A new azo dye, (E)-4((2-(benzylamino)phenyl)diazenyl)phenol [BPDP] was synthesized via diazotization-coupling reaction and characterized with major spectroscopic techniques. The inhibitory capacity of the compound on mild steel corrosion in 1 M HCl solution was evaluated via weight-loss, electrochemical, scanning electron microscope, and computational techniques. The weight loss revealed that on increasing the concentration of the inhibitor, there was a substantial increase in the inhibition efficiency, and at every 10 K rise in temperature for a particular concentration, the inhibition efficiency was reduced. Synergistic interaction was inferred between iodide ions and BPDP molecule as the synergistic index was greater than 1, resulting in a formulation with enhanced corrosion inhibition. BPDP inhibited both cathodic and anodic corrosion half-reactions and increased charge transfer resistance for mild steel corrosion in 1 M HCl. Adsorption of BPDP molecules on steel surface conforms to the Langmuir isotherm model. Scanning electron microscope (SEM) images revealed the formation of a protective layer on the mild steel surface in the presence of the inhibitor. The density functional theory (DFT) and Monte Carlo simulations laid credence to the adsorption potentials of BPDP molecules on the steel surface.

A Co3O4/V2O5 bilayer heterostructure was successfully fabricated on ITO/glass substrates via sequential electrodeposition and comprehensively evaluated for its structural, vibrational, and optoelectronic properties toward ultraviolet (UV) photodetection. SEM analysis revealed a morphological transformation from the granular V2O5 and densely packed Co3O4 textures to a uniform, compact nanostructured network in the Co3O4/V2O5 heterostructure, indicating enhanced interfacial adhesion and surface coverage. Elemental mapping confirmed a homogeneous distribution of V, Co, and O elements without phase segregation. XRD patterns verified the coexistence of orthorhombic V2O5 and cubic Co3O4 phases, exhibiting interfacial strain-induced peak shifts, suppression of the (301) plane of V2O5, and broadened diffraction peaks, signifying improved crystalline coherence and structural coupling. Raman spectra further validated the phase purity and distinct vibrational features of both oxides. UV-visible absorption spectra displayed modulated band transitions, while Tauc's plots revealed tunable optical bandgaps ranging from 2.35 to 2.59 eV, depending on material composition and heterostructure formation. The fabricated UV photodetector demonstrated excellent photoresponse characteristics, including high responsivity and strong detectivity, attributed to efficient charge separation and transport at the heterostructure Co3O4/V2O5 interface. These findings establish the Co3O4/V2O5 heterostructure as a promising and scalable oxide-based platform for high-performance UV photodetectors and related optoelectronic applications.

Proton batteries are a promising, sustainable alternative to lithium-ion batteries due to the abundance of hydrogen and its smaller ionic radius, which facilitates its seamless intercalation in electroactive materials. However, their progress depends on the development of cost-effective, high-capacity electrode materials. Herein, we report the successful fabrication of a binder-less, defect-engineered WO3-x/WO3 pseudocapacitive proton storage electrode (HTT_WO3-x) through scavenging of atomic sub-surface oxygen from hydrothermal-treated electro-coated WO3 films (HTT_WO3). The defect-engineered electrode (HTT_WO3-x) combined improved mass load with enhanced electronic and ionic transport behaviour. The electrode achieved an areal capacitance of 42.13 mF center dot cm-2 at 5.00 mV center dot s-1, approximately 300 % higher than the electro-coated WO3 seed electrode. The hydrothermal treatment yielded an increased mass load and areal capacity, further improved through lowered impedance parameters and better interfacial characteristics by defect engineering. This study offered a facile method for achieving binder-free coating of high-mass load proton storage active materials without compromising their ionic and electronic transport.

In an effort to improve the practical application of benzimidazoles as corrosion inhibitors, hydrophilic groups were introduced through the attachment of aldoses to the benzimidazole ring. In this study, computational techniques, including DFT calculations and Monte Carlo simulations were used to predict the potentials of new aldo-benzimidazoles (benzimidazolyl-pentane-1,2,3,4,5-pentaol) as corrosion inhibitors for mild steel in aqueous acid media. The results showed that the compounds, which are inherently more hydrophilic than native benzimidazoles promise to exhibit higher corrosion inhibition efficiencies than conventional benzimidazole derivatives. Highly electron-donating (e.g. -OCH3) and electron-withdrawing (e.g. -NO2) substituents increased the corrosion inhibition efficiencies, making g-bzm-methoxy and g-bzm-nitro to have the highest corrosion inhibition efficiencies as predicted from the QSAR model. All the compounds showed appreciable adsorption energies on Fe(1 1 0) surface with bond distances that suggest non-covalent interactions between the N-atom of the benzimidazole ring and Fe. All the compounds showed lower toxicity to fathead minnow than benzimidazole except g-bzm-benzophenone, g-bzm-diCl, and g-bzm-dimethyl. The compounds also exhibited lower toxicity to Daphnia magna and T. pyriformis, suggesting their eco-friendly attributes. The study provides insights into the sustainability of benzimidazolyl-pentane-1,2,3,4,5-pentaol derivatives as corrosion inhibitors and recommends complementary experimental studies on the compounds.

Supercapattery represents a new energy storage device technology aimed at closing the gap between the supercapacitor's high power density and the battery's high energy density. Therefore, this report unveiled the utilization of binder-free solution-grown Ni(OH)2/S@MnO2 heterostructured electrode film in the fabrication of a novel hybrid solid-state supercapattery planar device. Some surface characterization of the material revealed successful sulfurization of electrodeposited particulate MnO2 film (S@MnO2), forming a base core layer for the amalgamation of electroless deposited thinly flakelike Ni(OH)2 scaffold film. The electro-sulfurization process yielded the deposition of thin layer Mn-(O/S) composite film on ITO with enhanced pseudocapacitive responses. The electrochemical charge storage measurements also revealed highly stable Ni(OH)2/S@MnO2 supercapattery electrode via the synergistic S@MnO2 pseudocapacitive and scaffolding Ni(OH)2 battery-type, responses. Consequently, the as-grown heterostructure exhibited a capacitance value of 2825 F/g (113.56 mF cm- 2) and with capacity value of 1252 C/g at 1 A/g current density. In the two-electrode mode, a fabricated device encompassing Ni(OH)2/S@MnO2 positive electrode and thermally reduced graphene oxide (TRGO) negative electrode, exhibited comparable areal capacitance (8.7 mF cm- 2), high cell voltage (1.7 V) and areal energy density 3.542 mu Wh cm- 2 at 0.1 mAcm-2 current density. Excellent charge-discharge capacitance retention (87.1 % after 20,000 cycles) and voltage holding strength were also demonstrated by the cell.

Negatrodes with wide negative operating voltage, high electrochemical storage capacity, and intrinsic metal ion intercalation abilities are vital to the continuous development of storage devices with simultaneous energy and power density improvement. Herein, we report binder-less coating of non-stoichiometric vacancy-implanted Nb2O5-x as carbon additive-free negatrode on FTO substrate for asymmetric supercapacitor and sodium ion capacitor applications. The negatrode was fabricated through vacuum-less and low-temperature solvothermal-assisted electro-coating technique and yielded several orders of enhancement in its areal capacitance and retained ca. 90 % of its capacity after 5000 cycles of charge-discharge in aqueous Na+ electrolyte. The solvothermal treated electro-coated electrode (STT_Nb2O5-x) achieved an areal capacitance of 22.58 mF/cm2, which was far higher than those of hydrothermal-treated electro-coated HTT_Nb2O5 and Nb2O5 electrodes. The solvothermal treatment simultaneously enhanced the electro-coated samples' impedance properties and mass load through oxygen vacancy implantation and re-crystallization of the electro-coated Nb2O5 layer, respectively. This study presented a facile and energy-efficient technique of direct coating of defect-enhanced pseudocapacitive nanomaterials for the fabrication of electrochemical storage devices.

Herein, we report the implantation of oxygen vacancy dopants in electro-coated WO3 thin film electrodes for enhanced energy and environmental applications. The implantation method involved partial de-oxidation in sodium borohydride to introduce oxygen vacancies into the WO3 electrodes. The doped WO 3-x demonstrated a significantly lowered average band energy of 2.11 eV, indicating its ability to absorb over 75 % of the visible light spectrum. Moreover, a thin film asymmetric supercapacitor assembled with WO 3-x negatrode demonstrated an improved areal capacitance of 1.15 mFcm- 2 and energy density of 0.33 mu Whcm-2 while consuming power at 17.50 mu Wcm- 2 when cycled at 25 mu Acm- 2 . Our solution-processed technique allows for controllable vacancy implantation and binder-free coating of WO 3-x on various substrates. It significantly reduces the processing time and requires low energy consumption, making it a practical and efficient method for enhancing the overall photo-conversion and energy storage performances of WO3-based electrodes.

Miniaturized energy storage devices are currently gaining attention because of the growing need for portable, implantable, and wearable electronics. Micro-supercapacitors (MSC) have a shorter ionic diffusion path and may perform better than traditional electrochemical energy storage system because they are manufactured on a single substrate and can be easily integrated with other devices. In the meanwhile, they are easily produced and incorporated into miniaturized on-chip electronics, and this suggests that they could supply long-lasting power for sophisticated microelectronic systems. Although the subject of rigid MSC has been the subject of numerous influential reviews to date, no work has systematically compiled the evolution of Flexible MSCs with unique storage features, from microelectrode fabrication to functionalization and integration with various solar energy harvesters. This review therefore provided important characteristics and exciting prospects for the outstanding performance of flexible MSCs through a rigorous examination of the current state of advancement and challenges with flexible integrated photocharging power systems.

Herein, we presented the fabrication of α-MnO2 thin film pseudocapacitive electrodes with enhanced optical transparency and areal capacitance. The optimized electrodes were achieved through a low-energy, binder-free, hexamethylenetetramine-assisted electrodeposition. Before this, attempts to increase the optical transparency of MnO2 electrodes had only been successful by reducing its mass load and thickness, which compromised its storage capacity. In this study, analysis of the optical dispersion properties of MnO2 was combined with the electrochemical investigation to demonstrate a nexus between nano-morphology, transparency and storage capacity.

The tuning of optical and dielectric parameters, structural and microstructural properties of CdO synthesized via a solution growth two-electrode cell arrangement under ambient environment, with the incorporation of Co ion into its matrix was investigated. The energy band gaps of the films was estimated in the range of 1.69 eV</=Eg</= 1.96 eV. The extinction coefficient, k for all the samples decreases as the incident photon energy increases. The films exhibit considerably high optical conduction across the photon energy with estimated power of 1013 (Omega m)-1. The elemental composition of the samples was determined using the energy dispersive x-ray spectrometry technique. The micrograph images from scanning electron microscopy technique shown that the films are polycrystalline and well-adhered to the substrates with their crystal grains evenly dispersed across the substrates’ surface. The x-ray diffraction analysis confirmed that the deposited films are of polycrystalline in nature. The films show preference for orientation along the (111) plane.

We report a novel highly sensitive and pseudocapacitive transparent nickel oxide (NiO) thin film based electrode material fabricated on a conductive glass substrate using a facile binderless electrodeposition process. Effect of the incorporation of Mo-dopant ion on some surface structural and electrochemical properties of the electrode was examined for high performance optoelectronic and charge storage poten-tials. The material showed some uniqueness in some microstructural features and enhanced degree of crystallinity, suitable for charge extraction and transport with Mo doping. The deposited NiO film de-monstrated red shift in band structure by exhibiting optical band gap narrowing from 3.88 to 3.61 eV with increasing Mo content. The degree of disorder as revealed from Urbach response of NiO film was found varying with Mo-content. The material also exhibited enhanced Ni2+ electronic transition states with in-creasing Mo content which quenched at a critical dopant concentration of 2.4 %. The fabricated NiO thin film electrode showed increased supercapacitive specific capacitance and areal capacity up to a peak value of 1412 Fg-1 and 101 mAh m-2 for 3 % Mo dopant content at 5 mVs-1 scan rate and 0.5 mA cm-2, respectively, but returned diminished at higher dopant content. Excellent cycling stability at 85 % after 5000 cycles, was also exhibited. Impedance spectroscopic features of Mo-doped NiO electrode indicated fast electrolytic ion transfer response with high rate charge storage capability. The study presents successful fabrication of Mo-modified NiO nanostructured electrode film and demonstrated the influence of Mo impurity on tai-loring the properties of NiO host film as suitable electrode in high performance photocatalytic and su-percapacitor devices.(c) 2022 Elsevier B.V. All rights reserved.

Herein, we report the comparative gas sensing performance (at room temperature) of reduced graphene oxide sensors obtained by reducing graphene oxide using extracts of pumpkin leaf, neem leaf and methionine. An interdigitated pattern was designed on soda-lime glass using a stamp method and the dispersed solution of rGO was spin coated on the pattern. The electrical response of the sensors was investigated (using a simple in-house measurement set up) by measuring change in resistance of graphene with varying gas concentration on exposure to liquefied petroleum gas (LPG). From the characterization results using FTIR, SEM, EDX and UV-Visible, methionine reduced graphene oxide (MRGO 12H) indicated a greater degree of reduction compared to pumpkin reduced graphene oxide (PRGO 12H) and neem reduced graphene oxide (NRGO 12H). The LPG sensing results showed an increase in the resistance of the sensor materials upon the introduction of the gas and, an increased sensitivity as the concentration of the test gas increased from 100 ppm to 200 ppm while the MRGO 12H sensor was more selective towards LPG sensing. Furthermore, it was observed that the sensor response for the fabricated sensors is strongly dependent on the concentration of gas exposed to the sensors and the degree of removal of oxygen functional groups in the graphene-based materials. Hence, the MRGO 12H sensor had a sensor response of 23.58% at 200 ppm. PRGO 12H at 100 ppm illustrates the least sensor response while NRGO 12H showed very poor sensor response that ranged between 5.10% and 7.56%. The sensor response of the materials demonstrates an improvement in results obtained for pure rGO based sensors. We obtained a response time as low as 5.3 seconds for MRGO 12H while the recovery time of the sensors ranged between 6.46 seconds and 41.50 seconds. The MRGO 12H sensor typified the best recovery time and thus outperformed results from most of the reported literature. Considering different performance metrics such as sensor response, response time, recovery time and sensing period, MRGO 12H is more selective towards detecting LPG. Our results showed that a greater restoration of the sp(2) carbon chain brought about by increased reduction of graphene oxide is largely responsible for the sensing behavior of rGO towards LPG.

Direct coating and surface engineering of Nb2O5-based active storage materials are important techniques for improving their interfacial interactions with the current collector and electrolyte ions, which have been difficult to achieve in a facile and energy-efficient way. Herein, we report the binder-free coating of shear-structured Nb4+ implanted Nb2O5 (Nb2O5-x) sub-micron thin pseudocapacitive negatrode with wide negative operating voltage (-1.20 V vs Ag/AgCl), improved electronic and ionic conductivity, reduced charge transfer resistance and enhanced energy storage capacity. The Nb4+ implanted electrode exhibits 3.5 mF/cm2 c. a. At 5 mV/s and 100% capacity retention after 3000 constant charge-discharge cycles. The unique electrode was realized via mild deoxidation of electrodeposited Nb2O5 in a vacuum-less, low-temperature surface engineering process. This simple strategy is suitable for improving current collector-Nb2O5-zelectrolyte interfacial interactions and for industrial-scale production of improved pseudocapacitive negatrodes.

This research reported the effect of incorporating graphene oxide in the hybrid of ZnO and investigated the thermistor applications. ZnO-RGO were synthesized by the hydrothermal method and spin coated on glass to obtain the thin film. The SEM micrograph of ZnO-RGO showed mini ZnO nanorods decorated and formed on the RGO sheet. The adherence of the nanorods were improved as the loading mass of GO increased in the composite. ZnO-RGO had thermal sensing response of 3.1 respectively at 573K and showed improved electrical conductivity as temperature increased. ZnO sensors logged a negative temperature coefficient (NTC) value of 0.00236 /K and a sensitivity value of 0.01392 Ω/ K while ZnO-RGO had a NTC value of 0.00248139 /K (which is higher than values obtained in literature for silver and palladium based graphene composites) and a sensitivity value of 0.00769 Ω/ K. A value of 0.0561eV was obtained for the activation energy of ZnO sensor while 0.0615 eV was obtained for ZnO-RGO. This research has confirmed that incorporating GO in ZnO increased the activation energy of ZnO-RGO thermistor, and consequently increased the thermal sensing response thus resulting in improved thermal sensing properties of ZnO. With an improved NTC, sensor response and activation energy, ZnO-RGO can replace Pd based RGO and Ag nanoparticles based RGO as thermistors.

Copper-doped zinc oxide (5 % and 15 % Cu-doped ZnO) nanoparticles have been synthesised and incorporated into the polyaniline (PANI) matrix in an in-situ interfacial polymerisation of aniline with ammonium persulphate (APS) to obtain solution processable PANI/5 % and 15 % Cu-doped ZnO nanocomposites, without the aid of surfactants. The samples were characterised by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), UV–Vis spectroscopy, scanning electron microscopy/energy dispersive x-ray spectroscopy (SEM/EDX), and Four-point probe method. The XRD patterns of the nanoparticles revealed that they possess hexagonal wurtzite crystal structure of ZnO with slight shift of the diffraction peaks to higher 2θ values, and their estimated crystallite sizes were 27.165 and 32.450 nm, respectively. The estimated optical bandgaps of the nanoparticles decreased with Cu doping (3.09 and 2.85 eV at 5 and 15 % Cu doping, respectively) when compared with the standard value of pure ZnO (3.30 eV), consistent with the redshift in the absorption wavelength observed in the UV–Vis absorption spectra. In contrast to the significant reduction observed in the bandgaps of the nanoparticles, marginal changes were observed in the optical bandgaps of the PANI/Cu-doped ZnO nanocomposites with increasing nanoparticles loading ranging from 2.29 eV to 2.46 eV. The FTIR of the nanocomposite depicted the same characteristic peaks of PANI but were slightly shifted to higher wavenumbers attributed to the interaction between PANI and the nanoparticle, while the XRD patterns of the nanocomposites revealed the orthorhombic crystal structure of PANI and weak diffraction peaks of the nanoparticles. From the SEM/EDX, the observed elemental composition of the nanocomposite confirmed the presence of the nanoparticles within the PANI matrix. The electrical measurement revealed that the PANI/Cu-doped ZnO nanocomposites exhibited enhanced electrical conductivity, which reached maximum values at specific nanoparticles loadings. The obtained results and the solution processability of these nanocomposites make them suitable for applications in optoelectronics.

Oxygen vacancy-doped WO3-& delta; thin film electrode with improved conductivity and high areal capacitance was synthesized via mild electrochemical oxygen de-intercalation of electrodeposited WO3 thin film. The X-ray diffraction (XRD) analysis revealed the presence of monoclinic phase W18O49 of the doped thin film electrode. Raman spectroscopy analysis confirmed the presence of lower valence W5+ in the WO3-& delta; film. Electrical characterizations of doped WO3-& delta; and undoped WO3 films show that the doped electrode exhibits far lower sheet resistance and resistivity than the undoped WO3 sample. Mott-Schottky analysis of the samples shows that the vacancy-doped WO3-x possesses a higher donor concentration than the stoichiometric WO3. Electrochemical characterizations by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD,) and electrochemical impedance spectroscopy (EIS) confirmed the superior pseudocapacitive charge storage metrics via its improved volumetric capacitance of 366.12 F & BULL;cm  3 (16.0 mF & BULL;cm  2) and reduced equivalent series as well as charge transfer resistance over WO3 thin film. This study demonstrated the synthesis of oxygen vacancy-doped WO3-& delta; thin film using a homemade two-electrode cell facility instead of the popular energy-consuming vacuum-assisted film deposition under controlled-atmosphere conditions. Besides, the vacancy-doped WO3-& delta; electrode shows a strong charge storage capability in the far negative operating potential range, indicating its suitability as an anode electrode for fabricating high-energy asymmetric supercapacitors.

Herein, we have successfully grown transparent NiCo2 and Cu mixed oxide thin film electrode material by a facile electrodeposition process from electrolyte containing hydrated salts of its composite metals at two different temperatures. Microstructural and some other surface studies were carried out with the aid of suitable and appropriate probing facilities such as scanning electron microscope (SEM), atomic force microscope (AFM), X-ray diffractometer (XRD), Raman microscope and ultraviolet-visible spectrophotometer. Microstructural studies on the samples revealed the formation of seed flowerlike nanosheet by the film grown from room temperature electrolyte which was found to become porously stacked and agglomerated as observed for the one grown at higher temperature. Further probing showed that the grown film exhibit crystallinity and surface roughness of high degree. Optical energy band gap values were also found to be 3.08 and 3.00 eV depending on the synthesis protocols observed. The optimum electrode sample exhibited high specific capacitance and capacity of 1940.1 Fg 1 and 134.2 mAhg 1, respectively and with excellent cycling stability when tested as half-cell in threeelectrode mode and 1 M aqueous KOH electrolyte. It was further utilized as positrode in a fabricated solid state asymmetric supercapattery device with reduced graphene oxide (RGO) as negatrode and powdered PVAKOH electrolyte. The device displayed intriguing performance having demonstrated excellent cycling in high voltage (0 to 1.6 V) window and over 20,000 charge-discharge cycles, and with high areal capacitance, energy density and power density of 20.2 mFcm 2, 25.60 Whcm 2 and 2344.42 Wcm 2, respectively. The study demonstrated the significant supercapacitive potentials of the fabricated electrode material for high quality energy storage devices.

We report the fabrication of nanocystalline MnO2 thin film-based electrode on a predeposited indium tin oxide (ITO) film on the glass substrate, using a binderless and simple two-electrode electrofabrication approach. Effects of Co and Cu incorporation on microstructural and electrochemical performance of the electrode were optimally and extensively investigated. The experimental results for the optimum fabrication conditions for Co@MnO2 and Cu@MnO2 and pure MnO2 thin film-based electrode samples showed uniqueness in microstructural features, degrees of crystallinity and roughness, and high electrochemical energy storage performance. Co@MnO2 film electrode exhibited remarkable specific capacitance (1068 Fg(-1)) and areal capacity (25.78 mAh cm(-2)) as against other electrode films (Cu@MnO2 and pure MnO2) which exhibited specific capacitances 837 and 438 F g(-1) and areal capacities 10.6 and 4.9 mAh cm(-2), respectively. Exceptional stabilities were also recorded for the composite samples (87.2% and 84.4% for Cu@MnO2 and Co@MnO2 thin film electrodes, respectively) against the pure MnO2 film electrode sample (77.8%), after 2000 cycles. In addition, the short time constants (1.27 s and 1.31 s) were respectively realized for the fabricated Co@MnO2 and Cu@MnO2 electrode films as against the pure MnO2 electrodes (4.35 s). These features observed in the composite electrode samples demonstrated an exhibition of faster ion response and higher rate capability by the samples. Moreover, the incorporation of Co into the MnO2 electrode material relatively improved the supercapacitive activeness by enhancing the charge transition and transport.

We report the consequence of Zn doping on some surface and electrochemical characteristics of CuxO nanostructured film, obtained via a facile and cost effective two electrode electrochemistry. Impact of Zn dopant on photoabsorption and supercapacitive responses of CuxO thin film electrode was examined. Microstructural studies revealed anisotropic growth of monoclinic and cubic CuxO crystals featuring alternate arrangements of 0 and Cu ions. Some structural properties of Zn-doped CuxO film were also found varying with Zn content. CuxO film exhibited red shift in its band structure and its optical energy band gap consequently declined from 2.62 to 2.20 eV with increasing Zn dopant. Zn-doped CuxO film also demonstrated highly stable pseudocapacitive response with improved specific capacitance of 263 F g(-1) and areal capacity of 5.83 mA h cm(-2). Lower series and charge transfer resistances as well as huge ohmic resistivity drop were also observed in the CuxO electrode with Zn dopant, indicating better ionic conductivity and charge storage capability. The study demonstrates successful incorporation of Zn ion in CuxO lattice structure and showed that supercapacitive and photocatalytic properties of CuxO thin electrode can be tailored by simply introducing Zn dopant impurity. (C) 2021 Elsevier B.V. All rights reserved.

In this study, Molybdenum oxide (MoO3) and Vanadium oxide (V2O5) thin films were grown separately on pre-deposited cobalt oxide (Co3O4) thin film to form two different bilayer structures. The films were synthesized by spin-coating deposition technique. The precursors were prepared from common chemical reagents. Sample's surface microstructure, elemental composition and optical properties were investigated. The microstructural studies of the deposited bilayers show that the Co3O4 underlayer comprises crystalline grains with some overgrown clusters. Nanorod arrays of MoO3 adhering to the underlying Co3O4 layer with no chemical interaction are observed. In the second sample, the V2O5 top layer completely laminated the proximate Co3O4 film. Optical properties of the samples were examined from the UV/Vis spectra data. Energy band gap and band tail width changed with the adherence of top layer. Optical skin depths were also analyzed to reaffirm the suitability of the structures as potential window in thin film photovoltaics. The study demonstrated cheap process of developing interfacial layers of some transition metal oxide materials with high photoresponse. It also showed that the layers can offer the advantage of enhancing light harvesting, charge transport and storage.