Showing papers in "Nano-Structures and Nano-Objects in 2018"

Transition metal oxide nanoparticles as efficient catalysts in oxidation reactions

Abstract: Studies on nano-sized particles have been the range for the past 10–15 years. With rapid growth of metal oxide nanotechnologies during the last decades, the application of this material in the field of catalysis has become a substantial research area. In the past decades, the utilization of transition metal oxide nanoparticle catalysts for industrial application in the synthesis of important chemical intermediates has been investigated by industrial and academic communities. Compared to other catalysts, one of the outstanding properties of metal oxide nanoparticles in catalysis is represented by the high selectivity which allows discrimination within chemical groups and geometrical positions, favoring high yields of the desired product. This review is devoted to dealing with the application of transition metal oxide nanoparticles as catalyst for oxidations of sulfides, alcohols, olefins, and alkanes toward the synthesis of a variety of organic compounds, such as sulfoxides, aldehydes and ketones, carboxylic acids, epoxides and alcohols.

Ferrimagnetism in cobalt ferrite (CoFe2O4) nanoparticles

Abstract: Ferrimagnetic cobalt ferrite (CoFe2O4) nanoparticles were synthesized by employing co-precipitation method. Product physico-chemical and magnetic properties with respect to cetyl trimethylammonium bromide (CTAB), hexamethylenetetramine (HMT) and polyethylene glycol (PEG-400) surfactants were investigated. XRD pattern and Raman characteristic active modes revealed the cubic cobalt ferrite structure formation. SEM images explored spherical shaped product with different particle size. Identified strong PL emission peaks confirmed the product quality. IR metal oxygen vibration at 615 and 426 cm−1 revealed tetrahedral and octahedral site of cobalt ferrite system. Product electrochemical behavior was found to be size dependent and high specific capacitance was observed using CTAB. Room temperature ferrimagnetic behavior was confirmed through VSM studies. High saturation value as 66 emu/g was found using PEG. Particles with larger crystallite and particle size exhibited improved magnetic behavior.

Corrosion protective self-healing epoxy resin coatings based on inhibitor and polymeric healing agents encapsulated in organic and inorganic micro and nanocontainers

Abstract: Self-healing materials attract enormous scientific attention as they offer wide range of applications in conjunction with long-lasting performance. Self-healable polymers find potential candidates for construction materials, automotive parts, electrical encapsulation, adhesives, coatings, etc. Due to the lightweight, high thermo-mechanical performance, excellent adhesion, gloss, good chemical resistance, and corrosion resistance, epoxy resins are preferred over other polymers for coating applications. Although epoxy resin coatings are widely used in commercial vehicles and high compact aircraft, their susceptibility toward scratches and microcracks is a major concern. Such failures may be addressed by making use of self-healing epoxy coatings. In this review, we focus on inhibitor and polymeric healing agents encapsulated in organic and inorganic containers for the self-healing epoxy coating. The different organic and inorganic containers such as micro/nano polymer capsules, cellulose nanofibers, halloysite nanotubes, titanium dioxide nanocontainers, mesoporous silica, hollow glass fibers, and core–shell nanofibers have been utilized as reservoirs to store the self-healing agents. In addition, self-healing techniques such as layer-by-layer method, microvascular networks, ion exchange method, reversible crosslinks, and shape memory assisted self-healing are reviewed.

Biosynthesis protocols for colloidal metal oxide nanoparticles

Abstract: Metal oxide nanoparticles (MO-NPs) have attracted great attention among nanomaterials in many fields including environmental remediation, catalysis, drug delivery, agriculture, molecular sensing and medicine. This has led to the development of different synthetic pathways for these nanostructures. Currently, the synthesis of MO-NPs largely depends on chemical methods where synthetic routes involve toxic chemicals and harsh reaction conditions that have been identified as a major contributor to environmental pollution. As an alternative, synthesis based on green chemistry principles has recently gained a large audience because they are eco-friendly, cost-effective and minimize waste. In this review, we focus on the green synthetic approaches to metal oxide nanoparticles such as ZnO, TiO2, Fe3O4. The synthesis based on microbes such as bacteria, fungi, algae and plant-mediated route are given major attention. In addition, the possible mechanisms for some of the syntheses and, the merits and demerits of green synthesis of metal oxide nanoparticles are also discussed.

ZnO/CuO nanocomposite prepared in one-pot green synthesis using seed bark extract of Theobroma cacao

Abstract: A method for green synthesis of ZnO/CuO nanocomposite using Theobroma cacao seed bark extract (TBE) has been investigated ZnO/CuO nanocomposite synthesis aims to decrease a high band gap energy of ZnO Zn(NO3)2 and Cu(NO3)2 solutions were used as a precursors TBE can substitute NaOH as the base source material which contained alkaloids as shown from the phytochemical test Identification of nanocomposite was characterized by UV–Vis diffuse reflectance spectrophotometry (DRS), Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD) and Fluorescence Spectrophotometer ZnO/CuO nanocomposite had the band gap energy of 23 eV TEM result showed the size of ZnO/CuO nanocomposite was 20–50 nm

Microwave-mediated synthesis, photocatalytic degradation and antibacterial activity of α-Bi2O3 microflowers/novel γ-Bi2O3 microspindles

Abstract: The present article portray the microwave (MW) synthesis of alpha bismuth oxide microflowers ( α -Bi2O3 MFs) and novel gamma bismuth oxide microspindles ( γ -Bi2O3 MSs) using bismuth nitrate pentahydrate [Bi(NO3)3.5H2O], and polyvinylpyrrolidone (PVP) as a surfactant. The structural, BET surface area, morphological, photocatalytic activity under ultraviolet (UV) light and antibacterial performance was investigated with varying MW irradiation time. XRD study confirmed the formation of monoclinic ( α -phase) and body-centered cubic ( γ -phase) of Bi2O3 with variation of MW irradiation time for 10 min and 15 min respectively. SEM images revealed the formation of microflowers for α -Bi2O3 and microspindles for γ -Bi2O3. Further HR-TEM illustrated the appearance of nanoflakes (19–35 nm) and the rose-flowers, and back-bending man (15–30 nm) like structures for α -Bi2O3 MFs and γ -Bi2O3 MSs correspondingly. Interestingly, the comparative photocatalytic activity of α -Bi2O3 MFs and γ -Bi2O3 MSs were evaluated under UV-light irradiation for the degradation of five different dyes viz. malachite green (MG), eriochrome black-T (EBT), methyl thymol blue (MTB), bromophenol blue (BPB), and congo-red (CR). The α -Bi2O3 MFs show enhanced photocatalytic activity than γ -Bi2O3 MSs under UV light without decreasing efficiency up to four consecutive cycles and fallows the pseudo-first order reaction kinetics and degradation order: MTB>MG>EBT>CR>BPB. Furthermore, antibacterial assay of α -Bi2O3 MFs and γ -Bi2O3 MSs was carried out against gram-positive (Staphylococcus aureus (S a) and Pseudomonas aeruginosa (P a)) and gram-negative (Escherichia coli (E c), and Klebsiella Pneumonia (K p)) human pathogenic bacteria using agar well diffusion method. The α -Bi2O3 MFs show comparatively better antibacterial activity against P a than γ -Bi2O3 MSs. The current study provides a simple approach to design the α -Bi2O3 MFs and novel γ -Bi2O3 MSs as a photocatalyst for the environmental remediation of organic pollutants (OPs).

Natural saponin stabilized nano-catalyst as efficient dye-degradation catalyst

Abstract: Silver nanoparticles decorated reduced graphene oxide is a well-established nanoparticle for multifunctional applications. Herein, the aim of the work is to prepare the nanoparticles in an in situ green reduction fashion without using any external reducing agent and stabilizing agent. Thus, a new stabilizer cum reducing agent has been introduced for the first time to prepare the silver nanoparticle decorated reduced graphene oxide. The new stabilizer cum reducing agent was naturally occurring saponin which has been extracted as Brahmi leaf (Bacopa monniera) sap. The as-synthesized material has been confirmed by X-ray diffraction, UV–visible spectra and Raman spectra. The surface chemical features have been confirmed by X-ray photoelectron spectroscopy. Transmission electron micrograph revealed distinct nanoparticles abound range of 12-35 nm over reduced graphene oxide basal plane. The synthesized nanoparticles have been tested for dual applications, i.e., solid state catalytic activity and bactericidal activity.

Electrospun nanofibers, nanocomposites and characterization of art: Insight on establishing fibers as product

Abstract: Electrospun nanofibers generally result in as non-woven fibrous mats classified as high surface area materials as they pose surface-to-mass or volume ratio. Electrospinning technology has been widely used preparation of wide range of nano scale fibers for applications like high strength composite materials, electronic device making, drug delivery, food packaging, membrane filtration and energy applications. Since its reinvention in 1990s, electrospinning technique has undergone remarkable changes from lab scale single needle spinning process to multi-needle mass production and industrial scale nanofiber production using advanced bubble spinning technique. Electrospinning technique can be uniquely modified for specialty nanofiber spinning depending upon end use. With slight change in electrospinning parameters, process can yield from simple randomly arranged nanofiber webs to highly oriented and packed nanofibers mat are being used commercially in the form of air purifiers, filtrations membranes and wound dressing pads. This review evaluates electrospun nanofibers for their characteristic properties as a product and properties in conjunction with respect their applications. This review also evaluates novel characterization techniques employed in recent times with an emphasis on to understand the morphology, physico-chemical and mechanical properties. Large scale production of electrospun nanofibers are being aimed to be used in wearable electronics applications having nanofibers as flexible electrodes, as composite nanomaterials in automobile and aerospace manufacturing.

Influence of Mn substitution on morphological, thermal and optical properties of nanocrystalline GdFeO3 orthoferrite

Abstract: The current research work focuses on the preparation of nanocrystalline GdFe 1−x Mn x O 3 ( 0 ≤ x ≤ 0 . 3 ) samples via solid state reaction route to explore their microstructural, thermal and optical properties in detail. Scaning electron microscopy (SEM)/Transmission electron microscopy (TEM) results revealed coarse surface and highly agglomerated form of the particles in nanoscale region with increasing particle size on Mn substitution. Elemental composition and homogeneity of the ions were ensured from energy dispersive x-ray (EDX) and SEM-EDX analyses respectively. Fourier transform infrared (FTIR) spectra reflected characteristic peak of Fe–O band at ∼ 559 cm −1 for GdFeO 3 sample and shifted to 579 cm −1 by the substitution of Mn ions, signify the octahedral FeO 6 group of perovskite structure. The variation in heat flow and specific heat at constant pressure ( C p ) with the increase in temperature were monitored through differential thermal analysis (DTA) technique. An anomaly in the specific heat near the Neel temperature (565 K) of GdFeO 3 has been observed. This peak further shifts towards the lower temperature on Mn doping. Moreover, Mn substitution in GdFeO 3 reduces the values of C p . UV–visible absorption spectra exhibited two noticeable bands in the ultraviolet region and the band gap was found to decrease with the increase in Mn content as estimated by employing Tauc’s relation. However, Urbach energy calculated using absorption coefficient enhances. These results demonstrate that the physical properties of GaFeO 3 system could be tuned by the appropriate substitution of Mn for real applications.

Poly(N-isopropylacrylamide) based thermoresponsive polymer brushes for bioseparation, cellular tissue fabrication, and nano actuators

Abstract: Many thermoresponsive surfaces for biomedical applications have been developed using various techniques for modifying substrates with thermoresponsive polymers. In addition, surface-initiated living radical polymerization methods such as atom-transfer radical polymerization (ATRP) and reversible addition–fragmentation chain-transfer (RAFT) polymerization have been developed as nano structure controlled surface modification methods for modifying thermoresponsive polymers to substrates. These polymerization techniques allow the accurate control of polymerization and the formation of densely packed polymer brush structures. The present review article summarizes a variety of thermoresponsive polymer brushes, mainly comprising poly(N-isopropylacrylamide) (PIPAAm), prepared by surface-initiated ATRP and RAFT polymerization. Self-oscillating polymer brushes as new nano-actuators are also discussed.

Structural and surface modification of carbon nanotubes for enhanced hydrogen storage density

Abstract: In this paper, we report the synthesis of functionalized carbon nanotubes (F-CNTs) by acid treatment and their hydrogen storage properties. These F-CNTs have been characterized by XRD, FTIR, Raman spectroscopy and electron microscopy techniques. The results show that the structure and morphology of P-CNTs have been modified after the acid treatment. The hydrogen storage capacity was determined by volumetric measurements at room temperature and experimental results showed that the storage capacities of P-CNTs and F-CNTs were 0.65 wt% and 0.89 wt%, respectively. A notable enhancement in hydrogen storage capacity of F-CNTs was observed which could be attributed to the enhanced oxygen functionalities, opening of end caps and presence of surface defects that offered enhanced surface area for hydrogen adsorption. The key results of present research show that structural, morphological and chemical changes are responsible factors to enhance the hydrogen storage density.

Activated carbon nanoparticles from biowaste as new generation antimicrobial agents: A review

Abstract: There is a tremendous global threat by the microbes due to their ability to easily migrate and spread in the environment Alternatively, resistance mechanisms developed by the microbes against the conventional antimicrobial drugs is of great concern due to significant mortality and morbidity and estimates to about 10 million deaths and 100 trillion USD of the global economic burden by the year 2050 WHO’s global surveillance report of 2014 on antibiotic resistance states that at least50% or more of WHO regions including Africa (77%), West Pacific Region (72%), East Mediterranean region (50%), South East Asia (81%) have developed resistance towards various microbes such as Escherichia Coli, Staphylococcus aureus, Klebsiella pneumoniae etc This poses various challenges to overcome its pathogenic impacts in biomedical and healthcare sector creating a huge economic burden In recent years, the synthesis and development of novel and potential antimicrobial agents with high antimicrobial activity is an emerging field of interest The advent of novel nanomaterials is proven to have potential antimicrobial properties as they efficiently eradicate disease causing pathogens without any side effects due to their unique physico-chemical properties Among various nanomaterials including carbon, activated carbon based nanoparticles (ACNPs) are emerging as effective antimicrobial agents due to their anti-microbial properties Development of activated carbon nanoparticles, especially from biowaste derived carbon precursor materials, is a recent upcoming technology due to their easy availability, economic viability and low cost and easy methods of production This review mainly focuses on the recent trends in the development and use of various activated carbon nanoparticles as anti-microbial agents

Enhanced electrical and thermal properties of pure and Ni substituted ZnO Nanoparticles

Abstract: In this work, we report the key ideas of undoped and Ni-doped ZnO nanoparticles by chemical route via sol–gel method. The structural, optical, electrical and thermal properties of the samples have been studied. The XRD result reveals that ZnO shows hexagonal (wurtzite) crystal structure and Ni 2 + ions are well doped into the ZnO lattice. Moreover, we have studied comparative analysis of average crystallite size using both Debye–Scherrer and William–Hall (W–H) method which is found in the range of 33.03–16.01 nm and 33.61–18.26 nm, respectively. The SEM images show high porosity degree in the sample. The band gap energy have been determined using UV–visible spectroscopy and found in the range of 3.33 - 3.28 eV via Tauc model. The FTIR spectroscopy has been done for complete compositional analysis for all samples. The dielectric constants ( ϵ ′ , ϵ ′ ′ ) , AC conductivity ( σ a c ) and dielectric loss ( tan δ ) have also been examined as a function of frequency (50–300 KHz) and explained by “ Maxwell–Wagner model”. Eventually, we discussed thermal analysis of our materials which suggest three and two stage weight loss for Zn 1 − x Ni x O (x=0.0 to x= 0.03) and Zn 1 − x Ni x O(x=0.05) and came to know that the total weight loss are found 9.6%, 6.63%, 9.72% and 22.15% respectively.

Microwave assisted synthesis of Co3O4 and NiO nanoplates and structural, optical, magnetic characterizations

Abstract: The surfactant and template free Co3O4 and NiO nanoplates have synthesized using microwave assisted method. Synthesized Co 3 O 4 and NiO nanoplates were characterized using X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive spectrometer (EDS) for their Structural, morphological and elemental analysis respectively. The Fourier transform infrared (FTIR) spectra of both samples were recorded for the oxide compound confirmation. Optical and magnetic characterizations were studied by using UV–Visible absorption spectroscopy, photoluminescence (PL) and vibrating sample magnetometer (VSM) respectively. Average crystallite sizes for Co 3 O 4 and NiO nanoplates were found to be 21 nm and 17 nm respectively by using Debye–Scherrer’s formula. The energy band gaps for Co 3 O 4 and NiO nanoplates were calculated using Tauc plot and values are 3.3 eV and 3.1 eV respectively. BET surface areas of Co 3 O 4 and NiO nanoplates were measured to be 29 m2/g and 92 m2/g respectively. The magnetization of Co 3 O 4 and NiO nanoplates as a function of magnetic field were recorded at room temperature showing a small hysteresis loop with coercivity of ∼ 534 and ∼ 152 Oe respectively. Microwave assisted method can be useful for the synthesis of Co 3 O 4 and NiO nano morphological materials for supercapacitor application.

CdS sensitized TiO2 nano heterostructures as sunlight driven photocatalyst

Abstract: Sunlight harvesting nano heterostructure materials with excellent photocatalytic activity has received considerable attention in recent years. Here we meticulously investigated the effect of CdS nano crystal loading on the light absorption capacity and the photocatalytic activity of TiO2 nanomaterials by assembling TiO2-CdS heterostructures. A distinct heterostructure was established in the presently reported hybrid system with 10 wt% CdS incorporation into TiO2 and the photocatalytic study showed that TiO2-CdS10 has 3.5 times higher catalytic activity than bare TiO2. This superior photocatalytic performance is attributed to the excellent light absorption, high surface area and the slow rate of recombination of photogenerated charge carriers of TiO2-CdS10 hetero structures. A mechanism was also proposed for the CdS sensitized sunlight driven photocatalytic degradation of methyl orange dye in presence of CdS–TiO2 nano heterostructure.

Uptake of halloysite clay nanotubes by human cells: Colourimetric viability tests and microscopy study

Abstract: This study is a systemic investigation of the uptake and toxicity of halloysite nanotubes using human adenocarcinoma epithelial cells (A549). A549 cells were chosen as a popular model of cancer cells extensively studied in nanotoxicity and drug delivery research. The adverse effects of a range of halloysite concentrations were evaluated. The viability of A549 cells was determined using several colourimetric assays. Dark-field microscopy was used to visualize the uptake and distribution of halloysite nanotubes in cells. The morphology of the cells was evaluated using dark-field, transmission electron and atomic force microscopies. The results showed that halloysite had a dose-dependent effect on human cells at concentrations of 5–900 μ g per 10 5 cells in the MTT assay. The reduced toxicity of halloysite nanotubes at lower concentrations (5–75 μ g per 10 5 cells) was additionally supported by the results of other colorimetric assays. Microscopy assays have demonstrated that the nanotubes, though affecting the biochemical processes, do not alter the morphology of the cells and do not penetrate into the nuclei.

Shape-selective synthesis of gold nanoparticles and their catalytic activity towards reduction of p-nitroaniline

Abstract: Microwave assisted shape-selective synthesis of gold nanoparticles has been achieved in a short reaction time of 6 min. Shape of the gold nanoparticles has been found to be tuneable among truncated cube, cube, tetrahedral and octahedral by changing the concentration of aqueous NaOH into the reaction mixture containing HAuCl4, N,N-dimethylformamide (DMF) and polyvinylpyrrolidone (PVP) under microwave irradiation. The preferential adsorption of sodium ions on gold surface during crystal growth controls the shape of the nanoparticles. The chemical state, crystallographic structure, elemental composition and morphology of the as-prepared gold nanoparticles were analyzed using respective XPS, powder XRD, EDS and FEG-SEM analytical techniques. Catalytic performance and recyclability of the as-prepared gold nanoparticles were examined towards the reduction of p-nitroaniline into p-phenylenediamine using sodium borohydride and continuous monitoring the reaction progress using UV-Visible spectrophotometer under ambient conditions.

Aggrandize efficiency of ultra-thin silicon solar cell via topical clustering of silver nanoparticles

Abstract: A highly efficient photovoltaic nanocomposite device is demonstrated by fabrication of structural clusters of silver nanoparticles (Ag NPs) on silicon solar cells via a boil deposition method. The efficiency of silicon solar cell was augmented by coating Ag NPs ultra-thin-film deposition on silicon solar cell. Chemically synthesized silver NP’s, their consumption on a silicon thin layer and the operation of photovoltaic nanocomposite device were characterized by using several electron probe microscopic pectroscopic and spectrometric techniques viz. x -ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), Photoluminescence, UV–visible absorption, dielectric, current vs. voltage ( I ∼ V ) and capacitance vs. voltage ( C ∼ V ) characteristics. Poly-dispersed nature of ‘Ag’ nanoparticles established the anisotropy of these NPs when coated on silicon solar cells. Their efficiency enhancement was confirmed from HR-TEM image via time-domain finite-difference technique to deliberate the particle distribution effect on an ultra-thin film of silicon solar cell, indicating the sufficient enrichment in the efficiency of solar cell. Furthermore, the current work explores the developement of novel glass frits for utilization in next generation of high efficiency smart solar cells.

Disposable, efficient and highly selective electrochemical sensor based on Cadmium oxide nanoparticles decorated screen-printed carbon electrode for ascorbic acid determination in fruit juices

Abstract: Here, we report a Cadmium oxide (CdO) nanoparticles modified disposable screen-printed carbon electrode (SPCE) for non-enzymatic detection of ascorbic acid (AA) with excellent stability and nano-molar detection limit. CdO nanoparticles synthesized by a simple, low-cost one-step co-precipitation method exhibits uniform crystalline nature and surface functional groups confirmed by XRD and FTIR spectroscopy. As a model analyte, AA was used to evaluate the electrocatalytic activity of CdO by cyclic voltammetry and differential pulse voltammetry (DPV) methods. The newly developed electrode, i.e., CdO nanoparticles modified SPCE shows AA oxidation peak at potential, ∼ 0.2 V vs. Ag/AgCl. Under optimal DPV condition, CdO-SPCE detects a wide range of concentration from 5 to 150 μ M with a current sensitivity of 0.42 A M−1 cm−2 and ultra low-level detection (53.5 nM). Furthermore, the proposed sensor was highly stable and exhibited excellent selectivity towards the detection of AA in the presence of interfering electroactive agents such as urea, uric acid, glucose, citric acid, Na + ion and sucrose. For quick quality control assessment, a CdO modified SPCE (CdO-SPCE) was developed as a disposable sensor for real-time applications. A canned fruit juice (real sample) successfully analysed using CdO-SPCE exhibits a recovery value of ∼ 100%.

Electrochemical performance of Bi2O3 decorated graphene nano composites for supercapacitor applications

Abstract: Graphene based supercapacitors are being developed as potential devices for large scale energy storage applications with physical flexibility, because of their low cost and high electrochemical performance. This paper is mainly focused on the preparation of pure Bi2O3 and graphene / Bi2O3 based nanocomposite materials via sol–gel method and their physical / electrochemical characterization towards application in supercapacitors. The physical characterization like crystallinity, structure, morphological studies etc. were carried out by XRD, FTIR, SEM, EDAX and HR-TEM techniques. The capacitance behaviour of the prepared electrode materials was examined by cyclic voltammetry, galvanostatic charge–discharge and impedance analysis respectively. Among the two samples studied, Bi2O3/graphene nanocomposite electrode material has exhibited higher specific capacitance of 136.76 Fg−1, which is much higher than the specific capacitance of pure Bi2O 3 based electrode (81.03 Fg−1). Moreover, the synthesized nanocomposite electrode material has exhibited good cyclic stability (>95% over 1000 cycles) which may lead to applications in high-performance energy storage devices such as super capacitors.

Spherical nanosilver: Bio-inspired green synthesis, characterizations, and catalytic applications

Abstract: Bio-inspired green synthesis of noble metal nanocatalyst for visible light induced reductive degradation of organicpollutants is a promising strategy for water purification. This study reports a quick synthesis of spherical and stable M. charantia fruit extract supported silver nanoparticle (AgNPs) as a green catalyst and first time applied for the degradation of various industrial dyes pollutant. The bioinspired green protocol was followed for synthesis and the formulation mechanism of AgNPs was elucidated. Flavonoid worked as reducing agent and protein worked as a stabilizer during catalyst fabrication. The catalyst was characterized using TEM (spherical nanostructure with size AgNPs exhibited enhanced photocatalytic activity during degradation in presence of NaBH4 at room temperature under visible-light irradiation. The degradation time and apparent rate constant (from pseudo first order) for the AgNPs@MB, AgNPs@Rh-B, AgNPs@MO and AgNPs@4-NP system were t = 8 min (K = 0.277 min−1), t = 13 min (K = 0.162 min−1), t = 7.5 min (K = 0.269 min−1) and t = 7 min (K = 0.262 min−1), respectively. A discrepancy in degradation capacity among dye can be ascribed to relatively large molecular size and formation of the surface oxide layer. Results revealed that 91% of MB was degraded by 2.0 mg catalyst with rate constant 0.277 min−1. Degraded products were evidenced by FT-IR and degradation pattern followed pseudo-first order kinetics. The blend of green synthesis, intrinsic biocompatibility, superior photocatalytic activity, stability and recyclability of AgNPs are potentially applicable for industrial wastewater treatment and environmental remediation.

Novel nano-cocoon like structures of polyethylene glycol–multiwalled carbon nanotubes for biomedical applications

Abstract: In this article, we report the synthesis and use of a novel drug delivery particle, based on bio-compatible polymer polyethylene glycol (PEG-400) and multi-walled carbon nanotubes (MWCNTs). MWCNTs in PEG-400 were broken into small tubes by vortex mixing with tungsten-carbide balls for about 15 h. Length separation of MWCNTs was then done using differential centrifugation with various concentrations of PEG-400. The separated MWCNTs in PEG solution were further pelletized using high speed centrifugation and re-dispersed in water. Novel cocoon like oval nanoparticles of about 100–200 nm size was observed in one of the centrifuged fractions. TEM shows that the cocoons primarily have PEG enclosing few MWCNTs. However, similar structures were not found when differential centrifugation was done without MWCNTs. These nano-cocoons are hemo-compatible, non-toxic to mice fibroblast cell lines (L929), have great potential to be used as nano biomaterials and they could be loaded with naturally anti-cancerous drug curcumin. The cocoon–curcumin complex is dispersible in saline and could be internalized by brain cancer cells (C6 glioma) while free curcumin dispersed in saline could not enter C6 glioma cells.

One-step pyrolytic synthesis and growth mechanism of core–shell type Fe/Fe3C-graphite nanoparticles-embedded carbon globules

Abstract: We report the synthesis and detailed characterization of amorphous carbon globules containing Fe/Fe3C-graphite core–shell type nanoparticles. The samples were synthesized via a low-cost chemical vapour deposition (CVD) method by the single-step pyrolysis of precursors (benzene and ferrocene). The amount of precursors and the reaction temperature were found to control the morphology of the carbon globules, and the shape, size, composition and distribution of Fe/Fe–C based nanoparticles inside the carbon globules. At the CVD tube wall deposition of Fe derived from the decomposed-ferrocene forms Fe3C particles at high temperature, which are unstable in carbon rich environment and transforms to γ -Fe and carbon-product (graphite). Furthermore, γ -Fe is also unstable at RT and transforms to α -Fe and Fe3C phases while cooling. A fraction of γ -Fe is, however, kinetically arrested during the cooling process. This leads to the formation of ‘Fe/Fe3C (core)-graphite (shell)’ nanoparticles-embedded amorphous carbon globules.

Graphite doped Hydroxyapatite nanoceramic: Selective alcohol sensor

Abstract: Graphite doped Calcium Hydroxyapatite (GHAp) nano ceramic materials are prepared by liquid phase reinforce process. Six different composites of Graphite with variable weight concentrations doped in synthesized HAp are prepared for sensor material. Structural and morphological characterizations are performed using X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), Brunauer–Emmett–Teller (BET), and Scanning Electron Microscopy (SEM). The experimental study involves detection of alcoholic vapours like methanol, ethanol, and propanol at lower concentration level (100 ppm). Sensing ability of these films is investigated in the presence of atmospheric air and alcoholic vapours individually and in the form of mixture using two probe methods. Further the sensing parameters like stability, repeatability, response/recovery time and maximum vapour detection limit are also studied. The experimental results for gas sensing characteristics of HAp and Graphite doped HAp material reveals the role of dopant in enhanced detection of volatile pollutant (VOCs). An addition of Graphite shows six times higher sensitivity for alcoholic vapours than the synthesized HAp. The quantity of Graphite as the doping material also makes a noticeable effect on sensing performance of the device studied here. Such sensor matrix can be incorporated to monitor alcoholic vapours, discharged in the environment with their meagre concentrations. The novelty of GHAp sensor material is in detecting all the vapours individually, when collectively present in the ambient air.

Gold nanoflowers as efficient hosts for SERS based sensing and bio-imaging

Abstract: Intrinsically rich in hot spots, anisotropic gold nanostructures have been explored as efficient hosts for Surface Enhanced Raman Scattering (SERS). Limited toxicity, shape/size tunability and high stability of gold nanostructures makes them a better choice to be used as SERS tags compared to other plasmonic metals. In this article, gold nanoflowers using ‘green’ L-ascorbic acid have been synthesized and used as SERS tags to detect low concentrations of Rhodamine 6 G dye. It is found that the gold nanoflowers can detect the presence of R6G molecules up to 10−10 M. The nanoflower (AuNf) petals play an important role in Raman signal enhancement allowing signal improvement of the order of 106. This enhancement can be explained in terms of electromagnetic enhancement mechanism of the metal nanomaterials. We have also studied the cytotoxicity of these nanostructures using MTT assay where human lung carcinoma cell line A549 were treated with AuNf. The synthesized gold nanoflowers show high biocompatibility and improved signals when imaged through confocal microscope indicating its applicability as a multimodal in vitro SERS based sensor and imaging tag.

Pure and Cu metal doped WO3 prepared via co-precipitation method and studies on their structural, morphological, electrochemical and optical properties

Abstract: Pure and copper (3d transition metal) doped WO3 nanoparticles were synthesized by the co-precipitation method (CPM) for high yield at ambient temperature. The aim of present work is to study the effect of Cu-doped WO3 nanoparticles and its physico-chemical properties. The observed structure showed the monoclinic structure in Powder X-ray diffraction (PXRD) pattern for the all prepared sample. The surface morphology of the obtained samples was studied by Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (HR-TEM), which shows nanoplate morphology for pure and nanoplate with rod morphology for Cu doped WO3. From the UV–Vis (UV-DRS) diffuse reflectance spectra, the absorption edge of copper dopand sample found to shift towards ultraviolet region and photoluminescence (PL) emission spectrum divulge that the emission was observed at three different color bands which reveals a promising material for optoelectronics applications and lighting devices. The electrochemical properties were studied by cyclic voltammetry (CV) analysis which reveals that the Cu doped WO3 has lower peak to peak separation value than pure and it enhances the electrocatalytic activity and redox reactions.

Monodisperse palladium nanocatalysts for dehydrocoupling of dimethylamineborane

Abstract: Over the last several decades, dimethylamine borane, which is one of the ammonia borane derivatives, has been attracting attention as one of the most effective solid hydrogen storage materials. Herein, the preparation and characterization of activated carbon supported palladium nanoparticles was reported as a highly efficient catalyst for dehydrogenation of dimethylamine borane under ambient conditions. The characterization of prepared nanomaterials was made by using some analytical methods such as XRD, XPS, TEM, HR-TEM. The prepared nanomaterials were observed in the range of 3.46–4.36 nm with an approximate mean diameter of 4 nm. The results of these analyses showed that the new palladium nanoparticles were colloidally stable and crystalline. The catalytic activity and durability of prepared nanomaterials were investigated for the dehydrogenation of dimethylamine borane. The one of the best TOF (100.3 h −1 ) value was obtained for the dehydrogenation of dimethylamine borane. The investigations showed that the palladium nanoparticles have very high catalytic activity and stability at room conditions.

Green synthesis of gelatin-noble metal polymer nanocomposites for sensing of Hg2+ ions in aqueous media

Abstract: We herein report a greener method for the synthesis of silver (Ag), gold (Au) and platinum (Pt) nanoparticles (NPs) using gelatin and maltose as non-toxic, capping and reducing agents respectively. The formation of these noble metal NPs was monitored and confirmed by UV–visible absorption spectroscopy, Fourier transform infrared spectroscopy and transmission electron microscopy. The as-synthesized metal NPs were investigated for optical sensing of various metal ions in aqueous solutions by monitoring their surface plasmon resonance. The results showed that Ag NPs showed selective response to mercury (Hg 2 + ) ions, though all the metal NPs are sensitive to all the metal ions investigated. Taking this advantage, Ag NPs were then employed for quantitative detection of Hg 2 + ions in a local lake water and this was found to be 4 . 73 × 10 −6 ppm. The proposed method is simple, cost-effective and ecofriendly to prepare Ag NPs sensor in assessing the quality of real water samples.

Effect of solvents on the structure and magnetic properties of pyrolysis derived carbon globules embedded with iron/iron carbide nanoparticles and their applications in magnetorheological fluids

Abstract: Carbon globules embedded with magnetic iron/iron carbide nanoparticles were synthesized by pyrolysis route using different organic solvents (benzene/toluene/xylene) along with ferrocene as iron catalyst precursor. All other synthesis parameters were kept constant (e.g. reaction temperature ≈ 950 oC, heating rate of 3 oC/min). We observed a variation of magnetic phase composition with the type of solvent (carbon source) used for synthesis, although the morphology of all the samples was similar. Improved sample crystallinity, distribution of particles and saturation magnetization were obtained, when toluene was used as solvent. Interestingly, rod shaped magnetic particles were observed in case of benzene, whereas for toluene and xylene, all iron-based magnetic particles were spherical. Due to higher saturation magnetization, we have used the particles prepared using toluene as a solvent to demonstrate the magnetorheological behaviour of these carbon-coated magnetic nanoparticles. We observed good magneto-response for the samples suggesting that these particles are potential candidate for magnetorheological applications.

Nanostructured mesoporous NiO as an efficient photocatalyst for degradation of methylene blue: Structure, properties and performance

Abstract: Nanostructured NiO with an average crystallite size ∼ 2–3 nm is synthesized through a two step process. X-ray diffraction analysis reveals high value of microstrain indicating the presence of large concentration of point defects. Sample is found to be mesoporous with a high specific surface area of 187.27 m2/g. Raman and Infrared spectra shows the presence of surface modes and forbidden vibrations respectively due to the small size and broken symmetry. Ni 2p and O 1s X-ray photoelectron spectra confirms the presence of large percentage of Ni 2 + vacancies. UV–visible absorption spectra show efficient absorption in both ultraviolet and visible regions, while, Photoluminescence emission spectra show two emission bands characteristic of O 2 − vacancies. DC electrical conductivity studies reveal the semiconducting nature of the sample. The sample is found to be an efficient photocatalyst for the degradation of methylene blue in water with a pseudo first order rate constant of k = 1 . 97 × 10 −2 min−1. It is proposed that the high surface area, efficient absorption in the ultraviolet and visible regions and presence of Ni 2 + and O 2 − vacancies leads to the efficient photocatalytic activity.