Ranjit A. Patil

Efficient electrochromic performance of nanoparticulate WO3 thin films

This report highlights the suitability of electrodeposited nanoparticulate-WO3 (NP-WO3) electrodes for transmissive electrochromic devices (ECDs). The WO3 electrodes in the form of thin films are composed of 10–20 nm nanoparticles. An electrochromic (EC) device of dimensions 5 × 4 cm2 fabricated using NP-WO3 showed an Li insertion coefficient (x) of 0.43, which resulted in highest photopic transmittance modulation (88.51%), better Li-ion diffusion coefficient (∼3.16 × 10−9 cm2 s−1), fast electrochromic response time (5.2 s for coloration and 3.7 for bleaching) and excellent coloration efficiency (∼137 cm2 C−1). On reduction of WO3, the CIELAB 1931 2° color space coordinates show the transition from colorless to the deep blue state (Y = 97, a* = −1.93, b* = 0.46 and Y = 10, a* = 1.57, b* = −41.01) with steady decrease in relative luminance.

Photoluminescence mechanisms of metallic Zn nanospheres, semiconducting ZnO nanoballoons, and metal-semiconductor Zn/ZnO nanospheres

We utilized a thermal radiation method to synthesize semiconducting hollow ZnO nanoballoons and metal-semiconductor concentric solid Zn/ZnO nanospheres from metallic solid Zn nanospheres. The chemical properties, crystalline structures, and photoluminescence mechanisms for the metallic solid Zn nanospheres, semiconducting hollow ZnO nanoballoons, and metal-semiconductor concentric solid Zn/ZnO nanospheres are presented. The PL emissions of the metallic Zn solid nanospheres are mainly dependent on the electron transitions between the Fermi level (EF) and the 3d band, while those of the semiconducting hollow ZnO nanoballoons are ascribed to the near band edge (NBE) and deep level electron transitions. The PL emissions of the metal-semiconductor concentric solid Zn/ZnO nanospheres are attributed to the electron transitions across the metal-semiconductor junction, from the EF to the valence and 3d bands, and from the interface states to the valence band. All three nanostructures are excellent room-temperature light emitters.

Photoelectrochemical cell studies of Fe2+ doped ZnSe nanorods using the potentiostatic mode of electrodeposition

The Fe(2+) doped ZnSe nanorods are synthesized using simple potentiostatic mode of electrodeposition on the ITO substrate. In order to study the doping effect of Fe(2+) in ZnSe, varied the doing percent such as 0.5%, 1%, 1.5%. These films are characterized for structural, compositional, morphological, optical and electrochemical properties using the X-ray diffraction study (XRD), X-ray photoelectron spectroscopy, field emission scanning electron microscopy, UV-vis spectroscopy and electrochemical spectroscopy. Along with these Raman spectroscopy and photoluminescence spectroscopy have been studied for understanding the characteristics vibrations of ZnSe and luminescence of ZnSe nanorods. FE-SEM shows the nanorods like morphology. Photoelectrochemical cell performance studied using the J-V measurement and it shows the maximum efficiency at 1% Fe(2+) doped ZnSe nanorods. The observed maximum efficiency of Fe(2+) doped ZnSe nanorods is 0.32%.

Impact of Nanosize on Supercapacitance: Study of 1D Nanorods and 2D Thin-Films of Nickel Oxide

We synthesized unique one-dimensional (1D) nanorods and two-dimensional (2D) thin-films of NiO on indium-tin-oxide thin-films using a hot-filament metal-oxide vapor deposition technique. The 1D nanorods have an average width and length of ∼100 and ∼500 nm, respectively, and the densely packed 2D thin-films have an average thickness of ∼500 nm. The 1D nanorods perform as parallel units for charge storing. However, the 2D thin-films act as one single unit for charge storing. The 2D thin-films possess a high specific capacitance of ∼746 F/g compared to 1D nanorods (∼230 F/g) using galvanostatic charge-discharge measurements at a current density of 3 A/g. Because the 1D NiO nanorods provide more plentiful surface areas than those of the 2D thin-films, they are fully active at the first few cycles. However, the capacitance retention of the 1D nanorods decays faster than that of the 2D thin-films. Also, the 1D NiO nanorods suffer from instability due to the fast electrochemical dissolution and high nanocontact resistance. Electrochemical impedance spectroscopy verifies that the low dimensionality of the 1D NiO nanorods induces the unavoidable effects that lead them to have poor supercapacitive performances. On the other hand, the slow electrochemical dissolution and small contact resistance in the 2D NiO thin-films favor to achieve high specific capacitance and great stability.

An efficient methodology for measurement of the average electrical properties of single one-dimensional NiO nanorods

We utilized a metal tantalum (Ta) ball-probe to measure the electrical properties of vertical-aligned one-dimensional (1D) nickel-oxide (NiO) nanorods. The 1D NiO nanorods (on average, ~105 nm wide and ~700 nm long) are synthesized using the hot-filament metal-oxide vapor deposition (HFMOVD) technique, and they are cubic phased and have a wide bandgap of 3.68 eV. When the 1D NiO nanorods are arranged in a large-area array in ohmic-contact with the Ta ball-probe, they acted as many parallel resistors. By means of a rigorous calculation, we can easily acquire the average resistance RNR and resistivity ρNR of a single NiO nanorod, which were approximately 3.1 × 1013 Ω and 4.9 × 107 Ω.cm, respectively.

Large-area nanoscale farmland-like surfaces of one-dimensional NbO2 nanorods with multi-growth directions: studies on the purple-blue photoluminescence and low-field electron emissions

We synthesized a scenic morphological form of a large-area NbO2 nanoscale farmland using the hot-filament metal-oxide vapor deposition technique (HFMOVD). The nanoscale farmland is comprised of one-dimensional (1D) NbO2 nanorods arranged in various domains, which grow in multi-directions. Each domain contains ∼620 nanorods per square micrometer and has its own growth direction. The 1D NbO2 nanorods are found to have purple-blue photoluminescence (PL) emissions at room-temperature as well as very low turn-on and threshold fields for field emission (FE). The PL and FE results indicate that the 1D NbO2 nanorods are brilliant light and electron emitters.

Highly stable supercapacitive performance of one-dimensional (1D) brookite TiO 2 nanoneedles

We report the highly stable supercapacitive performance of one-dimensional (1D) nanoneedles of brookite (β) TiO2 synthesized on a conducting glass substrate. The 1D β-TiO2 nanoneedles synthesized over a large area array utilizing hot-filament metal vapor deposition (HFMVD) were ∼24–26 nm wide, ∼650 nm long and tapered in a downward direction. X-ray photoemission spectroscopy (XPS) revealed their chemical properties and stoichiometric Ti and O composition. The 1D β-TiO2 nanoneedles execute as parallel units for charge storage, yielding a specific capacitance of 34.1 mF g−1. Electrochemical impedance spectroscopy revealed that the large surface area and brookite crystalline nature of the 1D nanoneedles provided easy access to Na+ ions, and resulted in low diffusion resistance, playing a key role in their stable charging–discharging electrochemical mechanism. Moreover, the non-faradic mechanism of these nanoneedles delivered better durability and high stability up to 10 000 cycles, and a columbic efficiency of 98%. Therefore, 1D β-TiO2 nanoneedles hold potential as an electrode material for highly stable supercapacitive performance with long cycle lifetime.

Promising field electron emission performance of vertically aligned one dimensional (1D) brookite (β) TiO2 nanorods

We evidence field-electron emission (FE) studies on the large-area array of one-dimensional (1D) brookite (β) TiO2 nanorods. The pure 1D β-TiO2 nanorods of 10 nm width and 760 nm long were synthesized on Si substrate utilizing hot-filament metal vapor deposition technique. X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis evidenced the β-TiO2 nanorods to be composed of orthorhombic crystals in brookite (β) phase. X-ray photoemission spectroscopy (XPS) revealed the formation of pure stoichiometric (i.e. 1 : 1.98) 1D TiO2 nanorods. The values of turn-on field, required to draw current density of 10 μA cm−2, was observed 3.9 V μm−1 for pristine 1D β-TiO2 nanorods emitters, which were found significantly lower than doped/undoped 1D TiO2 nanostructures (i.e. nanotubes, nanowires, nanorods) based field emitters. The enhanced FE behavior of the TiO2/Si emitter can be attributed to modulation of electronic properties due to the high aspect ratio of vertically aligned TiO2 nanorods. Furthermore, the orthodox emission situation of pristine TiO2/Si emitters exhibit good emission stability and reveal their potentials as promising FE material.

Preparation, characterization and catalytic application of nano-Fe3O4-DOPA-SnO2 having high TON and TOF for non-toxic and sustainable synthesis of dihydroquinazolinone derivatives

A novel class of heterogeneous magnetically separable nano catalysts was designed by encapsulating SnO2 on nano-Fe3O4-DOPA. After the successful characterization of the synthesized catalyst by FT-IR, SEM, TEM, EDX, TGA, powder XRD, XPS, VSM and ICP-AES, it was employed in the greener synthesis of dihydroquinazolinone derivatives using water as a solvent. Nano-Fe3O4-DOPA-SnO2 was found to have high TON and TOF and showed high catalytic activity which is validated by good to excellent yields of the desired products. The application of the present protocol was also carried out for the synthesis of bis-dihydroquinazolinone compounds which leads to the formation of six new C–N bonds, two new C–C bonds, two new stereocentres and two new dihydroquinazolinone moieties in one step within a shorter period of time. Easy separation and reusability of the catalyst (five times), substrate variation, selectivity of desired products, shorter reaction time, greener reaction medium (water), column chromatography free separation, gram scale reaction and easy workup procedures rendered this procedure environmentally friendly and sustainable. Furthermore, biologically important quinazolinones were synthesized from dihydroquinazolinone derivatives by a simple oxidation technique.

Impact of cuticle photoluminescence on the color morphism of a male damselfly Ischnura senegalensis (Rambur, 1842)

In this study the damselfly Ischnura senegalensis (Rambur, 1842) was first found to produce strong photoluminescence (PL) emissions from various colored-body portions, such as the eighth abdominal segment of the tail. The colors of the colored-body portions can be enhanced or modified by the PL emissions for assistance in reducing intrasexual and male harassment, and improving mature mating and conspecific identity. Therefore, the PL emissions that contribute to the color modification and coloration are involved in the cuticle evolution of the damselflies. The micro-PL confocal images verify that the PL emissions can strongly influence the surface colors of the cuticle, and demonstrate why the damselfly Ischnura senegalensis is called a bluetail.