Simple synthesis of biogenic Pd Ag bimetallic nanostructures for an ultra-sensitive electrochemical sensor for sensitive determination of uric acid

Electrochemical immunosensor for ultrasensitive detection of human papillomaviruse type 16 L1 protein based on Ag@AuNPs-GO/SPA

Human papillomaviruse type 16 (HPV16) is a high-risk serotype. As the main protective antigen protein, L1 protein is also the target protein for diagnosis. A simple label free electrochemical immunosensor (ECIS) was fabricated for ultrasensitive detection of HPV16 L1 protein in this work. Quasi-spherical Ag@Au core-shell nanoparticles on graphene oxide (Ag@AuNPs-GO) was developed as current response amplifier and characterized by UV-Vis Spectroscopy, Transmission Electron Microscopy and energy dispersive X-ray spectroscopy. Staphylococcal protein A was decorated on the modified electrode and utilized to immobilized the Fc portion of the monoclonal antibody specific for HPV16 L1 protein. Cyclic Voltammetry, Differential Pulse Voltammetry and Electrochemical Impedance Spectroscopy were used to verify the electrochemical performance and interfacial kinetic property. The increased concentration of HPV16 L1 protein led to slow electron transport and linearly decreased differential pulse voltammetry peak current with a detection limit of 0.002 ng mL^-1 and a wide linear relationship in the range of 0.005-400 ng mL^-1at a regression coefficient (R²) of 0.9948. Furthermore, this ECIS demonstrated acceptable accuracy with good reproducibility, stability and selectivity, suggesting a promising immunological strategy for HPV typing and early screening.

Biosustainable production of nanoparticles via mycogenesis for biotechnological applications: A critical review

The demand for the green synthesis of nanoparticles has gained prominence over the conventional chemical and physical syntheses, which often entails toxic chemicals, energy consumption and ultimately lead to negative environmental impact. In the green synthesis approach, naturally available bio-compounds found in plants and fungi can be effective and have been proven to be alternative reducing agents. Fungi or mushrooms are particularly interesting due to their high content of bioactive compounds, which can serve as excellent reducing agents in the synthesis of nanoparticles. Apart from the economic and environmental benefits, such as ease of availability, low synthesis/production cost, safe and no toxicity, the nanoparticles synthesized from this green method have unique physical and chemical properties. Stabilisation of the nanoparticles in an aqueous solution is exceedingly high, even after prolonged storage with unperturbed size uniformity. Biological properties were significantly improved with higher biocompatibility, anti-microbial, anti-oxidant and anti-cancer properties. These remarkable properties allow further exploration in their applications both in the medical and agricultural fields. This review aims to explore the mushroom-mediated biosynthesis of nanomaterials, specifically the mechanism and bio-compounds involved in the synthesis and their interactions for the stabilisation of nanoparticles. Various metal and non-metal nanoparticles have been discussed along with their synthesis techniques and parameters, making them ideal for specific industrial, agricultural, and medical applications. Only recent developments have been explored in this review.

Dual-signal uric acid sensing based on carbon quantum dots and o-phenylenediamine

Fluorescent carbon quantum dots (CQDs), which showed excitation-dependent emission characteristics, were prepared using a facile hydrothermal method. The structure and optical properties of CQDs were characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, UV-Vis spectroscopy, and fluorescence spectroscopy. These CQDs also showed peroxidase-like activity and could catalyze the H₂O₂-mediated oxidation of o-phenylenediamine (OPD) to form 2,3-diaminophenazine (DAP) with an absorption peak at 420 nm. DAP exhibited an obvious fluorescence emission at 550 nm under the excitation of 360 nm. On the other hand, it decreased the fluorescence of CQDs at 450 nm via inner filter effect. The experimental results indicated that the H₂O₂ concentration affected the color of DAP and the fluorescence intensity of CQDs and DAP. Thus, a colorimetric and ratiometric fluorescence dual-signal method was established for measuring the concentrations of H₂O₂ and uric acid (UA). The effects of pH, incubation temperature, incubation time, and OPD concentration on the response were investigated. Under the conditions of pH 7.5, temperature 50 °C, incubation time 30 min, and OPD 1.5 mM, the absorbance and fluorescence intensity ratio responses were linearly dependent on UA concentration ranging from 5.0 μM to 100 μM. The limits of detection were 0.7 and 0.5 μM with a colorimetric method and ratiometric fluorescence method, respectively. More importantly, this dual responsive method has been applied to the determination of UA in urine samples with satisfactory results.

Phytogenic Synthesis of Pd-Ag/rGO Nanostructures Using Stevia Leaf Extract for Photocatalytic H2 Production and Antibacterial Studies

Continuously increasing energy demand and growing concern about energy resources has attracted much research in the field of clean and sustainable energy sources. In this context, zero-emission fuels are required for energy production to reduce the usage of fossil fuel resources. Here, we present the synthesis of Pd-Ag-decorated reduced graphene oxide (rGO) nanostructures using a green chemical approach with stevia extract for hydrogen production and antibacterial studies under light irradiation. Moreover, bimetallic nanostructures are potentially lime lighted due to their synergetic effect in both scientific and technical aspects. Structural characteristics such as crystal structure and morphological features of the synthesized nanostructures were analyzed using X-ray diffraction and transmission electron microscopy. Analysis of elemental composition and oxidation states was carried out by X-ray photoelectron spectroscopy. Optical characteristics of the biosynthesized nanostructures were obtained by UV-Vis absorption spectroscopy, and Fourier transform infrared spectroscopy was used to investigate possible functional groups that act as reducing and capping agents. The antimicrobial activity of the biosynthesized Pd-Ag-decorated rGO nanostructures was excellent, inactivating 96% of Escherichia coli cells during experiments over 150 min under visible light irradiation. Hence, these biosynthesized Pd-Ag-decorated rGO nanostructures can be utilized for alternative nanomaterial-based drug development in the future.

Application of biosynthesized metal nanoparticles in electrochemical sensors

Recently, the development of eco-friendly, cost-effective and reliable methods for synthesis of metal nanoparticles has drawn a considerable attention. The so-called green synthesis, using mild reaction conditions and natural resources as plant extracts and microorganisms, has established as a convenient, sustainable, cheap and environmentally safe approach for synthesis of a wide range of nanomaterials. Over the past decade, biosynthesis is regarded as an important tool for reducing the harmful effects of traditional nanoparticle synthesis methods commonly used in laboratories and industry. This review emphasizes the significance of biosynthesized metal nanoparticles in the field of electrochemical sensing. There is increasing evidence that green synthesis of nanoparticles provides a new direction in designing of cost-effective, highly sensitive and selective electrode-catalysts applicable in food, clinical and environmental analysis. The article is based on 157 references and provided a detailed overview on the main approaches for green synthesis of metal nanoparticles and their applications in designing of electrochemical sensor devices. Important operational characteristics including sensitivity, dynamic range, limit of detection, as well as data on stability and reproducibility of sensors have also been covered.

Modern Chemical Routes for the Controlled Synthesis of Anisotropic Bimetallic Nanostructures and Their Application in Catalysis

Bimetallic nanoparticles (BNPs) have attracted greater attention compared to its monometallic counterpart because of their chemical/physical properties. The BNPs have a wide range of applications in the fields of health, energy, water, and environment. These properties could be tuned with a number of parameters such as compositions of the bimetallic systems, their preparation method, and morphology. Monodisperse and anisotropic BNPs have gained considerable interest and numerous efforts have been made for the controlled synthesis of bimetallic nanostructures (BNS) of different sizes and shapes. This review offers a brief summary of the various synthetic routes adopted for the synthesis of Palladium(Pd), Platinum(Pt), Nickel(Ni), Gold(Au), Silver(Ag), Iron(Fe), Cobalt(Co), Rhodium(Rh), and Copper(Cu) based transition metal bimetallic anisotropic nanostructures, growth mechanisms e.g., seed mediated co-reduction, hydrothermal, galvanic replacement reactions, and antigalvanic reaction, and their application in the field of catalysis. The effect of surfactant, reducing agent, metal precursors ratio, pH, and reaction temperature for the synthesis of anisotropic nanostructures has been explained with examples. This review further discusses how slight modifications in one of the parameters could alter the growth mechanism, resulting in different anisotropic nanostructures which highly influence the catalytic activity. The progress or modification implied in the synthesis techniques within recent years is focused on in this article. Furthermore, this article discussed the improved activity, stability, and catalytic performance of BNS compared to the monometallic performance. The synthetic strategies reported here established a deeper understanding of the mechanisms and development of sophisticated and controlled BNS for widespread application.

Molecularly imprinted polydopamine modified with nickel nanoparticles wrapped with carbon: fabrication, characterization and electrochemical detection of uric acid

An electrochemical sensor is described for determination of uric acid (UA). Carbon-enwrapped nickel nanoparticles (Ni@BC) were coated with polydopamine (PDA) that was molecularly imprinted with UA. The biomass carbon (BC) was synthesized by one-step solid-state pyrolysis from leaves of Firmiana platanifolia. The imprinted polymer was obtained by electrodeposition of DA as the monomer. The amount of monomer, the scan cycles, pH value and adsorption time were optimized. Furthermore, the selectivity of the MIP for UA on a glassy carbon electrode (GCE) was evaluated by selectivity tests. The differential pulse voltammetric responses to UA with and without interferents were consistent. The modified GCE has a linear response in the 0.01-30 μM UA concentration range, and the limit of detection is 8 nM. The MIP electrode was applied to the analysis of UA in urine for which the initial concentrations were determined by the phosphotungstic acid kit. Recoveries ranged from 91.3 to 113.4%, with relative standard deviations between 1.3 and 9.7% (n = 3). Graphical abstract Schematic presentation of electrochemical detection of uric acid by molecularly imprinted polydopamine modified with nickel nanoparticles wrapped with carbon (Ni@BC-MIP).

Plasmonic spectral determination of Hg(II) based on surface etching of Au-Ag core-shell triangular nanoplates: From spectrum peak to dip

In this work, we develop a simple and selective sensing method for the detection of mercury ions based on surface plasmon resonance (SPR) spectrum change of Au-Ag core-shell triangular nanoplates. When the concentration of mercury is increased, the etching-induced change of particle size and shape also leads to the decrease of the absorption peak at the fixed wavelength, until a spectrum dip takes place. This spectral change of "peak-to-dip" greatly enlarges the detection range of mercury ions, which could be fine tuned by changing the initial thickness of the Ag coating. Under optimal conditions, the decrease of the logarithmic absorption intensity has a good linear response with the concentration of mercury ions increasing from 10 to 1000 μM, and the limit of detection (LOD) is 0.88 μM. Interference studies and real samples test indicate that, this new sensing method has a good selection for mercury ions and can be practically used in lake water. This work shows the surface etching-induced SPR shift can also leads to the intensity change with "peak-to-dip" fashion, which greatly enlarge the concentration range of the detection and could be widely applied in the spectroscopy sensing based on SPR.

Plant-mediated synthesis of AgPd/γ-Al2O3 catalysts for selective hydrogenation of 1,3-butadiene at low temperature

Plant-mediated synthesis of bimetallic AgPd/γ-Al₂O₃ catalysts for selective hydrogenation of low-temperature 1,3-butadiene was reported.

Gold nanorods decorated with graphene oxide and multi-walled carbon nanotubes for trace level voltammetric determination of ascorbic acid

An ultra-sensitive sensor is described for the voltammetric determination of ascorbic acid (AA). A glassy carbon electrode (GCE) was modified with graphene oxide (GO), multi-walled carbon nanotubes (MWCNTs) and gold nanorods (AuNRs). GO was used to prevent the aggregation of MWCNTs. The integration of positively charged AuNRs reduces the overpotential and increases the peak current of AA oxidation. Figures of merit of this sensor, typically operated at a low working potential of 0.036 V (vs. Ag/AgCl), include a low detection limit (0.85 nM), high sensitivity (7.61 μA·μM^-1·cm^-2) and two wide linear ranges (from 1 nM to 0.5 μM and from 1 μM to 8 mM). The use of GO simplifies the manufacture and results in a highly reproducible and stable sensor. It was applied to the quantification of AA in spiked serum. Graphical abstract Graphical abstract contains poor quality and small text inside the artwork. Please do not re-use the file that we have rejected or attempt to increase its resolution and re-save. It is originally poor, therefore, increasing the resolution will not solve the quality problem. We suggest that you provide us the original format. We prefer replacement figures containing vector/editable objects rather than embedded images. Preferred file formats are eps, ai, tiff and pdf.We have provided the original format with the attachments named g.tif. Graphene oxide (GO) in combination with multiwalled carbon nanotubes (MWCNTs) and gold nanorods (AuNRs) were used to construct a sensing interface with outstanding electrocatalytic performance for ascorbic acid detection.