Applied Nanoscience (v.7, #3-4)

The present study reports the comparative analysis for the synthesis of zinc oxide nano particles by precipitation techniques using different zinc precursors. The synthesized nano particles were characterized by X-ray diffractometry (XRD), energy dispersive X-ray analysis and scanning electron microscopy (SEM) analysis for their sizes, shapes and arrangement. SEM has been studied for the samples before as well as after calcination to know the effect of temperature on structural behaviours. The XRD pattern shows the purity of synthesized zinc oxide nano particles and using Debye–Scherrer equation, the average crystal size of synthesized nanoparticles was calculated. The results have been discussed in the light of variation of morphological structures of different samples. Apart from this, the band gap energies of the synthesized particles have also been calculated from UV–visible spectrophotometric analysis, which is quite appreciable with the reported results.
Keywords: ZnO nano particles; Precipitation technique; Debye–Scherrer equation; Scanning electron microscope; Band gap energy

Nanoparticle targeting of Gram-positive and Gram-negative bacteria for magnetic-based separations of bacterial pathogens by Hoang D. Lu; Shirley S. Yang; Brian K. Wilson; Simon A. McManus; Christopher V. H.-H. Chen; Robert K. Prud’homme (83-93).
Antimicrobial resistance is a healthcare problem of increasing significance, and there is increasing interest in developing new tools to address bacterial infections. Bacteria-targeting nanoparticles hold promise to improve drug efficacy, compliance, and safety. In addition, nanoparticles can also be used for novel applications, such as bacterial imaging or bioseperations. We here present the use of a scalable block-copolymer-directed self-assembly process, Flash NanoPrecipitation, to form zinc(II)-bis(dipicolylamine) modified nanoparticles that bind to both Gram-positive and Gram-negative bacteria with specificity. Particles have tunable surface ligand densities that change particle avidity and binding efficacy. A variety of materials can be encapsulated into the core of the particles, such as optical dyes or iron oxide colloids, to produce imageable and magnetically active bacterial targeting constructs. As a proof-of-concept, these particles are used to bind and separate bacteria from solution in a magnetic column. Magnetic manipulation and separation would translate to a platform for pathogen identification or removal. These magnetic and targeted nanoparticles enable new methods to address bacterial infections.
Keywords: Nanoparticle; Targeting; Bacteria; Filtering; Antimicrobial resistance; Magnetic separations

Novel magnesium 1,2,4-triazole-1-carbodithioates were sonochemically synthesized as water-dispersable nanoparticles owing to their water insolubility. The two-step reaction protocol was followed to synthesize the novel triazole ligand system for complexation with magnesium metal due to its low biological toxicity. Different concentrations of Poly Vinyl Pyrrolidine were used to stabilize and standardise the size of nanoparticles, which were characterised by TEM analysis. UV–Visible and infrared spectroscopies were used to analyse the metal ligand interaction, and CHNS analysis was used to propose the structure of the metal complex. The spore germination inhibition technique was used to evaluate the antifungal potential of synthesized nano-complexes against two phytopathogenic test fungi viz. A. alternata and F. moniliforme. The nanoparticles had inflicted moderate in vitro inhibition of fungal growth, which was comparable to standard fungicide Indofil M-45. The in silico toxicity of the compounds was made using the Toxtree analysis software that indicated the compounds belong to class III group of toxicity, which was same as that of commercial standards of DTC.
Keywords: Bioinorganic; Magnesium; Carbodithioate; 1,2,4-Triazole; Nanoparticles; PVP; Antifungal potential

Self-assembled nanotubes from single fluorescent amino acid by Dipak Gorakh Babar; Sabyasachi Sarkar (101-107).
Self-assembly of biomolecules has gained increasing attention as it generates various supramolecular structural assemblies having potential applications principally in biomedical sciences. Here, we show that amino acid like tryptophan or tyrosine readily aggregates as nanotubes via a simple self-assembly process. These were characterized by FTIR, scanning electron microscopy, and by fluorescence microscopy. Nanotubes prepared from tryptophan are having ~200 nm inner diameter and those from tyrosine are having the same around ~50 nm diameter.
Keywords: Self-assembly; Tyrosine; Tryptophan; Nanotubes

In this paper, methyl-orange-doped polystyrene (PS) microspheres covered with gold and silver nanoparticles (NPs) have been synthesized. The optical and structural properties of the porous polystyrene films before and after incorporation of Au and Ag nanoparticles were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), atomic force microscope (AFM), Fourier transformation infrared spectrophotometer (FT-IR), and UV–Vis spectrophotometer. The optical data showed that the optical energy gap of PS film was increased from 2 to 3.4 eV and to 3.5 eV after being filled with Ag and Au nanoparticles, respectively. The electrical and photoresponse properties of Ag–PS/p-Si and Au–PS/p-Si heterojunctions were studied. The rectification characteristics of the junction were improved after nanoparticle incorporation. The photoresponse results confirm the presence of two peaks of response located at 450 and 900 nm. The Au–PS/Si heterojunction gave the best photosensitivity.
Keywords: Polystyrene; Incorporation; Gold nanoparticles; Silver nanoparticles

Synthesis of ammonium and sulfate ion-functionalized titanium dioxide for photocatalytic applications by J. L. Cheng; J. Y. Mi; H. Miao; B. S. A. Sharifah Fatanah; S. F. Wong; B. K. Tay (117-124).
Due to high band gap energy the optimum photocatalytic activities can only be achieved under UV light, thus limiting the practical application of TiO2. In this study, a method combining NH4 +/SO4 2−-functionalization technique and post-treatment was developed and successfully applied to synthesize photoactive TiO2 samples which showed higher photocatalytic activity than the commercial P25 TiO2 under visible light radiation. The results also showed that the addition of (NH4)2SO4 surface functionalization on TiO2 increased the photocatalytic activity, which could be due to the combined effect of crystallinity and band gap energies. Moreover, the results showed that calcination temperature was inversely proportional to photocatalytic activity. The degradation efficiency for methylene blue under visible light was improved by ~2 times from 10.7% for P25 nano Degussa TiO2 to 20.2% for the synthesized sample. The band gap energies were also reduced from 3.7 to 3.4 eV (under UV–Vis direct transition mode) indicating a red shift towards higher wavelength.
Keywords: X-ray diffraction; Nanostructured materials; Ceramics; Powder metallurgy; Grain growth; Grain refinement

In this paper, a novel and easy technique is proposed for orientation controlled growth of MWNTs. The results indicate that when CNT growth was carried over the substrate, not treated with plasma, horizontal network of MWNTs was formed. Plasma treatment to the substrate prior to CNTs growth led to formation of vertically aligned MWNTs. An in situ growth as a function of plasma treatment time reveals the mechanism behind this flip process. All experiments were performed under atmospheric pressure. At every step during time-dependent growth process, CNTs were characterized using FESEM, HRTEM, and Raman spectroscopy. Iron sputtered silicon substrate was also investigated to validate the excellent formation of as-grown vertical CNTs and also to analyze the role of oxygen plasma behind the orientation-controlled growth. The as-grown CNTs over the iron sputtered silicon substrate with or without plasma treatment were characterized by FESEM and AFM. The successful orientation-controlled growth of CNTs was achieved.
Keywords: Vertically aligned MWNTs; Plasma treatment; Growth mechanism

Effects of concentration on CdO films grown by electrodeposition by Ayça Kıyak Yıldırım; Barış Altıokka (131-135).
Thin films of CdO were synthesized by electrodeposition via chronoamperometry. The concentrations of aqueous solutions of Cd(NO3)2 were chosen between 0.005 and 0.08 M. It was thought that the reaction rate would reach saturation at 0.02 M of concentration and it was measured as the concentration increased, the thicknesses of the films increased from the 452 nm to the 798 nm. The well-crystallized film was observed to be at 0.01 M of concentration. It was also found that the band gap increased at low concentrations and surface morphology of the films did not change much with concentration.
Keywords: CdO; Electrodeposition; Concentration; Thin film