Applied Nanoscience (v.6, #7)

Biological applications of zinc imidazole framework through protein encapsulation by Pawan Kumar; Vasudha Bansal; A. K. Paul; Lalit M. Bharadwaj; Akash Deep; Ki-Hyun Kim (951-957).
The robustness of biomolecules is always a significant challenge in the application of biostorage in biotechnology or pharmaceutical research. To learn more about biostorage in porous materials, we investigated the feasibility of using zeolite imidazolate framework (ZIF-8) with respect to protein encapsulation. Here, bovine serum albumin (BSA) was selected as a model protein for encapsulation with the synthesis of ZIF-8 using water as a media. ZIF-8 exhibited excellent protein adsorption capacity through successive adsorption of free BSA with the formation of hollow crystals. The loading of protein in ZIF-8 crystals is affected by the molecular weight due to diffusion-limited permeation inside the crystals and also by the affinity of the protein to the pendent group on the ZIF-8 surface. The polar nature of BSA not only supported adsorption on the solid surface, but also enhanced the affinity of crystal spheres through weak coordination interactions with the ZIF-8 framework. The novel approach tested in this study was therefore successful in achieving protein encapsulation with porous, biocompatible, and decomposable microcrystalline ZIF-8. The presence of both BSA and FITC–BSA in ZIF-8 was confirmed consistently by spectroscopy as well as optical and electron microscopy.
Keywords: Zeolitic imidazolate framework (ZIF-8); Proteins; BSA; Successive adsorption

Facile synthesis of vanadium oxide nanowires by Jesse Kysar; Praveen Kumar Sekhar (959-964).
A simple growth process is reported for the synthesis of vanadium (II) oxide nanowires with an average width of 65 nm and up to 5 μm in length for growth at 1000 °C for 3 h. The vanadium (II) oxide nanowires were grown on a gold-coated silicon substrate at ambient pressure using a single heat zone furnace with Ar as the carrier gas. Gold was utilized as a catalyst for the growth of the nanowires. The growth temperature and heating time were varied to observe the nanowire morphology. An increase in nanowire width was observed with an increase in the heating temperature. A ninefold increase in the number density of the nanowires was observed when the heating time was changed from 30 min to 3 h. This is the first time a simple growth process for producing VO nanowires at ambient pressure has been demonstrated. Such a scheme enables wider use of VO nanowires in critical applications such as energy storage, gas sensors, and optical devices.
Keywords: Nanowires; Vanadium oxide; Catalyst; Thermal evaporation

Mesoporous, nanocrystalline, Zinc-doped TiO2 nanoparticles were synthesized by surfactant-assisted sol–gel method. The X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), and UV–VIS spectrometer techniques were used to characterize the synthesized products. XRD results confirm the formation of the anatase phase for the TiO2 nanoparticles, with crystallite sizes in the range of 12.6–18.1 nm. The small crystallite size and doping with Zinc ion inhibit phase transformation and promote the growth of the TiO2 anatase phase. The SEM and TEM micrographs revealed the spherical-like morphology with average diameter of about 12–18 nm which is in agreement with XRD results. The optical study shows that doping ions lead to an increase in the absorption edge wavelength and a decrease in the band gap energy of titania. Photocatalytic activity of the synthesized nanomaterials was successfully tested for photodegradation of methyl red as model pollutant under UV light. The photocatalytic activity results confirm that the doped nanoparticles show higher activity than undoped titania. The small grain size, high crystallinity, high specific surface area and decrease in the band gap energy of doped titania may be responsible for the high photocatalytic activity.
Keywords: Sol–gel; XRD; SEM-EDX; TEM; BET; UV-DRS; Photodegradation of methyl red

Biogenic synthesis and spectroscopic characterization of silver nanoparticles using leaf extract of Indoneesiella echioides: in vitro assessment on antioxidant, antimicrobial and cytotoxicity potential by Gunaseelan Kuppurangan; Balaji Karuppasamy; Kanipandian Nagarajan; Rajkumar Krishnasamy Sekar; Nilmini Viswaprakash; Thirumurugan Ramasamy (973-982).
Natural synthesis of metal nanoparticles is gaining more attention in recent years. This article demonstrates the phytochemical synthesis of silver nanoparticles (AgNPs) by using Indoneesiella echioides (L) leaf extract as a reducing and stabilizing agent. Biosynthesis of AgNPs was monitored by UV–visible spectroscopy which revealed intense surface plasmon resonance bands at 420 nm. Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction were employed to identify various functional groups and crystalline nature of AgNPs. High-resolution transmission electron microscopy studies demonstrated that synthesized particles were spherical with average size of ~29 nm. In vitro antioxidant effects were analyzed by 2,2′-Azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH), which exhibited 69 and 71 % of scavenging activity, respectively. The antimicrobial activity of green AgNPs displayed better zone of inhibition against selected human pathogens. The present study also investigated the toxicity effect of biogenic AgNPs against human lung adenocarcinoma cancer cells (A549) and normal human epithelial cells (HBL-100) in vitro, and the inhibitory concentrations (IC50) were found to be 30 and 60 µg/mL, respectively. Herein, we propose a previously unexplored medicinal plant for the biological synthesis of AgNPs with potent biomedical applications.
Keywords: Indoneesiella echioides ; Silver nanoparticles; X-ray diffraction; Transmission electron microscope; Cytotoxicity

Fe2O3 magnetic nanoparticles to enhance S. lycopersicum (tomato) plant growth and their biomineralization by K. Shankramma; S. Yallappa; M. B. Shivanna; J. Manjanna (983-990).
In the present study, we demonstrate magnetic iron (III) oxide nanoparticles (Fe2O3 NPs) uptake by the Solanum lycopersicum (S. lycopersicum) plant. The S. lycopersicum seeds were coated with Fe2O3 NPs and allowed to germinate in moistened sand bed. The seedlings are observed for 20 days, and then, it was post-treated using different amounts of Fe2O3 NPs in hydroponic solution for 10 days. The plant was allowed to grow in green house for 3 months, and uptake of NPs through roots and translocation into different parts was studied. For this, we have segmented the plants and incubated with 10 % NaOH solution. It is found that the NPs are deposited preferentially in root hairs, root tips followed by nodal and middle zone of plant. The iron present in the whole plant was quantitatively estimated by treating dry biomass of the plant in acid. The Fe2+/Fetotal increased with increasing concentration of NPs and >45 % ferrous iron suggests the biomineralization of NPs due to rich phytochemicals in plants. We believe that the present study is useful to build a base line data for novel applications in agri-nanotechnology.
Keywords: Solanum lycopersicum ; Magnetic Fe2O3 nanoparticles; Nanoparticle uptake; Plant growth

Effect of preparation conditions on the nanostructure of hydroxyapatite and brushite phases by S. F. Mansour; S. I. El-dek; M. A. Ahmed; S. M. Abd-Elwahab; M. K. Ahmed (991-1000).
Hydroxyapatite (HAP) and dicalcium phosphate dihydrate (brushite) nanoparticles were prepared by co-precipitation method. The obtained products were characterized by X-ray powder diffraction (XRD), Fourier transformation infra-red spectroscopy (FTIR) and thermo-gravimetric analysis (TGA). Scanning electron microscopy (SEM) and transmission electron microscope (TEM) were used to investigate the morphology of the powdered samples as well as their microstructure, respectively. Brushite samples were obtained in a spherical shape, while hydroxyapatite was formed in a needle and rice shape depending on the pH value.
Keywords: Bioceramics; Brushite; Hydroxyapatite

Lippia javanica: a cheap natural source for the synthesis of antibacterial silver nanocolloid by Santosh Kumar; Mukesh Singh; Dipankar Halder; Atanu Mitra (1001-1007).
Aqueous silver nanocolloid was synthesized in a single step by a biogenic approach using aqueous leaf extract of Lippia javanica plant which acts as both reducing as well as capping agent. The as-synthesized silver nanoparticles were characterized by UV–visible absorption spectroscopy, high-resolution transmission electron microscopy and Fourier transform infrared spectroscopy (FTIR). The UV–Vis absorption spectra of colloidal silver nanoparticles showed characteristic surface plasmon resonance peak centered at a wavelength of 415 nm. The kinetic study showed that the reduction process was complete within 2 h of time. The TEM analysis showed that most of the particles were spherical in shape and their average diameter was about 17.5 nm. FTIR study confirmed the presence of some organic functional groups in leaf extract and their participation during the reduction as well as stabilization process. In addition, the as-synthesized silver nanoparticles showed antimicrobial activity against clinically isolated pathogenic strain of E. coli and B. subtilis.
Keywords: Synthesis; Silver nanocolloid; Lippia javanica ; Antibacterial; E. coli ; B. subtilis

A method was developed for generating transparent and hydrophobic nanolayers chemisorbed onto flexible substrates of ethylene tetrafluoroethylene–silicon oxide (ETFE–SiOx). In particular, the effect of the deposition time and of the precursor molecule on the nanocoating process was analyzed with the aim of pursuing an optimization of the above method in an industrial application perspective. It was found that precursor molecule of triethoxysilane allowed to obtain better hydrophobic properties on the SiOx surface in shorter times compared to trichlorosilane, reaching the 92 % of final contact angle (CA) value of 106° after only 1 h of deposition. The optical properties and surface morphology were also assessed in function of time, revealing that an initial transparency reduction is followed by a subsequent transmittance increase during the self assembly of fluoroalkylsilanes on the SiOx surface, coherently with the surface roughness analysis data. Encouraging results were also obtained in terms of oleophobic properties improvement of the nanocoated surfaces.
Keywords: Hydrophobic nanolayer; Self assembled monolayers; Ethylene tetrafluoroethylene–silicon oxide; Fluoroalkylsilanes

In situ thermally reduced graphene oxide/epoxy composites: thermal and mechanical properties by Ganiu B. Olowojoba; Salvador Eslava; Eduardo S. Gutierrez; Anthony J. Kinloch; Cecilia Mattevi; Victoria G. Rocha; Ambrose C. Taylor (1015-1022).
Graphene has excellent mechanical, thermal, optical and electrical properties and this has made it a prime target for use as a filler material in the development of multifunctional polymeric composites. However, several challenges need to be overcome to take full advantage of the aforementioned properties of graphene. These include achieving good dispersion and interfacial properties between the graphene filler and the polymeric matrix. In the present work, we report the thermal and mechanical properties of reduced graphene oxide/epoxy composites prepared via a facile, scalable and commercially viable method. Electron micrographs of the composites demonstrate that the reduced graphene oxide (rGO) is well dispersed throughout the composite. Although no improvements in glass transition temperature, tensile strength and thermal stability in air of the composites were observed, good improvements in thermal conductivity (about 36 %), tensile and storage moduli (more than 13 %) were recorded with the addition of 2 wt% of rGO.
Keywords: Thermal reduction; Graphene oxide; Reduced graphene oxide; Tensile modulus; Thermal conductivity; Glass transition temperature; Dispersion; In situ processing

Green synthesis and characterization of silver nanoparticles using Cydonia oblong seed extract by Faria Zia; Nida Ghafoor; Mudassir Iqbal; Saliha Mehboob (1023-1029).
The green synthesis of nanoparticles has emerged as a cost-effective and environmentally benign technique. The present study describes the synthesis of silver nanoparticles (Ag-NPs) using a seed extract of Cydonia oblonga. The conditions were optimized by adjusting pH, temperature, time and amount of seed extract. The nanoparticles produced were characterized by different techniques, namely UV–visible spectroscopy, Fourier transmission infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy. The formation of Ag-NPs was confirmed by UV–visible spectroscopic analysis. FTIR analysis was performed to identify the biomolecules, which played a key role in the reduction of Ag+ ions. XRD confirmed that the silver nanoparticles possessed face-centered cubic structure. The green chemistry approach has proven that Ag-NPs can be synthesized by using plant extract in which biomolecules effectively act as capping and reducing agent.
Keywords: Ag-nanoparticles; Green synthesis; Cydonia oblonga

Fabrication and optical simulation of vertically aligned silicon nanowires by M. K. Hossain; B. Salhi; A. W. Mukhaimer; F. A. Al-Sulaiman (1031-1036).
Silicon nanowires (Si-NWs) have been considered widely as a perfect light absorber with strong evidence of enhanced optical functionalities. Here we report finite-difference time-domain simulations for Si-NWs to elucidate the key factors that determine enhanced light absorption, energy flow behavior, electric field profile, and excitons generation rate distribution. To avoid further complexity, a single Si-NW of cylindrical shape was modeled on c-Si and optimized to elucidate the aforementioned characteristics. Light absorption and energy flow distribution confirmed that Si-NW facilitates to confine photon absorption of several orders of enhancement whereas the energy flow is also distributed along the wire itself. With reference to electric field and excitons generation distribution it was revealed that Si-NW possesses the sites of strongest field distributions compared to those of flat silicon wafer. To realize the potential of Si-NWs-based thin film solar cell, a simple process was adopted to acquire vertically aligned Si-NWs grown on c-Si wafer. Further topographic characterizations were conducted through scanning electron microscope and tunneling electron microscope-coupled energy-dispersive spectroscopy.
Keywords: Fabrication; FDTD simulation; Photovoltaic solar cell; Silicon nanowires

Fabrication of CdTe/Si heterojunction solar cell by Swades Ranjan Bera; Satyajit Saha (1037-1042).
A simple cost effective method is preferred to grow nanoparticles of CdTe. Nanoparticles of CdTe are grown by simple chemical reduction route using EDA as capping agent and Sodium Borohydride as reducing agent. The grown nanoparticles are characterized using transmission electron microscopy (TEM), X-ray diffraction, optical absorption, and photoluminescence study. From optical absorption study, the band-gap was found to be 2.46 eV. From TEM study, the average particle size was found to be within 8–12 nm which confirms the formation of CdTe nanoparticles. Pl spectra indicate the luminescence from surface states at 2.01 eV, which is less compared to the increased band-gap of 2.46 eV. The grown nanoparticles are used to fabricate a heterojunction of CdTe on P-Si by a spin coating technique for solar cell fabrication in a cost effective way. I–V characteristics of the grown heterojunction in dark as well as under light are measured. Efficiency and fill-factor of the device are estimated.
Keywords: Nanostructures; Semiconductors; Chemical synthesis; Transmission electron microscopy (TEM); Electrical properties

Lithium–germanium–phosphate glassceramic electrolytes: correlation between the nanocrystallization and electrical studies by Ch. Krishna Kishore Reddy; G. Suman; R. Balaji Rao; Naresh Kumar Katari; M. R. P. Reddy (1043-1052).
Investigations on the microstructural and electrical properties of a glassceramic system: (100 − x) [0.4Li2O − 0.1GeO2 − 0.6P2O5] + x [20 h ball milled Ga2O3] (0 ≤ x ≤ 10 mol%, in the regular steps of 2 mol%) via high-energy ball milling technique are reported. XRD spectra of LGePG glassceramic samples were identified major crystalline phases such as Li3Ge2(PO4)3 (NASICON-type phase), Ga2Li3(PO3)7 and GeO2 from the major diffraction peaks. Bulk conductivity of all these samples was measured for the powder-compressed pellets by ac impedance method. The correlation of log(σ) and M″ peaks suggests the presence of single conduction mechanism in the LGePG glassceramic samples. The results are discussed in the light of degree of crystallization of lithium phosphate glass network.
Keywords: Glasses; X-ray diffraction; Electrical properties

A simple method for the deposition of nanostructured tellurium synthesized in ammonia solution by C. D. Gutiérrez-Lazos; F. Solís-Pomar; M. F. Meléndrez; A. M. Espinoza-Rivas; M. A. Pérez-Guzmán; R. Ortega-Amaya; M. Ortega-López; E. Pérez-Tijerina (1053-1057).
In this work, we report a highly adherent, and uniform deposition of nanostructured tellurium. The deposition of the nanostructured tellurium was realized by the dripping of a modified solution of NaHTe based on the dissolution of NaBH4 and tellurium powder in an aqueous solution of NH4OH. This method allowed the relatively simple manipulation of tellurium nanostructures under laboratory ambient, without requiring the use of organic stabilizers. Transmission electron microscopy (TEM) was realized on a powder sample obtained by the reaction between H2Te and aqueous solution of NH4OH. TEM analysis indicated that tellurium nanorods and Y-type nanostructures are grown from tellurium nanoparticles, such as in a hydrothermal system. Then, the nanoparticles serve as seeds for the growth of more extended tellurium nanostructures. Electron diffraction and X-ray diffraction analysis showed that depositions have the hexagonal structure of tellurium highly oriented on (101) direction.
Keywords: Tellurium; Nanostructures; Transmission electron microscopy; X-ray diffraction

Structural investigation of nanomixed xSnO2–Al2O3 synthesized by sol–gel route by C. Kumar; N. K. Mishra; A. Kumar; M. Bhatt; P. Chaudhary; R. Singh (1059-1064).
Nanomixed SnO2–Al2O3 with variable composition has been synthesized by sol–gel technique using aluminium dichloride and stannous chloride as precursors. Synthesized nanocomposites have been characterized using various techniques such as X-ray diffraction (XRD), Fourier transform infrared, scanning electron microscopy and Energy-dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET). XRD shows decrease in crystallinity as alumina component increases in following series of nanomixed oxides. The specific surface area calculated by Brunauer–Emmett–Teller (BET) method was about 191 m2/g and average pore diameter of 158 Å.
Keywords: Nanomixed; Alumina; Cystallinity; Sol–gel

Preparation and characterization of nanosized Ag/SLN composite and its viability for improved occlusion by G. Cynthia Jemima Swarnavalli; S. Dinakaran; S. Divya (1065-1072).
Nanocomposites consisting of silver and solid lipid nanoparticles (SLN) elicit interest for their synergistic effect based enhanced properties in skin hydration. The nanocomposite preparation aims at combining the antimicrobial activity of silver with skin hydration performance of SLN. The nanocomposites designated Ag/SAN (silver/stearic acid nanoparticles), Ag/PAN (silver/palmitic acid nanoparticles) were prepared by incorporating silver nanoparticles into the dispersion of SLN and sonicating for 10 min followed by heating for 1 h at 50 °C in a thermostat. The occlusive property of the two nanocomposites was evaluated in comparison with the pure SLN by adopting de Vringer-de Ronde in vitro occlusion test. The incorporation of silver nanoparticles has improved occlusion factor by 10 % in the case of both composites at SLN concentration of 0.14 mmol. Characterization studies include XRD, DSC, HRSEM, DLS and zeta potential measurement. High resolution scanning electron microscopy (HRSEM) images divulge that the nanoparticles of composite (Ag/SAN) shows halo effect where the hydrophobic stearic acid is oriented at the core and is surrounded by silver nanoparticles while Ag/PAN shows cashew shaped SLN dispersed in silver nanoparticles matrix.
Keywords: Silver nanoparticles; SLN; Nanocomposite; Skin hydration; Zetapotential; HRSEM

Nanoscience offers the potential for great advances in medical technology and therapies in the form of nanomedicine. As such, developing controllable, predictable, and effective, nanoparticle-based therapeutic systems remains a significant challenge. Many polymer-based nanoparticle systems have been reported to date, but few harness materials with accepted biocompatibility. Phosphorylcholine (PC) based biomimetic materials have a long history of successful translation into effective commercial medical technologies. This study investigated the synthesis, characterisation, nanoprecipitation, and in vitro cellular uptake kinetics of PC-based polymeric nanoparticle micelles (PNM) formed by the biocompatible and pH responsive block copolymer poly(2-methacryloyloxyethyl phosphorylcholine)-b-poly(2-(diisopropylamino)ethyl methacrylate) (MPC-DPA). Atom transfer radical polymerisation (ATRP), and gel permeation chromatography (GPC) were used to synthesise and characterise the well-defined MPC100-DPA100 polymer, revealing organic GPC, using evaporative light scatter detection, to be more accurate than aqueous GPC for this application. Subsequent nanoprecipitation investigations utilising photon correlation spectroscopy (PCS) revealed PNM size increased with polymer concentration, and conferred Cryo-stability. PNM diameters ranged from circa 64–69 nm, and increased upon hydrophobic compound loading, circa 65–71 nm, with loading efficiencies of circa 60 % achieved, whilst remaining monodisperse. In vitro studies demonstrated that the PNM were of low cellular toxicity, with colony formation and MTT assays, utilising V79 and 3T3 cells, yielding comparable results. Investigation of the in vitro cellular uptake kinetics revealed rapid, 1 h, cellular uptake of MPC100-DPA100 PNM delivered fluorescent probes, with fluorescence persistence for 48 h. This paper presents the first report of these novel findings, which highlight the potential of the system for nanomedicine application development.
Keywords: Nanomedicine; Phosphorylcholine; MPC-DPA; Micelle; Nanoparticle; Drug delivery