Thiomalate Research Articles

AJIPHASE®: A Highly Efficient Synthetic Method for One-Pot Peptide Elongation in the Solution Phase by an Fmoc Strategy.

We previously reported an efficient peptide synthesis method, AJIPHASE®, that comprises repeated reactions and isolations by precipitation. This method utilizes an anchor molecule with long‐chain alkyl groups as a protecting group for the C‐terminus. To further improve this method, we developed a one‐pot synthesis of a peptide sequence wherein the synthetic intermediates were isolated by solvent extraction instead of precipitation. A branched‐chain anchor molecule was used in the new process, significantly enhancing the solubility of long peptides and the operational efficiency compared with the previous method, which employed precipitation for isolation and a straight‐chain aliphatic group. Another prerequisite for this solvent‐extraction‐based strategy was the use of thiomalic acid and DBU for Fmoc deprotection, which facilitates the removal of byproducts, such as the fulvene adduct.

AJIPHASE®: A Highly Efficient Synthetic Method for One‐Pot Peptide Elongation in the Solution Phase by an Fmoc Strategy

AbstractWe previously reported an efficient peptide synthesis method, AJIPHASE®, that comprises repeated reactions and isolations by precipitation. This method utilizes an anchor molecule with long‐chain alkyl groups as a protecting group for the C‐terminus. To further improve this method, we developed a one‐pot synthesis of a peptide sequence wherein the synthetic intermediates were isolated by solvent extraction instead of precipitation. A branched‐chain anchor molecule was used in the new process, significantly enhancing the solubility of long peptides and the operational efficiency compared with the previous method, which employed precipitation for isolation and a straight‐chain aliphatic group. Another prerequisite for this solvent‐extraction‐based strategy was the use of thiomalic acid and DBU for Fmoc deprotection, which facilitates the removal of byproducts, such as the fulvene adduct.

Can freshwater phytoplankton access cadmium bound to low‐molecular‐weight thiols?

AbstractRecent studies have suggested that low‐molecular‐weight (LMW) ligands can enhance trace metal uptake by marine diatoms. We have extended this work to freshwater phytoplankton and have investigated Cd bioavailability in the presence of LMW thiols, with two green algae (Chlamydomonas reinhardtii and Pseudokirchneriella subcapitata) and a cyanobacterium (Anabaena flos‐aquae). Using nitrilotriacetic acid (NTA) to hold the free Cd2+ concentration constant, we progressively added cysteine to the exposure medium and determined short‐term Cd uptake rates for each organism; the Cd uptake rates remained constant and were unaffected even when the concentrations of the Cd‐cysteine complexes exceeded that of the free Cd2+. Similar results were obtained with algae pre‐acclimated to different nitrogen sources or low zinc concentrations, even though such treatments affect their ability to utilize amino acids or take up Cd. A lack of effect was also observed for the two green algae with penicillamine, mercaptosuccinic acid, dithiothreitol and glutathione. These results suggest that the Cd‐thiol complexes do not contribute to Cd uptake. However, when the experiments were repeated with cysteine in the absence of NTA, at the same Cd2+ concentration, a significantly higher Cd uptake rate was observed in the presence of the L‐ or D‐cysteine stereoisomers than in the presence of NTA. This enhancement of Cd uptake in the presence of cysteine alone was sensitive to the nitrogen nutrition of these microorganisms, and we suggest that the enhancement likely results from biologically‐induced chemical oxidation of cysteine in the boundary layer adjacent to the algal cell.

Ultrasonic assisted synthesis of palladium-nickel/iron oxide core–shell nanoalloys as effective catalyst for Suzuki-Miyaura and p-nitrophenol reduction reactions

In this study, ultrasonic assisted synthesis of Pd-Ni/Fe3O4 core–shell nanoalloys is reported. Unique reaction condition was prepared by ultrasonic irradiation, releasing the stored energy in the collapsed bubbles and heats the bubble contents that leads to Pd(II) and Ni(II) reduction. Co-precipitation method was applied for the synthesis of Fe3O4 nanoparticles (NPs). Immobilized solution was produced by sonicating the aqueous mixture of Fe3O4 and mercaptosuccinic acid to obtain Pd-Ni alloys on Fe3O4 magnetic NP cores. The catalytic activity of the synthesized Pd-Ni/Fe3O4 core–shells was investigated in the Suzuki-Miyaura CC coupling reaction and 4-nitrophenol reduction, which exhibited a high catalytic activity in both reactions. These magnetic NPs can be separated from the reaction mixture by external magnetic field. This strategy is simple, economical and promising for industrial applications.

Antibacterial activity of nitric oxide releasing silver nanoparticles

Silver nanoparticles (AgNPs) are well known potent antimicrobial agents. Similarly, the free radical nitric oxide (NO) has important antibacterial activity, and due to its instability, the combination of NO and nanomaterials has been applied in several biomedical applications. The aim of this work was to synthesize, characterize and evaluate the antibacterial activity of a new NO-releasing AgNPs. Herein, AgNPs were synthesized by the reduction of silver ions (Ag+) by catechin, a natural polyphenol and potent antioxidant agent, derived from green tea extract. Catechin acts as a reducing agent and as a capping molecule on the surface of AgNPs, minimizing particle agglomeration. The as-synthesized nanoparticles were characterized by different techniques. The results showed the formation of AgNPs with average hydrodynamic size of 44 nm, polydispersity index of 0.21, and zeta potential of −35.9 mV. X-ray diffraction and Fourier transform infrared spectroscopy revealed the presence of the AgNP core and cathecin as capping agent. The low molecular weight mercaptosuccinic acid (MSA), which contain free thiol group, was added on the surface of catechin-AgNPs, leading to the formation of MSA-catechin-AgNPs (the NO precursor nanoparticle). Free thiol groups of MSA-catechin-AgNPs were nitrosated leading to the formation of S-nitroso-mercaptosuccinic acid (S-nitroso-MSA), the NO donor. The amount of 342 ± 16 µmol of NO was released per gram of S-nitroso-MSA-catechin-AgNPs. The antibacterial activities of catechin-AgNPs, MSA-catechin-AgNPs, and S-nitroso-MSA-catechin-AgNPs were evaluated towards different resistant bacterial strains. The results demonstrated an enhanced antibacterial activity of the NO-releasing AgNP. For instance, the minimal inhibitory concentration values for Pseudomonas aeruginosa (ATCC 27853) incubated with AgNPs-catechin, AgNPs-catechin-MSA, and AgNPs-catechin-S-nitroso-MSA were found to be 62, 125 and 3 µg/mL, respectively. While in the case of Klebsiella pneumoniae (ATCC 700603) the minimum bactericidal concentration values for treatments with AgNPs-catechin, AgNPs-catechin-MSA, and AgNPs-catechin-S-nitroso-MSA were found to be 1000, 500, and 125 µg/mL, respectively. The antibacterial actions of the NO-releasing nanoparticle were superior in comparison with the antibacterial effects of AgNPs, in most of the tested antibiotic resistant bacteria strains. These results highlight the promising uses of NO-releasing AgNPs against resistant bacteria in several biomedical applications.

One pot synthesis of carboxyl functionalized-polyhedral oligomeric siloxane based monolith via photoinitiated thiol-methacrylate polymerization for nano-hydrophilic interaction chromatography

A hybrid monolith exhibiting almost retention independent separation performance in hydrophilic interaction chromatography (HILIC) was obtained by one-pot photoinitiated thiol-methacrylate polymerization. Polyhedral oligomeric silsesquioxane containing methacrylate units (POSS-MA) was used as the main monomer and crosslinking agent, together with a hydrophilic ligand with two carboxyl groups, mercaptosuccinic acid (MSA) as the thiol agent and chromatographic ligand. The isocratic separation of nucleosides, nucleotides and organic acids on MSA attached-poly(POSS-MA) monolith was investigated in HILIC mode. The van-Deemter plots for obtained for nucleosides, nucleotides and benzoic acids clearly showed that there were two regions in each graph with two different slopes in the studied range of linear flow rate (i.e. 0.2–4.3mm/s). The slope of plate height-linear velocity curve was so small in the low linear velocity region between 0.2–2.1mm/s while the slope in high linear velocity region between 2.1–4.3mm/s was so higher with respect to the first region. The van-Deemter plots sketched for all analyte grous used in HILIC mode obeyed this tendency Almost “retention independent plate height behavior” was demonstrated in HILIC, using nucleotides, nucleotides or benzoic acids as the analytes in the linear velocity range of 0.2–2.1mm/s. This behavior was explained by the porous structure of the synthesized monolith facilitating the convective transport of analytes. The variation of plate height was not retention-independent within high linear velocity range (>3.2mm/s) when nucleosides were separated in HILIC mode.

Thiolated selenium as a new precursor for the aqueous synthesis of CdSe/CdS core/shell quantum dots

A new hydrothermal method for the synthesis of thiol-protected CdSe/CdS core/shell quantum dots (QDs) starting from thiolated cadmium and selenium is reported. Four different thiols namely; 3-mercaptopropane-1-sulfonic acid (MPSA), 2-mercaptosuccinic acid, 3-mercaptopropanoic acid (MPA) and 2-mercaptoacetic acid were used to prepare the precursors which also served as capping agent and sulphur source. The as-synthesized QDs were characterized by ultraviolet–visible (UV–Vis) and photoluminescence (PL) spectroscopy, fourier transform infrared spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy, Raman spectroscopy and transmission electron microscopy. The as-prepared QDs exhibited broad trap emission with longer lifetime (>100 ns) due to thiolate trap sites. The particle growth kinetics and the photoluminescent quantum yield (PLQY) of the resulting QDs were found to be depended on the type of thiol and pH. The MPA capped QDs synthesized at pH 11.0 exhibited the high PLQY among other thiol capped QDs. The size of the QDs was calculated to be ~3 nm by XRD analysis, which is consistent with TEM results. The possible mechanism of the core/shell formation is also presented.

Interaction of insulin with colloidal ZnS quantum dots functionalized by various surface capping agents

Interaction of quantum dots (QDs) and proteins strongly influenced by the surface characteristics of the QDs at the protein-QD interface. For a precise control of these surface-related interactions, it is necessary to improve our understanding in this field. In this regard, in the present work, the interaction between the insulin and differently functionalized ZnS quantum dots (QDs) were studied. The ZnS QDs were functionalized with various functional groups of hydroxyl (OH), carboxyl (COOH), amine (NH2), and amino acid (COOH and NH2). The effect of surface hydrophobicity was also studied by changing the alkyl-chain lengths of mercaptocarboxylic acid capping agents. The interaction between insulin and the ZnS QDs were investigated by fluorescence quenching, synchronous fluorescence, circular dichroism (CD), and thermal aggregation techniques. The results reveal that among the studied QDs, mercaptosuccinic acid functionalized QDs has the strongest interaction (∆G°=−51.50kJ/mol at 310K) with insulin, mercaptoethanol functionalized QDs destabilize insulin by increasing the beta-sheet contents, and only cysteine functionalized QDs improves the insulin stability by increasing the alpha-helix contents of the protein, and. Our results also indicate that by increasing the alkyl-chain length of capping agents, due to an increase in hydrophobicity of the QDs surface, the beta-sheet contents of insulin increase which results in the enhancement of insulin instability.

Inducible Sequential Oxidation Process in Water-Soluble Copper Nanoclusters for Direct Colorimetric Assay of Hydrogen Peroxide in a Wide Dynamic and Sampling Range.

Direct and fast detection methods for H2O2 have great demand in materials science, biology, and medicine. Colorimetric assay of H2O2 has been regarded as one versatile approach that can avoid tedious operation and complicated setup. In this report, we provided a cost-effective and time-saving H2O2 colorimetric assay strategy based on a mercaptosuccinic acid (MSA)-stabilized Cu nanocluster (NC) probe without using any chromogenic reagent. Direct and fast colorimetric detection of H2O2 was realized based on the color change of MSA-capped Cu NCs in aqueous medium. It was found that the Cu NCs presented eligible resistance to natural oxidation either in concentrated solution or in the powder state. However, the dissolved oxygen in a highly diluted solution of the Cu NCs could trigger the aggregation of the Cu NCs and their further fusion into small Cu nanoparticles (NPs). When this diluted solution served as a probe solution for detecting H2O2, a sequential oxidation process occurred in the newly formed Cu NPs, including the cleavage of MSAs on the surface and conversion of Cu into Cu2O, leading to the probe with capacity for H2O2 assay in a wide dynamic and sampling range. The sensitive solution color change was attributed to the growth of the Cu NPs (fading of plasmonic absorption) upon the addition of low levels of H2O2 and the transition of the valence states of Cu (color reactions) upon the addition of high levels of H2O2. A concentration range of H2O2 from 1 μM to 1 M could be detected by a small dose of the probe. Moreover, the Cu NCs powder subsequent to storage for 10 months could maintain a similar sensitivity for H2O2 assay, which provides possibilities for a wide range of practical applications in water samples.

Real-time monitoring of the UV-induced formation of quantum dots on a milliliter, microliter, and nanoliter scale

The authors report on a systematic study on the low-cost, low-temperature, and fast synthesis of water soluble quantum dots (QDs) stabilized by mercaptosuccinic acid by UV irradiation. The effects of UV irradiation (at 254 nm and 250 nm) and temperature on the precursors (Cd:Se, Cd:Te, Cd, Zn:S, Zn:Se and Zn) are described. Best results are achieved with a mixture of precursors containing cadmium, selenium and MSA where a 10-min irradiation with 254-nm light gives CdSe QDs with a quantum yield of 13.5%. The authors also describe the preparation and monitoring of the formation of QDs in sub-mg, sub-μg and sub-ng quantities, the smallest concentration being 258 pg in volume of 4 nL. The growth of the QDs can be monitored in real time by absorption, fluorescence and dynamic light scattering. The solutions of the particles also are characterized by fluorescence correlation spectroscopy and detected by LED-induced fluorescence. The preparation of such QDs by UV radiation is simple, easily controllable, and inexpensive. Conceivably, it can be integrated with lab-on-chip, micro total analysis systems or other instrumentation.

Mercaptan acids modified amphiphilic copolymers for efficient loading and release of doxorubicin

In this paper, four different kinds of mercaptan acids modified amphiphilic copolymers mPEG-b-PATMC-g-SRCOOH (R=CH2, CH2CH2, (CH2)10 and CH(COOH)CH2) were successfully synthesized by thiol-ene “click” reaction between pendent carbon-carbon double bonds of PEG-b-PATMC and thiol groups of thioglycolic acid, 3-mercaptopropionic acid, 11-mercaptoundecanoic acid or 2-mercaptosuccinic acid. DLS and TEM measurements showed that all the mPEG-b-PATMC-g-SRCOOH copolymers could self-assemble to form micelles which dispersed in spherical shape with nano-size before and after DOX loading. The positively-charged DOX could effectively load into copolymer micelles via synergistic hydrophobic and electrostatic interactions. All DOX-loaded mPEG-b-PATMC-g-SRCOOH micelles displayed sustained drug release behavior without an initial burst which could be further adjusted by the conditions of ionic strength and pH. Especially in the case of mPEG-b-PATMC-g-S(CH2)10COOH (P3) micelles, the suitable hydrophobility and charge density were not only beneficial to improve the DOX-loading efficiency, they were also good for obtaining smaller particle size, higher micelle stability and more timely drug delivery. Confocal laser scanning microscopy (CLSM) and MTT assays further demonstrated efficient cellular uptake of DOX delivered by mPEG-b-PATMC-g-SRCOOH micelles and potent cytotoxic activity against cancer cells.

Nitric oxide-releasing nanoparticles: synthesis, characterization, and cytotoxicity to tumorigenic cells

Nitric oxide (NO) is involved in several biological processes, including toxicity against tumor cells. The aim of this study was to synthesize, characterize, and evaluate the cytotoxicity of NO-releasing chitosan nanoparticles. A thiol-containing molecule, mercaptosuccinic acid (MSA), was encapsulated (encapsulation efficiency of 99%) in chitosan/sodium tripolyphosphate nanoparticles (CS NPs). The obtained nanoparticles showed an average hydrodynamic size of 108.40 ± 0.96 nm and polydispersity index of 0.26 ± 0.01. MSA-CS NPs were nitrosated leading to S-nitroso-MSA-CS NPs, which act as NO donor. The cytotoxicity of CS NPs, MSA-CS NPs, and S-nitroso-MSA-CS NPs were evaluated in several tumor cells, including human hepatocellular carcinoma (HepG2), mouse melanoma (B16F10), and human chronic myeloid leukemia (K562) cell lines and Lucena-1, a vincristine-resistant K562 cell line. Both CS NPs and MSA-CS NPs did not cause toxic effects in these cells, whereas S-nitroso-MSA-CS NPs caused potent cytotoxic effects in all the tested tumor cell lines. The half-maximal inhibitory concentration values of S-nitroso-MSA-CS NPs were 19.7, 10.5, 22.8, and 27.8 μg·mL−1 for HepG2, B16F10, K562, and Lucena-1 cells, respectively. In contrast, S-nitroso-MSA-CS NPs exhibited lower cytotoxic to non-tumorigenic melanocytes (Melan-A) when compared with melanoma B16F10. Therefore, the results highlight the potential use of NO-releasing CS NPs in antitumor chemotherapy.

Synthesis, molecular modelling, and preliminary anticonvulsant activity evaluation of novel naphthalen-2-yl acetate and 1,6-dithia-4,9-diazaspiro [4.4] nonane-3,8-dione derivatives

The synthesis, pharmacological evaluation and molecular modelling study of novel naphthalen-2-yl acetate and 1,6-dithia-4,9-diazaspiro [4.4]nonane-3,8-dione derivatives as potential anticonvulsant agents are described. The newly synthesized compounds were characterized by both analytical and spectral data. Alkylation of 1H-imidazole or substituted piperazine with 1-(2-naphthyl)-2-bromoethanone (2) gave naphthalen-2-yl 2-(1H-imidazol-1-yl) acetate (3) and naphthalen-2-yl 2-(substituted piperazin-1-yl) acetate (4–8). Moreover, condensation of naphthalen-2-yl 2-bromoacetate or 2-bromo-1-(naphthalen-2-yl) ethanone with hydrazine hydrate and acetylacetone resulted in the formation of the cyclic pyrazole products 9 and 13. Sonication of naphthalen-2-yl acetate (1) with 2-chloropyridine, 2-chloropyrimidine and 2-(chloromethyl) oxirane gave naphthalen-2-yl 2-(pyridin-2-yl) acetate (10), naphthalen-2-yl 2-(pyrimidin-2-yl) acetate (11) and naphthalen-2-yl-3-(oxiran-2-yl) propanoate (12) respectively. Cyclocondensation reaction of 2-iminothiazolidin-4-one (14) with thioglycolic acid, thiolactic acid and thiomalic acid gave 1,6-dithia-4,9-diazaspiro [4.4]nonane-3,8-dione derivatives (15–17). The compounds were testedin vivofor the anticonvulsant activity by delaying strychnine-induced seizures. The diazaspirononane (17) and 1-(2-naphthyl)-2-bromoethanone (2) showed a high significant delay in the onset of convulsion and prolongation of survival time compared to phenobarbital. The molecular modelling study of anticonvulsant activity of synthesized compounds showed a CNS depressant activity via modulation of benzodiazepine allosteric site in GABA-A receptors.

Quantum Dot Nanotoxicity Investigations Using Human Lung Cells and TOXOR Electrochemical Enzyme Assay Methodology.

Recent studies have suggested that certain nanomaterials can interfere with optically based cytotoxicity assays resulting in underestimations of nanomaterial toxicity. As a result there has been growing interest in the use of whole cell electrochemical biosensors for nanotoxicity applications. Herein we report application of an electrochemical cytotoxicity assay developed in house (TOXOR) in the evaluation of toxic effects of mercaptosuccinic acid capped cadmium telluride quantum dots (MSA capped CdTe QDs), toward mammalian cells. MSA capped CdTe QDs were synthesized, characterized, and their cytotoxicity toward A549 human lung epithelial cells investigated. The internalization of QDs within cells was scrutinized via confocal microscopy. The cytotoxicity assay is based on the measurement of changes in cellular enzyme acid phosphatase upon 24 h exposure to QDs. Acid phosphatase catalyzes dephosphorylation of 2-naphthyl phosphate to 2-naphthol (determined by chronocoulometry) and is indicative of metabolic activity in cells. The 24 h IC50 (concentration resulting in 50% reduction in acid phosphatase activity) value for MSA capped CdTe QDs was found to be 118 ± 49 μg/mL using the TOXOR assay and was in agreement with the MTT assay (157 ± 31 μg/mL). Potential uses of this electrochemical assay include the screening of nanomaterials, environmental toxins, in addition to applications in the pharmaceutical, food, and health sectors.

A chemically reduced graphene oxide–Au nanocage composite for the electrochemical detection of dopamine and uric acid

Herein, a chemically reduced graphene oxide–Au nanocage (CRGO–AuNCs) composite was synthesized by electrostatic assembly of poly-diallyldimethylammonium chloride (PDDA)-modified CRGO and mercaptosuccinic acid (MSA)-modified Au nanocages.

Cdse/Zns Capped Thiolate for Application in Glucose Sensing

A semiconducting water soluble core-shell quantum dot (QD) capped with thiolated ligand is used in this study for application in glucose sensing. These QDs were prepared in house based on hot injection technique. The ZnS shell at the outer surface of CdSe core QDs is made via specific process namely, SILAR (successive ionic layer adsorption and reaction). The distribution, morphology and optical characteristics of prepared core shell QDs have been assessed by transmission electron microscopy (TEM) and spectrofluorescence, respectively. The results show that the mean particle size of prepared QDs is in the range of 10-12 nm and the optimum emission condition was displayed at 620nm. The prepared CdSe/ZnS core shell QDs were modified by utilizing six organic ligands L-cysteine, L-histidine, thio-glycolic acid (TGA), mercapto-propionic acid (MPA), mercapto-succinic acid (MSA) and mercapto-undecanoic acid (MUA) at room temperature through a ligand-exchange procedure. This ligand exchange process was chosen in order to produce a very dense water solubilizing agent the QDs surrounding surface. The result shows that CdSe/ZnS capped with thioglycolic acid (CdSe/ZnS-TGA) exhibit the strongest fluorescence emission; therefore it was used in advanced sensing application for the detection of glucose. The highly active CdSe/ZnS-TGA was then interacted with Glucose Oxidase enzyme (GOx) and horseradish peroxidase enzyme (HRP). In this study, determination of glucose level is depending on the QDs fluorescence intensity quenching effect, which is correlated to reaction of the conjugated enzyme-QDs. In the presence of 0.1 mM glucose, fluorescence intensity of the bioconjugate QDs was quenched about 12, 000 a.u. This bioconjugated GOX/HRP/QDs-capped TGA was further analyzed with known concentrations of glucose. Quenched fluorescence intensity was proportionate with glucose concentration. The resultant GOX/HRP/QDs-capped TGA system can be a suitable platform for glucose determination in real samples.

Erratum to: Silver nanoparticles modified with thiomalic acid as a colorimetric probe for determination of cystamine

The authors describe a colorimetric method for highly selective determination of cystamine using silver nanoparticles capped with thiomalic acid (TMA-AgNPs). The TMA-AgNPs exhibit a strong surface plasmon resonance absorption band at 395 nm. After the addition of cystamine to their yellow colloidal solution, the absorption maximum at 395 nm decreases gradually, and a new absorption peak appears at around 560 nm. This is accompanied by a color change, first to green and then to purple. The aggregation of NPs induced by cystamine is assumed to be due to the electrostatic interaction between capped NPs and cystamine. Aggregation was confirmed by UV–vis absorptiometry and transmission electron microscopy. A linear correlation was obtained between the ratio of absorbances at 560 and 395 nm and the cystamine concentration in the range between 0.2 μM and 10.0 μM. The limit of detection is 46 nM. The method was successfully applied to the determination of cystamine in spiked human serum and urine samples. Recoveries ranged between 94.0 % and 100.9 %, and relative standard deviations are <9.50 % (for n = 3).

Facile synthesis of CuS nanosheets probe for resonance light scattering and visual detecting l-cysteine

A highly efficient resonance light scattering (RLS) and visual probe based on mercaptosuccinic acid (MA) modified copper sulfide (CuS) nanosheets has been successfully established for sensitive and selective detection of l-cysteine (l-Cys). The CuS nanosheets are facilely synthesized via a reductive solution route with MA as reductant and modifier at room temperature. The as-prepared CuS nanosheets have been characterized by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), UV–vis spectra and Fourier transform infrared spectroscopy (FTIR), respectively. Experimental results indicated that formation of hydrogen bonds and thiol-Cu chemical bonds between CuS nanosheets and l-Cys significantly contributed to the sensitivity and selectivity of the proposed method no matter for RLS or visual detection of l-Cys. Under the optimum experimental conditions, the linear range of the l-Cys RLS probe was 2.78 (10σ/K)-7000nmol/L (r=0.9944), and the detection limit was 0.83nmol/L (3σ/K). As to visual detection, the detection limit could also be extended to 75μmol/L.

Design of a selective regenerable cellulose microcolumn for selenium efficient recovery and economic determination

It is imperative to remove the toxic selenium compounds selenite and selenate from waste water before releasing to the environment. In this study, a functionalized regenerable cellulose, based on the chemical modification of cellulose grafted thiomalic acid (TMA-C), was prepared simply with an efficient methodology for removing and recovering selenium(IV) effectively. Optimization of the TMA-C synthesis was carried out at different temperatures, different molar ratios, and dosage of catalyst using response surface methodology. The surface functionalization effect was detected with FTIR, SEM, zeta potential, EDS and TGA technique. And under optimum adsorption conditions (pH=4.5, T=318K), TMA-C can remove toxic selenium compounds more than 99.9%, and have high adsorption capacity for Se(IV), which is 101.2mg/g. The adsorption isotherms data fitted the Langmuir model well, and pseudo-second-order kinetics showed better accordance. In addition, in the batch desorption experiments, the TMA-C could be regenerated completely with 3.0mol/L HCl and 2% KClO3 solutions. Finally regenerable cellulose microcolumn-UV-spectrophotometry was developed for effective and economic determination of trace Se(IV).

Chemometric approach to study the influence of synthesis parameters on the size of CdTe quantum dots obtained from aqueous solutions

This study reports CdTe quantum dots synthesis in an aqueous medium using cadmium chloride and sodium tellurite as precursors and sodium borohydride and mercaptosuccinic acid as reducing and capping agents, respectively. The synthesis process was optimized through experimental design, and particle characterization was carried out by UV-Vis spectroscopy and molecular fluorescence. In the first stage, a factorial design was used to establish the significance of each of the synthesis variables; i.e., the temperature, pH, reaction time and precursor molar ratios. In the second stage, a multivariate design was constructed to relate the synthesis variables with the maximum absorbance wavelengths, which allowed for predictions of the diameters of the CdTe quantum dots, which were compared with direct measurements of the particles analyzed by high-resolution transmission electron microscopy, HR-TEM and X-ray diffraction, XRD. Finally, there is a brief discussion regarding the existing models predicting particle sizes.