Showing papers by "Bharathiar University published in 2017"

Electrospun nanofibers: New generation materials for advanced applications

Abstract: Electrospinning (E-spin) is a unique technique to fabricate polymeric as well as metal oxide nanofibers. Research on electrospun nanofibers is a very active field in material science owing to their novel applications in diverse domains. The main focus of this review is to provide an insight into E-spin technique by understanding the working principle, influencing parameters and applications of nanofibers in different walks of life. Several hundreds of papers are published on the preparation, modification and applications of nanofibers produced by E-spin technique in the areas like sensor development, decontamination, energy storage, biomedical and catalysis etc. Details on the industrial scale development of E-spin technique, current scenario and future developments are also covered in this review.

Few-Layer Black Phosphorus Nanosheets as Electrocatalysts for Highly Efficient Oxygen Evolution Reaction

Abstract: Black phosphorus (BP) is a new rediscovered layered material, which has attracted enormous interests in the field of electrocatalysis. Recent investigations reveal that bulk BP is a promising electrocatalyst for oxygen evolution reactions (OER), whereas its bulk crystal structure restricts sufficient active sites for achieving highly efficient OER catalytic performances. Toward this end, few-layer BP nanosheets prepared by facile liquid exfoliation are applied as electrocatalysts and exhibit preferable electrocatalytic OER activity in association with structural robustness; subsequently, the dependence of current density and applied bias potential on the concentration of OH− has also been uncovered. Most importantly, we are aware that reduction in the thickness of BP nanosheets would generate extra active sites from the ultrathin planar structure and complimenting to the electrocatalytic activities. It is further anticipated that the current work might provide further implementation about the OER performance of BP nanosheets, thereby, offering extendable availabilities for BP-based electrocatalysts in constructing high-performance OER devices.

Emerging Trends in Phosphorene Fabrication towards Next Generation Devices.

Abstract: The challenge of science and technology is to design and make materials that will dominate the future of our society. In this context, black phosphorus has emerged as a new, intriguing two-dimensional (2D) material, together with its monolayer, which is referred to as phosphorene. The exploration of this new 2D material demands various fabrication methods to achieve potential applications- this demand motivated this review. This article is aimed at supplementing the concrete understanding of existing phosphorene fabrication techniques, which forms the foundation for a variety of applications. Here, the major issue of the degradation encountered in realizing devices based on few-layered black phosphorus and phosphorene is reviewed. The prospects of phosphorene in future research are also described by discussing its significance and explaining ways to advance state-of-art of phosphorene-based devices. In addition, a detailed presentation on the demand for future studies to promote well-systemized fabrication methods towards large-area, high-yield and perfectly protected phosphorene for the development of reliable devices in optoelectronic applications and other areas is offered.

2D Nonlayered Selenium Nanosheets: Facile Synthesis, Photoluminescence, and Ultrafast Photonics

Abstract: Investigations into 2D nanomaterials are of considerable significance from both an academic and industrial point of view. The present work addresses, for the first time, the fabrication of 2D nonlayered ultrathin selenium through a facile liquid-phase exfoliation method. The results reveal that the as-prepared 2D Se nanosheets are 40–120 nm in lateral dimension and 3–6 nm in thickness. The nanosheets exhibit a trigonal crystalline phase similar to their bulk counterpart, indicating the conservation of the crystalline features during the exfoliation procedure. The successful preparation of 2D Se nanosheets from nonlayered bulk Se can be ascribed to two kinds of anisotropy: (1) that of crystalline bulk Se with chain-like structures, where strong intrachain SeSe covalent bonds coexist with weak interchain van der Waals forces, and (2) that of probe sonication in the vertical direction. The results also show that the 2D Se nanosheets possess a size-dependent band gap (E g), strong photoluminescence effect and robust, chemical stability under ambient conditions. Furthermore, a 2D Se-nanosheet-based optical modulation device is demonstrated that allows for excellent ultrashort pulse generation of an optical communication band. It is therefore anticipated that 2D Se nanosheets may find significant applications in both photoluminescence and ultrafast photonics.

Green synthesis of Iron oxide nanoparticles using Lagenaria siceraria and evaluation of its Antimicrobial activity

Abstract: Magnetic iron oxide nanoparticles (MNPs) with appropriate surface chemistry exhibit many interesting properties that can be exploited in a variety of biomedical applications such as magnetic resonance imaging contrast enhancement, tissue repair, hyperthermia, drug delivery and in cell separation. In this study unexplored Lagenaria siceraria leaves extract was found to be capable in green synthesis of Iron oxide nanoparticles (Fe 3 O 4 -NPs) and their characteristics were studied by using UV-visible spectrophotometer, SEM, EDX, XRD, Zeta sizer and FT-IR. Thus synthesized Fe 3 O 4 -NPs were naturally stabilized, cubic shaped and in the size range of 30-100 nm. The phytochemicals present in the leaf has a main role as reducing agent that assists to the eco friendly synthesis of Fe 3 O 4 -NPs with enhanced antioxidant property. Functional groups present on the NPs are mainly –OH and –COOH (FT-IR) makes it hydrophilic hence NPs does not need any further functional modification for applications. The antimicrobial property of synthesized Fe 3 O 4 -NPs was evaluated against Gram negative - Escherchia coli, Gram positive- Staphylococcus aureus, The Zone of inhibition was found to be 10 mm for Escherchia coli, and 8 mm for Staphylococcus aureus. Thus naturally stabilized Fe 3 O 4 -NPs with herbal property can be used in various biological applications.

Malaria Parasite Detection From Peripheral Blood Smear Images Using Deep Belief Networks

Abstract: In this paper, we propose a novel method to identify the presence of malaria parasites in human peripheral blood smear images using a deep belief network (DBN). This paper introduces a trained model based on a DBN to classify 4100 peripheral blood smear images into the parasite or non-parasite class. The proposed DBN is pre-trained by stacking restricted Boltzmann machines using the contrastive divergence method for pre-training. To train the DBN, we extract features from the images and initialize the visible variables of the DBN. A concatenated feature of color and texture is used as a feature vector in this paper. Finally, the DBN is discriminatively fine-tuned using a backpropagation algorithm that computes the probability of class labels. The optimum size of the DBN architecture used in this paper is 484-600-600-600-600-2, in which the visible layer has 484 nodes and the output layer has two nodes with four hidden layers containing 600 hidden nodes in every layer. The proposed method has performed significantly better than the other state-of-the-art methods with an F-score of 89.66%, a sensitivity of 97.60%, and specificity of 95.92%. This paper is the first application of a DBN for malaria parasite detection in human peripheral blood smear images.

Biomimetic synthesis of silver nanoparticles from Streptomyces atrovirens and their potential anticancer activity against human breast cancer cells

Abstract: Silver nanoparticles (AgNPs) have been undeniable for its antimicrobial activity while its antitumour potential is still limited. Therefore, the present study focused on determining cytotoxic effects of AgNPs on Michigan cancer foundation-7 (MCF-7) breast cancer cells and its corresponding mechanism of cell death. Herein, the authors developed a bio-reduction method for AgNPs synthesis using actinomycetes isolated from marine soil sample. The isolated strain was identified by 16s ribotyping method and it was found to be Streptomyces atrovirens. Furthermore, the synthesised AgNPs were characterised by various bio-analytical techniques such as ultraviolet-visible spectrophotometer, atomic force microscopy, transmission electron microscopy, Fourier transform infra-red spectroscopy, and X-ray diffraction. Moreover, the results of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay reveals 44.51 µg of AgNPs to have profound inhibition of cancer cell growth; furthermore, the inhibition of MCF-7 breast cancer cell line was found to be dose dependent on treatment with AgNPs. Acridine orange and ethidium bromide double staining methods were performed for cell morphological analysis. The present results showed that biosynthesised AgNPs might be emerging alternative biomaterials for human breast cancer therapy.

Novel and highly efficient red luminescent sensor based SiO 2 @Y 2 O 3 :Eu 3+ , M + (M + = Li, Na, K) composite core–shell fluorescent markers for latent fingerprint recognition, security ink and solid state lightning applications

Abstract: Facile solution combustion route was used to prepare the optimized composite core shell SiO2@Y2O3:Eu3+, Li+ fluorescent nanopowders (NPs) with superior fluorescence intensity under UV light. Powder dusting technique was used for the visualization of latent fingerprints (LFPs) on different porous and non-porous surfaces. The results display that the amorphous SiO2 microspheres were covered by crystalline Y2O3:Eu3+, Li+ NPs, resulting in spherical core-shell structure. The phosphors exhibit intense pure strong red emission corresponding to characteristic Eu3+ ions 5D0→ 7F2 transitions under NUV excitation. The CIE co-ordinates were found to be (x = 0.63, y = 0.36) which is very close to standard NTSC values (x = 0.67, y = 0.33). Judd-Ofelt theory was used to estimate the intensity parameters (Ω2 and Ω4) as well as radiative properties. The CCT value was ∼ 3475 K which was less than 5000 K, as a result the phosphor was highly useful in warm light emitting diodes. Thus, results presented confirms that the developed method was simple, fast and optimized phosphor was effectively used for multifunctional applications namely luminescent sensor for visualization of LFPs, solid state lightning and security ink applications.

A novel bi-functional double-layer rGO–PVDF/PVDF composite nanofiber membrane separator with enhanced thermal stability and effective polysulfide inhibition for high-performance lithium–sulfur batteries

Abstract: A novel, bi-functional double-layer reduced graphene oxide (rGO)–polyvinylidene fluoride (PVDF)/PVDF membrane was fabricated by a simple electrospinning technique and was used as a promising separator for lithium–sulfur batteries. This double-layer membrane separator delivers two different functionalities: (i) the porous PVDF nanofiber framework in both rGO–PVDF and PVDF layers provides good thermal stability and maintains the structural integrity of the separator; and (ii) the conductive rGO–PVDF layer serves as a polysulfide inhibitor and ensures the fast transfer of lithium ions. Compared to conventional polypropylene membrane separators, this new separator design can significantly enhance the cycling stability and rate capability of the incorporated lithium–sulfur batteries. Overall, it is demonstrated that this new double-layer rGO–PVDF/PVDF composite membrane separator opens an alternate avenue in the structural design of high-performance lithium–sulfur batteries in dealing with multiple challenges.

Highly active MoS2/carbon electrocatalysts for the hydrogen evolution reaction – insight into the effect of the internal resistance and roughness factor on the Tafel slope

Abstract: Molybdenum disulphide (MoS2) nanomaterials are promising non-precious-metal electrocatalysts for the hydrogen evolution reaction. MoS2/carbon electrocatalysts have been synthesized with the carbon component serving the purpose of enhancing electron transport. The impedance method of Tafel analysis has been employed to evaluate the efficiency of various carbon supports in aiding facile electron transport. A MoS2/carbon nanofiber electrocatalyst has been found to be the most active towards hydrogen evolution with the lowest Tafel slope among the investigated electrocatalysts. Tafel analysis indicates that the hydrogen evolution reaction occurs through the Volmer-Heyrovsky mechanism with a rate determining Heyrovsky step in the MoS2 and MoS2/carbon electrocatalysts. Orderly variation of the Tafel slope with the mass loading has been observed in MoS2/Vulcan carbon and the cause for this has been investigated based on roughness factor measurements. A linear dependence of the Tafel slope on the roughness factor points to a concomitant increase in the limitations on mass transport. The results show that the benefit of increasing the roughness factor of the electrocatalyst is counterbalanced by increasing the Tafel slope, and hence the need for designing an optimal HER electrocatalyst balancing the roughness factor and Tafel slope is deduced.

Guazuma ulmifolia bark-synthesized Ag, Au and Ag/Au alloy nanoparticles: Photocatalytic potential, DNA/protein interactions, anticancer activity and toxicity against 14 species of microbial pathogens.

Abstract: In the present study, we focused on a quick and green method to fabricate Ag, Au and Ag/Au alloy nanoparticles (NPs) using the bark extract of Guazuma ulmifolia L. Green synthesized metal NPs were characterized using different techniques, including UV-Vis spectroscopy, FT-IR, XRD, AFM and HR-TEM analyses. The production of Ag, Au and Ag/Au alloy NPs was observed monitoring color change from colorless to brown, followed by pink and dark brown, as confirmed by UV-Vis spectroscopy characteristic peaks at 436, 522 and 510nm, respectively. TEM shed light on the spherical shapes of NPs with size ranges of 10-15, 20-25 and 10-20nm. Biosynthesized NPs showed good catalytic activity reducing two organic dyes, 4-nitrophenol (4-NP) and Congo red (CR). UV-vis spectroscopy, fluorescence, circular dichroism spectroscopy and viscosity analyses were used to investigate the NP binding with calf thymus DNA. The binding constant of NPs with DNA calculated in UV-Vis absorption studies were 1.18×104, 1.83×104 and 2.91×104M-1, respectively, indicating that NPs were able to bind DNA with variable binding affinity: Ag/Au alloy NPs>Ag NPs>Au NPs. Ag/Au alloy NPs also showed binding activity to bovine serum albumin (BSA) over the other NPs. Ag and Ag/Au alloy NPs exhibited good antimicrobial activity on 14 species of microbial pathogens. In addition, the cytotoxic effects of Ag/Au alloy NPs were studied on human cervical cancer cells (HeLa) using MTT assay. Overall, our work showed the promising potential of bark-synthesized Ag and Ag/Au alloy NPs as cheap sources to develop novel and safer photocatalytic, antimicrobial and anticancer agents.