Volume 8, Issue 3, March 2017

Progress in the graphene research since 2010

Ashutosh Tiwari

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 185-186
DOI: 10.5185/amlett.2017.3001

With exotic discovery of graphene, the focus of researchers brings initiatives in field of atom-thick two-dimensional (2D) materials having exceptional and extraordinary properties. In year 2010, Prof. Andre Geim and Prof. Konstantin Novoselov from the University of Manchester, UK were jointly awarded the Nobel Prize in Physics for their ground-breaking experiments on the two-dimensional material graphene. Data elucidated from Scopus indicates that since 2010, on graphene 77, 221 documents have been published from over 120 countries. Number of documents reported on graphene increased from 3,748 to 16,378 since 2010 to 2016. 

Review of environmental life cycle assessment studies of graphene production

Rickard Arvidsson

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 187-195
DOI: 10.5185/amlett.2017.1413

Environmentally benign production processes are required in order to ensure a sustainable graphene supply. Life cycle assessment (LCA) is an established method for assessing life cycle environmental impacts of products and production processes. In this paper, life cycle impacts of five production processes for graphene are reviewed: Chemical reduction of graphite oxide, ultrasonication exfoliation, thermal exfoliation, chemical vapour deposition, and epitaxial growth. The reduction step, including the production of the reduction agent hydrazine, was the main contributor for most impacts in the chemical reduction of graphite oxide. Production of the solvent diethyl ether was the step that contributed the most for ultrasonication exfoliation, so solvent recovery is advised. For thermal exfoliation, microwave heating was the step that contributed the most to environmental impacts of graphene nanoplatelets. For chemical vapour deposition, the methane feedstock production step contributed the most, but methane recovery could reduce the energy use considerably. The environmental impacts of epitaxial graphene were dominated by electricity use for production of the silicon wafer substrate, which means that a ‘greener’ electricity mix can reduce impacts considerably. Overall, it is shown that graphene need not be an energy-intensive material compared to conventional materials used in society today.

Recent advances in electrochemical biosensor and gas sensors based on graphene and carbon nanotubes (CNT) - A review 

Gounder Thangamani J.; Kalim Deshmukh; Kishor Kumar Sadasivuni; K. Chidambaram; M. Basheer Ahamed; Deepalekshmi Ponnamma; Mariam Al-Ali AlMaadeed; S. K. Khadheer Pasha

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 196-205
DOI: 10.5185/amlett.2017.7042

Graphene and carbon nanotubes (CNTs) based sensors have been extensively studied because of their applications in the detection of various chemicals and biomolecules. From an application point of view, high sensitivity and selectivity is a promising tool for fast detection of gas leakage and early diagnosis of diseases for health care. In the present review article, we provide a comprehensive overview on the recent advances in the development of graphene and CNT based electrochemical biosensors and gas sensors. From the future point of view, special attention is paid to the synthesis techniques for high-performance biosensors and gas sensors. This article focuses on detecting mechanism for various volatile organic compounds (VOCs) gas sensing behavior of the graphene and CNT based sensors. A comparative study of the sensing behavior of pure metal oxide nanoparticles as well as their hybrids with graphene and CNTs has been reported.

Three-dimensional nanocomposites of graphene/carbon nanotube matrix-embedded Si nanoparticles for superior lithium ion batteries

Dafang He; Lixian Li; Fengjuan Bai; Chenyang Zha; Liming Shen; Harold H. Kung; Ningzhong Bao

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 206-211
DOI: 10.5185/amlett.2017.7038

A unique hierarchically nanostructured composite of Si nanoparticles (Si NPs) embedded in a three-dimensional (3D) carbon nanotube (CNT)/graphene sheet (GS) matrix (Si@CNT/GS) is fabricated by freeze-drying and thermal reduction. In this novel nanostructured composite, since the intertwined elastic CNTs effectively disperse the Si NP anode material and provide extra physical connections between Si NPs and the surrounding 3D conductive matrix, the interconnected 3D CNT/GS matrix can serve to buffer the volume change of the Si NPs during cycling while simultaneously enhance the electrical conductivity of the overall electrode. As a result, Si@CNT/GS nanocomposite exhibits a high reversible capacity of 1362 mAh·g -1 at 500 mA·g -1 over 500 cycles, and an excellent rate capability of 504 mAh·g -1 at 8400 mA·g -1 , considerably improving the battery performance compared with those electrodes made from Si@graphene nanocomposites, thus exhibiting great potential as an anode composite structure for lithium storage. Copyright © 2017 VBRI Press.

Lamellar structures from graphene nanoparticles produced by anode oxidation

Mykola Kartel; Yuriy Sementsov; Galyna Dovbeshko; Liudmyla Karachevtseva; Stanislav Makhno; Tatiana Aleksyeyeva; Yulia Grebel

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 212-216
DOI: 10.5185/amlett.2017.1428

An effective cheap method for graphene nanoparticles (GNP) production with controlled size distribution was developed based on anodic oxidation of condensed exfoliated graphite. As it is shown, under certain condition the GNP could be self-organized into a 3-dimensional structure that could be important for understanding of the GNP interaction with different type of surfaces. Based on this feature, a synthesis method for preparation of composites containing GNP and polychlorotrifluoroethylene (PCTFE) was developed. Raman spectroscopy of GNP and GNP/PCTFE revealed a good crystalline structure of synthesized nanoparticles. Laser correlation spectroscopy and electron microscopy studies show that average size of particles ranges from tens to thousands nanometers and thickness consists ten or more graphene layers. We found that conductivity of GNP is of electronic nature. The real and imaginary parts of complex permittivity in the microwave range and electric conductivity at low frequencies were found to be a nonlinear function of a volume content of GNP in GNP/PCTFE composite. It could be explained by a presence of the percolation threshold equals to 0.5 wt.%. Low percolation threshold of GNP/PCTFE composite as self-organized 3D structure, could be a certificate of high surface energy for the particles strongly interacting with the surrounding media.

Temperature dependence green reduction of graphene oxide by urea

Pankaj Chamoli; Malay K. Das; Kamal K. Kar

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 217-222
DOI: 10.5185/amlett.2017.6559

In the present study, temperature dependence reduction of graphene oxide into graphene nanosheets has been demonstrated using green reducing agent, urea. As synthesized graphene nanosheets have been characterized by Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy(UV-Vis), X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and X-ray photon spectroscopy (XPS). Raman analysis confirms that the maximum reduction of graphene oxide is observed at 140 o C, and reached to high Raman D to G band intensity ratio of ~ 1.41. FTIR analysis supports the Raman signature of maximum reduction of oxygen functional groups from graphene oxide at 140 o C. XPS analysis validates the Raman and FTIR signature of maximum removal of oxygen species from graphene oxide at 140 o C, and confirms the attainment of the C/O ratio of ~ 5.66. Result indicates that the urea offers excellent reductive ability at high temperature to produce graphene nanosheets.

Nitrogen-doped graphene flakes/dots /Fe3N as oxygen reduction reaction electrocatalyst

Rui Yan; Huinian Zhang; Congwei Wang; Yongzhi Liu; Quangui Guo; Junzhong Wang

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 223-228
DOI: 10.5185/amlett.2017.1491

Nitrogen-doped graphene flakes/dots/Fe3N hybrids were synthesized by electrochemical charging/discharging of graphite in ionic liquid/water followed by thermal annealing at the presence of FeCl3. Rich edges of graphene dots and porous graphene flakes from electrochemical etching probably supply heteroatom-doping sites and active catalytic sites while porous graphene flakes support good electrical conductivity and pathway for electrons/ions/gases. The graphene flakes/dots/Fe3N material obtained at 700 °C shows the highest oxygen reduction reaction (ORR) activity with half-wave potential of 753 mV (vs RHE) and better durability and tolerance of methanol than Pt/C. 

Graphene bentonite supported ZnFe2O4 as superparamagnetic photocatalyst for antibiotic degradation 

Pardeep Singh; Sourav Gautam; Pooja Shandilya; Bhanu Priya; Virender P. Singh; Pankaj Raizada

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 229-238
DOI: 10.5185/amlett.2017.1467

The supported photocatalysis is emerging as an effective technology to overcome of inherent drawbacks of bare magnetic photocatalysts. Herein, ZnFe2O4 was immobilized over graphene sand composite (GSC) and bentonite (BT) to report ZnFe2O4/GSC and ZnFe2O4/BT photocatalyst. The size of ZnFe2O4/GSC and ZnFe2O4/BT was obtained as 100 and 50 nm, respectively. Both photocatalysts exhibited band gap of 1.95 eV.  ZnFe2O4/GSC and ZnFe2O4/BT had BET surface area of 15.6 and 14.5 cm 2 , respectively. The appearance of D and G band in Raman spectra indicated the formation of graphene sand composites. The superparamagnetic property of photocatalyst resulted in quick separation photocatalyst form reaction solution. The adsorption and photocatalytic capability of ZnFe2O4/GSC and ZnFe2O4/BT was evaluated for photo-mineralization of ampicillin and oxytetracycline antibiotics. The adsorption process showed significant effect on mineralization of selected antibiotics. Simultaneous adsorption and degradation (A+P) process was highly effective for antibiotic degradation. More than 90% of antibiotic mineralization was obtained in 10 hours. The power law model authorized the complex nature of degradation process. Magnetically recoverable photocatalyst exhibited significant recycling efficiency due to easier recovery of photocatalysts. 

Facile synthesis of few layer graphene from bituminous coal and its application towards electrochemical sensing of caffeine

E. Senthil Kumar; V. Sivasankar; R. Sureshbabu; S. Raghu; R. A. Kalaivani

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 239-245
DOI: 10.5185/amlett.2017.7048

A simple, cost-effective, sensitive and highly selective method for the detection of caffeine has been developed at graphene modified carbon paste electrodes (GME). We synthesis of graphene oxide (GO) derived from bituminous coal by improved modified Hummers method. The synthesized graphene were characterized by UV-Visible Spectroscopy, FT-IR and Raman Spectroscopy, X-ray Diffraction Studies, Field Emission Scanning Electron Microscopy (FE-SEM) and High Resolution Transmission Electron Microscopy (HR-TEM).  An electrochemical behavior of caffeine at the coal derived from graphene modified electrode was investigated by cyclic voltammetry (CV) and chronoamperometry (CA). By way of a result, graphene modified electrode (GME) showed good electrocatalytic activity towards the oxidation of caffeine. Under the optimized tentative conditions, caffeine was sensed in the concentration range from 0.2 to120 µmol L -1 with a detection limit of 90 nm molL -1 at a signal-to-noise ratio = 3. Hence, the graphene modified electrode (GME) could be used for the determination of caffeine in soft-drinks samples with high sensitivity and good selectivity. In this chronoamperometry shows a high catalytic currents are desirable for applications such as use in sensors. 

Spectroscopic investigation of charge and energy transfer in P3HT/GO nanocomposite for solar cell applications

Fokotsa V. Molefe; Mohammed Khenfouch; Mokhotjwa S. Dhlamini; Bakang M. Mothudi

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 246-250
DOI: 10.5185/amlett.2017.1409

As the world demand for energy continue to increase, it is vital to improve renewable energy technologies that will replace conventional fossil fuels. Carbonaceous graphene oxide (GO) is a promising nanomaterial, easy to prepare and scale up to commensurate with industrial requirements. The nanocomposite was prepared in the form of layered structure of GO nanomaterials and poly (3-hexylthiophene) (P3HT) for photovoltaic applications. The X-ray diffraction (XRD) revealed the interaction of P3HT with GO through decrease in lattice spacing. It was evident from scanning electron microscopy (SEM) that the presence of P3HT in GO modified flower like structure to the flaky structures. The interaction of GO with P3HT is presented by various vibrational frequencies in Fourier Transform infrared spectroscopy (FTIR). The increased absorbance and broadening of absorption was observed in the UV-vis spectrum for nanocomposite due to ionic interaction between P3HT and GO. The tunable photoluminescence (PL) measurements showed quenching and shifting of emission spectrum due to charge and energy-transfer. The nanocomposite establish the formation and existence of energy levels upon interaction of GO with P3HT which enhances charge transport. This work provides the direction on coating of thin films for photovoltaic device fabrication. Copyright © 2017 VBRI Press.

Catalytic reduction of 4-nitrophenol by  gamma radiation assisted synthesized Au-rGO nanocomposite 

K. Hareesh; R. P. Joshi; V. N. Bhoraskar; S. D. Dhole

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 251-255
DOI: 10.5185/amlett.2017.6556

Gold-reduced graphene oxide (AG) nanocomposites were synthesized by one-step gamma radiation assisted method. UV-Visible spectroscopic results showed the disappearance of 230 nm peak and appearance of a peak around 269 nm in AG nanocomposite confirming the reduction of GO, and also a peak around 534 nm appears confirming the formation of gold nanoparticles (AuNPs). X-ray diffractogram results of AG nanocomposite showed a broad peak around 25° corresponding to reduced graphene oxide and also it showed peak corresponding to face centered cubic structured AuNPs corroborating the UV-Visible spectroscopic results. The decoration of AuNPs of size 6 nm on reduced graphene oxide sheet was revealed by transmission electron microscopic results. X-ray photoelectron spectroscopic results confirmed the removal of oxygen functional groups from graphene oxide and formation of Au 4f in AG nanocomposite. The synthesized AG nanocomposite showed enhanced catalytic reduction of 4-Nitrophenol compared to rGO and AuNPs due to synergistic effect of individual component. Gamma radiation assisted method synthesis of Au-rGO nanocomposite may emerge as one-step synthesis that don’t require high temperature or harsh reducing agent.

Electronic and aromatic properties of graphene and nanographenes of various kinds: insights and results 

Aristides D. Zdetsis; Eleftherios N. Economou

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 256-261
DOI: 10.5185/amlett.2017.7104

Using suitable Density Functional Theory (DFT) methods and models of various sizes and symmetries, we have obtained the aromaticity pattern of infinite graphene, which is an intrinsically collective effect, by a process of “spatial” evolution. Using a similar process backwards we obtain the distinct aromaticity pattern(s) of finite nanographenes, graphene dots, antidots, and graphene nanoribbons. We have shown that the periodicities in the aromaticity patterns and the band gaps of graphene nanoribbons and carbon nanotubes, are rooted in the fundamental aromaticity pattern of graphene and its size evolution, which is uniquely determined by the number of edge zigzag rings. For graphene antidots the nature of the aromaticity and related properties are largely depended on the degree of antidot passivation. For atomically precise armchair nanoribbons (AGNRs), the aromaticity and the resulting band gaps, besides the number of zigzag rings which determines their widths, are also depended on the finite length of the ribbons, which is usually overlooked in the literature. Thus, we have fully rationalized the aromatic and electronic properties of graphene and various nanographene(s) and we have bridged some of the observed discrepancies for the band gaps in atomically precise AGNRs by judicially introducing the “effective” band gaps as well.

The freeze-thaw technique for exfoliation of graphite: A novel approach for bulk production of scroll-free graphene oxide sheets

Vishal S. Makadia; Lalit M. Manocha; Satish Manocha; Hasmukh L. Gajera

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 262-264
DOI: 10.5185/amlett.2017.6407

A freeze-thaw technique is put forth as a novel approach to exfoliating graphene oxide sheets (GO-sheets) in aqueous media.  This method does not use shear force or high-temperature treatment at any stage. Avoiding these factors prevents scrolling and promotes defect-free synthesis of the graphitic planes.  The research shows how the freeze-thaw technique successfully exfoliates graphitic planes without producing scrolls or defective graphene oxide planes. Further, when compared to conventional exfoliation methods, it was found that the freeze-thaw technique increased the surface area significantly. 

Engineering of electronic transmission in novel graphene super lattice by the means of dirac gap and fermi velocity

Mehdi Sattari-Esfahlan; Saeid Shojaei

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 265-268
DOI: 10.5185/amlett.2017.7070

The transmission spectrum and conductance of a graphenesuperlattice (GSL) have been studied theoretically by using the adopted transfer matrix method. Heterostructured substrate and series of grounded metallic planes placed over graphene sheet are used to induce periodically modulated Dirac gap and Fermi velocity barrier. As a main result, we found that the number of periods, energy gap and Fermi velocity barrier have considerable effect on transmission probability and conductance of the GSL. Our results reveal tunable transmission and conductance in GSLs which have promising applications in optoelectronic devices such as graphene based filter and switches. 

Supercritical CO2 aided polyindole-graphene nanocomposites for high power density electrode

Harish Mudila; Sweta Rana; Mohammad G. H. Zaidi

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 269-275
DOI: 10.5185/amlett.2017.7018

A series of Polyindole/Graphene nanocomposites (PGNCs) as electrochemical energy storage materials were fabricated at varying concentration (%, w/w) of graphene raging 3.0–9.0 in Polyindole (PIN) matrix in Supercritical CO2. The electrochemical behavior of PGNC prepared at different proportion of graphene was investigated. The PGNC@9% has rendered specific capacitance of 389.17 F/g, along with energy and power densities of 13.51 Wh/kg and 511.95 W/kg respectively, which is greater as compared to graphene prepared through thermal reduction of graphene oxide. However, PIN comprises low capacitance of 24.48 F/g. Successive scans of PGNCs electrode for 1000 cycles at the scan rate of 0.1 V/s in KOH (1.0 M) shows a capacitive retention of ~98.6% indicating the electrochemical stability of the electrodes, with successive charge-discharge behavior. PGNCs display all the major peaks in Fourier Transform-Infrared and X-Ray diffraction spectra. Scanning electron micrograph in permutation with XRD spectra indicates the exfoliation of graphene into the matrix of PIN. Simultaneous TG-DSC reveals increased thermal stability of PGNCs with fractions of graphene. The good capacitive and charge-discharge performance indicates that supercritically fabricated PGNCs may serve as potential electrode materials for electrochemical energy storage devices.

The effect of graphene layers on the growth of vanadium oxide nanostructures: Structural, morphological and optical investigations and mechanisms revelation

Issam Derkaoui; Mohammed Khenfouch; Ibrahim Elmokri; Bakang M. Mothudi; Mokhotjwa S. Dhlamini; Sabata J. Moloi. Anouar Jorio; Izeddine Zorkani; Malik Maaza

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 276-282
DOI: 10.5185/amlett.2017.1440

Most recently, Vanadium oxide nanoparticles/reduced Graphene oxide (VO-NPs/rGO) nanocomposite have attracted extensive attention due to their potential applications in energy-related areas. Hence, understanding the interactions on behalf the effect of graphene layers on the modification of VO-NPs properties as well as their growth mechanism are of great importance. In this work, our results are revealing that VO-NPs were efficiently grown and coated on the graphene surface and are clearly showing the strong effect of rGO layers on the growth of VO-NPs which leads to a modification in the form, the shape and also the phase. These interactions which were studied based on structural and morphological investigations will play an important role on the modification of these nanocomposites properties which is suitable for a wide range of potential applications and particularly as electrode in Li-ion batteries.

Spin transport in graphene monolayer antiferromagnetic calculated using the Kubo formalism

L. S. Lima

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 283-287
DOI: 10.5185/amlett.2017.7045

We have employed the Dirac's massless quasi-particles together with the Kubo's formalism of the linear response to study the spin transport properties by electrons in the graphene monolayer. We have calculated the electric conductivity and verified the behavior of the AC and DC currents of this system, which is a relativistic electron plasma. Our results show a superconductor behavior for the electron transport with the AC conductivity tending to infinity in the limit ω → 0. This superconductor behavior for the electron transport in the graphene is similar to one recently obtained theoretically for the spin transport in the quantum frustrated Heisenberg antiferromagnet in the honeycomb lattice, verifying so a similarity between these two different kinds of transport what can generate futures applications in the modern electronic. 

High- quality factor poly (vinylidenefluoride) based novel nanocomposites filled with graphene nanoplatelets and vanadium pentoxide for high-Q capacitor applications

Kumar Digvijay Satapathy; Kalim Deshmukh; M. Basheer Ahamed; Kishor Kumar Sadasivuni; Deepalekshmi Ponnamma; S. K. Khadheer Pasha; Mariam Al-Ali AlMaadeed; Jamil Ahmad

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 288-294
DOI: 10.5185/amlett.2017.6539

Herein, we report the synthesis of poly (vinylidene fluoride) (PVDF) based novel nanocomposites reinforced with graphene nanoplatelets (GNP) and vanadium pentoxide (V2O5) as nanofillers. The PVDF/V2O5/GNP nanocomposite films were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), polarized optical microscopy (POM) and scanning electron microscopy (SEM). The electrical properties of nanocomposites were investigated to ascertain the synergistic effect of fillers on the quality factor (Q-factor) of nanocomposites. The FTIR and XRD results infer good interaction between PVDF and V2O5 and the good dispersion of nanofillers in the PVDF matrix. The TGA results revealed that the thermal stability of PVDF/V2O5/GNP nanocomposite has improved at higher loading of nanofillers due to the good interaction between the nanofillers and the polymer matrix. The electrical analysis of nanocomposite films demonstrates high Q-factor value (1099.04) at 4.7 wt % V2O5 and 0.3 wt % GNP loading. With further increase in GNP loading to 1 wt %, the Q-factor becomes lower (356.52) which could be due to the enhanced conductivity of the samples. The significant enhancement in the value of Q-factor shows that the nanocomposites can be used as a potential candidate for high-Q capacitor applications. 

Lanthanum doped–TiO2 decorated on graphene oxide nanocomposite: A photocatalyst for enhanced degradation of acid blue 40 under simulated solar light 

Samuel O.B. Oppong; William W. Anku; Sudheesh K. Shukla; Poomani P. Govender

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 295-302
DOI: 10.5185/amlett.2017.6826

La-TiO2-GO nanocomposites were successfully synthesised via sol-gel method. Structures, morphologies and photocatalytic activities of the as-synthesized nanocomposites were determined using X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy (RS) and scanning electron microscopy (SEM). UV-Vis diffuse reflectance spectroscopy was used to estimate band gap energies. The photocatalytic activities of the as-synthesized nanocomposites were evaluated for the degradation of Acid Blue 40 in aqueous solutions under simulated solar light. The photocatalytic results show that the as-synthesized La-doped TiO2-GO (0.3% La) nanocomposite shows good photocatalytic activity and can be considered as a promising photocatalyst for the degradation of organic pollutants in water. The good photocatalytic efficiency is ascribed to the cooperative effect of improved visible light absorbance and separation of charge carriers due to the combined effect of La and the GO in the composite. Analysis from Total organic carbon (TOC) shows a high degree of complete mineralisation of Acid Blue 40 (TOC removal of 75%) which decreases the formation of possible degradation by-products. Due to the stability of La-TiO2-GO (0.3% La) nanocomposite, it was reused for five times reaching 84.0% maximum degradation efficiency during the five cycles.

Synergetic enhanced day-light driven photocatalytic reduction of heavy metal Cr(VI) by graphene supported ZnO nanocubes

P. V. Ramana; A. Viswadevarayulu; K. Kumar; S. Adinarayana Reddy

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 303-308
DOI: 10.5185/amlett.2017.7057

The potential of a novel photocatalyst graphene-ZnO (G-ZnO) obtained from graphene oxide and zinc acetate dihydrate was investigated for the reduction of heavy metal Cr(VI) ions from water. In which ZnO nanocubic crystals were finely doped on the graphene sheets, was well done by facile wet chemical/reflux method under N2 atmosphere. Due to hindered nature of photo-generated electron-hole pair recombination and enhanced light absorption shows efficient photocatalytic performance of G-ZnO nanocomposites (NCs) in the reduction of Cr(VI) ions with a degradation rate of 98% under daylight illumination as related with bare ZnO (42%), graphene oxide (GO) (19%) and mechanical mixture GO+ZnO (62%). The overall results demonstrated that the photocatalyst used in this study, is promising, efficient and economical when used to separate heavy metal ions from water.

Flexible cefalexin-immobilized graphene oxide film for antibacterial and drug delivery

Xun Xu; Fangwang Ming; Jinqing Hong; Zhoucheng Wang

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 309-314
DOI: 10.5185/amlett.2017.7103

The flexible and freestanding graphene oxide (GO) film was fabricated for drug delivery and antibacterial. The film was synthesized by covalently attaching cefalexin onto graphene oxide sheets and then made by filtration of the colloidal suspension. SEM and optical images show that the Cefalexin-grafted graphene oxide (GO-CE) film possesses the unique 2D layer-by-layer structure and it could form channels for drug release when immersed in water. The drug loading and release tests certify that the GO-CE film is a promising drug delivery membrane with high load capacity (0.621 mg mg -1 ) and long-acting release properties (72 h), and can effectively inhibit the growth of E. coli and S. aureus bacteria while showing minimal cytotoxicity for a long time. The cellular culture results of the HeLa Cells indicate that the GO-CE film exhibits excellent biocompatibility. Based on these advantages, the GO-CE film is expected to be used in the environmental and medical applications.

Effect of the precursor graphite on the structure and morphology of graphite oxide and reduced graphene oxide

Demudu B. Dommisa; Raj K. Dash*

Advanced Materials Letters, 2017, Volume 8, Issue 3, Pages 315-321
DOI: 10.5185/amlett.2017.1486

In this work the effect of the precursor graphite on the structure and morphology of the graphene oxide and reduced graphene oxide are investigated by considering three different sizes source graphite such as 2-15, <45 and 170-840μm respectively. All the three graphite were oxidized by Modified Hummer’s method and further reduced by hydrazine hydrate by maintaining same synthesis conditions. The results demonstrated that the oxidation process is size dependent of the source graphite.The results revealed that smaller size graphite is fully oxidised as compared to larger sizes and also functionalized more. Few layers (less than 4-5) crystalline, less disorder and unfolded reduced graphene oxides are obtained when smallest size graphite is used as the source material. The water molecules present in the graphene oxide synthesised from larger size graphite as source material are higher and that can lead to the the occurrence of polycrystalline in structure, more disorder and wrinkled or folding reduced graphene oxide. Therefore, this study can open a new pathway to synthesis more crystallinity, less disorder and wrinkled free or unfold reduced graphene oxide for several potential applications.