The influence of tip sonication on structural and morphological properties of graphene

Although ultrasound is frequently used to disperse carbon nanomaterials in suitable solvents, the propagation of high-amplitude ultrasonic vibrations from the tip sonicator was found to be aggressive and has the potential to break down graphene sheets. Here, the effects of tip sonication time on structural and morphological properties of two types of graphene (graphene oxide and electrochemically exfoliated graphene) was investigated by UV-vis spectroscopy and Atomic Force Microscopy. It was found that the structural composition of the graphene was not affected by ultrasounds emitted from the tip sonicator even for the prolonged period of sonication (60 min). Microscopy analysis showed an increased portion of smaller graphene sheets in the sonicated samples for both types of graphene as a result of graphene sheet fragmentation caused by tip sonication

The morphology of pani/graphene composites prepared under isothermal conditions

This article investigates the morphology of polyaniline/electrochemically exfoliated graphene composites prepared by oxidative polymerization with ammonium persulfate at a constant temperature (15 °C). During the polymerization, the pH of the reaction mixture decreases, which was used to monitor the rate of the reaction. A granular morphology with the presence of large sheet-like structures is found to be predominant for the composite prepared without added acid, while rod-shaped and tubular morphology is characteristic for the composite prepared with the addition of glacial acetic acid. The nanotubular and nanorod morphology of the sample prepared with the addition of glacial acetic acid was also confirmed by the presence of prominent phenazine structural units in Raman spectra. The composite prepared with the addition of HCl has granular morphology with a small amount of rod-like structures

Antioxidant and prooxidant features of N-CQD in photocatalytic testing of aquatic media

The modern age science is still searching for an effective photocatalytic material for the treatment of colored discharges from different industries which cause severe environmental issues. The excellent properties of nitrogen doped carbon quantum dots (N-CQD) enable their successful application as photocatalytic material in organic dye removal triggered under light absorption. With this in mind we first present a successfully performed microwave-assisted synthesis method, a green, simple and economically affordable method for N-CQD synthesis with high nitrogen percentage incorporated in the form of pyrrolic, pyridinic/NH2 and graphitic/NH3 groups. The pro-oxidant and antioxidant features of the synthesized N-CQD were further presented, with high removal efficiency of synthesized N-CQD towards the methylene blue (MB) organic dye, as one of the leading water pollutants with a major risk to aquatic and human life

Microwave-assisted synthesis of n-doped carbon quantum dots for the photocatalytic removal of methylene blue from wastewater

Wastewater treatment is an emerging problem in the industrialized world. The development of new semiconducting materials with the potential to be used in photocatalysis is the focus of the scientific community. Here, we present the synthesis of N-doped carbon quantum dots (NCQDs) using microwave radiation. N-CQDs were synthesized by irradiation of glucose solution in the presence of ammonia hydroxide as a nitrogen doping agent at low temperature (100 °C), low applied microwave power (100 and 200 W), and for a short period of time (60 s). The possible application of N-CQDs as a catalyst for photocatalytic degradation of Methylene Blue (MB) dye under blue light, green light, red light, and daylight was investigated. The highest values of MB degradation were observed for the samples exposed to red light with a maximum of 58.8 % for N-CQDs sample prepared at the reactor power of 200 W exposed to red light for 2 h

Measurement of EMI shielding performance of graphene oxide and electrochemically exfoliated graphene thin films

Graphene and its derivatives have become the scientific community's focus due to their remarkable electronic, mechanical, and optical properties. In this work, we prepared two graphene-based materials, graphene oxide (GO) and electrochemically exfoliated graphene (EEG), and performed morphological and structural analysis. Both materials showed good dispersibility in water. GO is composed of mainly single- and few-layer graphene sheets, while EEG is predominately multi-layer graphene. EEG showed better thermal stability under nitrogen flow compared to GO. We also performed ElectroMagnetic Interference (EMI) shielding performance measurements of these materials

Microwave synthesis of N-CQDs : effect of wavelength on degradation of organic pollution in water

Industries today realis high amounts of different hazards into the environment without any pre– treatment, which is why the remediation from organic pollution still represents one of the most important issues in waste water treatment. Organic dyes from textile industry are one of the extremely geno‒toxic and cyto‒toxic pollutants. Thus, finding the appropriate photocatalyst for the treatment of contaminated water under sunlight is still a challenging work from economical and green chemistry approach. Here we present a microwave assisted synthesis of nitrogen doped carbon quantum dots with high efficiency in degradation of Rose Bengal organic dye from water under visible, blue, green and red light irradiation in batch system. The effect of microwave irradiation power and time on size and photocatalytic activity of synthesized dots were also investigated

Gold nanoparticles/exfoliated graphene hybrid obtained by gamma irradiation

Gold nanoparticles decorated graphene sheets present a good surface-enhanced Raman spectroscopy (SERS) platform for the development of ultrasensitive analytical applications. Here, we prepared gold nanoparticles/exfoliated graphene hybrid by gamma irradiation of chloroauric acid as a precursor in the presence of electrochemically exfoliated highly oriented pyrolytic graphite (HOPG). The effects of various irradiation doses (1, 5, 10 and 20 kGy) on the size and shape of synthesized nanoparticles were studied. It was found that the presence of HOPG leads to the formation of gold nanoparticles of triangular, spherical, hexagonal, trapezoidal and rod-shape morphology. On the other hand, irradiation of chloroauric acid solution without HOPG results mainly in irregular shaped nanoparticles, however, certain amount of square shaped nanoparticles is observed. According to statistical analysis of gold nanoparticles/graphene hybrid, nearly half of the nanoparticles have sizes in the 11-20 nm range for all of the applied doses. The increase of irradiation dose results in the increase of the amount of smaller nanoparticles (up to 10 nm in size). Nevertheless, for the highest applied dose agglomeration of nanoparticles takes place leading to the formation of particles that exceed 100 nm in size. Presented synthetic route is fast, simple and low-cost since it does not require the use of a gold nanoparticle stabilizer

Degradation of organic dyes under visible light

We performed the “bottom-up” synthesis of N–doped CQDs via swift and easy one–step microwave–assisted method. The percentage of bound nitrogen in this short amount of time was about 11 at% in the form of pyrridinc/NH2, pyrrolic–N and graphitic–N. The synthesized N–doped CQDs showed good photocatalytic activiti in organic dyes degradation after only 30 min of expoisure to the visible light

Removal of rose bengal dye by hydrophobic carbon quantum dots and polyurethane nanocomposites

In the present study we report the removal of Rose Bengal dye by gamma irradiated nanocomposites composed of hydrophobic carbon quantum dots incorporated in the matrix of polyurethane (hCQD-PU). It is assumed that the removal is caused by the combination of two different mechanisms. First mechanism suggested is a photocatalytic degradation by lightinduced production of singlet oxygen and other reactive oxygen species by gamma irradiated hCQD and second mechanism is the adsorption of the remaining Rose Bengal dye from the solution, by polymer matrix. The removal efficiency of the dye reached up to 92% for 4 h of irradiation by visible lamp. We have investigated the effect of different parameters, such as the dose of gamma irradiation applied to the nanocomposite, as well as the exposure time of the sample to the blue lamp (470 nm). The proposed material has a potential in water purification systems

Covalent modification of single wall carbon nanotubes upon gamma irradiation in aqueous media

Single wall carbon nanotubes (SWCNTs) were exposed to gamma radiation, absorbing the doses of 25, 50 and 100 kGy in aqueous environment. After the irradiation treatment, the changes in the structure were studied using Fourier transform Infrared and Raman spectroscopy, thermogravimetric analysis and atomic force microscopy. Fourier Transform Infrared Spectroscopy has shown that the irradiation of SWCNTs in aqueous environment leads to covalent functionalization of SWCNTs. The irradiation of water leads to its radiolysis and the formation of free radical species of different types. These species react with nanotube sidewalls and in such way carboxylic and hydroxylic groups are covalently bonded to the sidewalls of SWCNTs. Thermogravimetric analysis was used to estimate the total amount of covalently bonded groups. The highest ratio of covalently bonded groups appears in nanotubes irradiated with the 100 kGy dose. Raman spectroscopy proved that the increase in irradiation doses leads to an increase of structural disorder of SWCNTs, presumably in the form of defects in carbon nanotube walls. Examination of I-D to I-G ratio shows a three times larger degree of structural disorder after the irradiation treatment with 100 kGy. The analysis of carbon nanotube Raman spectra RBM bands determined the presence of both semiconducting and metallic carbon nanotubes after gamma irradiation treatment. These measurements prove that gamma irradiation treatments have a nonselective effect regarding different chirality and therefore conductance of nanotubes. Atomic force microscopy shows a significant carbon nanotube shortening as the effect of gamma radiation treatment. Nanotubes with length between 500 nm and 1 mu m are predominant