Search

BR-102018076729-B1 - PROCESS FOR SYNTHESIS OF SILVER NANOPARTICLES USING GUAVA LEAF EXTRACT

BR102018076729B1BR 102018076729 B1BR102018076729 B1BR 102018076729B1BR-102018076729-B1

Abstract

PROCESS FOR SYNTHESIS OF SILVER NANOPARTICLES USING GUAVA LEAF EXTRACT. The present invention relates to a process for synthesizing silver nanoparticles from the leaf extract of Psidium guajava L. using silver nitrate as a precursor in a spontaneous self-organizing manner, possessing unique characteristics of sustainability, low cost, high efficiency, and being an eco-friendly process. Silver nanoparticles in colloidal and solid states are used for various technological purposes, and the present invention is qualified for these purposes as well as several possible technological innovations such as impregnation into fabric fibers for the production of smart textiles. Furthermore, they can be used in paints, dressings, and products that will incorporate nanotechnology and antimicrobial efficiency, among other diverse scientific and technological fields.

Inventors

  • BIANCA PIZZORNO BACKX
  • SÉRGIO ANTUNES FILHO

Assignees

  • UNIVERSIDADE FEDERAL DO RIO DE JANEIRO

Dates

Publication Date
20260310
Application Date
20181220

Claims (5)

  1. 1. Process for synthesizing silver nanoparticles using guava leaf extract, characterized by comprising the following steps: a) Mixing solid silver nitrate, preferably with a high degree of purity, or aqueous silver nitrate, preferably using deionized or distilled water, with guava leaf extract in an aqueous medium, where the concentration of the silver nitrate solution can vary from 10⁻⁷ to 2 grams of AgNO₃ per mL of solvent and the mass of the solid silver nitrate can vary up to a final concentration of 10⁻⁷ to 2 grams of silver nitrate per mL of extractive solution, and the concentration of the guava leaf extractive solution can contain concentrations of 10⁻⁵ to 5 grams of guava leaf per mL of aqueous, hydroalcoholic or any other solvent, and the extraction methodology used may be infusion, decoction, use of microwaves or any other extractive methodologies; b) If necessary, subsequent heating of the colloidal solution formed. spontaneously through self-organization and/or heating during the self-organization process, where the cooling or heating temperature, both in the extraction methodology and during or after the synthesis process, can vary from 2 °C to 110 °C, for up to 2 hours and with pressure from 0.1 Pa to 105 kPa, where the concentration of silver nitrate, the concentration of the extraction solution, the pressure and the time used in heating can result in variations in the concentration of synthesized nanoparticles from 1 to 1015 nanoparticles per milliliter, in the formation of nanoparticles from 1 to 100 nm in size and/or in the formation of silver nanoparticles with different morphologies such as dodecahedral, elliptical, dendritic, spicular, among others.
  2. 2. A process for synthesizing silver nanoparticles using guava leaf extract, according to claim 1, characterized in that the concentration of the silver nitrate solution can vary from 3x10-4 to 3.5x10-4 grams per mL of extractive solution.
  3. 3. A process for synthesizing silver nanoparticles using guava leaf extract, according to claim 1, characterized in that the extraction process can contain concentrations of 0.015 to 0.005 grams of guava leaf per mL of aqueous solvent.
  4. 4. A process for synthesizing silver nanoparticles using guava leaf extract, according to claim 3, characterized in that the extraction methodology uses a solvent at 90 to 110 °C in contact with the leaves for up to 4 minutes.
  5. 5. A process for synthesizing silver nanoparticles using guava leaf extract, according to claim 1, characterized by not heating the colloidal solution being formed or heating it at a temperature of 50°C to 70°C for up to 8 minutes.

Description

[0001] The present invention relates to the development of a process for synthesizing silver nanoparticles from the leaf extract of Psidium guajava L. (Guava) using silver nitrate as a precursor. FUNDAMENTALS OF THE INVENTION [0002] The guava tree (Siddúum uajávaa L.) is a typically tropical fruit tree, native to the American continent and extremely abundant in Brazil, especially because the country is the largest producer of red guavas in the world. This is one of the main reasons for choosing this tree as the basis for the development of the product, since there would be an abundant source of resources in agribusiness with the need to prune the trees at certain times of cultivation in plantations, and these byproducts can be used as a source for extracting fundamental compounds capable of promoting the synthesis and stabilization of metallic nanoparticles. [0003] The objective is to use guava leaf extract because it is the most abundant and bioavailable part throughout the year, not only during fruiting periods as is the case with flowers and fruits; scientific literature shows that guava leaves contain several important substances such as flavonoids, phenolic compounds in general, and various other antioxidant chemical species fundamental for the efficient maintenance of these nanostructures, as well as substances that are antimicrobial, hypoallergenic, and anti-inflammatory, having a high synergistic potential with the nanoparticles dispersed in the extract of Psidium uajávva L. for various bionanotechnological applications. Thus, guava leaves prove to be economically, phytochemically, and industrially advantageous for improving the synthesis of nanostructures from green, low-cost, reproducible routes on a laboratory and industrial scale, eco-friendly, and sustainable. Among the possibilities of metals and precursor compounds for the synthesis of nanoparticles, silver is obtained from the inorganic precursor salt silver nitrate (AgNO3), which in aqueous medium undergoes ionic dissociation and makes silver available in silver ions that are subsequently reduced to silver atoms in the ground state. Since antiquity, silver has possessed medicinal properties due to its widely established antimicrobial action, both in the state of the art and in popular culture. [0004] Nanoparticles typically, but not exclusively, have dimensions smaller than 100 nm according to ISO/TC 229 of 2005, and their efficiency, when compared to the action of fundamental silver used in technological bases, is greater mainly due to their bioactivity and size. The increased contact surface area relative to their volume and the nanometric size of silver provides a unique biochemical interaction that results in an antimicrobial potential capable of acting effectively on microorganisms from different domains, kingdoms, genera, and species; even when these are multi-resistant to already used antimicrobials. [0005] The green synthesis of silver nanoparticles is based on the bioreduction of silver ions, derived from silver nitrate dissolved in the liquid extractive medium, to fundamental silver (Ag°) followed by its nucleation for the growth of nanoparticles and subsequent stabilization of their colloidal structure by the properties of the extractive medium in which they are dispersed. [0006] Various characteristics such as pH, temperature, concentration of precursor and substances present in the extraction medium, action of light, among others, can interfere with the morphology, size, and biological activity of the final product of the synthesis. BRIEF DESCRIPTION OF THE INVENTION [0007] The synthesis process consists of extracting substances from guava leaves (Sidduum guajava L.) in an aqueous medium using microwaves, infusion, decoction, among other possible extraction methodologies, and using them to synthesize silver nanoparticles (AgNPs) by exposing silver nitrate (solid or aqueous) to the guava leaf extract, filtered or not. [0008] Within a few seconds or minutes, depending mainly on the temperature of the liquid extraction medium, it is possible to observe, spontaneously by “eif--sseeibyy” (a process in which the components of a system self-organize to assemble a more functional system), a gradual color change of the slightly yellow or greenish extraction medium, due to extraction, to orange when the formation of silver nanoparticles occurs. [0009] The self-organized colloidal solution can be heated to improve synthesis efficiency, and pH variations from 1 to 13 and changes in the concentrations of the extractive medium can affect the final product. In this sense, for example, heating below 100 °C for specific time intervals amplifies the efficiency of the synthesis. DESCRIPTION OF THE NUANCES IN THE SYNTHESIS PROCESS [0010] The synthesis process of the silver nanoparticles of the present invention is carried out using a green chemistry methodology and is free from the use of organic solvents or any solvent harmful to the environment.