Graphene/SiO2 nanocomposites: The enhancement of photocatalytic and biomedical activity of SiO2 nanoparticles by graphene

PREPRINTS Graphene/SiO2 nanocomposites: the enhancement of photocatalytic and biomedical activity of SiO2 nanoparticles by graphene Aqsa Arshad1,2,a), Javed Iqbal3,a), Qaisar Mansoor4, Ishaq Ahmed5 1Department of Physics, International Islamic University, Islamabad, Pakistan. 2Department of Physics, Durham University, South Road Durham DH1 3LE, United Kingdom. 3 Laboratory of Nanoscience and Technology, Department of Physics, Quaid i Azam University, Islamabad, Pakistan. 4Institute of Biomedical and Genetic Engineering (IBGE), Islamabad, Pakistan. 5Experimental Physics Labs, Professor Abdus Salam Centre of Physics, Islamabad, Pakistan. a) Corresponding author(s): aqsa.arshad@iiu.edu.pk ; javed.saggu@qau.edu.pk

This manuscript is accepted by Journal of Applied Physics (AIP) Volume 121 Issue 24 Page number 244901 Year 2017 doi: 10.10632/1.4979968 Comments & suggestions are welcome aqsa.arshad@iiu.edu.pk

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ABSTRACT: The exceptional conducting nature of graphene makes it a viable candidate for enhancing the effectiveness of photocatalytic and biomedical nanomaterials. Herein, the immobilization of monodispersed silicon dioxide (SiO2) nanoparticles on multiple graphene layers is demonstrated for intercalation of graphene nanoplatelets (GNPs). Interestingly, the loading of graphene nanoplatelets with SiO2 nanoparticles enhances the photocatalytic efficiency from 46% to 99%. For biomedical applications, it is found that 75% of Gram positive and 50% of Gram negative bacteria have been killed, hence bacterial proliferation is significantly restricted. Further, the cytotoxicity study reveals that the synthesised nanocomposites are non-toxic for both normal (HCEC) and cancerous (MCF-7, HEp-2) cell lines which signifies their potential as carriers for drug delivery. The prepared nanocomposites with controlled amount of carbon in the form of graphene can be employed for photocatalysis based waste water remediation, biomedicine and nano drug delivery. KEYWORDS: Toxic nanomaterials; Graphene nanocomposites; Photocatalysis; Waste water treatment; Cytotoxicity; Biomedicine

I. INTRODUCTION Health and ecological issues arising due to microorganism and rapid industrialization have posed the excessive risk of diseases and water contamination. These problems have enforced researchers to develop new environment friendly materials to cope with worldwide health hazards and treatment of waste water. Nowadays, finding solutions to clean the water contaminated by dyes is prime focus of research. At the same time, synthesis of bactericidal materials1 is equally significant for cleaning infected water, food packaging, hospital implants, and dentistry instruments.2-5 Furthermore, in the health sector, cancer is the most threatening and incurable disease known till now.6 Therefore, the chemotherapeutic

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treatments are essential and such treatments require nontoxic nanosized carriers for efficient drug delivery.7 Metal and non-metal oxides have been extensively studied for photocatalysis and biomedical applications.8-12 Among them, SiO2 has the prime importance as it is the promising candidate for future development of catalysts, adsorbents, nanodrug carriers and biomolecular transport agents.13-20 However, some demerits of SiO2 restrict its efficiency in photocatalysis and biomedicine, which are: the wide bandgap (~5eV), aggregation of NPs, quick charge carrier’s recombination and low surface area. These factors contribute towards its inert behaviour towards many catalytic processes and it shows only a slight catalytic activity under UV irradiation.21,22 To improve its photocatalytic performance, it is highly desirable to combine carbonaceous materials with SiO2, as various studies indeed describe their efficacy for remediation of contaminated water.23-26 The latest addition to carbonaceous materials is graphene which is a perfectly two dimensional, sp2 hybridized carbon. The ultrafast Dirac Fermions (near the k and k’ points) render exceptional transport properties in graphene.27 The enticing features that make graphene ideal for various applications are its high electrical and thermal conductivities, large specific surface area, good chemical stability and outstanding mechanical properties.28-30 These features pave the way for incorporation of graphene in hybrid materials (constituted by its combination with metals, ceramics, polymers, and chalcogenides).31-36 Harnessing the good electronic transport and other physical properties of graphene with those of ceramics can significantly enhance their performance in photocatalysis and biomedical applications.37-39 For instance, the activity of a nanomaterial to remove dye and bacterial contamination is mainly influenced by surface area, surface roughness and functionalization.40 SiO2 NPs decorated graphene nanoplatelets (GNPs) have hybrid properties of both nanomaterials e.g., improved interfacial cont

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