Synthetic Approaches, Modification Strategies and the Application of Quantum Dots in the Sensing of Priority Pollutants

Polycyclic aromatic hydrocarbons (PAHs) and nitro-aromatic compounds (NACs) are two classifications of environmental pollutants that have become a source of health concerns. As a result, there have been several efforts towards the development of analytical methods that are efficient and affordable that can sense these pollutants. In recent decades, a wide range of techniques has been developed for the detection of pollutants present in the environment. Among these different techniques, the use of semiconductor nanomaterials, also known as quantum dots, has continued to gain more attention in sensing because of the optical properties that make them useful in the identification and differentiation of pollutants in water bodies. Reported studies have shown great improvement in the sensing of these pollutants. This review article starts with an introduction on two types of organic pollutants, namely polycyclic aromatic hydrocarbons and nitro-aromatic explosives. This is then followed by different quantum dots used in sensing applications. Then, a detailed discussion on different groups of quantum dots, such as carbon-based quantum dots, binary and ternary quantum dots and quantum dot composites, and their application in the sensing of organic pollutants is presented. Different studies on the comparison of water-soluble quantum dots and organic-soluble quantum dots of a fluorescence sensing mechanism are reviewed. Then, different approaches on the improvement of their sensitivity and selectivity in addition to challenges associated with some of these approaches are also discussed. The review is concluded by looking at different mechanisms in the sensing of polycyclic aromatic hydrocarbons and nitro-aromatic compounds

Synthesis of graphene oxide (GO) decorated CuInS2/ZnS core/shell quantum dots (QDs) as fluorescence probe for the detection of environmental pollutants

Abstract: Recently, an increasing number of organic compounds including polycyclic aromatic hydrocarbons (PAHs) and nitro-aromatic compounds (NACs) are being released into the environment and most of them are hazardous to living organisms and ecosystems. Thus, the detection of those organic pollutants has become a major concern. Until now various techniques have been used to sense organic pollutants, and such methods have included surface-enhanced Raman spectroscopy (SERS), gas chromatography coupled with mass spectrometry (GC–MS), plasma desorption mass spectrometry (PDMS), energy dispersive X-ray diffraction (EDXRD), and various spectral imaging techniques. However, these conventional methods are not low-cost, not environmentally-friendly, not portable, and not suitable for rapid field detection. Over the past decades, fluorescence technology using organic pollutants detection provides an attractive and promising alternative owing to its unique advantages which include cost-effectiveness, environmentally-friendliness, rapid response and good portability. Therefore, this study explored aqueous synthesis, characterisation and application of CuInS2/ZnS-GO fluorescent probe for the fluorescence detection of the selected organic compounds such as polycyclic aromatic hydrocarbons and nitro-aromatic compounds in aqueous phase. The pollutants are; phenanthrene (Phe), pyrene (Py) and naphthalene (Naph) and trinitrophenol (TNP). A fluorescent nanocomposite was prepared by decorating graphene oxide (GO) with glutathione (GSH)-capped CuInS2/ZnS core/shell quantum dots (QDs). The composite was prepared via in-situ synthesis in which glutathione (GSH) and sodium citrate were used as dual stabilizers. The quantum dots nanocomposite was prepared through non- covalent functionalization of QDs with graphene oxide (GO). The as-synthesized composite was characterised using UV-Vis absorption, photoluminescence (PL) vi spectroscopy, high resolution transmission electron microscopy (HR-TEM), Fourier- transform infrared spectroscopy (FT-IR), Ultraviolet–visible spectroscopy (UV-Vis), X-ray diffraction (XRD) and Raman scattering. The photoluminescence (PL) spectrophotometry revealed the Forster resonance energy transfer (FRET) between the QDs and GO. The Raman scattering revealed the presence of QDs on the GO nanosheets. The TEM showed that the QDs were well distributed on the GO nanosheets. This was in agreement with the UV absorption bands which revealed the excitonic peaks for the QDs and the QDs-GO. In addition, the XRD patterns confirmed the crystalline nature of the as-prepared materials. The sensing studies indicated that the fluorescence intensity of the QDs-GO nanocomposite can be increased by both PAHs and NACs. However, the fluorescence intensity of pristine QDs does not show changes in the presence of PAHs. Though the presence of PAHs in the QDs did not show significant changes in the fluorescence intensity, however, the presence of the NAC, TNP, caused the fluorescence intensity of the QDs to decrease.M.Sc. (Chemistry

Synthetic Approaches, Modification Strategies and the Application of Quantum Dots in the Sensing of Priority Pollutants

Polycyclic aromatic hydrocarbons (PAHs) and nitro-aromatic compounds (NACs) are two classifications of environmental pollutants that have become a source of health concerns. As a result, there have been several efforts towards the development of analytical methods that are efficient and affordable that can sense these pollutants. In recent decades, a wide range of techniques has been developed for the detection of pollutants present in the environment. Among these different techniques, the use of semiconductor nanomaterials, also known as quantum dots, has continued to gain more attention in sensing because of the optical properties that make them useful in the identification and differentiation of pollutants in water bodies. Reported studies have shown great improvement in the sensing of these pollutants. This review article starts with an introduction on two types of organic pollutants, namely polycyclic aromatic hydrocarbons and nitro-aromatic explosives. This is then followed by different quantum dots used in sensing applications. Then, a detailed discussion on different groups of quantum dots, such as carbon-based quantum dots, binary and ternary quantum dots and quantum dot composites, and their application in the sensing of organic pollutants is presented. Different studies on the comparison of water-soluble quantum dots and organic-soluble quantum dots of a fluorescence sensing mechanism are reviewed. Then, different approaches on the improvement of their sensitivity and selectivity in addition to challenges associated with some of these approaches are also discussed. The review is concluded by looking at different mechanisms in the sensing of polycyclic aromatic hydrocarbons and nitro-aromatic compounds

Facile Green, Room-Temperature Synthesis of Gold Nanoparticles Using Combretum erythrophyllum Leaf Extract: Antibacterial and Cell Viability Studies against Normal and Cancerous Cells

We herein report a facile, green, cost-effective, plant-mediated synthesis of gold nanoparticles (AuNPs) for the first time using Combretum erythrophyllum (CE) plant leaves. The synthesis was conducted at room temperature using CE leaf extract serving as a reducing and capping agent. The as-synthesized AuNPs were found to be crystalline, well dispersed, and spherical in shape with an average diameter of 13.20 nm and an excellent stability of over 60 days. The AuNPs showed broad-spectrum antibacterial activities against both pathogenic Gram-positive (Staphylococcus epidermidis (ATCC14990), Staphylococcus aureus (ATCC 25923), Mycobacterium smegmatis (MC 215)) and Gram-negative bacteria (Proteus mirabilis (ATCC 7002), Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATCC 13822), Klebsiella oxytoca (ATCC 8724)), with a minimum inhibition concentration of 62.5 µg/mL. In addition, the as-synthesized AuNPs were highly stable with exceptional cell viability towards normal cells (BHK- 21) and cancerous cancer cell lines (cervical and lung cancer)

Synthesis of NIR-II Absorbing Gelatin Stabilized Gold Nanorods and Its Photothermal Therapy Application against Fibroblast Histiocytoma Cells

The excellent photothermal properties of gold nanorods (Au-NRs) make them one of the most researched plasmonic photothermal nanomaterials. However, their biological applications have been hampered greatly due to surfactant-induced cytotoxicity. We herein report a simple synthesis of highly biocompatible gelatin stabilized Au-NRs (gelatin@Au-NRs) to address this issue. The optical and structural properties of the as-synthesized gelatin@Au-NRs were investigated by Zetasizer, Ultraviolet-Visible-Near Infrared (UV-Vis-NIR) spectroscopy, high-resolution transmission electron microscopy (HR-TEM), and Fourier transform infrared spectroscopy (FTIR). The as-synthesized gelatin@Au-NRs were highly crystalline and rod-like in shape with an average length and diameter of 66.2 ± 2.3 nm and 10 ± 1.6 nm, respectively. The as-synthesized gelatin@Au-NRs showed high stability in common biological media (phosphate buffer saline and Dulbecco’s Modified Eagle’s Medium) compared to CTAB capped Au-NRs. Similarly, the gelatin@Au-NRs showed an improved heat production and outstanding cell viability against two different cancer cell lines; KM-Luc/GFP (mouse fibroblast histiocytoma cell line) and FM3A-Luc (breast carcinoma cell line) compared to CTAB capped Au-NRs and PEG@Au-NRs. An in vitro photothermal therapy study against KM-Luc/GFP showed that gelatin@Au-NRs effectively destroys the cancer cells

Highly Toughened Nanostructured Self-Assembled Epoxy-Based Material—Correlation Study between Nanostructured Morphology and Fracture Toughness—Impact Characteristics

We present an efficient and effective method for preparing a novel self-assembled nanostructured material with high toughness and impact strength from a blend of di-glycidyl ether of bisphenol-A (DGEBA) and epoxidized poly(styrene-block-butadiene-block-styrene) (eSBS55) tri-block copolymer. The field emission scanning electron microscopy and transmission electron microscope results show the nanostructured morphological characteristics of the blends. This study achieved the highest fracture toughness, with a fracture toughness in the form of critical stress intensity factors (KIC) value of 2.54 MPa m1/2, in epoxy/block copolymer blends compared to previous works in the field. The impact strength also increased by 116% compared to neat epoxy. This is a major advancement in epoxy toughening due to the use of a single secondary phase. The resulting highly tough and impact-resistant material is a promising candidate for coating applications in industries such as flooring, building, aerospace, and automobiles