A Reduced Graphene Oxide Quantum Dot-Based Adsorbent for Efficiently Binding with Organic Pollutants

Abstract

This paper, for the first time, presents a novel, robust, and efficient high-quality reduced graphene oxide quantum dot (GQD)-based adsorbent for addressing the alarming environmental pollution issues nowadays. Such GQDs were fabricated in a facile manner via a combined green chemistry (GC) and temperature-controlled sonication irradiation (TSI) process. The mechanism underlying the fragmentation of the reduced graphene oxide (RGO) sheets prepared by GC with vitamin C (VC) as the only reactant to regulate the microstructure of graphene oxide (GO) was clarified through various characterization techniques such as X-ray diffraction, Raman, Brunauer−Emmett−Teller specific surface area measurements, transmission electron microscopy, scanning electron microscopy, elemental mapping, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, selected area electron diffraction, and energy dispersive spectroscopy. The GQDs were assumed to be generated via cutting the nanometer-size sp 2 domains or clusters out of the RGO sheets along the defect sites decorated with oxygen groups and sp 3 carbons. The adsorption of the methylene blue (MB) dye onto the prepared GQDs was fast and obeyed the pseudo-second-order kinetic model, while the Freundlich adsorption isotherm was more suitable to fit the experimental data, as a result of the preferential enrichment of the organic dye molecules onto the edges rather than the homogeneous adsorption over the entire surface of GQDs. This could also be evidenced by the finding that the smaller was the lateral size of the RGO sheets, the stronger were the adsorption interactions with the MB dye. The dangling bonds with nonbonding electrons on the RGO edges were thus believed to play a significant role in the heterogeneous adsorption of the dye molecules through donor−acceptor charge transfer interactions. Impressively, the striking edge effect rendered the GQDs highly adsorptive toward the organic dye, with the maximum adsorption capacity calculated to be 827.5 mg g −1 for MB, outstripping most of the reported adsorbents. In addition, this GQDs-based adsorbent was found to be durable for many runs of repeated usage, and its universality was also demonstrated through efficiently binding with rhodamine B.

Biodegradable Polylactide/TiO2 Composite Fiber Scaffolds with Superhydrophobic and Superadhesive Porous Surfaces for Water Immobilization, Antibacterial Performance, and Deodorization

“…Conversely, the average number of the viable bacteria cells on the standard control test specimen in the absence of the ES PLA/TiO 2 fibers was dramatically increased after the 24 h of visible light irradiation, likely because bacterial proliferation readily proceeded without the inhibition effect from the destructive reactive oxygen species generated by the photocatalytic reactions over the PLA/TiO 2 fibers. As a result, the as-prepared PLA/TiO 2 fibers can find promising antimicrobial applications by considering its high antibacterial efficiency, as well as its robust and portable merits that cannot be obtained in the traditional powdery samples [34,35,36,37,38,39,40,41,42,43,44,45,46]. R 1 = (( N 0 – N 24h )/ N 0 ) × 100…”

Absence of giant dielectric permittivity in graphene oxide materials

“…The degree of oxidation is around 40% as measured by x-ray photoelectron spectroscopy (XPS) analysis (figure S3). The oxidized functions include approximately C-OH 284 eV, C=O 288 eV, O=C-OH 291 eV [42]. Milli-Q water (Q-Gard 00D2) with a resistivity above 18.2 MΩ cm at 25°C and 2-Propanol (IPA) absolute 99.9% were purchased from Sigma Aldrich and used as received.…”

Oxygen-less Carbon Nanodots with an Absolute Quantum Yield of 80% for Display Applications

“…Many researchers have reported that the oxygen-containing functional groups of CNDs are responsible for their interesting optical properties such as strong excitation-dependent photoluminescence (PL). − However, the specific role of oxygen in CNDs has not yet been fully elucidated because it is still difficult to prepare oxygen-less CNDs via conventional synthetic methods for comparative analysis in terms of the oxygen content. Although CNDs subjected to post-synthetic reduction have a lower oxygen content, they still contain a significant amount of oxygen. − Furthermore, the oxygen-containing groups generally render CNDs to be strongly hydrophilic. While this is advantageous in many applications such as in biomedicine, it could hinder applications that require the use of hydrophobic solvents.…”