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Synthesis and applications of graphene-based TiO(2) photocatalysts

Tan LL, Chai SP, Mohamed AR

ChemSusChem, 2012 Oct;5(10):1868-82.
PMID: 22987439 DOI: 10.1002/cssc.201200480

Graphene is one of the most promising materials in the field of nanotechnology and has attracted a tremendous amount of research interest in recent years. Due to its large specific surface area, high thermal conductivity, and superior electron mobility, graphene is regarded as an extremely attractive component for the preparation of composite materials. At the same time, the use of photocatalysts, particularly TiO(2), has also been widely studied for their potential in addressing various energy and environmental-related issues. However, bare TiO(2) suffers from low efficiency and a narrow light-response range. Therefore, the combination of graphene and TiO(2) is currently one of the most active interdisciplinary research areas and demonstrations of photocatalytic enhancement are abundant. This Review presents and discusses the current development of graphene-based TiO(2) photocatalysts. The theoretical framework of the composite, the synthetic strategies for the preparation and modification of graphene-based TiO(2) photocatalysts, and applications of the composite are reviewed, with particular attention on the photodegradation of pollutants and photocatalytic water splitting for hydrogen generation.

Matched MeSH terms: Graphite/chemical synthesis*
Fulltext Simple room-temperature preparation of high-yield large-area graphene oxide

Huang NM, Lim HN, Chia CH, Yarmo MA, Muhamad MR

Int J Nanomedicine, 2011;6:3443-8.
PMID: 22267928 DOI: 10.2147/IJN.S26812

Graphene has attracted much attention from researchers due to its interesting mechanical, electrochemical, and electronic properties. It has many potential applications such as polymer filler, sensor, energy conversion, and energy storage devices. Graphene-based nanocomposites are under an intense spotlight amongst researchers. A large amount of graphene is required for preparation of such samples. Lately, graphene-based materials have been the target for fundamental life science investigations. Despite graphene being a much sought-after raw material, the drawbacks in the preparation of graphene are that it is a challenge amongst researchers to produce this material in a scalable quantity and that there is a concern about its safety. Thus, a simple and efficient method for the preparation of graphene oxide (GO) is greatly desired to address these problems. In this work, one-pot chemical oxidation of graphite was carried out at room temperature for the preparation of large-area GO with ~100% conversion. This high-conversion preparation of large-area GO was achieved using a simplified Hummer's method from large graphite flakes (an average flake size of 500 μm). It was found that a high degree of oxidation of graphite could be realized by stirring graphite in a mixture of acids and potassium permanganate, resulting in GO with large lateral dimension and area, which could reach up to 120 μm and ~8000 μm(2), respectively. The simplified Hummer's method provides a facile approach for the preparation of large-area GO.

Matched MeSH terms: Graphite/chemical synthesis*
Fulltext Synthesis, Characterization, and Toxicity Assessment of Pluronic F127-Functionalized Graphene Oxide on the Embryonic Development of Zebrafish (Danio rerio)

Shamsi S, Alagan AA, Sarchio SNE, Md Yasin F

Int J Nanomedicine, 2020;15:8311-8329.
PMID: 33149578 DOI: 10.2147/IJN.S271159

Background: In the current literature, there are ongoing debates on the toxicity of graphene oxide (GO) that demonstrate contradictory findings regarding its toxicity profile. As a potential drug carrier, these findings are very concerning due to the safety concerns in humans, as well as the dramatic rise of GO being excreted into the environment. Therefore, there is an imperative need to mitigate the potential toxicity of GO to allow for a safer application in the future.
Purpose: The present study aims to address this issue by functionalizing GO with Pluronic F127 (PF) as a means to mitigate toxicity and resolve the biocompatibility of GO. Although results from previous studies generally indicated that Pluronic functionalized GO exhibits relatively low toxicity to living organisms, reports that emphasize on its toxicity, particularly during embryonic developmental stage, are still scarce.
Methods: In the present study, two different sizes of native GO samples, GO and NanoGO, as well as PF-functionalized GO, GO-PF and NanoGO-PF, were prepared and characterized using DLS, UV-Vis, Raman spectroscopy, FTIR, and FESEM analyses. Toxicological assessment of all GO samples (0-100 µg/mL) on zebrafish embryonic developmental stages (survival, hatching and heart rates, and morphological changes) was recorded daily for up to 96 hours post-fertilization (hpf).
Results: The toxicity effects of each GO sample were observed to be higher at increasing concentrations and upon prolonged exposure. NanoGO demonstrated lower toxicity effects compared to GO. GO-PF and NanoGO-PF were also found to have lower toxicity effects compared to native GO samples. GO-PF showed the lowest toxicity response on zebrafish embryo.
Conclusion: These findings highlight that toxicity is dependent on the concentration, size, and exposure period of GO. Functionalization of GO with PF through surface coating could potentially mitigate the toxicity effects of GO in embryonic developmental stages, but further investigation is warranted for broader future applications.

Matched MeSH terms: Graphite/chemical synthesis
Fulltext Environmental Synthesis of Few Layers Graphene Sheets Using Ultrasonic Exfoliation with Enhanced Electrical and Thermal Properties

Noroozi M, Zakaria A, Radiman S, Abdul Wahab Z

PLoS One, 2016;11(4):e0152699.
PMID: 27064575 DOI: 10.1371/journal.pone.0152699

In this paper, we report how few layers graphene that can be produced in large quantity with low defect ratio from exfoliation of graphite by using a high intensity probe sonication in water containing liquid hand soap and PVP. It was founded that the graphene powder obtained by this simple exfoliation method after the heat treatment had an excellent exfoliation into a single or layered graphene sheets. The UV-visible spectroscopy, FESEM, TEM, X-ray powder diffraction and Raman spectroscopy was used to analyse the graphene product. The thermal diffusivity of the samples was analysed using a highly accurate thermal-wave cavity photothermal technique. The data obtained showed excellent enhancement in the thermal diffusivity of the graphene dispersion. This well-dispersed graphene was then used to fabricate an electrically conductive polymer-graphene film composite. The results demonstrated that this low cost and environmental friendly technique allowed to the production of high quality layered graphene sheets, improved the thermal and electrical properties. This may find use in the wide range of applications based on graphene.

Matched MeSH terms: Graphite/chemical synthesis
Fulltext Graphene-based hybrid nanoparticle of doxorubicin for cancer chemotherapy

SreeHarsha N, Maheshwari R, Al-Dhubiab BE, Tekade M, Sharma MC, Venugopala KN, et al.

Int J Nanomedicine, 2019;14:7419-7429.
PMID: 31686814 DOI: 10.2147/IJN.S211224

Background: Prostate cancer (PC) has the highest prevalence in men and accounts for a high rate of neoplasia-related death. Doxorubicin (DOX) is one of the most widely used anti-neoplastic drugs for prostate cancer among others. However, it has low specificity and many side effects and affects normal cells. More recently, there have been newly developed drug delivery tools which are graphene or graphene-based, used to increase the specificity of the delivered drug molecules. The graphene derivatives possess both π-π stacking and increased hydrophobicity, factors that increase the likelihood of drug delivery. Despite this, the hydrophilicity of graphene remains problematic, as it induced problems with stability. For this reason, the use of a chitosan coating remains one way to modify the surface features of graphene.
Method: In this investigation, a hybrid nanoparticle that consisted of a DOX-loaded reduced graphene oxide that is stabilized with chitosan (rGOD-HNP) was developed.
Result: The newly developed rGOD-HNP demonstrated high biocompatibility and efficiency in entrapping DOX (~65%) and releasing it in a controlled manner (~50% release in 48 h). Furthermore, it was also demonstrated that rGOD-HNP can intracellularly deliver DOX and more specifically in PC-3 prostate cancer cells.
Conclusion: This delivery tool offers a feasible and viable method to deliver DOX photo-thermally in the treatment of prostate cancer.

Matched MeSH terms: Graphite/chemical synthesis
Graphene oxide exhibits differential mechanistic action towards Gram-positive and Gram-negative bacteria

Pulingam T, Thong KL, Ali ME, Appaturi JN, Dinshaw IJ, Ong ZY, et al.

Colloids Surf B Biointerfaces, 2019 Sep 01;181:6-15.
PMID: 31103799 DOI: 10.1016/j.colsurfb.2019.05.023

The antibacterial nature of graphene oxide (GO) has stimulated wide interest in the medical field. Although the antibacterial activity of GO towards bacteria has been well studied, a deeper understanding of the mechanism of action of GO is still lacking. The objective of the study was to elucidate the difference in the interactions of GO towards Gram-positive and Gram-negative bacteria. The synthesized GO was characterized by Ultraviolet-visible spectroscopy (UV-vis), Raman and Attenuated Total Reflectance-Fourier-transform infrared spectroscopy (ATR-FTIR). Viability, time-kill and Lactose Dehydrogenase (LDH) release assays were carried out along with FESEM, TEM and ATR-FTIR analysis of GO treated bacterial cells. Characterizations of synthesized GO confirmed the transition of graphene to GO and the antibacterial activity of GO was concentration and time-dependent. Loss of membrane integrity in bacteria was enhanced with increasing GO concentrations and this corresponded to the elevated release of LDH in the reaction medium. Surface morphology of GO treated bacterial culture showed apparent differences in the mechanism of action of GO towards Gram-positive and Gram-negative bacteria where cell entrapment was mainly observed for Gram-positive Staphylococcus aureus and Enterococcus faecalis whereas membrane disruption due to physical contact was noted for Gram-negative Escherichia coli and Pseudomonas aeruginosa. ATR-FTIR characterizations of the GO treated bacterial cells showed changes in the fatty acids, amide I and amide II of proteins, peptides and amino acid regions compared to untreated bacterial cells. Therefore, the data generated further enhance our understanding of the antibacterial activity of GO towards bacteria.

Matched MeSH terms: Graphite/chemical synthesis
Science stars of East Asia

Cyranoski D, Law YH, Ong S, Phillips N, Zastrow M

Nature, 2018 06;558(7711):502-510.
PMID: 29950631 DOI: 10.1038/d41586-018-05506-1
Matched MeSH terms: Graphite/chemical synthesis