Green Approach to Synthesis of Silver and Gold Nanoparticles from Shoots and Pomace Waste Extracts ^†

Introduction: The annual accumulation of viticultural and winery waste products has a negative impact on the environment and the economy, since their composition contains organic substances, different heavy metals, an acidic pH, and an increased salinity [1]. On the other hand, in the composition of these wastes, there are various quantities of bioactive compounds (phytochemicals) that can be exploited in different industries, such as the cosmetic, medical, or food industries. The phytochemicals present in the waste extracts that are directly involved in the phytosynthesis of metallic nanoparticles (NPs) are phenolic compounds, namely, flavonoids, terpenoids, or other biomolecules [2]. The aim of the current study is to use the rich extracts in phytoconstituents, obtained via different extraction methods (microwave, ultrasound, and temperature-assisted extractions) from vine shoots and pomace in order to phytosynthesize silver and gold nanoparticles (NPs).

Materials and methods: The high levels of biomolecules present in Feteasca Neagra vine shoots, and Muscat Otonel and Feteasca Neagra pomace extracts, have contributed to a reduction in metal ions leading to the formation of metallic nanomaterials. In order to determine the most efficient way of phytosynthesizing nanoparticles, different ratios between extracts and metal-containing solutions have been studied. The formation of metallic NPs has been monitored via UV–Vis spectrometry in the wavelength range of 300–700 nm (Figure 1). The properties and morphologies of the obtained nanostructures have been evaluated using analytical characterization techniques (UV–Vis spectroscopy, X-ray diffraction, X-ray fluorescence) and microscopic techniques (scanning electron microscopy).

Results:

Figure 1. UV–Vis spectra of the synthesized AgNP from Feteasca neagra shoot extract.

Figure 1. UV–Vis spectra of the synthesized AgNP from Feteasca neagra shoot extract.

Conclusions: The UV–Vis spectra of AgNP and AuNP present the characteristic absorption peaks between 417 and 420 nm for silver and between 540 and 545 for gold, respectively. The XRD and XFR spectra confirm the synthesis of AgNP and AuNP. According to scanning electron microscopy, both AgNP and AuNP present a uniform dispersion in solution.