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Purpose: Graphene is a wonder material with high potential for application in energy storage supercapacitors owing to its extremely high surface area. Here, a simple and detailed description of calculation of specific surface area of graphene is given in a tutorial like format. From geometric considerations and known values of interatomic distances, it is shown that we can estimate the theoretical surface area of graphene sheets to be ~2630 m2g-1. Using this approach, teachers will be able to educate their students in various fields where surface area is one of the important factors. Approach/Methodology: Calculation of theoretical maximum specific surface area of graphene using the data like area of a regular hexagon, C-C bond length within the layers in graphene and relative average atomic mass of carbon. Findings/Result: From geometric considerations and known value of interatomic distance in graphite, it is possible to show by calculations that the theoretical surface area of graphene sheets is ~ 2630 m2g-1. Originality/Value: It is a useful exercise for understanding the simple principles behind such calculations and to appreciate its usefulness in practical applications. Paper type: Review based Analysis.

We worked on the synthesis of an organic molecule, i.e., 2-(1H-pyrazol-5-yl) aniline by the microwave method via Amino Cinnamaldehyde and hydrated hydrazine in the presence of ethanol solvent and studied its Corrosion inhibition property on Aluminium-2014 alloy in the 1Molar Hydrochloric acid solution at 25⁰C and 35⁰C temperatures. The SEM micrographs are obtained and examined the surface nature of inhibitor-treated and untreated surfaces. It reveals that the 2-(1H-pyrazol-5-yl) aniline treated surface has more tendency of prevention to corrosion than the free Aluminium 2014 alloy. The potentiodynamic values revealed that Aluminium-2014 alloy possessing different concentrations exhibit a higher tendency to prevent corrosion in 1M Hydrochloric acid solution at 25⁰C and 35⁰C temperatures. We studied Tafel polarization and electrochemical impedance at different concentrations at 25⁰C and 35⁰C. The rate of adsorption increases with the inhibitor concentrations.

A thin layer of platinum coating (0.5 µgcm−2) on stainless steel surface was deposited by direct current (DC) and pulse current (PC) electrodeposition method for hydrogen evolution reaction (HER) application. Scanning electron microscopy, atomic force microscopy, and X-ray diffraction analysis were used to characterize the coatings. Linear sweep voltammetry and cyclic voltammetry studies were carried out to know the overpotential values for hydrogen evolution reaction (HER) on these coatings. The optimization of catalytic activity for hydrogen evolution using different coating methods helps in reducing the overall cost. Tafel polarization experiments were conducted for DC and PC platinum coating to know hydrogen generation trend. Cathodic slope and HER current values revealed that, coatings obtained at 75% duty cycle by PC method exhibit lower cathodic slope, high current density of 150 mA/cm2 and more corrosion current with highest hydrogen evolution. Chronopotentiometry experiments showed that 20 ml of hydrogen was collected from 75% sample.

We report the synthesis, characterization and effect of infusion of aluminium plasmons (Al3+) into titania/zinc oxide (TiO2/Al@ZnO or TAZ) nanocomposite photoanode on the efficiency of novel plasmonic Dye-Sensitized Solar Cells (DSSCs). On comparison with bare titania/zinc oxide (TiO2/ZnO or TZ) nanocomposite, plasmonic TAZ exhibits a negligible change in crystallographic and morphological properties, whereas the photoconduction and light harvesting capability are significantly enhanced. Prompted by surface plasmon modes, TAZ exhibits strong emissions in the blue-yellow region of visible spectrum, as observed with photoluminescence (PL) study. Owing to plasmon-induced PL, light enhancement takes place within the photoanode. Therefore, photoconductivity of TAZ is observed to be 4 folds higher than that of TZ. The narrowing of bandgap upon Al3+ infusion is confirmed by Kubelka-Munk plot and cyclic voltammetry. Specifically, we also focused on the architecture of novel DSSCs with silver counter electrode via a facile preparation method for the first time. Blending the advantages of nanocomposite, surface plasmon resonance and bandgap narrowing, the multifaceted TAZ features with short-circuit current density JSC ~ 33 mA cm−2, open-circuit voltage VOC ~ 0.41 V, Fill-factor FF ~ 0.81 and a remarkable efficiency of 11.4%, which opens up the opportunity to optimize and design a new class of next generation plasmonic DSSCs.

This article summarises the design of one dimensional Titanium dioxide (TiO2) nanorod array and its compatibility as Electron Transport Medium (ETM) for Solar Cell Application. The approach followed for the growth of the one-dimensional nanostructures was template-free, one-step hydrothermal synthesis which is convenient for commercialization. A series of microscopic characterisation such as XRD, SEM and EDAX were carried out to analyse the structure and morphology of the prepared TiO2 array. The optical properties were determined using UV-DRS analysis. Field dependent dark and photoconductivity studies showed positive response confirming the effective photo conducting nature of the as-prepared samples. As a result, all these features validate the usage of one dimensional titanium dioxide array as efficient ETM in the fabrication of Solid State solar cells.

Little millet ( Panicum sumatrense Roth ex Roem. and Schult.) is one of the hardiest minor cereal crop indigenous to Indian sub-continent. The crop is cultivated by tribal and poor farmers for food and feed. Leaf blight disease has been a major production constraint and fungicidal sprays for the management of the disease may not be economically viable and feasible. Hence, the present in vitro study was carried out to know the antifungal activity of six fungal and 10 bacterial bio-agents against Alternaria alternata inciting little millet leaf blight disease. Among the fungal bio-agents, Trichoderma harzianum (ThB5) and among the bacterial bio-agents, Bacillus velezensis (P42) showed mycelial growth inhibition of 75.18 and 84.75%, respectively.

In the present study, corrosion behavior of mild steel in the presence of 4-chloro,8-(trifluoromethyl)quinoline (CTQ) was experimentally investigated. Investigator conducted the experiments using electrochemical methods such as polarization and electrochemical impedance techniques at 303–333 K. The obtained results suggested that CTQ is a good corrosion inhibitor for mild steel in 1 M hydrochloric acid medium. The CTQ adsorbed over metal surface obeys Langmuir adsorption isotherm. The thermodynamic parameters such as −∆Gads0 , −∆Hads0 , −∆Sads0 were measured. The relationship between temperature and corrosion rate was explained by activation parameters.

To develop the durability and the reversibility of SnO2-based anodic materials for lithium-ion batteries, a binary composite of SnO2–CuO nanoparticles is obtained by effective ultrasonication method. Well-dispersed and high surface area particles are obtained by ultrasonication method. SnO2–CuO nanocomposite is also analysed for nitrite sensing and photocatalytic dye degradation applications. Synthesised composite is well characterised for the confirmation of elemental presence, crystallinity, surface area, topography and elemental composition. SnO2–CuO anode exhibits high initial discharge capacity of 1365 mA h g−1 and maintains 252 mA h g−1 at 100th cycle for C/10 rate. Stability of multistep electrochemical reversible reactions is confirmed by CV curves during the lithiation/de-lithiation process and also it retains 90 mA h g−1 capacity at higher 2C rate. This study is the first one to report that SnO2–CuO modified glassy carbon electrode for the sensing of 1 mM nitrite. It has proved the sensing activity with a detection limit of 0.82 μM. SnO2–CuO nanocomposite is also capable to degrade 86% of Methylene blue (MB) dye in 150 min under UV light interactions. Enhancement in the results attributed the synergistic effects of well-dispersed and nanoscaled composite particles.

Pure nickel (Ni) coating and nickel – vanadium pentoxide (Ni-V2O5) nanocomposite coatings have been developed on mild steel substrates by direct current (DC) & pulse current (PC) methods of electrodeposition using sulfamate electrolyte bath by optimizing all the suitable parameters. The surface morphology and texture characterization of pure Ni coating and Ni-V2O5nanocomposite coatings were analyzed by spectroscopic techniques such as Scanning Electron Microscopy (SEM) equipped with an attachment for Energy Dispersive Spectrometry (EDS) & X-ray Diffraction (XRD) spectroscopy analysis. The SEM study confirmed surface morphology of the pure Ni coating was changed by the incorporation of V2O5 nanoparticles in the nickel metal matrix and chemical composition of all the coatings was determined by EDS. XRD study proved highly corrosion resistant nanocomposites show preferred orientation towards (111) plane. The corrosion rate of all the coatings was investigated in 3.5% corrosive medium using electrochemical techniques such as Tafel extrapolation and AC impedance. The coatings developed by PC show enhanced corrosion resistance behavior compare to coatings developed by DC. The 0.125g/L Ni-V2O5nanocomposite coating obtained by PC show more widened semicircle with high Rp value and has more positive shift with high corrosion resistance during AC impedance and Tafel extrapolation analysis respectively. The coatings developed by PC showed improved micro hardness compare to coatings developed by DC during micro hardness testing of all the coatings.

Bright Zn–Ni coatings were developed by using thiamine hydrochloride as a brightener. Hull cell was used for the optimization of bath constituents and parameters. Galvanostatic electrodeposition from zinc sulfate and nickel sulfate with additives results in Zn-rich solid solution of nickel in zinc η-phase. Surface morphology was observed by scanning electron microscopy, chemical and phase composition determined by X-ray diffraction, and corrosion investigations by electrochemical techniques. Coatings obtained at 5 Adm−2 exhibited more corrosion resistance.

The present investigation deals with the electrofabrication of nanostructured Ni-Fe alloy coatings on a mild steel using sulfate bath. The electrolytic bath composition and the current density of the coatings were optimized. Composition analysis by energy dispersive X-ray spectroscopy revealed that the Ni–Fe alloy coatings are of anomalous type. Potentiodynamic polarization corrosion test and electrochemical impedance spectroscopy methods in 3.5% NaCl solution direct towards the lowest corrosion rate at 4 A dm–2. Hardness and roughness of the coatings were evaluated using Vickers hardness test and atomic force microscopy, respectively. The surface morphological analysis of the coatings was characterized by scanning electron microscopy with energy dispersive X-ray spectroscopy. The phase structure, the texture coefficient, and the crystallite grain size of the coatings were calculated and studied using X-ray diffraction.

Intergranular stress corrosion cracking (IGSCC) is common in boiling water reactor (BWR) components. Corrosion problem is a serious matter that has overwhelmed the light water reactor (LWR) industry for many years. The conditions in which IGSCC takes pace due to stress, a sharpen microstructure and an environment that will facilitate the cracking while injecting H2 into the feed water system. Nuclear reactor made up of stainless steel facing serious Intergranular stress corrosion cracking due to the injection of hydrogen dosage into the nuclear reactor in the form of heavy water chemistry. Moderately large concentrations of H2 may be essential in nuclear power plants to bring the ECP below the critical value of –230 mV (SHE) to ease Intergranular stress corrosion cracking, which in turn results in an increase of steam line dose rate and shutdown dose rate and hence heavy water chemistry is limited in the nuclear reactor plant. Hence this led to the development of the concept called noble metal chemical addition (NMCA) to control IGSCC even in the presence of H2. This review gives the insights and development of NMCA on corrosion control in BWRs.

Zn–Fe alloys were electrodeposited on mild steel plates and their morphology were evaluated. Electrodeposition was carried out using electrolytic sulphate bath with glycine as an additive. The composition of the electrolytic bath, experimental parameters and current density was optimized using Hull cell. The corrosion properties of developed coatings were evaluated in 3.5% NaCl solution using potentio-dynamic polarization and electrochemical impedance spectroscopic techniques. Zn-Fe alloy coatings at 4 A dm-2 presented a remarkable corrosion resistance performance due to morphology changes in the alloy.

This study discusses the effects of temperature on corrosion inhibition for soft-cast steel by the pharmaceutically active drug olmesartan in 1 mol dm−3 HCl. The sufficient number of electron-rich elements and non-bonding π electrons in its structure favored a good capability for coating onto the electron-deficient steel surfaces. Theoretical and electrochemical measurements were carried out at the temperature region of 303 K to 333 K. Therefore, the experiment suggests that the inhibition efficiency of olmesartan increases with its increasing concentrations due to the adsorption. Additionally, even at a higher temperature of 333 K, the inhibitor molecules attain their stability towards corrosion resistance of steel surfaces. The adsorption of inhibitors on steel surfaces is spontaneously found to include the mixture of physisorption and chemisorption, and it obeys Temkin’s adsorption isotherm model. Theoretical and computational considerations were made using quantum chemical parameters and molecular dynamics simulations, which confirmed that the olmesartan has a suitable corrosion inhibitive capability intended for soft-cast steel in 1 mol dm−3 HCl. Additionally, scanning electron microscopic measurement was used to obtain a visual idea of the inhibitive action of the inhibitor attained by forming an adsorbed protective layer onto the steel surfaces. The minute concentration of olmesartan of about 10–50 ppm shows high inhibition efficiency of ~80%, even at elevated temperatures.

Highly active Pt–Rh alloy catalyst coatings were developed by direct current (DC) and pulse current (PC) electrodeposition method for efficient hydrogen evolution reaction (HER) catalysts. The coatings were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), atomic force microscopy (AFM) and linear sweep voltammetry (LSV) studies. Pt–Rh alloy catalyst coatings showed almost similar behaviour as pure platinum metal. The Pt–Rh coating was obtained by the PC method showing low overpotential for HER. A very low slope of 41.2 mV/dec obtained represents the Volmer–Tafel mechanistic pathway for the HER process. Chronopotentiometry was conducted, and the amount of hydrogen collected during these experiments was 24 ml for the PC method 75% duty cycle sample.

The main focus of current research is on the synthesis and anticorrosive activity of novel heterocyclic compounds tert-butyl 4-[(4-methyl phenyl) carbonyl] piperazine-1-carboxylate [TBMPCPC]. Electrochemical, quantum chemical, and surface characterization studies at elevated temperatures (303–333 K) for carbon steel in 1M HCl solution studied this molecule's corrosion inhibition property. It is observed from the results of electrochemical studies that the TBMPCPC may be able to effectively protect the steel plate surface with an inhibition efficiency of 91.5 % at 25 ppm in corrosive media. The corrosion inhibition depends on concentration, as concentration also increases inhibition efficiency due to the strong and spontaneous adsorption on the metal's surface. The Tafel polarization measurements concluded that the inhibitor works as a mixed form to protect the carbon steel in the bulk solution from corrosion. The adsorption of the TBMPCPC onto the metal surface was in reliable with the isothermal model of the Langmuir adsorption. The scanning electron microscopy clearly showed that the inhibitor was substantially deposited on the metal surface, indicating substantial inhibition. The surface morphology of carbon steel in the absence and existence of an inhibitor in 1 M HCl is also studied using the Atomic Force Microscopic method., TBMPCPC; Corrosion inhibition; Electrochemical; SE.

Nanostructured Ni-Fe alloy coatings was developed on mild steel panels using electrolytic sulphate bath. The composition of the electrolytic bath and the experimental parameters were optimized. Corrosion behaviour of the developed Ni-Fe alloy coatings were evaluated in 3.5% NaCl solution using potentio-dynamic polarization and electrochemical impedance spectroscopic techniques. Highest corrosion resistance was observed for coatings at 3 A dm-2 Surface Morphology of the coatings was also characterised by SEM.

In this paper, a simple two-step hybrid electrochemical-thermal route was developed for the synthesis of cubic shaped Zn2SnO4 (ZTO) nanoparticles using aqueous sodium bicarbonate (NaHCO3) and sodium stannate (Na2SnO3) as an electrolyte. The sacrificial Zinc metal was used as both anode and cathode in an undivided cell under galvanostatic mode at room temperature. The bath concentration and current density were respectively varied from 30 to 120 mmol and 0.05 to 1.5 A/dm2 . The electrochemically generated precursor was calcined for an hour at different range of temperatures from 60 to 500°C. The crystallite sizes in the range of 24-53 nm were calculated based on the Debye-Scherrer equation. Scanning electron microscopy results reveal that all the particles have cubic morphology with a diameter of 40- 50 nm. The as-prepared ZTO nanoparticles showed higher catalytic activity towards the degradation of methylene blue (MB) dye, and the 90% degradation was found for the sample calcined at 500 °C, which is greater than that of commercial TiO2-P25 photocatalysts. These results indicate that the ZTO nanoparticles may be employed to remove dyes from waste water.

Eight distinct Zn–Fe alloy films have been galvanostatically electrodeposited with a current density ranging from 1 to 8 A dm−2. The surface morphology, chemical composition, phase structure and microhardness of these coatings were examined using scanning electron microscope coupled with energy dispersive x-ray spectroscopy (SEM-EDX), X-ray diffraction (XRD) and Vickers Microhardness Tester. XRD results suggest the formation of metastable crystal structure in all the electrodeposits and formation of η phase confirms the higher content of Zn in the coatings. To evaluate the corrosion resistance, the developed coatings were immersed in 3.5 wt% NaCl solution followed by the application of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests on each sample. The results indicated the greater impact of the coating characteristics on the corrosion resistance of electrodeposited Zn–Fe alloy.

The present work deals with the galvanostatic fabrication of Ni–Fe nanostructured composition-modulated multilayer alloy (CMMA) coatings on steel panel from the newly optimized acid-sulphate bath solution. The recurring cathode current density combination (RCCC) and the number of layers have been optimized for enhanced performance of the coatings against corrosion. Corrosion behaviour of the nanostructured multilayered coatings was evaluated by Tafel extrapolation and electrochemical impedance spectroscopy (EIS) methods in 3.5% NaCl solution. Under optimal conditions, the CMMA coatings developed were more corrosion-resistant than the monolithic alloy coatings obtained from the same bath. Least corrosion rate (CR) was witnessed at 300 layers, above which saturation of corrosion resistance at a high temperature was found, which is attributed to a shorter relaxation time for redistribution of metal ions during multilayer deposition. Hardness and roughness of the coatings were evaluated using Vickers hardness test and atomic force microscope, respectively. Phase structure of the coatings was discussed using X-ray diffraction technique. The cross-sectional view of the coatings was characterized by scanning electron microscope. CR analysis and the surface morphology of the optimized coatings exposed to high temperature revealed the better performance of CMMA coatings at the elevated temperatures compared to the monolithic coatings.

We present a detailed examination on the microstructural, structural, optical and electrical properties of one dimensional (1D) and three dimensional (3D) titania nanostructures in comparison with zero dimensional (0D) titania nanoparticles. Material characterization by X-ray Diffraction technique confirms the formation of anatase phased TiO2 nanoparticles and rutile phased nanorods and nanoflowers. Morphological investigations were done with Field Emission Scanning Electron Microscopy and High Resolution Transmission Electron Microscopy. Optical properties of the samples were studied using UV-Visible Diffuse Reflectance Spectroscopy and their optical band gap energies were calculated using Kubelka-Monk method. Although the 1D nanorods possess faster electron transport than the nanoparticle structure, their low surface area has detained that morphology to absorb more incident radiation. However, the 3D nanoflower morphology coupled with excellent light scattering capability and enhanced optical absorption resulted in a 7 fold increase in dark and 26 fold increase in photocurrents compared to nanorod and nanoparticles. Dye Sensitized Solar Cells (DSSCs) are developed using Safranine O dye and their I-V characteristics were examined. Improved performance of DSSC is observed in the case 3D nanoflower structures delivering efficiency of about 3.56 %. The findings of this work essentially suggest that the optical transport properties of the photoanode materials and therefore cell performances are significantly influenced by their respective morphologies.

We report herein a relative analysis of plasmon (Al) impregnated SnO2/TiO2 and ZnO/TiO2 nanocomposite systems synthesized using sol-gel method. The properties of the Al-SnO2/TiO2 and Al-ZnO/TiO2 have been studied using various characterisation techniques such as XRD, EDAX, FESEM, UV-DRS, and Photoconductivity techniques. The elemental composition and phase structures of the as-synthesized Al-SnO2/TiO2 and Al-ZnO/TiO2 nanocomposites were investigated using Energy Dispersive X-Ray (EDAX) and X-Ray Diffraction (XRD), which showed high degree of purity and crystallinity respectively. The crystallite sizes estimated with Scherrer’s formula were about 24 and 22 nm respectively. The FESEM images revealed that, both the samples were mesoporous in nature. The optical properties of both Al-SnO2/TiO2 and Al-ZnO/TiO2 samples exhibited strong absorption and diffused reflectance which suggested the possibility of the samples being used as photoelectrodes and the band gap value was found to be 3.38 eV and 3.07 eV using Kubelka-Munk plot. The photoconductivity studies suggested that Al-SnO2/TiO2 showed higher photo current values in reference to the Al-ZnO/TiO2 nanocomposite. Upon overall comparison, it is concluded that the Al doped SnO2/TiO2 exhibited enhanced characteristics over that of Al-ZnO/TiO2 nanocomposite and hence could be applied as efficient photoelectrodes for DSSCs.

A simple and facile means of developing a cost-efficient, easily reproducible perovskite solar cell (PSC) is presented in this report. This hole transport material (HTM)-free perovskite solar cell is based on electrochemically anodized titania nanotubes which enact the role of an electron transport layer in the defined configuration. The complete procedure involved in the fabrication of the PSC module is carried out under ambient air conditions depicting the moisture resilient nature of the designed module. The fundamental concept, however, relies upon understanding the effect of the length of the grown nanotubes on the efficiency of the PSC constructed with them. The dimensional (length) modulation is carried out by varying the anodizing voltage applied during the growth of the titania nanotubes as well as the anodization methods involved. The structural changes related to the morphology and dimensions of the grown nanotubes were confirmed with X-ray diffraction analysis and field emission scanning electron microscopy, while its effect on the optoelectrical properties was studied using UV-diffuse reflectance spectroscopy and photoconductivity measurements. Finally, PSC modules composed of these nanotube samples were constructed and the effective changes in their efficiency were determined. The current investigation detects an increase in the efficiency of the PSC module with increase in the length of the anodically grown titania nanotube, reiterating the importance of the thickness of the mesoporous layer in the performance of the PSC.

Nanomaterials when developed as thin films exhibit better properties compared to nanoparticles. Tin oxide with its outstanding properties such as wide band gap, low electrical resistivity, and good chemical stability is a versatile material in the field of nanomaterials. Metal doped SnO2 in addition exhibits enhanced properties. We report herein the preparation and analysis of the important properties of Al doped and pure SnO2 thin films through a simple sol-gel process and subsequent spin coating on FTO substrates. Microstructural characterization of the thin films was carried out for comparative evaluation of their physical properties. The as-grown thin films were studied using powder XRD technique and the crystallite sizes were estimated for Al doped and bare SnO2 thin films. The surface morphologies of the as-synthesized thin films were examined using High Resolution Scanning Electron Microscope. The observed images indicated lesser agglomeration and good homogeneity in the case of Al doped SnO2 thin films in comparison with its pure counterpart. The surface area, pore volume and pore radius of the samples were determined using BET analysis. The Fourier Transform Infrared Spectroscopy evidenced the presence of the various functional groups related to the materials of the films.

Cadmium Sulphide (CdS) [II-VI group n-type semiconductor] and Copper Sulphide (Cu2S) [I-VI group p-type semiconductor] have large commercial applications like solar cell, gas sensor etc. Wide band gap CdS semiconductor was used as the transparent window material together with narrow band gap Cu2S semiconductor used as the absorber layer. Thioglycerol capped CdS and Cu2S nanoparticles were synthesized by using the non-aqueous chemical method at room temperature. CdS and Cu2S films were prepared on fluorine doped tin oxide (FTO) glass substrates by using the simple dip coating method at different dip times and heat treated in air. CdS and Cu2S nanoparticles were analysed by Ultraviolet-Visible absorption spectroscopy, photoluminescence (PL) and transmission electron microscopy (TEM). CdS and Cu2S films were investigated by scanning electron microscopy (SEM), energy dispersive analysis by x-rays (EDAX), mapping and atomic force microscopy (AFM). Thicknesses of films were determined using laser profilometer. Previously, preparation of solar cells using CdS and Cu2S films deposited by dip coating method has not been reported. In this study, thin-film solar cells with p-n heterojunction having enhanced conductivity, excellent solar energy conversion efficiency, enhanced fill factor, low cost and easy fabrication were prepared to increase the quality of solar cells.

We report the synthesis and characteristic analysis of well defined vertically oriented TiO2 nanotubes using potentiostatic anodisation method. This method allows precise design and control of the geometric features of the nanotube arrays, enabling a material to be moulded with specific light absorption and propagation properties. Hence, in this work we studied the effect of applied potential on the nanotube dimensions. While the effect of the applied potential on the nanotube dimensions were found by the change in tube length and diameter, the effective change in the light absorption properties were also observed corresponding to the change in band gap of the respective anodized sample. These outstanding observations were analyzed by using different characterization techniques such as Field Emission Scanning Electron Microscopy (FESEM), Ultra-Violet Diffuse Reflectance Spectroscopy (UV-DRS) and Field effective Photoconductivity confirming the optical tuning of band gap corresponding to significant change in the specific nanotube dimensions.