Covalently Functionalized Nanoparticles of Semiconducting Metal Chalcogenides and Their Attributes

Abstract

Covalent functionalization of the semiconducting chalcogenide nanoparticles ZnS, ZnSea nd CdS by reaction with organic halides, specifically iodobenzenes, has been demonstrated. DFT calculations have thrown light on the electronic structure of the functionalized chalcogenides. Chalcogenides with bonded phenyl groups exhibit al ong wavelength charge-transfer band as predicted by theory.F unctionalization has been carried out with fluorophores as well. Functionalization of semiconductingc halcogenide particles offers many possibilities for study of their properties and application.Chemical modificationo fn anomaterials by appropriate functional groups has become an active area of research in recent years. Functionalization enables us to tune physical andc hemical properties of the materials,t hereby making them more suitable for various applications.[1-5] Stability and solventd ispersibility of materials can also be enhanced by surface functionalization.I th as been shown recently that organic halides can be used to functionalize MoS 2 sheets.[3] Thus, the reaction of iodobenzenes with the metallic 1T form of MoS 2 functionalizes the surface forming CÀSb onds. The nucleophilic reaction occurs because of electron transfer betweent he metallic1 T phase and the halide,r esulting in forming the covalentC ÀS bond. Interestingly,s emiconducting sheets of the stable 2H form have been functionalized by reactionw ith iodobenzenes in the presence of aP d 0 catalyst. [6,7] It has also been shown that other organic bromides and iodides including certain fluorophores react with the MoS 2 sheets forming CÀSb onds. Encouraged by these results, we have explored whether covalent functionalization of nanoparticles of semiconducting metal chalcogenides such as ZnS and CdS can be carriedo ut by the reactionw ith organic halides such as iodobenzenes. We find that it is indeed possible to do so by the use of the Pd 0 catalyst. Such covalent functionalization resultsi nc harge-transfer between the sulfide and the benzene, giving rise to al ongwavelength absorption band. DFT calculations, carried out to understand the electronic structure and properties of the functionalized chalcogenides, predict the occurrence of ac hargetransfer band. We shall first examine functionalization of ZnS nanoparticles by iodobenzenes. ZnS nanoparticles of % 5-10 nm diameter ( Figure S1;S upporting Information), prepared by ap rocedure reported in the literature, [8] were reactedw ith iodobenzene, 4-iodoanisole or 4-iodonitrobenzene (Scheme 1) by heating in toluene under an itrogen atmosphere.T he solid products obtained show evidencef or covalentl inking of the phenyl group with ZnS.

Reductant-Activated, High-Coverage, Covalent Functionalization of 1T′-MoS2

“…Figure S2 shows that the coverage of methyl-functionalized ceMoS 2 (methyl-MoS 2 ) was the same whether water/ isopropanol 18 or DMF was used as the solvent. Although palladium catalysts have been used to functionalize 2H-MoS 2 and metal chalcogenide nanoparticles with iodobenzene, 41,44 we have observed that functionalization of 2H-MoS 2 using one-electron metallocenes does not proceed as readily as for 1T′-MoS 2 . The details of how the strength of the metallocene reductant affects the functionalization of 2H-MoS 2 remains an area of active interest.…”

2D Elemental Nanomaterials Beyond Graphene

“…Chemical functionalization is a promising route to tune chemical and physical properties, improve processability as well as to develop novel structures . Abellán et al .…”