Improved hydrogen oxidation reaction under alkaline conditions by Au–Pt alloy nanoparticles

This work demonstrates the outstanding performance of alloyed Au_1 Pt_1 nanoparticles on hydrogen oxidation reaction(HOR) in alkaline solution. Due to the weakened hydrogen binding energy caused by uniform incorporation of Au, the alloyed Au_1 Pt_1/C nanoparticles exhibit superior HOR activity than commercial Pt Ru/C. On the contrary, the catalytic performance of the phase-segregated Au_2 Pt_1/C and Au_1 Pt_1/C bimetallic nanoparticles in HOR is significantly worse. Moreover, Au_1 Pt_1/C shows a remarkable durability with activity dropping only 4% after 3000 CV cycles, while performance attenuation of commercial Pt Ru/C is high up to 15% under the same condition. Our results indicate that the alloyed Au_1 Pt_1/C is a promising candidate to substitute commercial Pt Ru/C for hydrogen oxidation reaction in alkaline electrolyte.     

4-Aminothiophenol functionalized gold nanoparticles as colorimetric sensors for the detection of cobalt using UV–Visible spectrometry

The 4-aminothiophenol functionalized gold nanoparticles (4-ATP-Au NPs) were used as colorimetric sensors for the detection of Co²⁺ in aqueous solution by using UV–Visible spectrometry. The 4-ATP-Au NPs were characterized by UV–Visible, FT-IR, TEM and dynamic light scattering (DLS) which confirmed their higher binding affinity towards Co²⁺ through coordinate covalent interactions that can be observed with the naked eye. The absorbance ratio (A₅₇₀/A₅₂₃) was linear with Co²⁺ concentration in the range of 15 × 10^?3 to 1 × 10^?3 M with a correlation coefficient of (R ²) 0.994, and the limit of detection was 5.79 × 10^?5 M.     

Surface-imprinted core–shell Au nanoparticles for selective detection of bisphenol A based on surface-enhanced Raman scattering

Surface-imprinted core–shell Au nanoparticles (AuNPs) were explored for the highly selective detection of bisphenol A (BPA) by surface-enhanced Raman scattering (SERS). A triethoxysilane-template complex (BPA-Si) was synthesized and then utilized to fabricate a molecularly imprinted polymer (MIP) layer on the AuNPs via a sol–gel process. The imprinted BPA molecules were removed by a simple thermal treatment to generated the imprint-removed material, MIP-ir-AuNPs, with the desired recognition sites that could selectively rebind the BPA molecules. The morphological and polymeric characteristics of MIP-ir-AuNPs were investigated by transmission electron microscopy and Fourier-transform infrared spectroscopy. The results demonstrated that the MIP-ir-AuNPs were fabricated with a 2 nm MIP shell layer within which abundant amine groups were generated. The rebinding kinetics study showed that the MIP-ir-AuNPs could reach the equilibrium adsorption for BPA within 10 min owning to the advantage of ultrathin core–shell nanostructure. Moreover, a linear relationship between SERS intensity and the concentration of BPA on the MIP-ir-AuNPs was observed in the range of 0.5–22.8 mg L⁻¹, with a detection limit of 0.12 mg L⁻¹ (blank ± 3 × s.d.). When applied to SERS detection, the developed surface-imprinted core–shell MIP-ir-AuNPs could recognize BPA and prevent interference from the structural analogues such as hexafluorobisphenol A (BPAF) and diethylstilbestrol (DES). These results revealed that the proposed method displayed significant potential utility in rapid and selective detection of BPA in real samples.     

Nitrogen-doped mesoporous carbon nanospheres loaded with cobalt nanoparticles for oxygen reduction and Zn–air batteries

Mesoporous carbon supported with transition metals nanoparticles performs desired activities for oxygen reduction reaction (ORR) and clean energy conversion devices such as Zn–air batteries. In this work, we synthesized N-doped mesoporous carbon loaded with cobalt nanoparticles (CoMCN) through self-assembly method. There are sufficient mesopores on the carbon substrate which stem from the pore-forming agent. These mesopores can provide enough accessible active sites and profitable charge/mass transport for ORR. The high content of pyridinic and graphitic N is beneficial for promoting O₂ adsorption and reduction. The smaller value of I_D/I_G indicates the higher degree of graphitization of CoMCN, providing better electronic conductivity. The half-wave potential of CoMCN is 0.865 V in basic solution, which is 24 mV more positive than that of the commercial Pt/C (0.841 V). In addition, CoMCN performs excellent methanol tolerance and stability under both basic and acidic conditions. The Zn–air battery assembled with CoMCN performs the larger power density and open-circuit voltage than the commercial Pt/C-based battery, indicating the potential application in energy conversion systems. This work provides thoughtful ideas for fabricating transition metal nanoparticles based porous carbon for electrocatalysis and metal–air batteries.     

Gold nanoparticles immobilized on metal–organic frameworks with enhanced catalytic performance for DNA detection

In this work, gold nanoparticles (AuNPs) assembled on the surface of iron based metal–organic frameworks (MOFs), Fe-MIL-88, are facilely prepared through electrostatic interactions using polyethyleneimine (PEI) molecules as linker. The resulting hybrid materials possess synergetic peroxidase-like activity. Because iron based metal–organic frameworks, Fe-MIL-88, exhibits highly peroxidase-like activity, and AuNPs has the distinct adsorption property to single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA). The peroxidase-like activity of Au@Fe-MIL-88 exhibit excellent switchable in response to specific DNA, ssDNA is easily adsorbed on the surface of the Au@Fe-MIL-88 hybrids, resulting in the reduce of the peroxidase-like activity of the hybrids. While it is recovered by the addition of target DNA, and the recovery degree is proportional to the target DNA concentration over the range of 30–150 nM with a detection limit of 11.4 nM. Based on these unique properties, we develop a label-free colorimetric method for DNA hybridization detection. In control experiment, base-mismatched DNA cannot induce recovery of the peroxidase-like activity. This detection method is simple, cheap, rapid and colorimetric.     

Ag@C core–shell structure composites-decorated Ag nanoparticles: zero current potentiometry for detection of hydrogen peroxide

Ag@C core–shell structure composites were successfully synthesized by hydrothermal method, and then Ag nanoparticles were decorated on the surface of Ag@C by reduction of AgNO₃. The morphology, composition and structure of the Ag@C@Ag composites were characterized by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD). Cyclic voltammetry and amperometry were used to evaluate the electrocatalytic performance of the Ag@C@Ag/GCE for detection of H₂O₂. Meanwhile, a new electrochemical method of zero current potentiometry was used for electrochemical detection of H₂O₂. The linear range and the detection limit were from 0.2 to 10, and 0.07 μM, respectively.     

Core-shell Ag–Pt nanoparticles: A versatile platform for the synthesis of heterogeneous nanostructures towards catalyzing electrochemical reactions

Heterogeneous nanostructures that are defined as a hybrid structure consisting of two or more nanoscale domains with distinct chemical compositions or physical characteristics have attracted intense efforts in recent years. In this review, we focus on the introduction of a number of heterogeneous nanostructures derived using core-shell Ag–Pt nanoparticles as starting materials, including hollow, dimeric and composite structures and also highlight their application in catalyzing electrochemical reactions, e.g., methanol oxidation reaction and oxygen reduction reaction. This review not only shows the capability of core-shell Ag–Pt nanoparticles in producing various heterogeneous nanostructures as starting templates, but also highlights the structural design or electronic interaction that endows the heterogeneous nanostructures with enhanced catalytic properties either in methanol oxidation or in oxygen reduction. Further, we also make some perspectives for more heterogeneous nanostructures that may be prepared by using core-shell Ag–Pt particles or their derivatives so as to offer the readers the opportunities and challenges in this field.     

An aptamer based assay for the β-adrenergic agonist ractopamine based on aggregation of gold nanoparticles in combination with a molecularly imprinted polymer

A sensitive visual aptamer-based assay is presented for the determination of ractopamine (RAC) in animal feed beef. In the absence of RAC, the aptamer binds to gold nanoparticles (AuNPs) and this prevents the AuNPs to undergo salt-induced aggregation which usually is accompanied by a color change from red to blue. If however, RAC is present, it will bind to the aptamer while the AuNPs remain uncoated so that aggregation and a color change will occur due to salt-induced aggregation. This can be monitored by spectrophotometer or even with bare eyes. Under optimal conditions, the aptasensor exhibits a linear range that covers the 10 to 400 ng.mL￣¹ RAC concentration range. The limit of detection is as low as 10 ng.mL￣¹. In order to further improve selectivity, a RAC-selective molecularly imprinted membrane was prepared and used to pre-extract RAC from complex samples. The combined method (molecularly imprinted membrane and aptasensor) was applied to the determination of RAC in spiked animal feed and beef and gave recoveries that ranged from 72.7 % to 87.3 % for complete feed and from 78.2 % to 86.5 % for beef, respectively.

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Graphical abstract A sensitive visual aptamer-based assay based on aggregation of gold nanoparticles in combination with a molecularly imprinted polymer was developed for the determination of ractopamine (RAC) in animal feed and beef.

     

A novel method for Co(Ⅱ) and Cu(Ⅱ) analysis by capillary electrophoresis with chemiluminescence detection

Based on the fact that some metal ions can catalyze the chemiluminescence(CL)reaction of luminol with K_3Fe(CN)_6,a novel capillary electrophoresis CL method was developed for the determination of Co(Ⅱ)and Cu(Ⅱ).The separation was carried out with a 10 mmol/L sodium acetate solution containing 0.8 mmol/L luminol and 2.0 mmol/Lα-HIBA(adjusted to pH 4.8 by HAc solution).The post-capillary reagent was 2.0 mmol/L K_3Fe(CN)_6 which was adjusted to pH 13.0 by NaOH solution.Under the optimum conditions,the detection limits(S/N=3)for Co(Ⅱ)and Cu(Ⅱ)were 7.5×10~(-11)mol/L and 7.5×10~(-9)mol/L,with the linear range of 7.5×10~(-9)mol/L to 1.0×10~(-6)mol/L and 7.5×10~(-8)mol/L to 5.0×10~(-5)mol/L, respectively.     

Evaluation of hair roots for detection of methamphetamine and 3,4-methylenedioxymethamphetamine abuse by use of an HPLC–chemiluminescence method

We describe the use of hair roots as a matrix for detection of methamphetamine (MP) and 3,4-methylenedioxymethamphetamine (MDMA) abuse. The concentration of drugs was determined in rat hair roots, hair shafts, and plasma after a single administration of MP or MDMA, by use of an HPLC-peroxyoxalate chemiluminescence (PO-CL) method involving column switching. Plasma and hair roots and shafts were collected from male Wistar rats before and after administration of MP (10 mg kg(-1), i.p.). In addition, the roots and shafts of pigmented and non-pigmented hair of male Lister hooded rats were collected after administration of MDMA (10 mg kg(-1), i.p.). The concentrations of MP and MDMA in plasma and hair were determined by use of the HPLC-PO-CL method, with satisfactory sensitivity and reproducibility. The concentration of MP in hair roots 1-14 days after administration ranged from 0.038 to 0.115 ng mg(-1) (n = 3). By use of the HPLC-PO-CL method, MP could be detected in hair roots for longer (up to 14 days) than it could be detected in conventional biological specimens, for example plasma (~1 day), and MDMA was detected in hair roots from 1 to 10 days after administration. The AUC(1-10) (ng day mg(-1)) for MDMA in roots of non-pigmented and pigmented hair was comparable (4.93 ± 2.09 vs. 6.67 ± 1.28, n = 3), whereas AUC(1-14) for hair shafts differed significantly (1.86 ± 0.93 vs. 4.58 ± 0.63, P < 0.05, n = 3). The window for detecting MP (or MDMA) in hair roots under our conditions was 1-14 (or 1-10) days.     

Derivatization of pinacolyl alcohol with phenyldimethylchlorosilane for enhanced detection by gas chromatography–mass spectrometry

A derivatization procedure for the qualitative gas chromatography–mass spectrometry (GC-MS) analysis of pinacolyl alcohol (PA) that employs phenyldimethylchlorosilane (PhDMClS) and the promoter N-methylimidazole is described. While PA, underivatized, can be detected using conventional gas chromatographic methods, its polarity and low boiling point make its detection in complex matrices challenging. The silylation procedure described herein generates a PA-derivative exhibiting an increased on-column retention time, thus shifting its GC-MS signal away from commonly encountered, volatile, interfering analytes. Derivatized PA could be distinguished from other PhDMClS-derivatized isomeric alcohols by its unique retention time and mass spectrum. The derivatization was demonstrated to perform well in the GC-MS analysis and identification of PA in samples from Proficiency Tests administered by the Organisation for the Prohibition of Chemical Weapons (OPCW).

Marker peptide combination for source identification of gelatins obtained from Equidae hides by LC–MS/MS detection

Gelatin, which is a soluble, natural polymer produced by partial hydrolysis of collagens, has been extensively used in food and pharmaceuticals. Donkey-hide gelatin is a well-known traditional Chinese medicine. The certification of donkey-hide gelatin is one of the most concerned issues for consumers. Currently, the source identification of the homologous family species, including donkey, horse and their hybrids, remains a major challenge. Here, three peptides (SGQPGTVGPAGVR, GASGPAGVR and GATGPAGVR) of the equine family species were screened using high-resolution LC-MS. The combination of these three peptides has been used as a high-performance marker in LC-MS/MS to identify the animal source (donkey, horse, and their hybrids) of donkey-hide-gelatin-containing products. Horse-hide gelatin and hybrid-hide gelatin can be detected in gelatin-based products even at very low percentages (0.05% and 0.10%, respectively). The marker peptide combination method is useful for source identification of homologous family species and is not only highly sensitive but also rapid.     

Chemo–immunotherapy for chemo-resistance and metastasis of triple-negative breast cancer by combination of iron-oxide nanoparticles and dual-targeting doxorubicin liposomes

Triple-negative breast cancer (TNBC) lacks specific regimens for targeted therapy. Repeat chemotherapy promotes the evolution of TNBC into highly chemo-resistant tumors that metastasize to multiple organs simultaneously. Herein, polyacrylic acid-coated ultrasmall superparamagnetic iron-oxide nanoparticles (PAA@IONs) and dual-targeting doxorubicin liposomes achieved chemo–immunotherapy through intermittent administration. They inhibited tumor-drug resistance and multiorgan-specific metastasis significantly by targeting tumors and the microenvironment. We deciphered an immunosuppressive pre-metastatic niche and discovered that PAA@IONs could target tumors, tumor-draining lymph nodes (TDLNs), the liver, bone, and lungs. They promoted the polarization of macrophages into M1 macrophages in these organs and tissues. This action remodeled the immunosuppressive microenvironment and induced a sustained immune response, thereby reducing organ-specific metastasis. Overcoming the disadvantages of doxorubicin-induced cardiotoxicity as well as low tumor specificity, dual peptide-modified liposomes could target CD206 and CD13 simultaneously, and reverse chemo-resistance. These properties resulted in a significant decrease in the numbers of myeloid-derived suppressor cells (MDSCs) and cancer stem cells (CSCs) in the liver, lungs, and bone, thereby reducing protein expression of Ki-67 in TDLNs, and dramatically increasing the number of cluster of differentiation (CD)8⁺ T cells and CD8⁺ T cell/T-regulatory-cell ratio in tumors and TDLNs (P < 0.0001). Compared with the control (P < 0.05 and P < 0.01, respectively) or free drug (P < 0.0001 and P < 0.01, respectively), multi-organ metastases were suppressed significantly, tumor-growth rate reduced, and survival prolonged. Our drug-delivery system overcame TNBC chemo-resistance and inhibited multiorgan-specific metastases. It circumvents the lack of effective therapeutic targets, the problem of patient selection due to a low mutation rate, and can simultaneously offer the possibility of avoiding surgery and considerable postoperative complications.     

Application of primary plasma standardization to Nd-YAG laser-induced shock wave plasma spectrometry for quantitative analysis of high concentration Au–Ag–Cu alloy

A study was performed on a laser-induced shock wave plasma generated on high concentration Au–Ag–Cu alloys by a Q-switched Nd-YAG laser of 4.8 mJ under reduced air pressure of 2 torr. It was found that the total emission intensity of the secondary plasma is proportional to the intensity of the primary plasma. Assuming linear proportionality between the intensity of the primary plasma and the number of atoms vaporized from the target, it is proposed that quantitative analysis can be applied to the intensities of the analytical emission lines normalized by the total intensity of the primary plasma. This experimental result demonstrated for each metal element shows an excellent linear relationship between the normalized emission line intensity and the content of the corresponding element.     

Aptamer-conjugated bio-bar-code Au–Fe3O4 nanoparticles as amplification station for electrochemiluminescence detection of tumor cells

An electrochemiluminescence (ECL) assay has been developed for highly sensitive and selective detection of tumor cells based on cell-SELEX aptamer-target cell interactions through a cascaded amplification process by using bio-bar-code Au–Fe₃O₄ as amplification station. Firstly, bio-bar-code toehold-aptamer/DNA primer/Au–Fe₃O₄ (TA/DP/Au–Fe₃O₄) nanoconjugates are fabricated with a ratio of 1:10 to efficiently avoid cross-linking reaction and recognize target cells, which are immobilized on the substrate by hybridizing aptamer to capture probe with 18-mer. Through strand displacement reaction (SDR), the TA/DP/Au–Fe₃O₄ composites further act as the amplification station to initiate rolling circle amplification (RCA). As a result, on the surface of TA/DP/Au–Fe₃O₄, a large number of Ru(bpy)₂(dcbpy)NHS-labeled probes hybridize to RCA products, which are easily trapped by magnetic electrode to perform the magnetic particle-based ECL platform. Under isothermal conditions, this powerful amplification strategy permits detection of Ramos cells as low as 16 cells with an excellent selectivity. Moreover, analysis of Ramos cells in complex samples and whole blood samples further show the great potential of this ultrasensitive approach in clinical application involving cancer cells-related biological processes.     

Simplified multiresidue method for determination of pesticide residues in lettuce by gas chromatography with nitrogen–phosphorus detection

A rapid and simple method has been developed for simultaneous determination of different classes of pesticide in different varieties of lettuce (Lactuca sativum). Lettuce samples were extracted by homogenization with acetone and partitioned into ethyl acetate-cyclohexane. Subsequent sample clean-up was not needed. Pesticide residues were determined by capillary gas chromatography with nitrogen-phosphorus detection (NPD). Confirmatory analysis of the pesticides was performed by capillary gas chromatography coupled with mass spectrometry in selected-ion-monitoring (SIM) mode. Recovery at two levels of fortification (ca. 0.05 and 0.20 mg kg(-1)) ranged from 63.9 to 118.6%, and relative standard deviations were below 9.5%. The proposed method was used to determine pesticide levels in different types of lettuce grown in soil from experimental fields.     

Highly Efficient and Easily Recoverable Ag3PO4–TiO2–Fe2O3 Magnetic Photocatalyst with Wide Spectral Range for Water Treatment

Russian Journal of Physical Chemistry A - A new magnetic Ag3PO4–TiO2–Fe2O3 photocatalyst (Ag–Ti–Fe) has been synthesized by a solid-state blending method. The sample was...     

Preparation of trout liver microsomes for iron speciation in P-450 enzymes by AE–FPLC with ICP–(ORS)MS detection

Cytochromes P-450 are members of a superfamily of hemoproteins involved in the oxidative metabolism of various physiological and xenobiotic compounds in eukaryotes and prokaryotes. The multiplicity of this group of enzymes has been widely studied by chromatographic techniques, mainly high-performance liquid chromatography (HPLC). Because these enzymes are membrane-bound proteins, sample preparation for chromatographic separation of P-450 enzymes requires a solubilization step. The sample-preparation procedures are critical, because detergents affect not only the efficiency of protein solubilization but also their further chromatographic resolution. Trout liver microsomes have been taken here as a model sample to investigate iron speciation in cytochrome P-450. Trouts were treated intraperitoneally with -naphthoflavone, a potent inducer of some P-450 enzymes, and a microsomal suspension containing 7.4±0.1 nmol mL^–1 P-450 enzymes was obtained by ultracentrifugation. Lubrol PX was selected as detergent for solubilization, resulting in about 90% solubilization recovery. The solubilized cytochromes P-450 were further separated by AE–FPLC, with UV detection, or coupled to ICP–MS with an octapole reaction system, ICP–(ORS)MS (monitoring Fe signals at masses 54, 56, and 57). A sampling procedure and chromatographic conditions are developed and were successfully applied to iron speciation in trout liver P-450 enzymes. ICP–(ORS)MS detection of P-450 enzymes is Fe-specific and so will give accurate information on the prosthetic group of the protein, which can constitute an advantageous alternative to classical methods for detection of these hemoproteins.     

Rapid and sensitive method for the determination of acetaldehyde in fuel ethanol by high-performance liquid chromatography with UV–Vis detection

A high-performance liquid chromatography (HPLC) method for the determination of acetaldehyde in fuel ethanol was developed. Acetaldehyde was derivatized with 0.900 mL 2,4-dinitrophenylhydrazine (DNPHi) reagent and 50 L phosphoric acid 1 mol L^–1 at a controlled room temperature of 15°C for 20 min. The separation of acetaldehyde-DNPH (ADNPH) was carried out on a Shimadzu Shim-pack C₁₈ column, using methanol/LiCl_(aq) 1.0 mM (80/20, v/v) as a mobile phase under isocratic elution and UV–Vis detection at 365 nm. The standard curve of ADNPH was linear in the range 3–300 mg L^–1 per injection (20 L) and the limit of detection (LOD) for acetaldehyde was 2.03 g L^–1, with a correlation coefficient greater than 0.999 and a precision (relative standard deviation, RSD) of 5.6% (n=5). Recovery studies were performed by fortifying fuel samples with acetaldehyde at various concentrations and the results were in the range 98.7–102%, with a coefficient of variation (CV) from 0.2% to 7.2%. Several fuel samples collected from various gas stations were analyzed and the method was successfully applied to the analysis of acetaldehyde in fuel ethanol samples.     

Determination of twelve herbicides in tobacco by a combination of solid–liquid–solid dispersive extraction using multi-walled carbon nanotubes, dispersive liquid-liquid micro-extraction, and detection by GC with triple quadrupole mass spectrometry

We report on a method for the determination of twelve herbicides using solid–liquid–solid dispersive extraction (SLSDE), followed by dispersive liquid-liquid micro-extraction (DLLME) and quantitation by gas chromatography with triple quadrupole mass spectrometric detection. SLSDE was applied to the extraction of herbicides from tobacco samples using multi-walled carbon nanotubes (MWCNTs) as clean-up adsorbents. The effect of the quantity of MWCNTs on SLSDE, and of type and volume of extraction and disperser solvents and of salt effect on DLLME were optimized. Good linearity is obtained in the 5.0 - 500 μg kg^?1 concentration range, with regression coefficients of >0.99. Intra-day and inter-day repeatability, expressed as relative standard deviations, are between 3 and 9 %. The recoveries in case of herbicide-spiked tobacco at concentration levels of 20.0, 50.0 and 100.0 g kg^?1 ranged from 79 to 105 %, and LODs are between 1.5 and 6.1 μg kg^?1. All the tobacco samples were found to contain butralin and pendimethalin at levels ranging from 15.8 to 500.0 μg kg^?1.