Article

5‐(2‐Mercaptoethyl)‐1H‐tetrazole: Facile Synthesis and Application for the Preparation of Water Soluble Nanocrystals and Their Gels

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Abstract

A facile method for the preparation of the novel capping ligand 5-(2-mercaptoethyl)-1H-tetrazole for the stabilization of water-soluble nanocrystals was developed. This effective synthetic procedure is based on the cycloaddition of sodium azide to 3,3′-dithiobis(propionitrile) followed by the reductive cleavage of a S−S bond with triphenylphosphine. The structure of the synthesized compound was confirmed by single-crystal X-ray analysis. A target tetrazole was successfully applied for the direct aqueous synthesis of CdTe and Au nanocrystals. CdTe nanocrystals capped with 5-(2-mercaptoethyl)-1H-tetrazole were found to reveal high photoluminescence efficiencies (up to 77 %). Nanocrystals capped with this tetrazole ligand are able to build 3D structures in a metal-ion-assisted gelation process in aqueous solution. Critical point drying of the as-formed hydrogels allowed the preparation of the corresponding aerogels, while preserving the mesoporous structure.

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... 57,58 Therefore, tetrazoles could stabilize the supramolecular selfassembled structure by participating in hydrogen bond formation. 59 The metallogels were obtained after 2 h, and gelation was confirmed by the test tube inversion method. This gelation procedure is considered to be an in situ process, in which the cooperative effects of all the components in the solution mixture, including the ligand, solvent, and metal, prepared with a suitable ratio play essential roles. ...
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Published data on the synthesis, structure, properties and applications of metal derivatives of tetrazoles are generalised and described systematically. Compounds based on the anionic and neutral tetrazole forms, C- and N-mono- and C,N-disubstituted tetrazoles are considered.
Article
We report on the state-of-the art synthesis and improved luminescence properties of thiol-capped CdTe nanocrystals (NCs) synthesized in water. The optimized pH (12) and molar ratio of thiol to Cd ions (1.3:1) increases the room-temperature photoluminescence quantum efficiency of as-synthesized CdTe NCs capped by thioglycolic acid (TGA) to values of 40−60%. By employing mercaptopropionic acid (MPA) as a stabilizer, we have synthesized large (up to 6.0 nm in diameter) NCs so that the spectral range of the NCs' emission currently available within this synthetic route extends from 500 to 800 nm. Sizing curve for thiol-capped CdTe NCs is provided. In contrast to CdTe NCs capped by TGA, MPA-capped CdTe NCs show up to 1 order of magnitude longer (up to 145 ns) emission decay times, which become monoexponential for larger particles. This phenomenon is explained by considering the energetics of the Te-related traps in respect to the valence-band position of CdTe NCs. The correlation between luminescence quantum efficiencies, luminescence lifetimes, and Stokes shifts of CdTe NC fractions is demonstrated, being in agreement with a model proposed previously that connects the emission properties of NCs with their surface quality determined by the Oswald ripening conditions during growth. imaging, and plasmonics.
Article
High-performance oxygen reduction reaction (ORR) catalysts based on metal-free nitrogen-containing precursors and carbon nanotubes are reported. The investigated systems allow the evaluation of the effect of nitrogen-containing groups towards ORR and the results show that the catalysts are compatible with the conditions encountered in alkaline fuel cells, exhibiting good catalytic activity and stability compared with conventional Pt/C electrocatalyst.
Article
A 3D metal ion assisted assembly of nanoparticles has been developed. The approach relies on the efficient complexation of cadmium ions and 5-mercaptomethyltetrazole employed as the stabilizer of both colloidal CdTe and Au nanoparticles. It enables in a facile way the formation of hybrid metal-semiconductor 3D structures with controllable and tunable composition in aqueous media. By means of critical point drying, these assemblies form highly porous aerogels. The hybrid architectures obtained are characterized by electron microscopy, nitrogen adsorption, and optical spectroscopy methods.
Article
A novel ligand, 5-mercaptomethyltetrazole, is applied to the direct colloidal synthesis of highly luminescent (quantum yield of up to 60%) water-soluble CdTe nanocrystals. In the synthesis the 5-mercaptomethyltetrazole behaves analogously to the widely used thioglycolic acid, providing the additional advantage of solubility of the resulting nanocrystals in methanol. Moreover, the 5-mercaptomethyltetrazole-capped nanocrystals possess the unique ability to reversibly form fine 3D networks (hydrogels) upon the addition of metal salts.
Article
Nanoporous metal foams (NMFs) have been a long sought-after class of materials in the quest for high-surface-area conductive and catalytic materials. Herein we present an overview of newly developed synthetic strategies for producing NMFs along with an in-depth discussion of combustion synthesis as a versatile and scalable approach for the preparation of nanoporous, nanostructured metal foams. Current applications of NMFs prepared using combustion synthesis are also presented including hydrogen storage and catalysis.
Article
A strong photoluminescence enhancement effect of illumination on CdTe nanocrystals stabilized by thioglycolic acid (TGA) was observed. Under optimized conditions, the fluorescence quantum yield of CdTe nanocrystals in aqueous solution reached 85% at room temperature. Optical measurements indicated that the photodegradation of TGA rather than NCs was the main reason for the PL enhancement effect since sulfide ions released from TGA during illumination coordinated with cadmium ions on the surface of CdTe and formed a shell structure of CdS there. X-ray photoelectron spectroscopic results further proved the formation of CdS shell on the CdTe core during illumination. The colloidal solution of CdTe/CdS core−shell nanocrystals with photoluminescence quantum yield higher than 80% turned out to be very stable. Therefore, the current investigations not only reveal the PL enhancement effect of illumination, but also provide a useful synthetic route for producing water-soluble and highly fluorescent CdTe/CdS core−shell nanocrystals
Article
5-Substituted-1H-tetrazoles (RCN4H) are often used as metabolism-resistant isosteric replacements for carboxylic acids (RCO2H) in SAR-driven medicinal chemistry analogue syntheses. This review provides a brief summary of the medicinal chemistry of tetrazolic acids and highlights some examples of tetrazole-containing drug substances in the current literature. A survey of representative literature procedures for the preparation of 5-substituted-1H-tetrazoles, focusing on preparations from aryl and alkyl nitriles, is presented in sections by generalized synthetic methods.
Angew. Chem. 2010, 122, 4648–4669