Applications of Green Nanomaterials
The above discussions on the synthesis and structure-based unique properties of green nanomaterials have given the reader considerable indications of the scope of their applications. The research literature is rich with such studies and endeavors, most of which are multi-disciplinary. It is outside the scope of this book chapter to engage in any exhaustive discussion of the manifold uses of green nanomaterials. Thus, the following sub-sections focus on the current applications of green nanomaterials in certain specific fields, i.e. functional materials, semiconductors, optoelectronics and spectral analysis. Where possible, future scopes of green nanomaterials are elaborated on with extrapolation from present research findings.
Applications as Functional Materials
Thrombin (ТВ) can be classified as a significant protein in molecular biology. Its activity and concentration are vital signs of pathological and physiological illness. So, a simple but relatively fast scheme for the detection of ТВ, with both high sensitivity and high selectivity, is definitely of huge importance in clinical applications.
For this purpose, a novel anodic electrochemiluminescent (ECL) aptasensor for finding ТВ has been made using carbon dot capped gold nanoflower (CD/AuNF) nanohybrid synthesis (You etal., 2018). The prepared CD/AuNF nanohybrids have gold nanoflowers in the center and a coating of carbon dots on the exterior. The hybrids are of uniform size ranging from 50 to 60 nm. Self-assembly along with biomolecules of AuNFs and the exceptional ECL activities of the CDs make CD/AuNF nanohybrids capable of biosensing. The specificity of the aptasensor was measured by reacting it with several other potential interferences like adenosine triphosphate (ATP), human IgG (IgG), bovine serum albumin (BSA), L-glutamate (L-Glu), L-cysteine (L-Cys) and lysosome (Lys). The sensor showed excellent selectivity for ТВ with a wide limit from 0.5 nM to 40 nM, and a low detection range (S/N = 3) of 0.08 nM.
Mostly CDs are required to be hybridized with additional nanomaterials for biosensing application, for detection of biomolecules, and/or signal amplification (Dong et al., 2015). Nanogold materials exhibit brilliant functionalization and biocompatibility.
As nuclear technology grows, vast numbers of radionuclides eventually go to the natural world. Therefore, for health and safety concerns, radionuclides need to be separated from drainage. Due to their high specific surface regions, broad amounts of binding sites, numerous functional groups, controllable pore sizes and ease of simple surface adjustments, nanomaterials are considered possible candidates for the efficient and systematic removal of radionuclides from aqueous solutions.
Developmental defects, birth abnormalities, obesity and many forms of cancer may be directly triggered if radionuclides from radioactive sources are inhaled. Uranium (U(VI)) release may result in severe biological harm such as toxic hepatitis, degradation of the skin, histopathological system harm 90, loss of kidney function and cancerous tumor (Song et al., 2017). Strontium (Sr(II)) has an important role in hepatocellular carcinoma diagnosis and the care of sixty other tumors of the liver (Banerjee et al., 2016; Bevara et al., 2018). Cobalt (Co(II)) can lead to several medical conditions, including low blood pressure, inflammation of the lungs, paralysis and diarrhea. Hence, one of the main environmental remediation priorities today is the detection and subsequent elimination of these radionuclides from polluted water. However, effective and selective methods for eliminating radionuclides from wastewater remain very much to be established (Wen et al., 2017).
Superior sorption efficiency, high selectivity and ecological sustainability are attractive features of modern nanomaterials including graphene oxides (GO), covalent organic frameworks (COF), carbon nitride (C3N4), metal-organic frameworks (MOFs), nanoscale zerovalent iron (NZVI), Mxenes, carbon nanofiber (CNF) and carbon nanotubes (CNTs). GO, a significant graphene derivative has a practical base plane with large enough oxygen-containing groups and edges as epoxy, hieroglyph and carboxy. GO nanosheets have a strong adsorption potential in preconcentrations for radionuclides in broad quantities of aqueous liquids, given the oxygen-containing functional groups and wide surface areas (Wang et al., 2016; Lingamdinne et al., 2019; Koduru et al., 2019; Lingamdinne et al., 2017).
MOFs offer the ability to be customized for different applications by adjusting their pores and geometry. This function may have major impacts on the production of structural isomer molecules adsorbent-based separation processes, which typically rely on the subtle match of adsorbates and micropore adsorbents (Li et al., 2018; Gao et al., 2019). Thanks to their attractive transparent structural properties and functionality, COFs have achieved considerable attention. The architectures and large surface areas are flexible, and are ideal for radionuclide pre-concentration (Salonen etal., 2017).
The treatment of a variable number of radionuclides by manageable particle size, strong reactivity and ample reactive surface space was successfully achieved by NZVI (Zou et al., 2016; Chen et al., 2018). Because it was calculated that C3N4 is super hard and diamond equivalent, C3N4 has stimulated significant interest (Shen et al., 2015). The structural units (-NH2/-NH-/=N-) in g-C3N4 enable radionuclide deletion at the sample sites. Such groups even demonstrate outstanding radionuclide sorption by complexation or redox reactions (Hu et al., 2015).
Utilizing adequate etching agents from MAX phases at room temp, the MXens are typically made with specific grading of A element layers. MXenes are regarded as an outstanding tool for the solidification of radionuclides because of their strong physical and chemical durability, their hydrophilic properties and their environmentally-friendly nature (Wang et al., 2019). CNFs and CNTs are carbon-based nanomaterials, which have been thoroughly investigated in the removal of extremely soluble, heavy sorption and specific radionuclides after surface alteration (Xiao et al., 2013; Wang et al., 2005). The technique for synthesizing new nanomaterials allows various forms of older nanomaterials to be synthesized in broad volume at a low cost, which would allow nanomaterials to be cleaned up in the light of ecological radionuclide emissions.
