ARTICLE pubs.acs.org/JPCC
1-Substituted Tetrazole-5-thiol-Capped Noble Metal Nanoparticles Maria N. Nichick,† Sergei V. Voitekhovich,*,† Vladimir Lesnyak,‡ Vitaly E. Matulis,† Ryma A. Zheldakova,§ Anatoly I. Lesnikovich,† and Oleg A. Ivashkevich† †
Research Institute for Physical Chemical Problems of Belarusian State University, 220030 Minsk, Leningradskaya 14, Belarus Physical Chemistry, TU Dresden, Bergstrasse 66b, 01062 Dresden, Germany § Microbiology Department, Faculty of Biology, Belarusian State University, 220108 Minsk, Kurchatova 10, Belarus ‡
bS Supporting Information ABSTRACT: Stable and nearly monodispersed silver, palladium, and platinum nanoparticles with an average size of 24 nm were synthesized by the reduction of metal precursors (CF3COOAg, [NMeAlk3]2MCl4, where M = Pd, Pt) in a biphasic toluenewater system in the presence of easily available 1-R-tetrazole-5-thiols (R = ethyl, tert-butyl, 1-adamantyl, and phenyl) characterized by low carbon content and unique thermal behavior. The obtained noble metal nanoparticles capped with tetrazole-5-thiols were characterized by TEM, TGA, UVvis, and FTIR spectroscopy. Based on quantum-chemical calculations, preferred coordination mode of the ligands under their binding with surfaces of nanoparticles, namely N(4), S-bridging was proposed. The synthesized silver nanoparticles capped with 1-phenyltetrazole-5-thiol were found to have antifungal and antimicrobial activity against various bacterial strains.
’ INTRODUCTION During the past few years, significant progress has been achieved in a chemical synthesis of metal, semiconductor, and magnetic nanoparticles (NPs) holding great promise in the areas of catalysis, electronics, photovoltaics, biotechnology, and others.13 Colloidally grown NPs comprise a crystalline core surrounded by a layer of capping agent (so-called surface or stabilizing ligand, surfactant) bound to the NPs surface. Capping agents play an important role in the synthesis of colloidal nanomaterials since they control nucleation and growth of particles, as well as their chemical and colloidal stability. Moreover, they provide solubility of NPs in various media which is very important for their processing. Until now a huge variety of compounds have been investigated for their use as capping agents for NPs. The most common ligand coatings described in the literature are based on organic hydrocarbon molecules with anchoring end groups, like HS, HOOC, H2N, and (HO)2(O)P.1,4,5 Previously, more and more sophisticated organic molecules have been used for the preparation and postpreparative manipulation of NPs. In particular, tetrazole derivatives (Scheme 1) were proposed as capping agents for stabilization of metal and semiconductor NPs. It was shown that easily available 1-Rtetrazole-5-thiols (1, R = alkyl, phenyl), also known as 1-R-1,4dihydrotetrazole-5-thiones,6 can be used for chemical synthesis of cadmium sulphide7 and gold8 NPs. Interest in these novel capping agents was determined by their thermally induced decomposition leading to a high percentage of gaseous products which is an interesting feature for future applications in coatings, since the removal of capping agents provides great opportunity to improve charge transfer, sensing, and catalytic properties of the NPs and their assemblies.9 r 2011 American Chemical Society
5-Mercaptomethyltetrazole (2) was found to be a good substitute for thioglycolic acid, which is widely used as a capping agent in the aqueous synthesis of colloidal semiconductor NPs.10,11 Usage of this ligand allows preparation of high luminescent (quantum yield up to 60%) water-soluble semiconductor CdTe NPs possessing the unique ability to reversibly form fine 3D networks (hydrogels) upon addition of metal salts.12b This observed phenomenon is based on strong coordination ability of the tetrazole ring13 and isosterism between tetrazol-5-yl and carboxyl moieties.14 Lately, 5-aminotetrazole (3) and 5-methyltetrazole (4) were applied for a synthesis of silver NPs in water.15 Although the obtained NPs are characterized by quite a broad size distribution, they are of interest due to their controllable agglomeration accompanied with drastic changes in optical properties. In this work we have extended the area of application of tetrazoles for NPs synthesis, having developed a two-phase approach for synthesis of monodispersed palladium, platinum and silver particles capped by tetrazole-5-thiols 1 (1-ethyl-, 1-tertbutyl-, 1-(1-adamantyl)-, and 1-phenyltetrazole-5-thiol).
’ EXPERIMENTAL SECTION Materials. 1-Phenyltetrazole-5-thiol was purchased from Sigma-Aldrich. Other thiolic tetrazoles were prepared by reaction of commercial alkyl isothiocyanates with sodium azide in refluxing aqueous 2-propanol.16 Silver trifluoroacetate and sodium Received: June 16, 2011 Revised: July 25, 2011 Published: July 26, 2011 16928
dx.doi.org/10.1021/jp205649y | J. Phys. Chem. C 2011, 115, 16928–16933
The Journal of Physical Chemistry C Scheme 1. Structural Formulas of the Tetrazole Derivatives Used As Capping Ligands
ARTICLE
Table 1. Size [nm] of the Noble Metal NPs Capped with 1-RTetrazole-5-thiols substituent R
Ag
Pd 2.8 ( 0.6
2.4 ( 0.5
tert-butyl (t-Bu) 1-adamantyl (Ad)
4.2 ( 1.2 3.5 ( 0.9
2.8 ( 0.5 3.3 ( 0.6
