Synthesis Of Thiol Research Articles

The structure of gold nanoparticles and Au based thiol self-organized monolayers

Spatial and electronic structure of gold nanoparticles (AuNPs) and AuNPs with thiol base self-assambled monolayers (SAMs) are reviewed. Theoretical and experimental data on the symmetry, bond lengths, band gaps and binding energies are presented. Coordination of sulfur and its compounds to Au structures and AuS bond length emphasized especially. The works on synthesis of thiol based SAMs on AuNPs are reviewed. The applications of EXAFS and photoelectron spectroscopy for the investigated SAMs on AuNPs are considered.

Synthesis of short chain thiol capped gold nanoparticles, their stabilization and immobilization on silicon surface

Tethering between nanoparticles and a supporting substrate, especially in the form of covalent bonding, is a highly useful way of ensuring development of robust systems for various applications. This requires bestowing specific functionalities on nanoparticle surfaces that can also prevent aggregation between nanoparticles. In this work, short chain thiol (4-aminothiophenol)-capped gold nanoparticles functionalized with amine-termination have been synthesized and changes in their morphology by varying the process conditions as well as the dispersion medium were studied. Subsequently, the nanoparticles (which are prone to agglomerate due to amine–amine hydrogen bonding), were stabilized in solution and by anhydride capping. Finally, these stabilized nanoparticles were immobilized on a SiO 2 substrate. X-ray photoelectron spectroscopy (XPS) confirmed the absence of non-reacted thiol groups in the synthesized nanoparticles and presence of nanoparticles on the Si surface after the immobilization process. Transmission electron microscope (TEM) and UV–visible spectroscopy have been used to study particle morphology. Cross-sectional HR-TEM images show direct evidence that the particles are anchored to the silicon surface.

Study of steady state and time resolved photoluminescence of thiol capped CdS nanocrystalline powders dispersed in N,N-dimethylformamide

The microwave (MW) assisted synthesis of thiol capped cadmium sulfide (CdS) nanocrystallites/quantum dots (QDs) was performed through the reaction of cadmium acetate with thiourea in N,N-dimethylformamide (DMF) by keeping the MW irradiation time fixed (40 s) in the presence of a thiol containing capping agent. Three capping agents, namely, benzyl mercaptan (BM), 1-butanethiol (BT) and 2-mercaptoethanol (ME) were used. The concentration of the precursors was varied to check the change in the average size of the thiol capped CdS nanocrystals formed. The nanocrystallites were characterized by usual procedure. The UV–vis absorption spectra and the photoluminescence (PL) spectra of the CdS nanocrystalline powders dispersed in DMF were studied. It was observed that with increase in concentration of the capping agent (BM), there is a shift in the nature of emission (PL) from trap associated PL to the band edge luminescence in the case of BM capped CdS nanocrystalline powders dispersed in DMF possibly due to better surface passivation. The relative PL quantum yield of the thiol capped CdS nanocrystalline powders dispersed in DMF was calculated under various experimental conditions. Time-correlated single-photon counting experiments were performed to study the time-resolved photoluminescence of the CdS nanocrystalline powders dispersed in DMF. The observed emission decay profiles have been simulated using the multiexponential model. The emission decay profiles for thiol capped CdS nanocrystalline powders dispersed in DMF depend on the nature of the capping agents (thiols) used to passivate the CdS nanocrystallites. The time resolved PL studies show that the average values of PL lifetime are related to the size and size distribution of the prepared thiol capped CdS nanocrystallites.

Thiol Functionalized Diphenyl Bithiophene for Monomolecular Bistable Layers

Diphenyl bithiophene derivatives (DPBTs), known for their electrical bistable behavior, have been used in bulk resistive memory cells. In this article, we present the design and synthesis of a ω-alkyl thiol functionalized 3,3′-diphenyl 2,2′-bithiophene; such functionalization confers the ability to anchor on a metal surface, which may be conveniently applied for the development of monomolecular bistable devices. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

Stable dye-labelled oligonucleotide-nanoparticle conjugates for nucleic acid detection

Metallic nanoparticles functionalized with oligonucleotides are used for a number of nucleic acid detection strategies. However, oligonucleotide-nanoparticle conjugates suffer from a lack of stability when exposed to certain conditions associated with DNA detection assays. In this study, we report the synthesis of thiol and thioctic acid-modified oligonucleotide gold nanoparticle (OGNs) conjugates functionalized with a dye label and varying spacer groups. The thioctic acid-modified conjugates exhibit increased stability when treated with dithiothreitol (DTT) compared to the more commonly used thiol modification. When the dye labelled oligonucleotide nanoparticle conjugates are exposed to the same conditions there is a pronounced increase in the stability for both thioctic acid and thiol modified sequences. These results open up the possibility of simply using a dye label to enhance the stability of oligonucleotide-nanoparticle conjugates in DNA detection assays where the enhanced stability of the conjugate system can be advantageous in more complex biological environments.

Microwave Assisted Synthesis of Thiol Modified Polymethacrylic acid and Its Cross‐Linking with Allyl Modified Polymethacrylic acid via Thiol‐ene “Click” Reaction

AbstractIn this paper, we describe the thiol‐ene “click” reaction with modified poly methacrylic acid in water. The thiol group was implemented by a polymer analogous condensation reaction of polymethacrylic acid (1) and cysteamine (2), which was carried out in bulk by use of microwave. The allyl modified polymethacrylic acid (5) was obtained by DCC‐coupling of the allyl amine onto the polymethacrylic acid backbone. By combination of cysteamine (3) and allyl modified polymethacrylic acid (5) the thiol‐ene click reaction could be started with a redox initiator in aqueous solution at room temperature. The kinetics of this reaction were determined by1H NMR spectroscopy and the resulting hydrogels were analyzed by rheological measurements and differential scanning calorimetry (DSC).magnified image

Synthesis of thiol capped CdS nanocrystallites using microwave irradiation and studies on their steady state and time resolved photoluminescence

Synthesis of cadmium sulfide (CdS) nanocrystallites has been performed through the microwave (MW) assisted reaction of cadmium acetate with thiourea in N,N-dimethylformamide (DMF) in the presence of two capping agents, 1-butanethiol and 2-mercaptoethanol. Attempts were made to control the size and size distribution of the thiol capped CdS nanocrystallites by controlling the number of MW irradiations/exposures for a fixed time (duration). The prepared nanocrystallites have been characterized by UV-vis spectroscopy, FTIR, XRD, FESEM and TEM. The peak position of the absorption band of the 1-butanethiol caped CdS nanocrystals in DMF solution shifted towards longer wavelength with the increasing number of MW exposures indicating the growth of particle size. In contrast, the peak position of absorption band for the 2-mercaptoethanol capped CdS nanocrystals remained nearly at the same wavelength and only the intensity of the absorption band increased with the increasing number of MW exposures. The observed steady state photoluminescence (visible range) of the 1-butanethiol capped CdS nanocrystals in DMF solution shifted towards higher wavelength, showing a decrease in intensity, with the increase in the number of MW exposures. Whereas in the case of 2-mercaptoethanol capped CdS nanocrystals in DMF solution, the photoluminescence peak remained nearly at the same position showing a decrease in intensity with increase in the number of MW exposures. The interesting results on the size-dependent steady state and time resolved photoluminescence (PL) of the CdS nanocrystallites are discussed in the present article. Possible application of such studies in the area of biotechnology has been mentioned.

Thiol appended, fluorinated phosphonium ionic liquids as covalent superhydrophobic coatings

The synthesis and characterization of thiol terminated fluorinated phosphonium ionic liquids and their application as superhydrophobic coatings are reported. The thiol functionality enables a covalent link to rough silver substrates installing a durable, non-wetting, ionic film. Variables such as the fluorine loading and the mode of interaction of the salt at the surface of the substrate were adapted and their corresponding effects on the wettability were examined. It was found that a thiolated phosphonium ionic liquid could tolerate a lower fluorine loading and maintain flexibility in the type of anion while still imposing superhydrophobic behaviour.

Synthesis of a photo-caged aminooxy alkane thiol.

A photo-caged aminooxy alkane thiol synthesized in 7 steps and 15% overall yield was used to form a self-assembled monolayer (SAM). Photo-deprotection on the surface was confirmed by FT-IR spectroscopy and contact angle goniometry. Conjugation of a small molecule ketone, ethyl levulinate, further confirmed the presence of aminooxy groups on the surface.

Highly efficient condensation of hydroxyl-terminated polyethylene oxide with 3-mercaptopropionic acid catalyzed by hafnium salt

A general, highly efficient, one-step synthesis of thiol functionalized polymer was described. In the presence of 1–5mol% of HfCl4·2THF, the hydroxyl group of polyethylene oxide monomether (MPEO) directly reacted with 3-mercaptopropionic acid to yield thiol functional MPEO. For MPEO with molecular weight from 550 to 5000, the degree of functionalization was almost quantitative (>96%), and the reaction proceeded without side reaction.

Air and Water Free Solid-Phase Synthesis of Thiol Stabilized Au Nanoparticles with Anchored, Recyclable Dendrimer Templates

Solid-phase synthetic templates for Au nanoparticles were developed using Merrifield resins and polyamidoamine (PAMAM) dendrimers. This synthetic scheme affords the opportunity to prepare metal nanoparticles in the absence of air and water, and it does not necessitate phase transfer agents that can be difficult to remove in subsequent steps. Amine-terminated generation 5 PAMAM (G5NH2) dendrimers were grafted to anhydride functionalized polystyrene resin beads and alkylated with 1,2-epoxydodecane to produce G5C12anch. The anchored dendrimers bound both CoII and AuIII salts from toluene solutions at ratios comparable to those of solution phase alkyl-terminated PAMAM dendrimers. The encapsulated AuIII salts could be reduced with NaBH4 to produce anchored dendrimer encapsulated nanoparticles (DENs). Treatment of the anchored DENs with decanethiol in toluene extracted the Au nanoparticles from the dendrimers as monolayer protected clusters (MPCs). After a brief NaCN etch, the anchored dendrimers were readily recycled and a subsequent synthesis of decanethiol Au MPCs was performed with comparable MPC yield and particle size distribution.

Self-Assembled Monolayers with Latent Aldehydes for Protein Immobilization

Aldehyde functions are widely used for immobilization of biomolecules on glass surfaces but have found little attention for biofunctionalization of self-assembled monolayers (SAMs) on gold, due to interference between thiol and aldehyde functions. This problem was recently solved by synthesis of an alkanethiol that carried a vicinal diol group [Jang et al. (2003) Nano Lett. 3, 691-694]. The latter served as a latent aldehyde function that was unmasked by short exposure of the vicinal diol-terminated SAM to aqueous periodate. However, the synthesis of the new vicinal diol-terminated alkane thiol was time-consuming and had an overall yield of approximately 3.5%. In the present study, a general modular strategy was introduced by which SAM components with vicinal diol functions were rapidly synthesized with high yield: this was accomplished by amide bond formation between a SAM-forming carboxylic acid (exemplified by lipoic acid and 16-mercaptohexadecanoic acid) with 3-aminopropane-1,2-diol, using suitable protecting groups. The disulfide or free thiol group afforded SAM formation on gold and, after periodate oxidation of the vicinal diol functions, proteins were covalently bound via their lysine residues. At 1 mg/mL protein concentration, complete surface coverage was reached within minutes. No further protein was bound by nonspecific adsorption, but cognate proteins were specifically bound with high capacity. Pyrogallol-O-hexadecanoic acid and 10-undecenoic acid were also coupled with 3-aminopropane-1,2-diol by amide bond formation, thereby producing latent aldehyde-containing SAM components for metal oxides and hydrogen-terminated silicon, respectively, to show the general usefulness of the new synthetic design.

Synthesis and Quality Control of Thiol Tagged Compound Libraries for Chemical Microarrays

AbstractA method for the synthesis and quality control of compound collections containing reactive thiol functions was developed. Such libraries form the basis for the construction of chemical microarrays to be used in fragment‐based screening. Amino‐modified polymer membranes fixed into the wells of microtiter plates were used as the solid phase for the nanomole‐scale synthesis of a thiol‐tagged small molecule library using a spatial one‐compound/one‐well strategy. A thiolselective Liquid Chromatography‐Mass Spectroscopy (LC‐MS) protocol of each compound before attachment to the microarray surface was established, allowing an exact determination of compound purity and concentration. The established synthesis and quality control method is an important prerequisite for an accurate read‐out of the array compound–target interaction data, and simplifies the usage of small molecule microarrays for low affinity screening.

Synthesis of thiol functionalized gold nanoparticles using a continuous flow microfluidic reactor

Microfluidic devices show much promise for the controlled synthesis of materials on the nanoscale. In this work the first report of a synthetic method for the preparation of nanoparticles of gold stabilized by an adsorbed monolayer of a thiol (monolayer protected clusters) using a microfluidic device is described. Improvements in monodispersity are observed relative to bulk synthetic methods.

Tetrathiafulvalene-based podands bearing one or two thiol functions: immobilization as self-assembled monolayers or polymer films, and recognition properties

The synthesis of various thiol and dithiol derivatives of a tetrathiafulvalene-based receptor is presented, as well as their immobilization on gold as self-assembled monolayers (SAMs). The formation of films incorporating TTF units is also shown by electrooxidation of TTF–dithiol derivatives. The ability of the monolayers to electrochemically recognize Pb 2+ is demonstrated.

Bifunctional Surface Imprinting of Silica: Thermolytic Synthesis and Characterization of Discrete Thiol−Amine Functional Group Pairs

In this article we demonstrate the sub-nanometer patterning of mixed chemical functional groups consisting of thiol and primary amine functionality on the surface of silica and characterize the local organization of thiols and amines within these materials. Our approach has required the development of a synthetic method for the thermolytic imprinting of thiols based on a xanthate protection scheme, which enables bifunctional imprints containing carbamate and xanthate functionality to be condensed onto a silica surface and thermolytically deprotected in a single step. This imprinting process is demonstrated for the synthesis of bifunctional imprinted sites containing thiol−amine pairs and groups of two thiols and an amine per imprinted site, and is characterized using solid-state UV/Visible, 29Si CP/MAS NMR, and 13C CP/MAS NMR spectroscopies. Independent titration of thiols with Ellman's reagent and amines with perchloric acid demonstrates that the bulk surface coverage of thiol and amine functionality reflects the expected ratios based on imprint molecule stoichiometry, with yields of accessible bifunctional imprinted sites greater than 80% relative to the amount of imprint used. The high yields in the current methodology overcome previous limitations for the imprinting of mixed functional groups and are facilitated by the low entropic penalty for imprinting multiple groups provided by the unimolecular nature of the thermolysis process. Local chemical functional group organization is investigated by using o-phthalaldehyde as a specific binding probe for thiol−amine pairing on the length scale of ∼3 Å. The paired imprinted material shows 2.5-fold higher yield of paired sites relative to a mixed control material consisting of monofunctional thiol and amine sites at the same bulk surface coverage of 0.02 thiol and amine functional groups per nm2. This result demonstrates that silica surface imprinting can be used to control the local density of mixed chemical functional groups on sub-nanometer length scales in a fashion that is impossible to achieve with most other synthetic methods. Our ability to imprint mixed chemical functionality on the surface of silica and quantitatively characterize the resulting amount of thiol−amine pairing is further used to rigorously investigate imprinted site isolation in mixed control materials. Our results demonstrate that nonrandom surface distributions of immobilized imprint result in these materials, despite low surface coverages, and draw attention to the need for further investigating degree of site isolation when surface-imprinting silica.

Synthesis and Characterization of Thiol Containing Furoxan Derivatives as Coligands for the Preparation of Potential Bioreductive Radiopharmaceuticals

The synthesis and characterization of thiol-containing 1,2,5-oxadiazole N-oxide (TONO) derivatives and their use as monodentate coligands for the preparation of (99m)Tc complexes is presented. 3-Mercaptomethyl-4-phenyl-1,2,5-oxadiazol N(2)-oxide and 3-(4-mercaptophenylmethylidenhydrazinocarbonyloxymethyl)-4-phenyl-1,2,5-oxadiazol N(2)-oxide were successfully synthesized and combined with the tridentate ligand N,N-bis(2-mercaptoethyl)-N',N'-diethylethylenediamine (BMEDA) to prepare "3+1 mixed ligand" technetium complexes. The( 99m)Tc complexes were obtained in high yield and radiochemical purity using low concentration of ligand and coligand. An alternative procedure using a xantate and a disulphide precursor of 3-mercaptomethyl-4-phenyl-1,2,5-oxadiazol N(2)-oxide yielded the same complex. Biological evaluation of the potentiality of the( 99m)Tc complexes as bioreductive radiopharmaceuticals was performed in normal CD1 mice and in mice bearing induced sarcoma. Tumour uptake was moderate but tumour/soft tissue ratio was favourable. Although these results are encouraging, further development is still necessary in order to achieve higher tumour uptake and lower gastrointestinal activity.

Low molecular weight thiols in arsenic hyperaccumulator Pteris vittata upon exposure to arsenic and other trace elements

Low molecular weight thiol-containing compounds have been reported to play an important role in metal detoxification and accumulation in some higher plants. The formation of these low molecular weight thiols in the recently discovered arsenic hyperaccumulator, Chinese Brake fern (Pteris vittata) upon exposure to arsenic and other trace metals was investigated. In addition to cysteine and glutathione, an unidentified thiol was observed in the plants exposed to arsenic, which was not found in the control. The concentration of the unidentified thiol showed a very strong and positive correlation with arsenic concentration in the leaflets. The unidentified thiol was low in rachises and undetectable in the roots for As-treated plants. Total and acid-soluble thiols were also measured and the results indicated that arsenic mainly stimulated the synthesis of acid-soluble thiol in Chinese Brake. The investigations of other trace elements (Cd, Cu, Cr, Zn, Pb, Hg, and Se) showed that these elements were not accumulated in Chinese Brake to high levels and the synthesis of the unidentified thiol in the plant was not observed. Our study suggests that the unidentified thiol was induced specifically by arsenic and the distribution patterns of the unidentified thiol and arsenic in the plant were consistent, indicating that the synthesis of this compound was related to As exposure.

Synthesis of thiol substituted oligoanilines for molecular device candidates

The synthesis of thioacetate derivatized oligoanilines designed for molecular electronic device purposes is described. Reversible oxidation between the non-conductive leuco base and conductive emeraldine salt forms of these compounds may produce switching effects and device behavior. The targeted compounds contain a sulfur moiety as a means to connect the molecules to metallic electrodes.

Synthesis of thiol functionalized organo–ceramic adsorbent by sol–gel technology

A new high performance adsorbent (SOL-AD) is synthesized by the sol–gel processing technique for the purpose of treatment of cadmium and mercury ions contaminated aqueous streams. In order to synthesize this adsorbent, the functional precursor (3-merceptopropyltrimethoxysilane) and the cross-linking agent (tetraethoxysilane) are hydrolyzed and co-condensed in an acidic water and ethanol mixture followed by gelation in a basic solution. This organo–ceramic adsorbent has high uptake capacities for cadmium and mercury ions. Especially, SOL-AD-IV synthesized at the optimal conditions has uptake capacities of 222 and 1284 mg/g of cadmium and mercury ions, respectively. These uptake capacities are considerably higher than those of covalently functionalized ceramic adsorbents and other functionalized polymeric resins. In addition, the beneficial properties of ceramic adsorbents, such as strong mechanical, thermal, and chemical stabilities are maintained. This paper discusses the effects of sol–gel processing parameters on the properties of SOL-AD adsorbents and the adsorption/desorption of cadmium and mercury ions on the SOL-AD-IV adsorbent.