Sensitive Detection of Rifampicin Based on Au-Carbon Nanocomposite.

Gold nanoparticles-supported Cabot Vulcan XC72R (Au/VXC72R) nanocomposite was synthesized by chemical reduction of gold (III) chloride with VXC72R. A novel electrochemical sensor based on the Au/VXC72R nanocomposite has been fabricated for the sensitive detection of rifampicin (RIF). Field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray powder diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the morphology, structure and compositions of the nanocomposite. Under the optimal conditions, the Au/VXC72R-chitosan/GCE can be used to determine RIF concentration in a linear range from 5 × 10-7 mol/L to 1 × 10-5 mol/L with the detection limit of 1.1 × 107 M (S/N = 3). The proposed approach exhibits good stability, acceptable reproducibility and applicability, which will probably bring widespread applications in quality monitoring in real samples.

Sensitive Determination of Dopamine and Paracetamol Based on Carbon Nanotubes-Supported Pd Nanoparticles.

A novel chemically modified electrode was constructed in this study based on the carbon nanotubes-supported Pd nanoparticles (Pd/CNTs). It was demonstrated that the sensor could be used for the determination of dopamine (DA) and paracetamol (PA). The measurements were carried out through application of cyclic voltammetry (CV), differential pulse voltammetry (DPV) and amperometric i-t curve. Under optimum conditions and using the amperometric i-t curve method, the modified electrode provided linear response versus dopamine concentrations in the range of 0.3 × 10-6-5.0 × 10-5 M and PA concentrations in the range of 0.2 × 10-6-6.0 × 10-5 M, respectively. The detection limits for the DA and PA were 9.1 × 10-8 M and 8.9 × 10-8 M (S/N = 3), respectively. The sensitivities for of the electrode were 0.928 and 1.532 µA µM-1 cm-1, respectively.

Graphenol defects induced blue emission enhancement in chemically reduced graphene quantum dots.

In this work, few layer graphene quantum dots (GQDs) with a size of 3-5 nm are purposely treated with highly concentrated aqueous NaBH4 solutions to obtain the reduced graphene quantum dots (rGQDs). Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy demonstrate that the number of carbonyl groups decreases but -OH related defects increase during chemical reduction. Green and weak emissions of original GQDs originate from carrier recombination in the disorder-induced localized state (mainly including carbonyl and carboxyl and epoxy groups). As the reduction degree increases, the photoluminescence (PL) quantum efficiency of GQDs increases dramatically from 2.6% to 10.1%. In the meantime, the PL peak position blue shifts rapidly, and full width at half maximum (FWHM) becomes narrower. Thus we can infer that graphenol topological defects (hydroxyl functionalized graphene) are gradually formed during reduction. Besides, graphenol defect related PL features a longer fluorescence lifetime, excitation wavelength dependence but less pH sensitivity.

Graphene-supported nanoscale zero-valent iron: removal of phosphorus from aqueous solution and mechanistic study.

Excess phosphorus from non-point pollution sources is one of the key factors causing eutrophication in many lakes in China, so finding a cost-effective method to remove phosphorus from non-point pollution sources is very important for the health of the aqueous environment. Graphene was selected to support nanoscale zero-valent iron (nZVI) for phosphorus removal from synthetic rainwater runoff in this article. Compared with nZVI supported on other porous materials, graphene-supported nZVI (G-nZVI) could remove phosphorus more efficiently. The amount of nZVI in G-nZVI was an important factor in the removal of phosphorus by G-nZVI, and G-nZVI with 20 wt.% nZVI (20% G-nZVI) could remove phosphorus most efficiently. The nZVI was very stable and could disperse very well on graphene, as characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS), Fourier Transform infrared spectroscopy (FT-IR) and Raman spectroscopy were used to elucidate the reaction process, and the results indicated that Fe-O-P was formed after phosphorus was adsorbed by G-nZVI. The results obtained from X-ray diffraction (XRD) indicated that the reaction product between nZVI supported on graphene and phosphorus was Fe3(PO4)2·8H2O (Vivianite). It was confirmed that the specific reaction mechanism for the removal of phosphorus with nZVI or G-nZVI was mainly due to chemical reaction between nZVI and phosphorus.

Unraveling the causes of sarcopenia: Roles of neuromuscular junction impairment and mitochondrial dysfunction.

Sarcopenia is a systemic skeletal muscle disease characterized by a decline in skeletal muscle mass and function. Originally defined as an age-associated condition, sarcopenia presently also encompasses muscular atrophy due to various pathological factors, such as intensive care unit-acquired weakness, inactivity, and malnutrition. The exact pathogenesis of sarcopenia is still unknown; herein, we review the pathological roles of the neuromuscular junction and mitochondria in this condition. Sarcopenia is caused by complex and interdependent pathophysiological mechanisms, including aging, neuromuscular junction impairment, mitochondrial dysfunction, insulin resistance, lipotoxicity, endocrine factors, oxidative stress, and inflammation. Among these, neuromuscular junction instability and mitochondrial dysfunction are particularly significant. Dysfunction in neuromuscular junction can lead to muscle weakness or paralysis. Mitochondria, which are plentiful in neurons and muscle fibers, play an important role in neuromuscular junction transmission. Therefore, impairments in both mitochondria and neuromuscular junction may be one of the key pathophysiological mechanisms leading to sarcopenia. Moreover, this article explores the structural and functional alterations in the neuromuscular junction and mitochondria in sarcopenia, suggesting that a deeper understanding of these changes could provide valuable insights for the prevention or treatment of sarcopenia.

Large scale uniform Ni-P plated carbon fiber for boosting urea electro-oxidation and electro-detection.

Seeking an excellent electrocatalyst is the trickiest issue for the application of urea electro-oxidation and electro-detection. Phosphorus-doped nickel plating on carbon fibers (Ni-P/CF) is synthesized by simple electroless plating. SEM results exhibit that the Ni-P densely and uniformly grows onto the surface of carbon fibers (CF), forming carbon fibers-like nanoarchitectures. Benefiting from the carbon fibers-like nano architectures with abundant exposed active sites on the surface of CF, electron transfer can be synchronously facilitated, and Ni-P/CF displays superior urea electrooxidation (UOR) performance with potentials of 1.40 V to reach 100 mA cm-2. Impressively, it can maintain at 20 mA cm-2 for 48 h without evident activity attenuation, demonstrating robust durability. Cycle stability shows that the voltage has only increased by 10 mV at 300 mA cm-2 from the 10th to 20000th cycles. Most importantly, Ni-P/CF at a length of 100 cm with good reproducibility was successfully synthesized, denoting great potential for large-scale industrial production. Therefore, this work not only affords cost-effective tactics for urea-rich wastewater degradation but also can achieve practical medical applications.

Flow-injection chemiluminescent determination of estrogen benzoate using the tris(1,10-phenanthroline) ruthenium(II)-permanganate system.

Chemiluminescence (CL) detection for the determination of estrogen benzoate, using the reaction of tris(1,10-phenanthroline)ruthenium(II)-Na(2)SO(3)-permanganate, is described. This method is based on the CL reaction of estrogen benzoate (EB) with acidic potassium permanganate and tris(1,10-phenanthroline)ruthenium(II). The CL intensity is greatly enhanced when Na(2)SO(3) is added. After optimization of the different experimental parameters, a calibration graph for estrogen benzoate is linear in the range 0.05-10 µg/mL. The 3 s limit of detection is 0.024 µg/mL and the relative standard deviation was 1.3% for 1.0 µg/mL estrogen benzoate (n = 11). This proposed method was successfully applied to commercial injection samples and emulsion cosmetics. The mechanism of CL reaction was also studied.

Fluorescence enhancement of the silver nanoparticales--curcumin-cetyltrimethylammonium bromide-nucleic acids system and its analytical application.

It is found that silver nanoparticles (AgNPs) can further enhance the fluorescence intensity of curcumin (CU)-cetyltrimethylammonium bromide (CTAB)-nucleic acids and improve its anti-photobleaching activity. Under optimum conditions, the enhanced fluorescence intensity is proportion to the concentration of nucleic acids in the range of 2.0 x 10(-8)-1.0 x 10(-6) g mL(-1) for fish sperm DNA (fsDNA), 2.0 x 10(-8)-1.0 x 10(-6) g mL(-1) for calf thymus DNA (ctDNA), 1.0 x 10(-8)-1.0 x 10(-6) g mL(-1) for yeast RNA (yRNA), and their detection limits (S/N = 3) are 8.0 ng mL(-1), 10.5 ng mL(-1) and 5.8 ng mL(-1), respectively. This method is used for determining the concentration of DNA in actual sample with satisfactory results. The interaction mechanism is also studied.

Cobalt Phosphide-Embedded Reduced Graphene Oxide as a Bifunctional Catalyst for Overall Water Splitting.

It is highly desirable to design high-efficiency stable and low-price catalysts in the electrocatalysis field. Herein, we reported a cobalt phosphide (Co2P)-loaded reduced graphene oxide (rGO) composite catalyst (rGO/Co2P) prepared via the convenient hydrothermal and H2 reduction methods. The rGO/Co2P catalyst reduced at 800 °C (rGO/Co2P-800) shows superior electrocatalytic activities for hydrogen evolution reaction and oxygen evolution reaction in 1.0 M KOH solution, achieving an overpotential of 134 and 378 mV, respectively, at a current density of 10 mA cm-2. Moreover, the catalyst can not only maintain stability for a long time in alkaline solution but also in acid media because of the protection of the rGO layers. The superior performance of this catalyst is attributed to the synergy between the carbon layer and transition-metal phosphides. The Co2P nanoparticles have a high degree of dispersion, which prevents agglomeration, thereby exposing more active sites. Moreover, rGO protects the exposed metal particles while providing more electroconductivity to the material. This work provides an efficient route for the development of bifunctional electrocatalysts with excellent performance and stability, which provides new ideas toward overall water splitting.

Sensitive determination of protein based on the fluorescence enhancement effect of terbium (III)-epinephrine-protein-sodium dodecylsulfate system.

It was found that the fluorescence of Tb(3+)-epinephrine (E) complex can be enhanced by both bovine serum albumin (BSA) and sodium dodecylsulfate (SDS), and stabilized by ascorbic acid (AA). It is considered that the fluorescence enhancement of the Tb(3+)-E-BSA-AA-SDS system originates not only from the hydrophobic microenvironment provided by BSA-SDS, but also from the energy transfer from BSA to Tb(3+) in this system. Therefore, a new fluorescence method for the determination of protein concentrations as low as 1.3 x 10(-9) g mL(-1) BSA is established using Tb(3+)-epinephrine complex as probe. The method has been applied for the determination of BSA and human serum albumin in actual samples, and the results obtained are satisfactory. Compared with other fluorescence methods, this method is simpler and more sensitive for the determination of protein. The mechanism of the fluorescence enhancement of the system is studied in detail.

The fluorescence enhancement of quercetin-nucleic acid system and the analytical application.

Nucleic acid can greatly enhance the fluorescence intensity of quercetin in HMTA-HCl (pH 5.5) buffer. The enhanced intensity is in proportion to the concentration of nucleic acids in the range 5.0 x 10(-9) to 1.0 x 10(-6) g/mL for fsDNA, 5.0 x 10(-9) to 7.0 x 10(-7) g/mL for ctDNA and 5.0 x 10(-9) to 1.0 x 10(-6) g/mL for yRNA, and their detection limits (S/N = 3) are 3.5 x 10(-9), 7.8 x 10(-10) and 2.6 x 10(-9) g/mL, respectively. In comparison with most reported fluorescent probes for the determination of nucleic acids, the proposed probe has higher sensitivity and lower toxicity. The interaction investigation indicates that quercetin binds with double-strand DNA in groove binding mode, resulting in fluorescence enhancement of this system.

New Insights into Layered Graphene Materials as Substrates to Regulate Synthesis of Ni-P Nanomaterials for Electrocatalytic Oxidation of Methanol and Water.

The doping ring-core nickel phosphide/graphene nanomaterial is obtained by H2 reduction of the flower-like nickel phosphates/graphene oxide (NiPOGO) and sea urchin-like nickel phosphates/chemically converted graphene (NiPOG) substrates. The obtained structure of nickel phosphates depends on the influence of different kinds of oxygen-containing groups on the graphene substrate. The substrate can also affect the particle size and distribution of nickel phosphate nanoparticles. The substrate can adjust the particle size, distribution, and exposed growth direction of nickel phosphide. These materials with high activity are employed as electrochemical catalysts for methanol oxidation reactions, which is ∼7 times that of pure nickel phosphide, and there is a very small Tafel slope of 47 mV decade-1 in the water oxidation reaction. Our results highlight that the substrate structure is essential to catalytic materials for electrochemical oxidation of methanol and water.

Iron Carbides: Control Synthesis and Catalytic Applications in COx Hydrogenation and Electrochemical HER.

Catalytic transformation of COx (x = 1, 2) with renewable H2 into valuable fuels and chemicals provides practical processes to mitigate the worldwide energy crisis. Fe-based catalytic materials are widely used for those reactions due to their abundance and low cost. Novel iron carbides are particularly promising catalytic materials among the reported ferrous catalysts. Recently, a series of strategies has been developed for the preparation of iron carbide nanoparticles and their nanocomposites. Control synthesis of FeCx -based nanomaterials and their catalytic applications in COx hydrogenation and electrochemical hydrogen evolution reaction (HER) are reviewed. The discussion is focused on the unique catalytic activities of iron carbides in COx hydrogenation and HER and the correlation between structure and catalytic performance. Future synthesis and potential catalytic applications of iron carbides are also summarized.

Fluorescence enhancement effect of morin-nucleic acid-L-cysteine-capped nano-ZnS system and the determination of nucleic acid.

It is found that L-cysteine-capped nano-ZnS can further enhance the fluorescence intensity of the morin-nucleic acid system. Under optimum conditions, the enhanced intensity of fluorescence is proportional to the concentration of nucleic acid in the range of 7.0 x 10(-8)-1.0 x 10(-5) g mL(-1) for fish sperm DNA (fsDNA) and 9.0 x 10(-8)-5.0 x 10(-6) g mL(-1) for yeast RNA (yRNA). The corresponding detection limits (S/N = 3) are 2.0 x 10(-8) g mL(-1) and 4.0 x 10(-8) g mL(-1), respectively. The interaction mechanisms of morin-nucleic acid-L-cysteine-capped nano-ZnS system are studied by multiple techniques. It is considered that there exists synergistic effects of groove binding and electrostatic interaction between morin, L-cysteine-capped nano-ZnS and nucleic acid, and the complex of morin-L-cysteine-capped nano-ZnS-nucleic acid is formed.

Resonance light-scattering enhancement effect of the protein-Y3+-TTA-SLS system and its analytical application.

In this paper, a sensitive resonance light scattering (RLS) method for the determination of protein is reported. In the Tris-HCl (pH 7.50) buffer, protein enhanced the RLS intensity of the Y(3+)-2-thenoyltrifluoroacetone (TTA)-sodium dodecyl sulphate (SLS) system. The enhanced RLS intensities were in proportion to the concentrations of proteins in the range 8.0 x 10(-9)-1.0 x 10(-5) g/mL for BSA, 1.0 x 10(-8)-1.0 x 10(-5) g/mL for HSA and 1.0 x 10(-8)-1.0 x 10(-6 )g/mL for EA, and their detection limits were 5.0, 5.4 and 6.7 ng/mL, respectively. Actual samples were satisfactorily determined. The interaction mechanism was also studied.

A new method for the determination of nucleic acid using an Eu3+- nicotinic acid complex as a resonance light scattering probe.

This study found that in Tris-HCl buffer, the resonance light scattering (RLS) intensity of the Eu(3+)-nicotinic acid system can be greatly enhanced by nucleic acids and the enhanced intensity is proportional to the concentration of nucleic acid in the range of 7 x 10(-8)-1 x 10(-5 ) g x mL(-1) for fsDNA, and its detection limit is 2 x 10(-8 ) g x mL(-1). Based on this, a new method for the determination of nucleic acids is proposed. Synthetic and actual samples are determined satisfactorily. The interaction mechanism is also studied. It is thought that nucleic acid can bind with the Eu(3+)-nicotinic acid complex through electrostatic attraction and thus form a large Eu(3+)-nicotinic acid-nucleic acid complex.

Scopoletine as fluorescence probe for determination of protein.

Scopoletine (SLT), 7-hydroxy-6-methoxylcoumarin, is known to possess biological activities such as abirritating and anti-tumor, it can quench intrinsic fluorescence of bovine serum albumin (BSA) and the fluorescence intensity of itself is enhanced. So, SLT is used as fluorescence probe for quantitative determination of protein. The experiments indicate that under optimum conditions, the enhanced intensity of fluorescence is in proportion to the concentration of proteins in a wide range, and their detection limits (S/N=3) are 1.4 x 10(-8)g mL(-1) for BSA and 1.1 x 10(-8)g mL(-1) for HSA, respectively. Samples were satisfactorily determined. The interaction mechanism is also discussed.

Flow injection-chemiluminescence determination of phenol using potassium permanganate and formaldehyde system.

It is found that phenol can react with potassium permanganate in the acidic medium and produce chemiluminescence, which is greatly enhanced by formaldehyde. The optimum conditions for this chemiluminescent reaction are in detail studied using a flow injection system. The experiments indicate that under optimum conditions, the chemiluminescence intensity is linearly related to the concentration of phenol in the range 5.0x10(-9) to 1.0x10(-6)gmL-1 with a detection limit (3sigma) of 3x10(-9)gmL-1. The relative standard deviation is 1.2% for 4.0x10(-7)gmL-1 phenol solution in 11 repeated measurements. This method has the advantages of simple operation, fast response and high sensitivity. The method is successfully applied to the determination of phenol in the waste water.

Investigation of the interaction between curcumin and nucleic acids in the presence of CTAB.

It is found that nucleic acid can enhance the resonance light scattering (RLS) enhancement effect of curcumin (CU) in the presence of cationic surfactant cetyltrimethylammonium bromide (CTAB). The investigation indicates that in BR (pH 4.3) buffer, both the positive CTAB and negative yeast RNA (yRNA) combine and form a positive large association, then which is bound on the two carbon atoms of the carbonyls of CU through hydrogen bond and hydrophobic force and form CU-CTAB-yRNA ternary complex, resulting in the RLS enhancement of this system. Based on it, a sensitive method for determination of nucleic acids at ngml(-1) is established.

Molecular self-assembling and the fluorescence enhancement in morin-Al3+-cetyltrimethylammonium bromide-protein system.

Fluorescence enhancement effect of the morin-Al3+-cetyltrimethylammonium bromide (CTAB)-bovine serum albumin (BSA) system is reported here and the interaction mechanism is studied using fluorescence, resonance light scattering (RLS), absorption spectroscopy, Far-UV circular dichroism (CD) spectrum and small angle X-ray scattering (SAXS) measurement. It is considered that protein can bind with Al3+, morin and CTAB through self-assembling function with electrostatic attraction, hydrogen bond, hydrophobic interaction and Vander Waal force etc, and forms a supermolecular association with multilayer structure, in which morin-Al3+ is clamped between BSA and CTAB. In this system, the fluorescence enhancement of morin originates from both intermolecular energy transfer between BSA and morin, and the hydrophobic microenvironment provided by BSA and CTAB. Whereas Al3+ plays a key role for the enhancement of energy transfer efficiency because it provides an efficient channel for the energy transfer between BSA and morin.