Ru(ii)–polypyridyl complex-grafted silica nanohybrids: versatile hybrid materials for Raman spectroscopy and photocatalysis

Abstract

Ruthenium(II)–polypyridyl complex-grafted silica nanohybrids with and without silver nanoparticles (Ag NP) as core–shell nanohybrids were prepared by reacting with different coupling reagents 3-aminopropyl-trimethoxysilane (3-APTMS) and 3-iodopropyltrimethoxysilane (3-IPTMS). The morphological features of the resulting surface-grafted silica nanohybrids were studied using various electron microscopic techniques (TEM, STEM, SEM, EDS) and their chemical components were analysed using spectral techniques such as mass spectrometry, UV-vis, Fourier transform-infrared (FT-IR) spectroscopies and thermogravimetric analysis (TGA). Photoluminescence (PL) studies of the functionalized silica nanohybrids in the solution and solid states proved them to be luminescent nanohybrids. The molecular vibrational bands of the covalently-grafted Ru(II)–polypyridyl complexes on silica nanohybrids and Ag@SiO₂ core–shell nanohybrids were studied using Raman spectroscopy. The obtained Ru(II)–polypyridyl complex-functionalized silica nanohybrids were utilized as photocatalysts for Rhodamine 6G degradation under visible light illumination. The presence of a thick SiO₂ nanoshell over the Ag NP surface limits direct charge transfer to the covalently-grafted Ru(II)–polypyridyl complex and the Ag NPs are proved as a plasmonic photosensitizer for enhanced Rhodamine 6G degradation, and molecular probing substrates for Raman spectroscopy. Among functionalized silica nanohybrids, the Ag@SiO₂ core–shell nanohybrid showed enhanced photocatalytic activity towards Rhodamine 6G degradation compared to other functionalized silica nanohybrids without Ag NP cores and bare MCM-41 SiO₂ NPs.