PEI-conjugated AuNPs as a sensing platform for arsenic (AS-III)

We have developed a simple method for synthesis of spherical gold nanoparticles (AuNPs) with enhanced surface properties. The polyethyleneimine (PEI) has good potential to minimise the size of the precursor. The UV–vis spectra of synthesised AuNPs with reducing agents (PEI) have been characterised with a peak at 530?nm. The size and shape measurement of AuNPs was confirmed by transmission electron microscopy (TEM) which shows that the mean diameter is 3.9?nm. The optimal concentration of reducing agents was found to be 1% for synthesis of AuNPs. PEI-conjugated AuNP shows binding with arsenic III (0.1?ppm) as confirmed by scanning electron microscope (SEM)/energy dispersive X-rays mapping. TEM revealed the particle shape and size. Zeta potential, zeta deviation, effective particle size, Z-average diameter, polydispersity index and electrophoretic mobility have been observed in order to understand the stability of AuNPs. The image of SEM confirmed that As (III) particles were eventually distributed in PEI-conjugated AuNPs matrix. Further, this study demonstrated that PEI-conjugated AuNPs is a sensing platform of As (III).     

Efficient one pot synthesis of chitosan-induced gold nanoparticles by microwave irradiation

An efficient and rapid method for the preparation of gold nanoparticles (AuNPs) within a few minutes has been developed by direct microwave irradiation of HAuCl₄ and chitosan mixed solution in one pot. Herein, chitosan molecules acted as both the reducing and stabilizing agent for the preparation of AuNPs. The obtained AuNPs have different shapes, such as the spherical nanoparticles, triangular nanoplates and nanorods, which were characterized by ultraviolet-visible (UV-Vis) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and fourier transform infrared spectroscopy (FTIR). Additionally, the results showed that microwave power could affect the required time for preparing the AuNPs arising from the distinction of heating rate, and long irradiation time was favorable for complete reduction of HAuCl₄ when a low microwave power was applied.     

Synthesised magnetic nanoparticles coated zeolite (MNCZ) for the removal of arsenic (As) from aqueous solution

A novel adsorbent, magnetic nanoparticle (γ-Fe₂O₃)-coated zeolite (MNCZ), was prepared for the removal of arsenic (As) ions from aqueous solution. The influence of different sorption parameters, that is, contact time, acidic reaction (pH) and initial arsenic concentration were studied using batch equilibrium techniques. The results obtained showed that the MNCZ was effective for the removal of As from aqueous solution, and the percentage removal of As could reach over 95.6% at a pH value of 2.5 within 15?min. Moreover, the removal of As depended on the initial concentration of As. For the regeneration of MNCZ material, 0.1?M NaOH was suitable for the desorption of As (70% after 15?min), and the regenerated material showed an adsorption capacity of 93.95% within five cycles. We concluded that MNCZ presents a reusable adsorbent for a fast, convenient and highly efficient removal of As from aqueous solution.     

顺序注射-化学发光联用技术测定氢化可的松含量

基于酸性条件下,氢化可的松对高锰酸钾-亚硫酸钠体系发光反应具有明显的增敏作用,本文研究建立了顺序注射化学发光测定氢化可的松含量的分析新方法。在优化的实验条件下,氢化可的松的质量浓度在1.0×10-9～1.0×10-6 g/mL范围内与发光强度呈良好的线性关系,检出限(3σ)为5.6×10-10g/mL。对浓度为5×10-8g/mL氢化可的松进行11次平行测定,其相对标准偏差为1.99%。经实验,本体系具有快速、准确、简便、试剂消耗少、灵敏度高、线性范围宽等特点,应用于注射液中氢化可的松含量的测定,结果与标准方法一致。     

Design of pH-responsive gold nanoparticles in oncology

Gold nanoparticles (AuNPs) hold promising applications in many fields such as electronics, optics and catalysis. In the past decades, there has been a growing interest for their application in medicine, in particular in nano-oncology as contrast agents, drug delivery vehicles or for diagnosis. Once injected intravenously and thanks to their small size, the AuNPs can circulate in the whole body via the blood stream and reach easily the tumour. However, what makes them very attractive for cancer treatment is their ability to distinguish healthy cells from cancer cells. While the current anticancer agents lack specific targeting, AuNPs, with their targeting efficiency, will enable the use of lower amount of drugs with all the positive aspects for the health of the patient. Additionally, their optical properties give them the ability to be used in imaging as an incredibly powerful contrast agent. For these reasons, they are believed to be one of the tools that, in the future, will enable to considerably increase the efficiency of cancer treatments by simultaneously imaging the tumour and treat it. They constitute an ideal theranostic drug delivery platform, in other words a unique combination of diagnostics and therapy. Many researches focus on the engineering of the nanoparticle surface in order to increase their biocompatibility and enable their further conjugation with bioactive ligands such as drugs, targeting or imaging agents for the design of multifunctional platforms. pH responsiveness, the ability to change properties with a change of proton concentration, is a remarkable asset for drug delivery carrier. Indeed, it has been demonstrated that cancer cells show very particular pHs in their environment: extracellular as well as intracellular. This characteristic has been exploited to create a more specific and efficient way to treat cancer. The present review focuses on the design of pH responsive AuNPs and particularly on the advantages and the potential applications of such hybrid nanomaterials in oncology.     

Anodic stripping voltammetry of arsenic(III) using gold nanoparticle-modified electrodes

A novel method for the detection of arsenic(III) in 1 M HCl at a gold nanoparticle-modified glassy carbon electrode has been developed. The gold nanoparticles were electrodeposited onto the glassy carbon electrode via a potential step from +1.055 to -0.045 V vs SCE for 15 s from 0.5 M H2SO4 containing 0.1 mM HAuCl4. The resulting electrode surfaces were characterized with both AFM and cyclic voltammetry. Anodic stripping voltammetry of arsenic(III) on the modified electrode was performed. After optimization, a LOD of 0.0096 ppb was obtained with LSV.     

Studies on the removal of arsenic (III) from water by a novel hybrid material

The present work provides a method for removal of the arsenic (III) from water. An ion-exchanger hybrid material zirconium (IV) oxide-ethanolamine (ZrO-EA) is synthesized and characterized which is subsequently used for the removal of selective arsenic (III) from water containing 10,50,100 mg/L of arsenic (III) solution. The probable practical application for arsenic removal from water by this material has also been studied. The various parameters affecting the removal process like initial concentration of As (III), adsorbent dose, contact time, temperature, ionic strength, and pH are investigated. From the data of results, it is indicated that, the adsorbent dose of 0.7 mg/L, contact time 50 min after which the adsorption process comes to equilibrium, temperature (25 ± 2), solution pH (5-7), which are the optimum conditions for adsorption. The typical adsorption isotherms are calculated to know the suitability of the process. The column studies showed 98% recovery of arsenic from water especially at low concentration of arsenic in water samples.     

Characterization of arsenic (V) and arsenic (III) in water samples using ammonium molybdate and estimation by graphite furnace atomic absorption spectroscopy

Arsenic (V) is known to form heteropolyacid with ammonium molybdate in acidic aqueous solutions, which can be quantitatively extracted into certain organic solvents. In the present work, 12-molybdoarsenic acid extracted in butan-1-ol is used for quantification of As (V). Total arsenic is estimated by converting arsenic (III) to arsenic (V) by digesting samples with concentrated nitric acid before extraction. Concentration of As (III) in the sample solutions could be calculated by the difference in total arsenic and arsenic (V). The characterization of arsenic was carried out by GFAAS using Pd as modifier. Optimization of the experimental conditions and instrumental parameters was investigated in detail. Recoveries of (90-110%) were obtained in the spiked samples. The detection limit was 0.2 microg l(-1). The proposed method was successfully applied for the determination of trace amount of arsenic (III) and arsenic (V) in process water samples.     

我国生活饮用水中铅、砷检测能力验证分析

分析2012年由中国测试技术研究院承担的国家认监委能力验证项目＂CNCA-12-A08生活饮用水中重金属及无机阴离子的检测＂中铅、砷的能力验证结果,对生活饮用水中铅、砷检测方法进行比较和探讨。能力验证结果表明：ICP-MS法测定铅和砷的结果满意率最高,测定结果中位值及平均值与理论值最为接近。     

碘量法测定锌精矿中的砷

试样以硝酸、氯酸钾分解、硫酸冒烟,再以碘量法测定锌精矿中的砷含量。方法准确、简便,加标回收率为98．20％-101．6％,RSD〈2．0％,方法测定范围0．20～3．00％。     

Characterization of gold nanoparticles in organic or inorganic medium (ethanol/water) fabricated by spark discharge method

In this paper a method of spark discharge method (SDM) for producing gold nanoparticles in organic or inorganic medium (pure ethanol/deionized water) is proposed. The microstructure of SDM-produced gold nanoparticles was examined by Transmission Electron Microscopy. The crystal structure and surface plasmon resonance of the nanoscale gold particles were studied using X-ray diffraction and UV-Visible spectroscopy. Zeta potential analysis showed that negative charges on the particle surface may be contributing to the stability of the suspension. The experiment's results revealed that SDM is an alternative process to synthesize gold nanoparticle suspension with different particle sizes and shapes in different media without any surfactant.     

Flow injection on-line sorption preconcentration coupled with hydride generation atomic fluorescence spectrometry for determination of (ultra)trace amounts of arsenic(III) and arsenic(V) in natural water samples

A flow injection on-line sorption preconcentration and separation in a knotted reactor (KR) was coupled to hydride generation atomic fluorescence spectrometry (HG-AFS) for speciation of inorganic arsenic in natural water samples. The method involved on-line formation of the As(III)-pyrrolidinedithiocarbamate (PDC) complex over a sample acidity of 0.001-0.1 mol L(-1) HCl, its adsorption onto the inner walls of the KR made from 150-cm long x 0.5-mm i.d. PTFE tubing, elution withmol L(-1) HCl, and detection by HG-AFS. Total inorganic arsenic was determined after prereduction of As(V) to As(III) with 1% m/v L-cysteine. The concentration of As(V) was calculated by the difference of the total inorganic arsenic and As(III). A 1 mol L(-1) concentration of HCl was employed not only as the efficient eluent but also as the required medium for subsequent hydride generation. Potential factors that affect adsorption, rinsing, elution, and hydride generation were investigated in detail. The low cost, easy operation, and high sensitivity are the obvious advantages of the present system. With consumption of a 6 mL sample solution, an enhancement factor of 11 and a detection limit (3s) of 0.023 microg L(-1) As(III) were obtained at a sample throughput of 32 h(-1). The precision for 14 replicate measurements of 1 microg L(-1) As(III) was 1.3% (RSD). The recoveries from natural water samples varied from 96.7 to 105% for 2 microg L(-1) of As(III) spike and from 97.1 to 107% for 2 microg L(-1) of As(V) spike. The analytical results obtained by the present method for total arsenic in the certified reference materials, SLRS-4 (river water) and NASS-5 (seawater), agreed well with the certified values. The developed method was also successfully applied to the speciation of inorganic arsenic in local natural water samples.     

Optimization of the Simultaneous Determination of Cr(III) and Cr(VI) by Ion Chromatography with Chemiluminescence Detection

An optimized method for the simultaneous determination of Cr(III) and Cr(VI) in aqueous solutions using ion chromatography with chemiluminescence detection is described. Excellent resolution of the two chromium species was obtained using a single mixed-bed ion-exchange column with continuous elution. After postcolumn reduction of Cr(VI) to Cr(III), the light emitted during the Cr(III)-catalyzed oxidation of luminol with hydrogen peroxide was measured. Parameters affecting the postcolumn reactions such as reductant concentration, reductant mixing, point of luminol introduction, and luminol flow rate were optimized. The calibration curves in the range tested (0.01-50 μg L(-)(1)) were linear, and detection limits of 0.002 μg L(-)(1) for both Cr(III) and Cr(VI) were obtained. The results of the analyses of the water reference materials LGC CRM6010 and NIST SRM1643d with certified chromium values of 49 ± 4 and 18.53 ± 0.20 μg L(-)(1) and found to contain only Cr(III) were 49.2 ± 1.8 and 19.0 ± 1.5 μg L(-)(1), respectively. Values of 10.6 ± 0.5 and 10.1 ± 0.5 μg L(-)(1) were obtained when a simulated water sample containing 10 μg L(-)(1) Cr(III) and Cr(VI) was analyzed.     

Microwave-hydrothermal synthesis of nanostructured Na-birnessites and phase transformation by arsenic(III) oxidation

Microwave-hydrothermal synthesis was employed to produce Na-birnessites. Crystalline, single-phase materials were obtained at temperatures as low as 120 °C and times as short as 1 min. X-ray diffraction and Raman spectroscopy were used to characterize the structural features of the nanostructured powders. Birnessites possessed a monoclinic structure in space group C2/m with nine Raman-active bands, all of which were observed for the first time due to optimized acquisition of the spectroscopic data. The highly reactive materials produced were submitted to sorption experiments with As(III). An oxidative precipitation occurred with the production of Mn(II) arsenate at higher arsenic concentrations. In addition, the formation of hausmannite (Mn₃O₄) was confirmed by X-ray diffraction and Raman analyses of the reacted solid phase. The observed 14 Raman-active modes were adjusted according to the tetragonal I4₁/amd space group for hausmannite. An additional band related to the breathing mode of the arsenate was observed, leading to the conclusion that adsorption onto hausmannite takes place in addition to the oxidative precipitation of manganese arsenate.     

Trace Analysis of Zn(II), Be(II), and Bi(III) by Enzyme-Catalyzed Chemiluminescence

A novel technique for the trace analysis of metal ions Zn(II), Be(II), and Bi(III) in bulk solutions is discussed. This technique involves the generation of a chemiluminescence signal from alkaline phosphatase catalyzed hydrolysis of a phosphate derivative of 1,2-dioxetane. Zn(II) can be determined by two methods, reactivation of the alkaline phosphatase apoenzyme and inhibition of the native enzyme. Be(II) and Bi(III) can be determined quantitatively by inhibition of the native enzyme. Subppb to ppm level detection of Zn(II), Be(II), and Bi(III) has been achieved. Initial studies with mixed metals are also reported. The technique described is rapid and sensitive and can be readily applied to the microassay of heavy metal ions.     

Importance of nanoparticle size in colorimetric and SERS-based multimodal trace detection of Ni(II) ions with functional gold nanoparticles

Colorimetric detection of analytes using gold nanoparticles along with surface-enhanced Raman spectroscopy (SERS) are areas of intense research activity since they both offer sensing of very low concentrations of target species. Multimodal detection promotes the simultaneous detection of a sample by a combination of different techniques; consequently, surface chemistry design in the development of multimodal nanosensors is important for rapid and sensitive evaluation of the analytes by diverse analytical methods. Herein it is shown that nanoparticle size plays an important role in the design of functional nanoparticles for colorimetric and SERS-based sensing applications, allowing controlled nanoparticle assembly and tunable sensor response. The design and preparation of robust nanoparticle systems and their assembly is reported for trace detection of Ni(II) ions as a model system in an aqueous solution. The combination of covalently attached nitrilotriacetic acid moieties along with the L-carnosine dipeptide on the nanoparticle surface represents a highly sensitive platform for rapid and selective detection of Ni(II) ions. This systematic study demonstrates that significantly lower detection limits can be achieved by finely tuning the assembly of gold nanoparticles of different core sizes. The results clearly demonstrate the feasibility and usefulness of a multimodal approach.     

Amine-terminated TEG-derived PAMAM dendrimer as template for preparation of gold nanoparticles in water

Nano-sized monodisperse gold particles (AuNPs) have received significant attention in the past decade, due to their unique physical properties and good chemical stability, which can lead to a wide variety of potential applications. In this work, TEG-derived PAMAM dendrimers with amine-terminating groups were synthesized and characterized by ¹H NMR and FT-IR. These dendrimers were investigated as the templates for preparation of gold nanoparticles through the reduction of HAuCl₄ by NaBH₄ in water. Stable gold nanoparticles with diameters around 10 nm were obtained in the presence of G2.0 – G5.0 dendrimers and characterized by UV-Vis spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS). The particle size of the produced AuNPs decreased with increasing dendrimer generations. A dendrimer of higher generation has a rigid structure with many end groups on the surface and may play a powerful role in the growth of the AuNPs, as well as having a solid stabilization effect on the AuNPs.     

Reducing HAuCl(4) by the C(60) dianion: C(60)-directed self-assembly of gold nanoparticles into novel fullerene bound gold nanoassemblies

The C(60) dianion is used to reduce tetrachloroauric acid (HAuCl(4)) for the first time; three-dimensional C(60) bound gold (Au-C(60)) nanoclusters are obtained from C(60)-directed self-assembly of gold nanoparticles due to the strong affinities of Au-C(60) and C(60)-C(60). The?process was monitored in situ by UV-vis-NIR spectroscopy. The resulting Au-C(60) nanoclusters were characterized using transmission electron microscopy (TEM), selected area electron diffraction (SAED), energy-dispersive spectroscopy (EDS), x-ray powder diffraction (XRD), x-ray photoelectron spectroscopy (XPS), and FT-IR and Raman spectroscopies. TEM demonstrates the formation of 3D nanonetwork aggregates, which are composed of discrete gold nanocores covered with a C(60) monolayer. The SAED and XRD patterns indicate that the gold nanocores inside the capped C(60) molecules belong to the face-centred cubic crystal structure, while the C(60) molecules are amorphous. The EDS and XPS measurements validate that the Au-C(60) nanoclusters contain only Au and C elements and Au(3+) is reduced to Au(0). FT-IR spectroscopy shows the chemiadsorption of C(60) to the gold nanocores, while Raman spectroscopy demonstrates the electron transfer from the gold nanocores to the chemiadsorbed C(60) molecules. Au-C(60) nanoclusters embedded in tetraoctyl-n-ammonium bromide (TOAB) on glassy carbon electrodes (GCEs) have been fabricated and have shown stable and well-defined electrochemical responses in aqueous solution.     

Amine-terminated TEG-derived PAMAM dendrimer as template for preparation of gold nanoparticles in water

Nano-sized monodisperse gold particles (AuNPs) have received significant attention in the past decade, due to their unique physical properties and good chemical stability, which can lead to a wide variety of potential applications. In this work, TEG-derived PAMAM dendrimers with amine-terminating groups were synthesized and characterized by ¹H NMR and FT-IR. These dendrimers were investigated as the templates for preparation of gold nanoparticles through the reduction of HAuCl₄ by NaBH₄ in water. Stable gold nanoparticles with diameters around 10 nm were obtained in the presence of G2.0–G5.0 dendrimers and characterized by UV-Vis spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS). The particle size of the produced AuNPs decreased with increasing dendrimer generations. A dendrimer of higher generation has a rigid structure with many end groups on the surface and may play a powerful role in the growth of the AuNPs, as well as having a solid stabilization effect on the AuNPs.     

Recognition of potassium ion in water by 15-crown-5 functionalized gold nanoparticles.

Reported here is an efficient recognition of K+ by 15-crown-5 functionalized gold nanoparticles in aqueous matrix containing physiologically important cations, such as Li+, Cs+, NH4+, Mg2+, Ca2+, and excess amount of Na+. Upon exposure to K+, the colloidal solution changes from red to blue, in response to surface plasmon absorption of dispersed and aggregated nanoparticles. The concentration ranges of K+ detected in this study are 0.099-0.48 mM and 7.6 microM-0.14 mM, when concentrations of colloidal gold are 54.9 and 7.1 nM, respectively. Recognition of K+ and formation of the aggregates are proposed via a sandwich complex of 2:1 between 15-crown-5 moiety and K+. Also discussed is the possibility of a preorganized structure of 15-crown-5 at the water-organic interface for the efficient complexation with K+.