Gopalu Karunakaran

Synthesis of five metal based nanocomposite via ultrasonic high temperature spray pyrolysis with excellent antioxidant and antibacterial activity

A unique five metal (Zn, Cu, Ni, Fe, and Mg) based nanocomposite material was prepared via ultrasonication high temperature spray pyrolysis maintained at 1200 °C. The influence of different concentrations (0.001 M, 0.01 M, and 1 M) on size and crystalline phase were analyzed. The nanocomposite exhibited excellent antioxidant and antibacterial activity.

Nitrobacter sp. extract mediated biosynthesis of Ag2O NPs with excellent antioxidant and antibacterial potential for biomedical application

In this study, extracellular extract of plant growth promoting bacterium, Nitrobacter sp. is used for the bioconversion of AgNO3 (silver nitrate) into Ag2O (silver oxide nanoparticles). It is an easy, ecofriendly and single step method for Ag2O NPs synthesis. The bio-synthesized nanoparticles were characterized using different techniques. UV-Vis results showed the maximum absorbance around 450 nm. XRD result shows the particles to have faced centered cubic (fcc) crystalline nature. FTIR analysis reveals the functional groups that are involved in bioconversion such as C-N, N-H and C=O. Energy-dispersive X-ray spectroscopy (EDAX) spectrum confirms that the prepared nanoparticle is Ag2O NPs. Particle size distribution result reveals that the average particle size is around 40 nm. The synthesized Ag2O NPs found to be almost spherical in shape. Biosynthesized Ag2O NPs possess good antibacterial activity against selected Gram positive and Gram negative bacterial strains namely Salmonella typhimurium, Staphylococcus aureus, Escherichia coli and Klebsiella pneumoniae when compared to standard antibiotic. In addition, Ag2O NPs exhibits excellent free radical scavenging activity with respect to dosage. Thus, this study is a new approach to use soil bacterial extract for the production of Ag2O NPs for biomedical application.

Investigation of discharged aerosol nanoparticles during chemical precipitation and spray pyrolysis for developing safety measures in the nano research laboratory

Nowadays, the demands for the nanoparticles are increasing due to their tremendous applications in various fields. As a consequence, the discharge of nanoparticles into the atmosphere and environment is also increasing, posing a health threat and environmental damage in terms of pollution. Thus, an extensive research is essential to evaluate the discharge of these nanoparticles into the environment. Keeping this in mind, the present investigation aimed to analyze the discharge of aerosol nanoparticles that are synthesized in the laboratory via chemical precipitation and spray pyrolysis methods. The results indicated that the chemical precipitation method discharges a higher concentration of nanoparticles in the work site when compared to the spray pyrolysis method. The aerosol concentration also varied with the different steps involved during the synthesis of nanoparticles. The average particles concentration in air for chemical precipitation and spray pyrolysis methods was around 1,037,476 and 883,421particles/cm3. In addition, the average total discharge of nanoparticles in the entire laboratory was also examined. A significant variation in the concentration of nanoparticles was noticed, during the processing of materials and the concentration of particles (14-723nm) exceeding the daily allowed concentration to about 70-170 times was observed over a period of 6 months. Thus, the results of the present study will be very useful in developing safety measures and would help in organizing the rules for people working in nanotechnology laboratories to minimize the hazardous effects.

Curcuma longa tuber extract mediated synthesis of hydroxyapatite nanorods using biowaste as a calcium source for the treatment of bone infections

AbstractBone fillers based on hydroxyapatite (HAp) having antimicrobial activity are extensively applied for treatment of bone-related inflammation created by infectious micro-organisms. We report the biogenic preparation of HAp nanorods with the aid of Curcuma longa tuber extract as solvent and eggshell biowaste as a calcium source. The prepared powder was analyzed by various analytical tools to explore the phase purity and morphological feature. The obtained results indicate that the prepared powder was magnesium (Mg) and carbonate (CO32−) containing HAp nanorods having nanocrystalline characteristics. Further, the prepared HAp nanorods significantly hinder the growth of E. coli and S. aureus. Comparative studies were also carried out with HAp prepared using water as solvent. The obtained results clearly shows that developed method can be a prospective approach to acquire precursor material for making bone fillers with antibacterial activity. Hydroxyapatite (HAp) nanorods with antibacterial activity were prepared by simple biogenic synthesis using Curcuma longa tuber extract, eggshell, and Na2HPO4 as the source for the treatment of bone infections in orthopedics.

Sono-synthesis approach of reduced graphene oxide for ammonia vapour detection at room temperature

In this paper, we report the sono-synthesis of reduced graphene oxide (rGO) using polyethyleneimine (PEI), and its performance for ammonia vapour detection at room temperature. Graphene oxide (GO) and reduced graphene oxide (rGO) were prepared by sonication method by using low-frequency ultrasound under ambient condition and films were deposited by Doctor Blade method. The rGO, which has vapour accessible structure showed a good sensing response with a minimum detection limit of 1 ppm and the detection range from 1 ppm to 100 ppm. The sensing response was found to be 2% at 1 ppm and 34% at 100 ppm of ammonia and the developed sensor operated at room temperature. The sensor displays a response time of 6 s and a recovery time of 45 s towards 100 ppm of ammonia vapour. The source for the highly sensitive, selective and stable detection of ammonia with negligible interference from other vapours is discussed and reported. We believe reduced graphene oxide (rGO) could potentially be used to manufacture a new generation of low-power portable ammonia sensors.

Enhancement of densification and sintering behavior of tungsten material via nano modification and magnetic mixing processed under spark plasma sintering

In the present study, the influence of nano additives (Ni, Fe) and different mixing (turbular and magnetic) on the densification, microstructure and micro-hardness of the tungsten material under spark plasma sintering is analyzed. After turbulent mixing the nanoparticles are distributed widely in the W interparticle gaps but after magnetic mixing the nanoparticles are distributed not only on the gaps of the W particles but also on the broken surfaces. Ni incorporated tungsten materials achieved the maximum density of 98.3% at 1400 °C (turbular mixing) and 97.9% at 1300 °C (magnetic mixing). Fe incorporated tungsten material showed density of 97.7% at 1600 °C and 97.2% at 1400 °C after turbular and magnetic mixing. The influence of nanoparticles in the densification process was explained by Laplace force, boundary slip and Agte-Vacek effect. The microstructural analysis showed that nano-modification reduced the degree of porosity, and provides a compact material at low temperatures. X-ray fluorescence analysis reveals that magnetic mixing shows more uniform distribution of nanoparticles than turbular mixing. The nanoparticles incorporation increased the micro hardness of tungsten material. Hence, it is clear that magnetic mixing and nano modification greatly improved the densification and sintering behavior of the tungsten material.