Applied Nanoscience (v.5, #6)

Effect of LaCl3 concentration and annealing temperature on the diode ideality factor of LaF3/PS heterojunction has been investigated in this report. LaF3 layers have been deposited by a novel chemical bath deposition (CBD) technique. With this simple technique LaF3 produced as LaCl3 are made to react with hydrofluoric acid on the porous silicon (PS) substrate. This enables direct deposition of LaF3 on the pore walls of the PS leading to a successful passivation of PS. The compositions of the deposited LaF3 were confirmed by energy dispersive of X-ray analysis. The diode ideality factor increases with LaCl3 concentration and decreases with annealing temperature. Therefore, by changing the LaCl3 concentration and annealing temperature quality of the LaF3 layer on PS can be optimized. It was also seen that the Ag/LaF3/PS/Si/Ag structure showed the formation of Schottky diode with a threshold voltage of about 5.5 V. From the experimental results it can be concluded that lanthanum fluorides can be deposited into the pores as well as on the top of PS by the CBD technique, which provides the required passivation for PS. This passivation can enable the PS to be considered as an important material for photonics.
Keywords: Porous silicon; Passivation; Photonics; Chemical bath deposition (CBD); Diode ideality factor

Thermal and rheological properties improvement of drilling fluids using functionalized carbon nanotubes by Babak Fazelabdolabadi; Abbas Ali Khodadadi; Mostafa Sedaghatzadeh (651-659).
The application of functionalized/unfunctionalized (multi-walled) carbon nanotubes (CNT) was investigated in the context of formulating nano-based drilling fluids from water/oil-based fluid templates. CNT functionalization was attempted by applying hydrophilic functional groups onto the surface of the nanotubes via acid treatment. Experimental data were collected for thermal conductivity, viscosity/yield point, and filtrate amount in all samples. The time evolution of thermal conductivity was studied, as well as the effects of temperature and CNTs volume fraction on the parameter. Scanning electron microscopy (SEM) was used to monitor CNTs dispersion quality. The thermal conductivity results unveil considerable enhancements, by as much as 23.2 % (1 % vol. functionalized CNT) in CNT-water-based case at ambient temperature, with extended improvement of 31.8 % at an elevated temperature of 50 °C. Corresponding results for the CNT-oil-based case exhibit an improvement in thermal conductivity by 40.3 % (unfunctionalized) and 43.1 % (functionalized) and 1 % volume fraction of CNT. The rheological results follow an analogous improvement trend. For the CNT-oil-based case, the filtration tests conducted at 138 °C and 500 (psi) show a 16.67 % reduction in filtrate amount (1 % vol. CNT). The time evolution of thermal conductivity was found to nearly equalize (at an amount of 9.7 %) after 100 h of sample preparation in both functionalized and unfunctionalized CNT-oil-based cases.
Keywords: Thermal conductivity; Annular viscosity; API filtration; Scanning electron microscopy (SEM)

Formulation of enrofloxacin SLNs and its pharmacokinetics in emu (Dromaius novaehollandiae) birds by P. Senthil Kumar; A. Arivuchelvan; A. Jagadeeswaran; N. Punniamurthy; P. Selvaraj; P. N. Richard Jagatheesan; P. Mekala (661-671).
The study was conducted to formulate the enrofloxacin solid lipid nanoparticles (SLNs) with sustained release profile and improved pharmacological activity and evaluate the pharmacokinetic behaviour of enrofloxacin SLNs after oral routes of administration in emus. The SLNs were prepared using tripalmitin as lipid carrier, Tween 80 and Span 80 as surfactants and polyvinyl alcohol (PVA) as a stabilizer by a hot homogenization coupled with ultrasonication method. The prepared enrofloxacin SLNs formulations were characterized for further investigation in emu birds. The pharmacokinetics of native enrofloxacin was studied after i.v. and oral bolus administration at 10 mg/kg in emu birds and compared with the disposition kinetics of enrofloxacin SLNs. Enrofloxacin and its metabolite ciprofloxacin in plasma were estimated using HPLC and the pharmacokinetic parameters were calculated by a non-compartmental analysis. The results demonstrated that the particle size, polydispersity index, zeta potential, encapsulation efficiency and loading capacity of the SLNs were 154.72 ± 6.11 nm, 0.42 ± 0.11, −28.83 ± 0.60 mV, 59.66 ± 3.22 and 6.13 ± 0.32 %, respectively. AFM and TEM images showed spherical to circular particles with well-defined periphery. In vitro drug release exhibited biphasic pattern with an initial burst release of 18 % within 2 h followed by sustained release over 96 h. Pharmacokinetic results showed that the t1/2β, AUC0–∞, Vdarea/F, MRT and bioavailability were 3.107, 1.894, 1.594, 2.993 and 1.895 times enhanced (p < 0.01), while CLB and β were significantly (p < 0.01) decreased by 1.958 and 3.056 times compared to the values of native enrofloxacin administered orally. The ratio of AUC0–t cipro/AUC0–t enro after administration of native enrofloxacin and enrofloxacin SLNs was less than 10 %. The t1/2β and MRT of the metabolite were longer than those of the parent substance. The PK/PD results confirmed that the SLNs extended the enrofloxacin concentration upto 48 h against pathogens susceptible to 0.125 μg/mL in emus. The results indicated that SLNs might be a promising delivery system to prolong and enhance the pharmacological activity of enrofloxacin.
Keywords: Enrofloxacin; Pharmacokinetics; SLNs; Tripalmitin; PK/PD integration

The advantages of the hetero-junction CdS/CuAl2O4 for the photocatalytic eosin degradation are reported. Composite semiconductors are elaborated by co-precipitation of CdS on the spinel CuAl2O4 giving a core–shell structure with a uniform dispersion and intimate contact of the spinel nanoparticles inside the hexagonal CdS. The Mott–Schottky plots (C−2V) of both materials show linear behaviors from which flat band potentials are determined. The photoactivity increases with increasing the mass of the sensitizer CdS and the best performance is achieved on CdS/CuAl2O4 (85 %/15 %). The pH has a strong influence on the degradation and the photoactivity peaks at pH 7.78. The dark adsorption eosin is weak (~4 %), hence the change in the eosin concentration is attributed to the photocatalytic process. The degradation follows a zero-order kinetic with a rate constant of 5.2 × 10−8 mol L−1 mn−1 while that of the photolysis is seven times lower (0.75 × 10−8 mol L−1 mn−1).
Keywords: Hetero-junction CdS/CuAl2O4Core–shell; Eosin; Photocatalytic degradation

This study explores double-walled carbon nanotubes as the sensing devices for biological objects including viruses and bacteria. The biological objects studied include alanine with amino terminal residue, deoxyadenosine with free residue, Coronaviridae and Bartonella bacilliformis. An expression has been articulated to identify the mass of biological objects from the shift of frequency. Sensitivity of the sensor has been calculated when subjected to such biological objects. Molecular structural mechanics approach has been used for investigating the vibrational responses of zigzag and armchair double-walled carbon nanotube-based nano biosensors. The elastic properties of beam element are calculated by considering mechanical characteristics of covalent bonds between the carbon atoms in the hexagonal lattice. Spring elements are used to describe the interlayer interactions between the inner and outer tubes caused due to the van der Waals forces. The mass of each beam element is assumed as point mass at nodes coinciding with carbon atoms at inner and outer wall of DWCNT. Based on the sensitivity and the frequency shift it can be concluded that cantilever zigzag DWCNTs are better candidates for detecting the biological objects.
Keywords: DWCNT; Biosensor; Coronaviridae; Bartonella bacilliformis ; Sensitivity

Study on effective thermal conductivity of zinc sulphide/poly(methyl methacrylate) nanocomposites by Sonalika Agarwal; Narendra Sahai Saxena; Vipin Kumar (697-702).
Zinc sulphide/poly(methyl methacrylate) (ZnS/PMMA) nanocomposites with different (0, 2, 4, 6 and 8) wt% of ZnS nanoparticles have been prepared by solution casting method. The obtained ZnS/PMMA nanocomposites have been characterized through X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. Transient plane source (TPS) technique was used to determine the effective thermal conductivity of ZnS/PMMA nanocomposites over the temperature range from room (30° C) to 120° C. The results indicated that the effective thermal conductivity shows increasing behavior up to glass transition temperature beyond which, it becomes constant due to the straightening of chains and vacant site scattering of phonons, respectively. It is also observed that effective thermal conductivity of ZnS/PMMA nanocomposites increases with the increase of concentration of ZnS nanoparticles up to 6 wt% and decreases at 8 wt%. This increase and decrease of thermal conductivity of these nanocomposites are explained on the basis of their structure.
Keywords: Poly(methyl methacrylate); Polymer nanocomposites; Thermal conductivity

In the present study, we report the aqueous extract of Pithophora oedogonia to produce silver nanoparticles (AgNPs) by reduction of silver nitrate. It was noted that synthesis process was considerably rapid and silver nanoparticles were generated within few minutes of silver ions coming in contact with the algal extract. A peak at 445 nm corresponding to the plasmon absorbance of AgNPs was noted in the UV–vis spectrum of the aqueous medium that contained silver ions. Scanning electron microscopic (SEM) and dynamic light scattering analysis of colloidal AgNPs indicated the size of 34.03 nm. Energy-dispersive X-ray spectroscopy revealed strong signals in the silver region and confirmed of the AgNPs. Fourier transform infrared spectroscopic analysis of the nanoparticles indicated the presence of protein which was regarding a capping agent surrounding the AgNPs. Moreover, the antibacterial activity of synthesized nanoparticles exhibited potential inhibitory activity against seven tested pathogenic bacteria.
Keywords: Green synthesis; Silver nanoparticles; Pithophora oedogonia ; Antibacterial activity

Role of mode of heating on the synthesis of nanocrystalline zinc ferrite by Prashant R. Chaudhari; V. M. Gaikwad; S. A. Acharya (711-717).
In the present work, microwave-assisted coprecipitation route was used for synthesis of nanocrystalline zinc ferrite and results were compared with conventionally prepared zinc ferrite. Synthesis conditions were kept uniform in both cases, except that the mode of heating was changed. The effects of mode of heating on the material properties were studied systematically. Microstructures of both samples were studied by scanning electron microscopy and transmission electron microscopy and the particle size was found to be in the range of 3–4 nm. Particle size distribution in microwave-processed MS-ZnFe2O4 is found to be highly uniform compared to conventionally processed samples (CS-ZnFe2O4). XRD data confirmed the presence of single-phase face-centered cubic structure for both the samples. The XRD data fitted well with Reitveld refinement. The functional groups were analyzed by FT-IR. Local distortions in the structures were studied by FT-Raman spectra of zinc ferrites at room temperature. This study concludes that the microwave-assisted synthesis route reduced the time of reaction by around 23 h and developed uniformly distributed fine-scaled particles. This method has high potential to synthesize other ferrite materials also.
Keywords: Nanocrystalline zinc ferrite; Coprecipitation route; Microwave- and conventional-processing techniques; Raman spectra

Photodegradation of odorous 2-mercaptobenzoxazole through zinc oxide/hydroxyapatite nanocomposite by F. Buazar; S. Alipouryan; F. Kroushawi; S. A. Hossieni (719-729).
In this study, ZnO/HAP nanocomposite with excellent photocatalytic activities was successfully synthesized by sol–gel method and used for degradation of 2-mercaptobenzoxazole (MBO) as model of odorous mercaptan compound in water. To optimize the performance of ZnO/HAP photocatalytic capabilities, ZnO/HAP loading (0.05–0.3 g/L), irradiation time (15–180 min), pH (3–11) and initial concentration of MBO (10–100 ppm) were investigated. At neutral pH of 7, the highest amount of the MBO (99.45 %) was degraded by ZnO/HAP nanocomposite through photocatalytic oxidation process within 2 h of irradiation time. A maximum adsorption capacity of 197.64 mg g−1 was obtained for ZnO/HAP under optimized conditions. BET results indicated that ZnO/HAP had a surface area of 182.36 mg2g−1 which was much greater than pure ZnO nanoparticles (31.2 mg2g−1). TEM image demonstrated a spherical shape structure of ZnO/HAP with average particle size of 25 nm in diameter. The XRD patterns revealed the principal components of ZnO/HAP including HAP and ZnO. FTIR spectrum results supported formation ZnO and HAP by their stretching mode in composite. Comparison of photocatalytic activity of ZnO/HAP with pure ZnO and HAP nanoparticles had clearly recognized that latter is the most active photocatalyst in the degradation of MBO using UV light as source energy. The reason for greater activity of ZnO/HAP was due to its larger specific surface area (182.36 m2g−1) and high generation of active $${ ext{HO}}^{cdot}$$ HO · and $${ ext{O}}_{2}^{- 2 cdot}$$ O 2 - 2 · species.
Keywords: Nanocomposite; 2-Mercaptobenzoxazole; ZnO/HAP; Photodegradation

Ultra-rapid photocatalytic activity of Azadirachta indica engineered colloidal titanium dioxide nanoparticles by Renu Sankar; Kadarmohideen Rizwana; Kanchi Subramanian Shivashangari; Vilwanathan Ravikumar (731-736).
Titanium dioxide nanoparticles were effectively synthesized from aqueous leaf extract of Azadirachta indica under pH and temperature-dependent condition. 5 mM titanium isopropoxide solution worked as a primary source for the synthesis of titanium dioxide nanoparticles. The green synthesized titanium dioxide nanoparticles were confirmed by UV–Vis spectroscopy. Fourier transform infrared spectrum of synthesized titanium dioxide nanoparticles authorized the presence of bioactive compounds in the leaf extract, which may play a role as capping and reducing agent. The high-resolution scanning electron microscopy and dynamic light scattering analyses results showed the interconnected spherical in shape titanium dioxide nanoparticles having a mean particle size of 124 nm and a zeta potential of −24 mV. Besides, the colloidal titanium dioxide nanoparticles energetically degrade the industrially harmful methyl red dye under bright sunlight.
Keywords: Green synthesis; Azadirachta indica ; Titanium dioxide nanoparticles; FT-IR; Photocatalytic activity

Synthesis of nanosized ZSM-5 zeolite using extracted silica from rice husk without adding any alumina source by Zahra Ghasemi Laleh Vajheh Sari; Habibollah Younesi; Hossein Kazemian (737-745).
The synthesis of analcime and nanosized ZSM-5 zeolites was carried out by a hydrothermal method with silica extracted from rice husk, available as an inexpensive local biowaste, and without the use of an extra alumina source. Amorphous silica (with 88 wt% of SiO2) was extracted from rice husk ash by a suitable alkali solution. The effects of crystallization temperature, time and SiO2/Al2O3 ratio of the initial system on the properties of final products were investigated. For the characterization of the synthesized product, X-ray diffraction, scanning electron microscope, energy dispersive X-ray techniques, Fourier transform infrared and Brunauer-Emmett-Teller method were applied. Crystallinity percentages of analcime and nanosized ZSM-5 were 95.86 and 89.56, respectively, with specific surface area of 353.5 m2 g−1 for ZSM-5. The experimental results revealed that the synthesis of analcime and nanosized ZSM-5 zeolites was more practical with using silica extracted from inexpensive raw materials, while the whole crystallization process was accomplished without adding any alumina source during.
Keywords: Rice husk; Hydrothermal; Analcime; Nanosized ZSM-5

Ascorbic acid-functionalized Ag NPs as a probe for colorimetric sensing of glutathione by Stephanie L. D’souza; Ranjan Pati; Suresh Kumar Kailasa (747-753).
In this work, we report the use of ascorbic acid-capped silver nanoparticles (AA–Ag NPs) as a probe for selective colorimetric detection of glutathione (GSH) in aqueous solution. This detection system was based on the GSH-induced aggregation of AA–Ag NPs, resulting in drastic changes in the absorption spectra and color of the AA–Ag NPs system. The GSH-induced AA–Ag NPs aggregation was confirmed by UV–visible spectrometry, dynamic light scattering (DLS) and transmission electron microscopic (TEM) techniques. Under optimal conditions, this method exhibited good linearity over the concentration ranges from 5.0 to 50 µM, with the limit of detection 2.4 × 10−7 M. This method was successfully applied to detect GSH in the presence of other biomolecules, which confirms that this probe can be used for the detection of GSH in real samples.
Keywords: AA–Ag NPs; GSH; UV–visible spectrometry; DLS and TEM

Synthesis of silver nanoparticles using medicinal Zizyphus xylopyrus bark extract by Babu Sumi Maria; Aishwarya Devadiga; Vidya Shetty Kodialbail; M. B. Saidutta (755-762).
In the present paper, biosynthesis of silver nanoparticles using Zizyphus xylopyrus bark extract is reported. Z. xylopyrus bark extract is efficiently used for the biosynthesis of silver nanoparticles. UV–Visible spectroscopy showed surface plasmon resonance peaks in the range 413–420 nm confirming the formation of silver nanoparticles. Different factors affecting the synthesis of silver nanoparticles like methodology for the preparation of extract, concentration of silver nitrate solution used for biosynthesis and initial pH of the reaction mixture were studied. The extract prepared with 10 mM AgNO3 solution by reflux extraction method at optimum initial pH of 11, resulted in higher conversion of silver ions to silver nanoparticles as compared with those prepared by open heating or ultrasonication. SEM analysis showed that the biosynthesized nanoparticles are spherical in nature and ranged from 60 to 70 nm in size. EDX suggested that the silver nanoparticles must be capped by the organic components present in the plant extract. This simple process for the biosynthesis of silver nanoparticles using aqueous extract of Z. xylopyrus is a green technology without the usage of hazardous and toxic solvents and chemicals and hence is environment friendly. The process has several advantages with reference to cost, compatibility for its application in medical and drug delivery, as well as for large-scale commercial production.
Keywords: Silver nanoparticles; Surface plasmon resonance; Biosynthesis; Zizyphus xylopyrus ; pH conditions; Reflux extraction

There is need for devices that decrease detection time of food-borne pathogens from days to real-time. In this study, a rapid-detection device is being developed and assessed for potential cytotoxicity. The device is comprised of melt-spun polypropylene coupons coated via oxidative chemical vapor deposition (oCVD) with 3,4-Ethylenedioxythiophene (EDOT), for conductivity and 3-Thiopheneethanol (3TE), allowing antibody attachment. The Ames test and comet assay have been used in this study to examine the toxicity potentials of EDOT, 3TE, and polymerized EDOT-co-3TE. For this study, Salmonella typhimurium strain TA1535 was used to assess the mutagenic potential of EDOT, 3TE and the copolymer. The average mutagenic potential of EDOT, 3TE and copolymer was calculated to be 0.86, 0.56, and 0.92, respectively. For mutagenic potential, on a scale from 0 to 1, close to 1 indicates low potential for toxicity, whereas a value of 0 indicates a high potential for toxicity. The comet assay is a single-cell gel electrophoresis technique that is widely used for this purpose. This assay measures toxicity based on the area or intensity of the comet-like shape that DNA fragments produce when DNA damage has occurred. Three cell lines were assessed; FRhK-4, BHK-21, and Vero cells. After averaging the results of all three strains, the tail intensity of the copolymer was 8.8 % and tail moment was 3.0, and is most similar to the untreated control, with average tail intensity of 5.7 % and tail moment of 1.7. The assays conducted in this study provide evidence that the copolymer is non-toxic to humans.
Keywords: Biosensor; Cytotoxicity; oCVD; P(EDOT-co-3TE)