JOURNAL OF NANOSTRUCTURE IN CHEMISTRY
Year:2013 | Volume:3 | Issue:3|Papers Count:18

The influence of the incorporation of nitric acid-treated (functionalized) multi-walled carbon nanotubes (f-MWCNTs) and unmodified MWCNTs in TiO2 films are investigated by observing the photocurrent-voltage characteristics of dye-sensitized solar cells (DSSCs) with and without MWCNTs. The short-circuit photocurrent (Jsc) of the modified DSSC increased by 46% compared with that of a cell with plain TiO2 film. The open-circuit voltage remained the same for all cases. The enhanced Jsc is explained by the increased surface area of the film, enhanced cluster formation of TiO2 particles around f-MWCNTs, and improved interconnectivity of TiO2 particles in the presence of f-MWCNTs. The efficiency of the cell increased by 45% due to Jsc enhancement.

The morphology of porous silicon (p-Si) depends on several parameters such as the doping type and the carriers’ concentration of the crystalline silicon substrate. The electrolytes used in the p- Si fabrication also have an important role. The final structure determines if p-Si is luminescent or suitable for photonic applications. Experimental results on p-Si produced by electrochemical etching show that although the carriers are greatly reduced by the etching process, boron atoms remain in the bulk. The study of p-type porous silicon nanostructures by means of anab initio computational simulation might help to understand how boron atoms influence the p-Si final structure. Here, we report electronic and topological properties of ten p-type porous silicon structures as an extension of our previous paper on p-type crystalline silicon. Our results suggest that the boron atoms can not remain bonded on the porous surface but do so in the bulk. The presence of impurities changes the bond distance of their neighbors within a radius of 5 Ao. The energy of the models is essentially the same for all the boron positions in the silicon backbone. The high electronic density around the boron impurity could influence the trajectory of an HF ion entering a p-Si pore during the fabrication process.

This finding focuses on the optimization of synthesis time for the transformation of Fe-filled spherical-like graphene shell (GS) to almost catalyst-free carbon nanotube (CNT) structure using two-stage catalytic chemical vapor deposition apparatus. The camphor oil and ferrocene were used as carbon precursor and catalyst respectively, following the variety growth of graphene-family nanomaterials for 2, 4, 6, 8, 10, 30, and 60 min at 800oC synthesis temperature. The graphene-family nanomaterial properties were characterized using field emission scanning electron microscope, high resolution transmission electron microscope, micro-Raman spectrometer, thermogravimetric, and carbon-hydrogen-nitrogen-sulfur/oxygen (CHNS/O) analyzer. The result of field emission scanning electron microscopy analysis reveals that the CNTs were observed with high aspect ratio at 60-min synthesis time. The dependence of integrated intensity ratio of D-band and G-band (ID/IG) presented that ID/IG ratio sharply decreases with longer synthesis time. At higher synthesis time, thermogravimetric and CHNS/O analysis of CNT can obviously improve with decreases of non-carbonaceous material and transition metal catalyst. The nucleation-growth model of Fe-filled spherical-like GS to almost catalyst-free CNT has been highlighted to explain the change in growth mode.

At the present time, usage of nanotubes in medicinal science and biology is further studied. Nanotubes can pass through cell walls, transfer, and liberate drugs in particular tissues. The goal of this article is to survey the interaction of a nanotube with an anticancer drug. In this study, transferring of an anticancer drug called cytarabine with zigzag (5, 0) carbon nanotube is studied. All computations are surveyed by quantum mechanics and molecular mechanics (MM) /Monte Carlo simulation (in various force fields such as MM+, assisted model building with energy refinement, and optimized potential for liquid simulations) in various temperatures, and their results are achieved in gas phase, water solvent, and methanol solvent, respectively.

Nowadays, nanotubes are used widely as container agents to transport bioactive peptides, proteins, nucleic acids, and drugs, and used to deliver their cargos to cells and organs in human bodies. In this work, the possibility of the formation of stable composite between carbon nanotubes and skin anti-cancer drugs has been investigated. The nanotube used in this study includes 60 C atoms of (6, 6) type. Density functional theory-based methods (B3LYP/6- 31G) show that the composites between drugs (aminolevulinic acid and tretinoin) and nanotube are more stable than the single agents. The difference in the hybridization of C and O atoms can cause to a difference between bond lengths, angles, and charges. The natural bond orbital calculations indicate that some donor atoms (lone pair of oxygen or nitrogen atoms) can transfer electron to acceptor atoms (s* or p* in carbon nanotube) and the occupancy of the oxygen lone pair with increasingp orbital share of the lone pair electrons of oxygen decreases. Then, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), the HOMO-LUMO bandgap, and the electronic chemical potential (m) for the lowest energy derived to estimate the structural stability of the composites have been investigated. Results show that nanotube-tretinoin is more stable than nanotube - aminolevulinic acid.

The essence of modern nanotechnology is manifested in the formation of well-ordered nanostructures by a process of self-association. Peptides are among the most useful building blocks for organic bionanostructures such as nanotubes, nanospheres, nanotapes, nanofibrils, and other different ordered structures at the nanoscale. Peptides are biocompatible, chemically diverse, and much more stable and can be readily synthesized on a large scale. Also, they have diverse application in biosensors, tissue engineering, drug delivery, etc. Here, we report a short cystine-based dipeptide, which spontaneously self-associates to form straight, unbranched nanotubes. Such self-assembled nanobiomaterials provide a novel possibility of designing new functional biomaterials with potential applications in nanobiotechnology. The formation of nanotubes in solution state has been demonstrated by atomic force microscopy and scanning electron microscopy. Infrared absorption and circular dichroism demonstrated the intermolecular b-sheet-like backbone hydrogen bonding in juxtaposing and stacking of aromatic side chains.

Some undesired nanoparticles, such as malformed structures or incomplete core/shell Fe3O4-Au nanocomposites, might be formed when Fe3O4-Au core/shell nanocomposites are being synthesized. These impurities should be separated before any applications are performed. In this investigation, magnetic cores (Fe3O4) were synthesized using a conventional fabrication method involving coprecipitation of Fe2+and Fe3+. Carboxyl-capped magnetite-gold composite nanoparticles, measuring£50 nm, were then synthesized using a plant extract (Eucalyptus camaldulensis). The prepared carboxyl-capped magnetite-gold composite nanoparticles were further subjected to acid treatment for 18 h and characterized with different instrumentation methods. The results of the investigation showed that acid treatment can be applied successfully to separate defect-free Fe3O4-Au core/shell nanoparticles from different types of Fe3O4-Au nanocomposites, without any considerable changes in their physiochemical properties.

Co3O4 nanoparticles were prepared using [Co(NH3)6] (NO3)2 as a starting material via a solid-state thermal decomposition route at low temperature (150oC). The product was characterized by thermal analysis (thermogravimetric/derivative thermogravimetric/differential thermal analysis), X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, Brunauer-Emmett-Teller specific surface area measurement, UV-visible spectroscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy, and magnetic measurements. The results confirmed that the nanoparticles are highly pure Co3O4 with weak ferromagnetic properties. TEM images showed that the Co3O4 nanoparticles have an average diameter size of around 13 nm. The optical spectrum indicated two direct bandgaps at 2.3 and 3.2 eV which are blueshifted relative to reported values for the bulk sample. By this fast and simple method, Co3O4 nanoparticles can be produced without expensive and toxic solvents or complicated equipment.

Myconanotechnology is a study of nanoparticle synthesis using fungi and their application mainly in medicine. Myconanotechnology has great advantage due to wide range and diversity of the fungi. Recently, fungal-mediated synthesis of nanoparticles is a reliable and ecofriendly method. The present work investigates the synthesis of silver nanoparticles using Trichoderma viride which is a non-pathogenic fungus. The cell filtrate of T. viride was used for the reduction of silver nitrate to silver nanoparticles. The pH of the cell filtrate was changed, and the effect of the pH was monitored on the synthesis of the silver nanoparticles. While changing the pH of the medium, the shape and size of the nanoparticles were controlled. The silver nanobowls were synthesized at first time using T. viride. The synthesized silver nanoparticles were characterized using UV spectrophotometer, X-ray diffractometer, Fourier transform infrared spectrophotometer, scanning Electron microscope (SEM), and transmission electron microscope (TEM). The SEM and TEM images showed the shape and size of the nanoparticles, and the synthesized nanoparticles were nanobowl in shape and polydispersed in size. The antibacterial activity of silver nanoparticles was carried out against gram-positive and gram-negative organisms. The maximum zone of inhibition occurred at 50μl, while the concentration of the nanoparticles increased the inhibition activity also increased.

In this work, we report the effect of a capping agent on the structural and optical properties of nanocrystalline ZnS particles, which have been synthesized by co-precipitation method. The structural properties of ZnS nanoparticles have been characterized by X-ray diffraction (XRD) analysis. The XRD patterns show a hexagonal structure in the nanoparticles. The mean crystallite size calculated from the XRD patterns has been found to be in the range of 1.80 to 2.45 nm with the increase in molar concentration of the capping agent. Absorption spectra have been obtained using a UV-vis spectrophotometer to find the optical direct band gap. We also found that optical band gap (Eg) increases with the increase in molar concentration of the capping agent. This behavior is related to size quantization effect due to the small size of the particles.

A preparation method for hollow particles composed of silica shell containing gadolinium compound (GdC) is proposed. GdC nanoparticles with an average size of 40.5±6.2 nm were prepared with a homogeneous precipitation method at 80oC using 1.0´10-3 M Gd (NO3)3 and 0.5 M urea in the presence of 2.0´10-4 M ethylenediaminetetraacetic acid disodium salt dihydrate. Silica-coated GdC (GdC/SiO2) nanoparticles with an average size of 100.9±9.9 nm were fabricated with a sol-gel method at 35°C using 5.0´10-3 M tetraethylorthosilicate, 11 M H2O, and 1.5´10-3 M NaOH in ethanol in the presence of 1.0´10-3 M GdC nanoparticles. The GdC/SiO2 particles were aged at 80°C in water after replacement of solvent of the as-prepared GdC/SiO2 particle colloid solution with water, which provided diffusion of GdC into the silica shell and then formation of a hollow structure. The hollow particle colloid solution revealed good MRI properties. A relaxivity value for longitudinal relaxation time-weighted imaging was as high as 3.38 mM-1· s-1 that attained 80% of that for a commercial Gd complex contrast agent.

This paper presents evidence-based results of clinical trial on the use of nanosized particles in homoeopathic Terminalia arjunatincture. Dynamic light scattering technique demonstrates that homoeopathic tincture is a mixture of particles varying from micron to nanometre sizes. The process of succussion, homogenization and filtration brings down the particles of source material to nanosize as a ‘top-down’ process. As compared to the conventionally used micron-sized T. arjuna powder, the results show significant clinical improvement due to the presence of nanoparticles in tincture by the above method. Similar results were reconfirmed on experiments with bacterial cultures. From clinical trials, it has been confirmed that the dose of medicine required by the patient is significantly reduced with the reduction in particle size. No toxicity was observed even after giving medicine for more than 8 weeks. Size-dependent sensitivity of the drug can help to tackle the problem of drug resistance in bacteria.

Three-dimensional self-assembled rugby-ball-shaped microarchitectures of tetragonal Na0.5La0.5MoO4: Eu3+ crystal structure were synthesized by facile hydrothermal method at 200oC for 8 h using ethylenediaminetetraacetic acid (EDTA) as surfactant. Structure and morphology of Na0.5La0.5MoO4: Eu3+ were investigated by X-ray diffraction and scanning electron microscopy. In the hydrothermal process, EDTA not only acts as a chelating reagent to facilitate the formation of Na0.5La0.5MoO4: Eu3+ but also acts as a surface capping agent to adhere to the newly created surface and to promote crystal splitting. The molar concentration of EDTA plays an important role and can effectively tune the size of the particles. Photoluminescence study reveals that hierarchical structures of Na0.5La0.5MoO4: Eu3+ show a strong emission in the red region under 395-nm UV excitation.

Quantum dot cellular automata (QCA) is a emerging nanotechnology that promises smaller size and lower power consumption, with faster speed compared to the transistor-based technology. In this paper, we have proposed novel 8-into-3 bit simple encoder, 4-into-2 bit priority encoder, scan flip-flop, and pseudo-random bit sequence generator designs in QCA. These circuits are useful components for the design of many logical and functional circuits. Simulation results of the proposed QCA circuits are obtained by using the QCA designer tool. The correctness of the proposed circuits is hence confirmed.

Phytosynthesis process of silver nanoparticles using plant extract is simple, cost-effective, and ecofriendly. In this present investigation, we report the green nanoparticles prepared by using stem extract ofCissus quadrangularis and assess the physical and chemical factors such as time duration, metal ion concentration, pH, and temperature that play vital role in the nanoparticles synthesis. The maximum synthesis of silver nanoparticles was attained within 1 h, at pH 8 and 1 mM AgNO3 concentration, and 70oC. The nanoparticles obtained are characterized by UV–vis spectroscopy. Silver nanoparticles that were synthesized under these conditions show crystalline nature confirmed by X-ray diffraction and show mostly spherical and some rod and triangle shapes with sizes ranging from 37 to 44 nm, which were characterized by scanning electron microscopy. Fourier transform infrared spectroscopy shows that the functional groups are carboxyl, amine, and phenolic compounds of stem extract which are involved in the reduction of silver ions. Thus, synthesized silver nanoparticles show more antibacterial activity againstKlebsiella planticolaand Bacillus subtilis, which was analyzed by disc diffusion method.

Carbon nanotubes (CNTs), due to their superlative mechanical and physical properties, have shown a high potential to improve properties of polymeric composites. Adding CNTs into polymers at very low weight fractions can improve mechanical properties of the resulting nanocomposites. In the present paper, multi-walled carbon nanotubes (MWCNTs) at different weight ratios (0.05, 0.1, and 0.5 wt.%) were added to polyester. Mechanical stirring and sonication technique were used to achieve good dispersion state of MWCNTs in the polymeric matrix. The results of mechanical tests (tensile and flexural) exhibit improvements of tensile and flexural strengths by 6% and 20%, respectively, at only 0.05 wt.% MWCNT. Improvements in Young’s modulus and flexural modulus were also observed. Scanning electron microscopy was employed to determine the dispersion state of nanotubes in the matrix as well as the fracture surface properties.

Nanocomposite of clay-carbon nanotubes (CNTs) is prepared by using carboxyl-modified multiwalled carbon nanotubes and amino-functionalized organophilic montmorillonite (clay). The nanocomposite is characterized by scanning electron microscopy to evaluate the morphology. The findings show uniform dispersion of CNTs.

In the present study, green synthesis of densely dispersed and stable silver nanoparticles (Ag NPs) using myrrh extract as green-reducing and stabilizing agent was investigated. The Ag NPs were synthesized by exposing a mixture of AgNO3 and myrrh extract to UV irradiation for different time intervals. The effects of parameters such as concentration of AgNO3 and reaction time onto the physicochemical characteristics of the developed Ag NPs were studied. Formation of the Ag NPs was noted upon changing the solution color from pale yellow into brown and was confirmed by the appearance of surface plasmon resonance peaks at about 445 nm. The resulting Ag NPs were characterized by UV-vis spectrophotometry, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray diffraction. The developed NPs demonstrated a relatively high antibacterial activity against Bacillus thuringiensisand Pseudomonas aeruginosa bacteria as compared to that of myrrh extract. The antibacterial activity increased with increasing the Ag NP concentration.