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Problems and diseases with eye are common in diabetic patients. Early diagnosis and detection of various diseases like retinopathy, neuropathy and nephropathy is crucial in diabetic patients. Certain demographic and diagnostic parameters play a significant role in predicting diseases related to diabetes. Development of a novel diagnostic method which helps to predict the disease by establishing a significant correlation with the demographic and diagnostic parameters is of prime importance. This study proposes a new methodology in which retinal fractals are obtained for the images and the derived retinal fractals are analysed to aid in disease prediction. This study comprises of images from patients with retinopathy, non retinopathy, neuropathy, nephropathy and hypertension. The proposed research is carried out in two aspects: 1) to correlate the retinal fractals of retinopathy and non retinopathy images with certain demographic and diagnostic parameters and interpret its significance, and 2) to exhibit a relationship between the retinal fractals and various diseases/addictive habit to facilitate the prediction of the disease/addictive habit. Hausdorff fractal dimension (HFD) was applied and higher fractal dimension was obtained for healthy cases. Then using Statistical Package for the Social Sciences (SPSS) various statistical parameters and significance were calculated to analyse the relationship. Analysis results showed that fractal value helped in distinguishing between the retinopathy and non retinopathy conditions. It also helped in diagnosing the presence and absence of hypertension. Correlation analysis between certain demographic parameters and fractal value showed a positive correlation whereas few exhibited negative correlation.

Sodium tantalate (NaTaO3), a typical mixed metal oxide with orthorhombic structure, has been modified by incorporation of lanthana (LaxNa(1 − x)TaO(3 + y) or LNTO), followed by doping/co-doping with N and Fe3+, with the objective of improving visible light absorption and photo physical properties. XRD and XPS results reveal that La3+ occupies Na+ ion sites, Fe3+ ions Ta5+ ion sites and N the O2− ion sites, possibly as N3− in the tantalate matrix. Incorporation of the dopants in the tantalate matrix has been confirmed by SEM-EDXA and STEM-EDS elemental mapping and surface composition analysis by XPS. Fe and N co-doping in tantalate matrix results in the narrowing of the band gap due to the creation of additional energy levels within the band gap and consequently, visible light absorption. Presence of Fe3+ and La3+ dopants in the tantalate lattice ensures electro-neutrality. Efficient charge trapping and de-trapping by Fe3+ and Fe4+ ions reduce the probability of charge carrier recombination as revealed by photo luminescence spectroscopy and further promote charge migration and interfacial charge transfer. The catalysts display significant activity for photo catalytic reduction of carbon dioxide (PCRC) in aqueous alkaline medium, with methanol as major product. Synergetic effect due to co-doping of LNTO with Fe and N improves visible light absorption, retards recombination of charge carriers and thus helps to enhance PCRC activity by nearly three times vis-a-vis pristine NaTaO3.

Strontium titanates, SrTiO3, Sr3Ti2O7 and Sr4Ti3O10, with perovskite structure, have been modified by co-doping with N, S and Fe and characterized by X-ray diffraction (XRD), Diffuse reflectance Spectroscopy (DRS), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDXA), X-ray Photoelectron Spectroscopy (XPS) and Photo Luminescence Spectroscopy (PLS) techniques. XRD, EDXA and XPS results substantiate the incorporation of the three dopants into the titanate matrices. Based on the XPS binding energy data, it is inferred that doped nitrogen in SrTiO3 and Sr4Ti3O10 phases occupies O2− ion sites by substitution and interstitial sites in Sr3Ti2O7. Fe as Fe3+ and S as cationic S6+ occupy Ti4+ ion sites in the respective lattice in all three titanates. Additional energy levels created by the dopants within the band gap result in narrowing of the band gap, as revealed by DRS data and thus enable visible light absorption by the modified titanates. Significant reduction in the intensity of photo luminescence emission lines of modified titanates indicates that doping retards the recombination rates of charge carriers, enhancing their life time. Changes in the photo-physical properties brought out by modification with dopants improve the activity for photo catalytic reduction of CO2 vis-a-vis pristine titanates. Both Sr3Ti2O7 and Sr4Ti3O10, perovskites with layered structure, display higher activity when compared to simple perovskite, SrTiO3. Layered structure facilitates faster transport of charge carriers and the interlayer space could function as oxidation/reduction reaction sites, leading to the separation of charge carriers. Amongst the two layered perovskites, double layered Sr3Ti2O7 displays higher activity compared to triple layered Sr4Ti3O10 since the conduction band minimum of Sr3Ti2O7 is at higher negative energy level vis-a-vis that for Sr4Ti3O10 and the inter layer spacing is appropriate for CO2 reduction and splitting of water as well.

Carbon dots (CDs) with 48% quantum yield (QY) were synthesized by simple hydrothermal treatment using Pseudo-stem of banana plant as carbon source. As synthesized CDs were characterized using UV–vis, fluorescence, dynamic light scattering (DLS), Fourier transform infrared (FT-IR), Raman, X-ray photoelectron spectroscopy (XPS) and High resolution transmission electron microscopic (HRTEM) techniques. A fluorescent nanosensor which exhibits highly specific recognition capability towards Fe 3+ over other competing metal ions has been reported. CD exhibits fluorescent “turn-off” sensing nature with high selectivity towards Fe 3+ with a detection limit as low as 6.4 nM and “turn-on” property towards S 2 O 3 2− anion. The biocompatibility of CDs was revealed from the cytotoxicity studies on cancerous cells (HeLa, MCF-7 (Michigan Cancer Foundation-7)) and was employed as fluorescent probes for multi-coloured (blue, green and red) imaging of HeLa and MCF-7 cells. Due to the bright fluorescence, water solubility, high photo-stability, low toxicity, cell-membrane permeability and good biocompatibility, as-prepared carbon nanodots are demonstrated to be excellent probe as bio-imaging agent.

Retinal vessels are known to behave like a fractal, waherein a part of a geometrical pattern resembles the whole. Although the box counting method has been used most commonly, currently there exists no "best method" for fractal analysis on retinal vessels. In the present study we compared the different methods of fractal analysis of retinal images. This study included 43 normal retinal images from public databases (STARE & DRIVE) and 40 retinal images (20 normal and 20 diseased) collected from an epidemiological study database (Sankara Nethralaya diabetic retinopathy epidemiology and molecular genetics study; SNDREAMS). In our study we calculated and compared the values of fractal dimensions by Box counting method, Hausdorff Fractal Dimension (HFD), Modified Hausdorff Fractal Dimension (MHFD) and Fourier Fractal Dimension (FFD). The coefficient of variation(CV) was the least with HFD methods in different databases (DRIVE & STARE: −0.088, SNDREAMS Normal retinal images: −0.117, SNDREAMS Diseased retinal images: −0.103). Our study showed that HFD method was the best method to calculate the fractal dimensions of normal and diseased retinal images.

Lanthanum modified sodium tantalate, Na (1−x) La x TaO (3+x) , in conjunction with cobalt (II) tetra phenyl porphyrin (CoTPP) as sensitizer, has been explored for photo catalytic reduction of carbon dioxide (PCRC) with water. HOMO and LUMO energy level characteristics/redox potentials for ground (S 0 ) and excited states (S 1 singlet) of CoTPP have been calculated by Density Functional Theory (DFT). HOMO and LUMO energy levels enable sensitization of the tantalate, a typical wide band gap semi-conductor, with visible light. Visible light absorption by CoTPP results in the direct transfer of photo generated electrons to the conduction band of the tantalate, in addition to the intrinsic UV light excitation. Besides, sensitization also retards charge carrier recombination rate, as indicated by the photo luminescence spectral data for the pristine and sensitized Na (1−x) La x TaO (3+x) . A co-operative effect of these factors contributes towards nearly 3 fold increase in apparent quantum yield value for PCRC with the 1% w/w CoTPP/tantalate composite vis-a-vis pristine tantalate. After 20 h of irradiation, rate of methanol formation remains constant with pristine and sensitized tantalates, while the rate of formation of ethanol increases on sensitization, indicating multi electron reduction process. Chemical composition and structural characteristics of the composite are preserved even after 20 h of irradiation.

Lanthanum doped sodium tantalate (Na(1−x)LaxTaO(3+x)) with Pt, Ag, Au, CuO, NiO and RuO2 as co-catalysts, have been prepared and characterized by XRD, DRS, photoluminescence spectroscopy, SEM and TEM. Photocatalytic reduction of CO2 on these catalysts in alkaline medium under UV–Visible radiation yields methanol and ethanol as major products with traces of methane, ethane, ethylene, etc. Maximum apparent quantum yield (AQY) for CO2 reduction is achieved on the formulation with 0.2 wt% NiO, followed by 1 wt% CuO as co-catalysts. DRS studies reveal that the addition of co-catalysts brings about reduction in band gap energy of NaTaO3 and its light absorption onset edge is extended into the visible region. Coupling of the conduction band bottom energy levels of NiO and CuO with that of Na(1−x)LaxTaO(3+x) shows that they facilitate easy transfer of photo-generated electrons from the doped tantalate to NiO/CuO, wherein these electrons participate in simultaneous hydrogen generation by water splitting and CO2 photoreduction processes. Other co-catalysts, like, Pt, Ag, Au and RuO2 act as electron traps, resulting in charge separation, which, in turn, leads to improvement in photo-catalytic activity. Besides, significant reduction in the intensity of photoluminescence lines observed for Na(1−x)LaxTaO(3+x) with different co-catalysts also indicates longer life time of the charge carriers. Used catalysts retain the cubic perovskite structure of the fresh catalyst during the reaction for 20 h and stable activity is displayed for three cycles. The alkaline medium plays multiple roles, acting as scavenger of holes, increasing the solubility of CO2 and stabilization of NiO. NaTaO3 based catalysts could become viable alternatives to titania for this application.

Photo catalytic reduction of carbon dioxide orartificial photo synthesisto yield hydrogen and hydrocarbons like methane, methanol etc., has emerged as a subject/process of intensive study due to its potential applications towards abatement of atmospheric CO2levels and conversion to fuels and chemicals. This Chapter provides a comprehensive picture of the process that has posed several scientific and technological challenges, like activation of most stable molecules-CO2and water, extremely low conversion rates, complex reaction pathways involving multi electron transfer steps and short catalyst life. All the major aspects/developments on this process like, the salient features and technological aspects, thermodynamic and kinetic characteristics, various types of photo-active catalysts-, like, titania based catalysts and titania with various dopants and modifiers, various metal oxides/sulfides/nitrides/ layered titanates, binary and ternary oxides of Nb, Ta, Ga & In mixed oxide catalysts, metal complexes, and supra molecular catalysts-, sensitization by macro cylic ligands, influence of process parameters, catalyst structure-property-activity correlations, aspects of deactivation of catalysts, reaction mechanistic aspects and sequential surface reaction pathways, recent trends and future directions have been covered. Design and development of efficient catalyst systems and achieving higher yield of desired products (higher selectivity) and extending the catalyst life are the key issues being pursued by the researchers. The process is in nascent stage and further improvements are needed as CO2conversion rates are extremely small, with products formed in terms of 1-10 micro moles/hr. One of the means of improving the process efficiency is to carry out electrochemical reduction of CO2using solar electric power, with an integrated Photo electrochemical cell (PEC). Yet another option is to reduce CO2to methanol with hydrogen produced using solar powered PEC.

Layered perovskite type Sr3Ti2O7 catalysts, doped with N, S and Fe have been prepared by modified polymer complex method, characterized and evaluated for photo reduction of CO2 in aqueous alkaline medium using UV-visible radiation. EDXA and XRD data reveal the incorporation of the dopants into the titanate matrix. The presence of N in substitutional and interstitial locations, S as S6+ and Fe as Fe3+ species are indicated by XPS analysis. DRS and photo luminescence studies show that the dopants form additional energy levels within the band gap, promoting visible light absorption and retarding recombination of the charge carriers. Morphological changes and smaller crystallites also minimize recombination. Layered structure of Sr3Ti2O7 facilitates easy transport of charge carriers and separation of oxidation/reduction reaction centres. Structural, morphological and photo physical characteristics of doped catalysts improve the activity significantly. Sr3Ti2O7 co-doped with N, S and Fe together, displays maximum apparent quantum yield for CO2 reduction products. This journal is � The Royal Society of Chemistry.