Adverse effects of graphene incorporated in TiO2 photocatalyst on minuscule animals under solar light irradiation

The adverse effect of graphene–titanium oxide composite films (containing sheet-like surface morphology) on Caenorhabditis elegans nematodes (as a model for minuscule animals) was investigated in a solar light-induced photocatalytic process. X-ray photoelectron spectroscopy demonstrated photocatalytic reduction of the chemically exfoliated graphene oxide sheets included in the TiO2 film. Furthermore, formation of TiC and Ti–O–C bonds in the composite film (obtained through annealing at 450 °C in air) resulted in a substantial delay in the recombination rate of the photoexcited electron–hole pairs and more efficient photocatalytic processes. The composite film showed a type of concentration-dependent cytotoxic effect on the nematodes under irradiation. The rapid (4 h) photoinactivation of the nematodes by the composite films was assigned to a high generation of reactive oxygen species (ROS) under solar light irradiation (∼25× of the ROS level of a control sample in dark), rather than the strong photoinactivation of Escherichia coli bacteria, which was utilized as the food of the nematodes in a culture medium. The threshold ROS level for inactivation of the nematodes was found ∼19× of the control level which was unreachable using TiO2. These results warn us of the destruction of minuscule animals of our environment through extensive application of highly efficient graphene–titanium oxide photocatalysts.

[1]  Hiromi Yamashita,et al.  Graphene Coating of TiO2 Nanoparticles Loaded on Mesoporous Silica for Enhancement of Photocatalytic Activity , 2010 .

[2]  O. Akhavan,et al.  Protein Degradation and RNA Efflux of Viruses Photocatalyzed by Graphene–Tungsten Oxide Composite Under Visible Light Irradiation , 2012 .

[3]  Chunhai Fan,et al.  Graphene-based antibacterial paper. , 2010, ACS nano.

[4]  H. Dai,et al.  Ultrasmall reduced graphene oxide with high near-infrared absorbance for photothermal therapy. , 2011, Journal of the American Chemical Society.

[5]  M. I. Katsnelson,et al.  Graphene: New bridge between condensed matter physics and quantum electrodynamics , 2007, cond-mat/0703374.

[6]  Omid Akhavan,et al.  Escherichia coli bacteria reduce graphene oxide to bactericidal graphene in a self-limiting manner , 2012 .

[7]  O. Akhavan,et al.  Lasting antibacterial activities of Ag-TiO2/Ag/a-TiO2 nanocomposite thin film photocatalysts under solar light irradiation. , 2009, Journal of colloid and interface science.

[8]  Zhijun Zhang,et al.  Functional graphene oxide as a nanocarrier for controlled loading and targeted delivery of mixed anticancer drugs. , 2010, Small.

[9]  Omid Akhavan,et al.  The use of a glucose-reduced graphene oxide suspension for photothermal cancer therapy , 2012 .

[10]  M. Suh,et al.  The control of neural cell-to-cell interactions through non-contact electrical field stimulation using graphene electrodes. , 2011, Biomaterials.

[11]  Yuyan Shao,et al.  Graphene Based Electrochemical Sensors and Biosensors: A Review , 2010 .

[12]  Andre K. Geim,et al.  Electric Field Effect in Atomically Thin Carbon Films , 2004, Science.

[13]  O. Akhavan,et al.  Increasing the antioxidant activity of green tea polyphenols in the presence of iron for the reduction of graphene oxide , 2012 .

[14]  Peng Chen,et al.  Interfacing live cells with nanocarbon substrates. , 2010, Langmuir : the ACS journal of surfaces and colloids.

[15]  T. Seo,et al.  A Controllable Self‐Assembly Method for Large‐Scale Synthesis of Graphene Sponges and Free‐Standing Graphene Films , 2010 .

[16]  Z. Marković,et al.  In vitro comparison of the photothermal anticancer activity of graphene nanoparticles and carbon nanotubes. , 2011, Biomaterials.

[17]  O. Akhavan,et al.  Visible light photo-induced antibacterial activity of CNT–doped TiO2 thin films with various CNT contents , 2010 .

[18]  Kai Yang,et al.  The influence of surface chemistry and size of nanoscale graphene oxide on photothermal therapy of cancer using ultra-low laser power. , 2012, Biomaterials.

[19]  Zhuang Liu,et al.  PEGylated nanographene oxide for delivery of water-insoluble cancer drugs. , 2008, Journal of the American Chemical Society.

[20]  Christy L Haynes,et al.  Cytotoxicity of graphene oxide and graphene in human erythrocytes and skin fibroblasts. , 2011, ACS applied materials & interfaces.

[21]  P. Kim,et al.  Experimental observation of the quantum Hall effect and Berry's phase in graphene , 2005, Nature.

[22]  Kai Yang,et al.  Graphene in mice: ultrahigh in vivo tumor uptake and efficient photothermal therapy. , 2010, Nano letters.

[23]  Yanli Chang,et al.  In vitro toxicity evaluation of graphene oxide on A549 cells. , 2011, Toxicology letters.

[24]  Zhouyi Guo,et al.  Synergistic effect of chemo-photothermal therapy using PEGylated graphene oxide. , 2011, Biomaterials.

[25]  Omid Akhavan,et al.  Photodegradation of Graphene Oxide Sheets by TiO2 Nanoparticles after a Photocatalytic Reduction , 2010 .

[26]  O. Akhavan,et al.  Wrapping bacteria by graphene nanosheets for isolation from environment, reactivation by sonication, and inactivation by near-infrared irradiation. , 2011, The journal of physical chemistry. B.

[27]  C. Pan,et al.  TiO2/graphene composite from thermal reaction of graphene oxide and its photocatalytic activity in visible light , 2011 .

[28]  Omid Akhavan,et al.  Toxicity of graphene and graphene oxide nanowalls against bacteria. , 2010, ACS nano.

[29]  N. Mohanty,et al.  Graphene-based single-bacterium resolution biodevice and DNA transistor: interfacing graphene derivatives with nanoscale and microscale biocomponents. , 2008, Nano letters.

[30]  O. Akhavan,et al.  Toward single-DNA electrochemical biosensing by graphene nanowalls. , 2012, ACS nano.

[31]  Qin Song,et al.  The promotion of neurite sprouting and outgrowth of mouse hippocampal cells in culture by graphene substrates. , 2011, Biomaterials.

[32]  J. Robertson,et al.  Interpretation of Raman spectra of disordered and amorphous carbon , 2000 .

[33]  O. Akhavan,et al.  Self-accumulated Ag nanoparticles on mesoporous TiO2 thin film with high bactericidal activities , 2010 .

[34]  O. Akhavan.  Graphene nanomesh by ZnO nanorod photocatalysts. , 2010, ACS nano.

[35]  C. Fan,et al.  Protein corona-mediated mitigation of cytotoxicity of graphene oxide. , 2011, ACS nano.

[36]  A. Irajizad,et al.  Melatonin as a powerful bio-antioxidant for reduction of graphene oxide , 2011 .

[37]  J. Yao,et al.  Extended visible light response of binary TiO2-Ti2O3 photocatalyst prepared by a photo-assisted sol-gel method , 2006 .

[38]  Yang Xu,et al.  Cytotoxicity effects of graphene and single-wall carbon nanotubes in neural phaeochromocytoma-derived PC12 cells. , 2010, ACS nano.

[39]  Zhuang Liu,et al.  Nano-graphene oxide for cellular imaging and drug delivery , 2008, Nano research.

[40]  K. Novoselov,et al.  Detection of individual gas molecules adsorbed on graphene. , 2006, Nature materials.

[41]  Wanhong Ma,et al.  Preparation of titania/carbon nanotube composites using supercritical ethanol and their photocatalytic activity for phenol degradation under visible light irradiation , 2007 .

[42]  H. Emamy,et al.  Nontoxic concentrations of PEGylated graphene nanoribbons for selective cancer cell imaging and photothermal therapy , 2012 .

[43]  Wei Zhang,et al.  Photoluminescence in anatase titanium dioxide nanocrystals , 2000 .

[44]  Omid Akhavan,et al.  Photocatalytic Reduction of Graphene Oxide Nanosheets on TiO2 Thin Film for Photoinactivation of Bacteria in Solar Light Irradiation , 2009 .

[45]  Z. Xiong,et al.  Preparation, characterization and antibacterial properties of silver-modified graphene oxide , 2011 .

[46]  Omid Akhavan,et al.  Size-dependent genotoxicity of graphene nanoplatelets in human stem cells. , 2012, Biomaterials.

[47]  S. Mohajerzadeh,et al.  Synthesis of titania/carbon nanotube heterojunction arrays for photoinactivation of E. coli in visible light irradiation , 2009 .

[48]  Chen Liqiang,et al.  Toxicity of graphene oxide and multi-walled carbon nanotubes against human cells and zebrafish , 2012 .

[49]  A. Geim,et al.  Two-dimensional gas of massless Dirac fermions in graphene , 2005, Nature.

[50]  Xin Wang,et al.  Graphene−Metal Particle Nanocomposites , 2008 .

[51]  C. Hierold,et al.  Spatially resolved Raman spectroscopy of single- and few-layer graphene. , 2006, Nano letters.