ADS) has been investigated in this report. Ag3pz3 shows very strong adsorptive affinity for aromatic sulfur compounds with the maximum adsorption capacity at 298 K being 58.5 and 51.5 mg S/g for dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (DMDBT), respectively. This adsorbent (used in the form of Ag3pz3·toulene) can reduce the S-content in iso-octane containing DBT or DMDBT from 100 mg S/L to ∼ 1 mg S/L after a static adsorption with an adsorbent dose of 4.52 g/L at 298 K. The adsorption mechanism can be well understood on the basis of weak intermolecular interactions, supported via the single-crystal structural determination and theoretical study. Ag3pz3 would represent a new type of adsorbent, which may find use in the adsorptive removal of dibenzothiophenes to achieve ultra-deep desulfurization.

Cost-effective large-area Ag nanotube arrays for SERS detections: effects of nanotube geometry

This study demonstrated highly-ordered metallic nanotube arrays (MeNTAs) with a precisely controlled geometric shape to promote surface-enhanced Raman scattering (SERS). Using both simulation and experimental methods, we designed and fabricated MeNTAs with nanotube geometries that possess a large surface area to absorb probe molecules as well as geometric features capable of inducing hot spots for SERS enhancement. The proposed top-down wafer-scale lithographic and sputter-deposition process is a simple and cost-effective approach to the fabrication of 1 mm × 1 mm MeNTA at room temperature. Simulation results of nanotubes with various materials (Au, Ag, and Cu), diameters (100–1500 nm), geometric shapes (circle, equilateral triangle and square) and triangle corner curvatures (ranging from 0 to 300 nm) identified Ag triangles with sharp tips as the geometry best suited to SERS enhancement. The SERS spectra of crystal violet molecules generated from the Ag MeNTAs verified the patterns observed in computational simulations, wherein the effects of MeNTA on SERS decreased with an increase in the size of the nanotubes. Enhancement factor of 1.06 × 109 was obtained from our triangular Ag MeNTA, confirming its efficacy as an ultrahigh sensitivity SERS-active substrate.

Efficient Adsorptive Removal of Dibenzothiophenes from Liquid Fuel Over a Novel Triangular Ag(I) Complex

Efficient Adsorptive Removal of Dibenzothiophenes from Liquid Fuel Over a Novel Triangular Ag(I) Complex

Liquid-liquid interfacial self-assembled triangular Ag nanoplate-based high-density and ordered SERS-active arrays for the sensitive detection of dibutyl phthalate (DBP) in edible oils.

DBP, one of the phthalic acid esters (PAEs), is known as an endocrine disruptor and is toxic to humans in abnormal concentrations. Here, a high-density and ordered SERS substrate based on the self-assembly of triangular Ag nanoplate (TAgNP) arrays is developed for DBP detection. Benefiting from the ordered arrangement and sharp corners of TAgNPS, the arrays can provide sufficient and uniform hotspots for reproducible and highly active SERS effects. Using Rhodamine 6G (R6G) as a reporter molecule, the SERS enhancement factor (EF) of the TAgNP arrays was found to be as high as 1.2 × 107 and the relative standard deviation was 6.56%. As a trial for practical applications, the TAgNP array substrates were used for the detection of dibutyl phthalate (DBP) in edible oils. In this assay, edible oil samples were added to hexane as an organic phase for the formation of the TAgNP arrays, which caused DBP to be loaded at hotspots. DBP in edible oils could be identified at concentrations as low as 10-7 M. This SERS substrate based on the TAgNP arrays has great potential applications in the high sensitivity and reproducible detection of contaminants in food.

Tunable LSPR of silver/gold bimetallic nanoframes and their SERS activity for methyl red detection.

Ag/Au bimetallic nanostructures have received much attention in surface-enhanced Raman scattering (SERS). However, the synthesis of this nanostructure type still remains a challenge. In the present research, Ag/Au nanoframes were synthesized via a simple room temperature solution phase chemical reduction method using pre-synthesized triangular Ag nanoplates as templates in the presence of appropriate amounts of HAuCl4. Controlling experimental parameters was applied for understanding of the growth mechanism. The galvanic exchange reaction resulted in a uniform deposition of the Au shell on the Ag nanoplates and the Ag core was removed which generated triangular hollow nanoframes. It is found that the amount of HAuCl4 added to the growth solution played a key role in controlling the Ag/Au nanoframes. The resultant silver/gold nanoframes with average size of 50 nm were applied in detecting methyl red (MR) in the solution-phase using an excitation wavelength laser of 532 nm. The SERS signal was greatly enhanced owing to the tunable plasmonic peaks in the visible region (400–650 nm). The limit of detection (LOD) of MR in diluted solution was 10−6 M. The enhancement factor (EF) was about 8 × 104 toward 10−5 M of MR. Interestingly, the linear dependence between the logarithm of the SERS signal intensity (log I) and the logarithm of the MR concentration (log C) occurred in the range from 10−6 to 10−4 M. Our work promises the application of Ag/Au nanoframes as a chemical sensor in detecting MR molecules at low concentration with high performance.

Fascinating approach for using metabolites products of living microorganisms as reducing agents for preparing silver nanoparticles

A crucial area of research in nanotechnology is the formation of environmentally benign nanoparticles. Both unicellular and multicellular play an important role in synthesis nanoparticles through the production of inorganic materials either intracellularly or extracellularly. The agents (pigments, siderophores, cell extracted metabolites and reducing compounds) were used to prepare silver nanparticles with different sizes and shapes. The color variations (dark yellow, slightly dark yellow and golden yellow) arising from changes in the composition, size, and shape of nanoparticles, surrounding medium can be monitored using UV-visible spectrophotometer. These effects are due to the phenomena called surface plasmon resonance. The silver nanoparticles have Plasmon resonances ranged between (390, 383 and 365) nm which they are among the limitation of silver nanoparticles (360 – 420 nm). AFM analysis of Ag NP’s showed partially purified big triangular Ag NP having edge length around ~1. mm. Hexagonal particles on the background of a matrix made up of some molecules which may be metabolites products are found. Small spherical nanoparticles embedded in some kind of matrix indicate that this molecule acts as capping agent, which inhibits further growth of nanoparticles. Also ribbons like structures of width around 50 nm which are intertwined are the noble and rare structures which are synthesized by this method. MIC of silver Nanoparticles for. E coli, ranges between 80-90 µg/ml.., Serrtia, ranges between 50-60 µg/ml and Shagilla, ranges between 90-100 µg/ml. Keywords: Metabolites product of microorganisms, silver nanoparticles.

Enhancement of Tb–Yb quantum cutting luminescence with Ag nanostructures and photonic crystals

NIR(near infrared)-emitting rare-earth ion doped quantum cutting materials has attracted interest in the recent years due to its potential applications in solar cells, bio-sensing, food-processing industry, and night-vision technologies, among others. However, these applications are limited by their low quantum cutting luminescent intensity and efficiency, low 4f-4f transition excitation, and high unwanted spontaneous decay of dopant. Here, two strategies of local electromagnetic field modulation to improve the quantum cutting NIR emissions of Tb–Yb in NaYF 4 nanoparticles were used synergistically. The photonic band-gap could effectively suppress the spontaneous emission of Tb 3+ , and enhance the energy transfer efficiency of Tb–Yb. Additionally, triangular Ag nanoparticles could provide a suitable plasma resonance local field to improve Tb 3+ excitation efficiency. According to the findings of this study, the quantum cutting efficiency of Tb–Yb could be increased up to 145.93%. • YPO 4 inverse opal PCs were fabricated to modify the quantum cutting energy transfer of Tb–Yb in NaYF 4 NPs. • The Tb–Yb cooperative quantum cutting energy transfer efficiency is enhanced by suppressing the spontaneous emission of Tb 3+ ions by photonic band gap. • The co-embedding of Ag NPs could increase the quantum cutting energy transfer of Tb–Yb to 145.93%.

Modification and SERS Optimization of Triangular Ag Nanoplates

Triangular Ag nanoplates have been synthesized via the seed-mediated method, which has good morphology and can be reproduced stably. The wavelength of local surface plasmon resonance (LSPR) can be easily controlled in the range of 500–900 nm. When triangular Ag nanoplates were applied to surface-enhanced Raman scattering (SERS) based on suspension aggregates and solid aggregates, the detection limit of rhodamine 6G (R6G) were greatly increased to 3.125 × 10−7 M and 10−11 M, respectively, and there was an excellent linear relationship between the intensity of Raman peak and the concentration of R6G. In addition, when the excitation light was tuned to the LSPR wavelength, the surface plasmon resonance will be excited to the maximum extent, and the enhanced electromagnetic field will maximize the Raman scattering. Furthermore, some progress has been made in the optimization of SERS by compounding graphene hydrogels in solid aggregates and adding mercapto polyethylene glycol in suspension aggregates.

Refractive index sensitivity of triangular Ag nanoplates in solution and on glass substrate

We report the synthesis of Ag triangular nanoplates and its application for the detection of bulk refractive index change resulting from low molecular weight analyte molecules. Triangular nanoplates of different edge lengths were synthesized using seed mediated approach with small modification in the earlier reported method [Adv. Funct. Mater. 18, 2005–2016 (2008)]. Increase in the edge length of nanoplates was observed with decrease in the volume of seed nanoparticle used. The synthesized nanoplates in colloidal solution were investigated for the refractive index sensing. The nanoplates synthesized with 100 μL seed volume showed maximum sensitivity for glucose and glycerol as 465 and 461 nm/RIU respectively. Triangular nanoplates with highest sensitivity in the solution were immobilized on silanized glass surface using 3-aminopropyl-trimethoxysilane as an adhesion layer. The refractive index sensitivity of immobilized nanoplates was found to be 193 and 204 nm/RIU for glucose and glycerol solutions respectively. The significant decrease in sensitivity could be due to damping of plasmon resonance on substrate or non-availability of all surfaces. The immobilized nanoplates on glass surface can be used as nanoplasmonic sensor chip for chemical and biological analyte detection.

Oriented attachment mechanism of triangular Ag nanoplates: a molecular dynamics study.

We use molecular-dynamics simulations to probe the experimentally observed aggregation of PVP-covered triangular Ag nanoplates to form 2D sheets in solution. We find lateral plate attachment is the most favorable aggregation pathway – consistent with experiment. The mechanism is general and suggests new processing strategies for creating 2D architectures in solution-phase syntheses.