Fabrication of highly stable platinum organosols over DNA-scaffolds for enriched catalytic and SERS applications

Abstract

The use of nanomaterials (NMs) in various applications via multidisciplinary approaches is highly necessary in this era. In this line, the impact of noble metals in organic media for both catalysis and surface-enhanced Raman spectroscopic (SERS) studies is most interesting and also has a wider scope in various fields. Nonetheless, the catalytic reduction of aromatic nitro compounds is difficult with poor solubility in aqueous media, and reduction also is less feasible in the absence of noble metal-based catalysts. Thus, the choice of noble metal-based catalysts for the catalytic reduction of nitro compounds in organic media is one of the emerging methods with high selectivity towards products. Moreover, the superior catalytic activity of Pt NPs provides a higher rate constant value with a low dielectric constant of organic solvents. Herein, for the first time, we synthesised highly stable metallic Pt nanoparticles (NPs) anchored on bio-scaffold deoxyribonucleic acid (DNA) for two different applications. The advantage of highly controlled nucleation of NPs over DNA in organic media results in a spherical morphology with a particle diameter of 2.47 ± 2.11 nm and 2.84 ± 1.14 nm. A stable colloidal solution of Pt NPs was prepared by a simple wet chemical sodium borohydride reduction method within 15 minutes from the start of the reaction. Two sets of Pt NPs were synthesised by varying the molar ratio of the concentration of DNA to PtCl₄ concentration and were named Pt@DNA (0.05 M) and Pt@DNA (0.06 M), respectively. The prepared Pt@DNA was effectively studied for two potential applications such as the SERS studies and catalytic reduction of nitro compounds. In catalysis, a higher catalytic rate was observed in the case of 4-nitrophenol (4-NP) at a rate of 8.43 × 10⁻² min⁻¹. In the SERS study, the reduction of the interparticle distance to below 5 nm facilitates the creation of a large number of hot spots for probe detection. Here, we used 10⁻³ M methylene blue (MB) as a probe molecule, and the enhancement factor (EF) value was calculated at different concentrations ranging from 10⁻³ M to 10⁻⁶ M. The highest enhancement factor (EF) value obtained was 2.91 × 10⁵ for Pt@DNA (0.05 M). The as-synthesised stable Pt@DNA organosol can be exploited for other potential applications related to energy, sensor and medicinal fields in the near future.