Applied Nanoscience (v.5, #5)

The structure, morphology, and the metal-enhanced fluorescence of nano-Ag/ZnO core–shell structure by Yue Zhao; Yanli Ding; Xiang Peng; Mingtao Zhou; Xiaoyan Liang; Jiahua Min; Linjun Wang; Weimin Shi (521-525).
Nano-polyc rystalline silver (Ag) particles with the diameter of 60 nm were synthesized by the reducing agent sodium citrate. An amorphous zinc oxide (ZnO) shell layer was then coated on the surface of silver particles using wet chemical method. The Ag/ZnO core–shell structure was characterized by scanning electron microscope, transmission electron microscopy, ultraviolet–visible spectroscopy and fluorescence (FL) measurement. The results showed that nano-Ag/ZnO core–shell particles with an average diameter of ~100 nm were prepared successfully, and the FL intensity of Rhodamine 6G (R6G) mixed with Ag/ZnO nanoparticle was 53 % greater than that of the same amount of R6G without any nanoparticles, which may be related to the effect of surface plasmon resonance.
Keywords: Silver particles; Ag/ZnO core–shell structure; Metal-enhanced fluorescence

Molecularly imprinted titania nanoparticles for selective recognition and assay of uric acid by Adnan Mujahid; Aimen Idrees Khan; Adeel Afzal; Tajamal Hussain; Muhammad Hamid Raza; Asma Tufail Shah; Waheed uz Zaman (527-534).
Molecularly imprinted titania nanoparticles are su ccessfully synthesized by sol–gel method for the selective recognition of uric acid. Atomic force microscopy is used to study the morphology of uric acid imprinted titania nanoparticles with diameter in the range of 100–150 nm. Scanning electron microscopy images of thick titania layer indicate the formation of fine network of titania nanoparticles with uniform distribution. Molecular imprinting of uric acid as well as its subsequent washing is confirmed by Fourier transformation infrared spectroscopy measurements. Uric acid rebinding studies reveal the recognition capability of imprinted particles in the range of 0.01–0.095 mmol, which is applicable in monitoring normal to elevated levels of uric acid in human blood. The optical shift (signal) of imprinted particles is six times higher in comparison with non-imprinted particles for the same concentration of uric acid. Imprinted titania particles have shown substantially reduced binding affinity toward interfering and structurally related substances, e.g. ascorbic acid and guanine. These results suggest the possible application of titania nanoparticles in uric acid recognition and quantification in blood serum.
Keywords: Molecular imprinting; Nanoparticles; Spectroscopy; Titania; Uric acid

Gum kondagogu reduced/stabilized silver nanoparticles (GK-AgNPs) were evaluated for their increased antibacterial and antibiofilm activities in combination with various antibiotics (ciprofloxacin, streptomycin and gentamicin) against Gram-positive (Staphylococcus aureus 25923, Staphylococcus aureus 49834) and Gram-negative (Escherichia coli 25922, Pseudomonas aeruginosa 27853) bacteria. The micro-broth dilution assay suggested an enhanced antibacterial activity of GK-AgNPs in combination with ciprofloxacin and aminoglycosides (streptomycin and gentamicin) against tested strains. Though the antibacterial activity of GK-AgNPs was found to increase significantly in the presence of antibiotics, the % enhancement was found to depend on both types of antibiotic and bacterial strain. It was also found that GK-AgNPs (1 µg/mL) in combination with various antibiotics at sub-MIC concentrations could inhibit 70 % of the bacterial biofilm formation as compared to respective controls. The enhanced antibacterial activity was due to the increased production of intracellular reactive oxygen species in bacteria when treated with a combination of GK-AgNPs and streptomycin as compared to individual treatment. The increased oxidative stress led to increased membrane damage as assessed by live/dead assay and higher levels of potassium ion release from the cells treated with both silver nanoparticles and streptomycin. The results suggested that the combination of antibiotics with GK-AgNPs has an enhanced antibacterial action. Further, the GK-AgNPs were found to be biocompatible up to a concentration of 2.5 µg/mL as assessed with MTT assay on HeLa cell line. The results suggest that GK-AgNPs could potentially be used as in vivo antibacterial agent in combination with antibiotics to overcome the problem of antibiotic resistance.
Keywords: Antibacterial; Antibiofilm; Antibiotics; Gum kondagogu; Reactive oxygen species; Silver nanoparticles

First evidence on phloem transport of nanoscale calcium oxide in groundnut using solution culture technique by Manchala Deepa; Palagiri Sudhakar; Kandula Venkata Nagamadhuri; Kota Balakrishna Reddy; Thimmavajjula Giridhara Krishna; Tollamadugu Naga Venkata Krishna Vara Prasad (545-551).
Nanoscale materials, whose size typically falls below 100 nm, exhibit novel chemical, physical and biological properties which are different from their bulk counterparts. In the present investigation, we demonstrated that nanoscale calcium oxide particles (n-CaO) could transport through phloem tissue of groundnut unlike the corresponding bulk materials. n-CaO particles are prepared using sol–gel method. The size of the as prepared n-CaO measured (69.9 nm) using transmission electron microscopic technique (TEM). Results of the hydroponics experiment using solution culture technique revealed that foliar application of n-CaO at different concentrations (10, 50, 100, 500, 1,000 ppm) on groundnut plants confirmed the entry of calcium into leaves and stems through phloem compared to bulk source of calcium sprayed (CaO and CaNO3). After spraying of n-CaO, calcium content in roots, shoots and leaves significantly increased. Based on visual scoring of calcium deficiency correction and calcium content in plant parts, we may establish the fact that nanoscale calcium oxide particles (size 69.9 nm) could move through phloem tissue in groundnut. This is the first report on phloem transport of nanoscale calcium oxide particles in plants and this result points to the use of nanoscale calcium oxide particles as calcium source to the plants through foliar application, agricultural crops in particular, as bulk calcium application through foliar nutrition is restricted due to its non-mobility in phloem.
Keywords: Nanotechnology; Nanomaterials; Calcium oxide; Phloem; Mobility; Groundnut

To improve electromagnetic shielding effectiveness of light weight carbon foam (CF), magnetic nanoparticles were embedded in it during processing. The CF was developed from the coal tar pitch and mixture of coal tar pitch-Nickel (Ni) nanoparticles by sacrificial template technique and heat treated to up 1,000 °C. To ascertain the effect of Ni nanoparticles embedded in CF, it was characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, vector network analyzer and vibration sample magnetometer. It is observed that Ni nanoparticles embedded in the carbon material play an important role for improving the structure and electrical conductivity of CF-Ni by catalytic carbonization. The structural investigation suggests that the Ni nanoparticles embedded in the carbon material in bulk as well on the surface of CF. The CF demonstrates excellent shielding response in the frequency range 8.2–12.4 GHz in which total shielding effectiveness (SE) dominated by absorption losses. The total SE is −25 and −61 dB of CF and CF-Ni, it is governed by absorption losses −48.5 dB in CF-Ni. This increase is due to the increase in dielectric and magnetic losses of ferromagnetic Ni nanoparticles with high surface area. Thus, light weight CF embedded with small amount of magnetic nanoparticles can be useful material for stealth technology.
Keywords: Carbon foam; Nickel nanoparticles; Raman spectroscopy; Electromagnetic shielding effectiveness; Magnetization

Nanoparticle analysis for various medicinal drugs and human body saliva at macromolecular level by G. S. Uthayakumar; Senthilkumar; S. Inbasekaran; A. Sivasubramanian; S. Justin Packia Jacob (563-568).
The spectral bio-diagnosis of normal human body saliva sample shows the following functional compounds and it is related to various proteins and enzymes. Because of the presence of water in the saliva sample, the hydroxyl group is observed in the form of O–H at 3,305 cm−1, because of the presence of lipids, the functional group C–H is obtained from 2,928 to 2,856 cm−1, due to the presence of amide-I in the form of C=N and C=C obtained at 1,658 cm−1, the proteins are exhibited. Due to the presence of aliphatic CH2, the Lipids, Adenine, Cytosine, Collagen are observed at 1,455 cm−1, because of the presence of Carbohydrates, Phospholipids, Nucleic acids, the functional groups C=O and P=O from 1,159 to 1,064 cm−1 are exhibited. Due to the presence of Phenylalanine, Tyrosine, Cystine and Hydroxyapatite C–C twist, C–C stretch, C–S stretch and PO42− are observed at 748 and 483 cm−1. Silver nanoparticle has attracted considerable interest due to their extensive applicability in various areas such as electronics, catalysis, chemistry, energy and medicine. To study the opto-electronics properties of the samples, it was mixed with silver nanoparticles and characterized.
Keywords: Nano-optics; Raman spectroscopy; SEM; Saliva; Human body

Steady, two-dimensional mixed convection boundary layer flow of an incompressible $${ m Al}_2{ m O}_3$$ Al 2 O 3 –water nanofluid along an inclined permeable plate in the presence of transverse magnetic field has been examined numerically. The governing equations (Boussinesq approximation) with associated boundary condition are solved using FEM for nanofluid containing spherical-shaped nanoparticles having volume fraction ranging from 1 to 4 %. Static-based model for calculating the effective thermal conductivity at 300 K, proposed by Leong et al. (J Nanopart Res 8:245–254, 2006) and Murshed et al. (Int J Therm Sci 47:560–568, 2008) has been implemented. Effect of various pertinent parameters with different classical and experimental models for effective dynamic viscosity is discussed.
Keywords: Nanofluid; Inclined plate; Mixed convection; Static mechanism; FEM

Six new complexes of Zn(II), Cd(II) and Hg(II) with sulphur containing ligand, tetraethylthiuram disulphide in 2:2 and 1:4 ratio have been synthesized. The resulting complexes have been characterized on the basis of molar conductance measurement, elemental analyses, FT-IR, 1H-NMR, and FAB/ESI-mass studies. The complexes were used as a single-source precursor for the synthesis of ZnS/CdS/HgS nanoparticles by their thermal decomposition in the presence of different surfactants. The precursor:surfactant ratio and temperature play an important role in determining the size of the nanoparticles. The size and morphology of nanoparticles have been ascertained by ultra violet–visible spectroscopy, X-ray diffraction measurements and transmission electron microscopy. Schiff bases, complexes and nanoparticles were tested for antibacterial activity and minimum inhibitory concentration values against Escherichia coli. The complexes were found more potent than the corresponding Schiff bases and nanoparticles.
Keywords: Metal sulphide nanoparticles; Thermal decomposition; Disulfiram; X-ray diffraction; Transmission electron microscopy

Evaluation of the antimicrobial activity and cytotoxicity of phytogenic gold nanoparticles by T. V. M. Sreekanth; P. C. Nagajyothi; N. Supraja; T. N. V. K. V. Prasad (595-602).
Among the nanoscale materials, noble metal nanoparticles have been attracting the scientific community due to their unique properties and selectivity in biological applications. In the present investigation, gold nanoparticles (AuNPs) were synthesized using rhizome extract of Dioscorea batatas through a simple, clean, inexpensive and eco-friendly method. Treating 1 mM chloroauric acid (HAuCl4) with the rhizome extract at 50 °C resulted in the formation of AuNPs. The reduction of AuNPs was observed by the color change of the solution from colorless to dark red wine. The synthesized nanoparticles were characterized using the techniques UV–Vis spectrophotometers, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy and transmission electron microscopy. Green synthesized AuNPs were found to be toxic against gram-positive and gram-negative bacteria in liquid media. MTT (dimethyl thiazolyl diphenyl tetrazolium salt) assay showed 21.5 % cell inhibition in lower concentration (0.2 mM) and >50 % cell inhibition after 48 h exposure at higher concentrations (0.8–1 mM).
Keywords: Green synthesis; Dioscorea batatas ; Antibacterial studies; Cytotoxicity; AuNPs

In this study, biosynthesis of self-assembled gold nanoparticles (GNPs) was accomplished using an aqueous extract of green microalga, Chlorella vulgaris. The optical, physical, chemical and bactericidal properties of the GNPs were investigated to identify their average shape and size, crystal nature, surface chemistry and toxicity, via UV–visible spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and antimicrobial activity. The sizes of the spherical self-assembled cores of the synthesized GNPs ranged from 2 to 10 nm. The XRD patterns showed a (111) preferential orientation and the crystalline nature of the GNPs. The results of the FTIR analysis suggested that the peptides, proteins, phenol and flavonoid carried out the dual function of effective Au III reduction and successful capping of the GNPs. Human pathogen Candida albicans and Staphylococcus aureus were susceptible to synthesized aqueous GNPs. Thus, biosynthesis, stabilization and self-assembly of the GNPs by Chlorella vulgaris extract can be an example of green chemistry and effective drug in the medicinal field.
Keywords: GNPs; Green synthesis; Toxicity; Human pathogens

Influence of water soluble carbon dots on the growth of wheat plant by Shweta Tripathi; Sabyasachi Sarkar (609-616).
The effect of water soluble carbon nano-dots (wsCND) on the growth of root and shoot of wheat plants under light and dark conditions has been studied. The wsCND enhances the growth of root and shoot both in light and dark conditions. The effect of wsCND on the growth of root was relatively more compared to that of shoot. Scanning electron and Fluorescence microscopic analysis show that wsCNDs enter inside the plant. Raman spectroscopy also confirms this. The present study shows that wsCNDs are non-toxic to the wheat plant and can be used to enhance the production of this cereal crop.
Keywords: Plant; Carbon nano-dots; Growth

In the present investigation, simple and eco-friendly chemical reaction for the synthesis reported on biological synthesis of nano-sized silver and biosynthesis of silver nanoparticles using Hypnea musciformis at room temperature along with photocatalytic degradation of methyl orange dye. The nanoparticles of silver were formed by the reduction of silver nitrate to aqueous silver metal ions during exposure to the extract of red alga H. musciformis. The optical properties of the obtained silver nanoparticles were characterized by applying UV–visible absorption and room temperature photoluminescence. The X-ray diffraction results revealed that the synthesized silver nanoparticles were in the cubic phase. The existence of functional groups was identified using Fourier transform infrared spectroscopy. The morphology and size of the synthesized particles were studied with atomic force microscope measurements. Photocatalytic degradation of methyl orange was measured spectrophotometrically by using silver as nanocatalyst under visible light illumination. The results revealed that biosynthesized silver nanoparticles using H. musciformis was found to be impressive in degrading methyl orange.
Keywords: Hypnea musciformis ; Cubical phase; Silver nanoparticles; XRD; FT-IR; AFM; Photocatalytic degradation

The effect of dispersion of CdS nano-filler particles in respective PS/PVC and PS/PMMA polymer blend matrices on the effective thermal conductivity has been studied through Hot Disk Thermal Constant Analyzer based on transient plane source (TPS) technique. The thick film samples have been prepared by dispersing nano-filler particles of CdS (6 wt%) in respective PS/PVC and PS/PMMA binary blend matrices. The nanocomposite nature of prepared samples ascertained through small angle X-ray scattering (SAXS) as well as transmission electron microscopy (TEM) measurements. It is observed that at room temperature nano CdS dispersed polymeric blend samples offer higher effective thermal conductivity.
Keywords: Polymer nanocomposite; Effective thermal conductivity; Transient plane source method

The electronic sub-band structure, potential profile and charge distribution of delta(δ)-doped GaAs/Al0.3Ga0.7As and In0.53Ga0.47As/InP core–shell nanowires have been investigated in the effective mass approximation by varying systematically the position and sheet density of the δ-layer. The one-dimensional electron gas charge distribution has a maximum at the core but not at the GaAs/Al0.3Ga0.7As or In0.53Ga0.47As/InP interfaces, as in the case of epitaxial layer heterojunctions, irrespective of the position of the δ-layer. In contrast, carriers can be confined in a quasi-triangular potential well occupying several sub-bands that fall below the Fermi level at an InP/In0.53Ga0.47As core–shell heterojunction with a wider bandgap core, resembling the case of epitaxial layer heterojunctions, or in an InP/InGaAs/InP multiple core–shell nanowire. We discuss the need for adjusting the doping level to avoid strong band bending causing a shift of the charge distribution to the core.
Keywords: Delta(δ)-Doping; III-V; Nanowires; Charge Control

Improved microwave shielding properties of polyaniline grown over three-dimensional hybrid carbon assemblage substrate by Ashok K. Sharma; Preetam Bhardwaj; Kamal Kant Singh; Sundeep K. Dhawan (635-644).
Novel composites were prepared by oxidative polymerization of aniline over hybrid carbon nanostructured assemblage consisting of graphene and amine functionalized multiwalled carbon nanotubes. The chemical structure of the obtained composites has been confirmed by UV–visible Spectroscopy and Fourier transform infrared spectroscopy. To know about the crystalline properties of the composites, X-ray diffraction studies have been done. The structural and morphological properties of the composites were examined by scanning electron microscopy. The composite having thinnest polymer film exhibited highest conductivity of 0.11 S/cm and maximum electromagnetic interference shielding effectiveness value of 21 dB obtained in the frequency range 12–18 GHz (KU-band).
Keywords: Amine functionalised CNTs; Graphene; Polyaniline; Composites; Microwave shielding