Efficient visible light photodegradation of Methylene blue using TiO 2 -graphene based composites has been reported. DFT calculations corroborate the mechanism for Ti-O-C bond formation, leading to an additional band edge and band gap tuning. AbstractHere we report experimental and theoretical study of two TiO 2 -graphene oxide (TG) and TiO 2 -reduced graphene oxide (TR) composites synthesized by a facile and ecological route, for enhanced visible light (~470nm) photocatalyc degradation of Methylene Blue (MB) (99% efficiency), with high rate constant value (1800% over bare TiO 2 ). TG couples TiO 2 nanopowder with Graphene Oxide (GO) while TR couples it with reduced graphene oxide (RGO). The present study, unlike previous reports, discusses never before reported double absorption edges obtained for both TG (3.51 eV and 2.51 eV) and TR (3.42 eV and 2.39 eV) composites, which marks the reason behind feasible visible light (2.56 eV) induced photocatalysis. TiO 2 domains in the composites dominate the higher band edge, while GO/RGO domains explain the lower band edge. Formation of Ti-O-C bond in both TG and TR drives the shifting up of the valence band edge and reduction in band gap. Further, these bonds provide a conductive pathway for charge carriers from TiO 2 nanopowder to the degrading species via the GO/RGO matrix, resulting in decreased charge carrier recombination in TiO 2 and enhanced efficiency.To attest that the developed theory is proof-positive, density function theory (DFT) calculations were performed. DFT obtained energetics and electronic structures support experimental findings by showcasing the play of Ti-O-C bond, resulting in double band edge phenomenon in composites.Finally, the mechanism behind MB degradation is discussed comprehensively and the effect of weight percent of GO/RGO in composite on rate constant and photodegradation efficiency has been studied experimentally and explained by developing analytical equations. 4 promising as it simultaneously possesses excellent absorptivity, transparency, conductivity and reachability, which could assist effective photodegradation of pollutants.There is a pool of reports showing the enhanced photocatalytic activity of TiO 2 nanoparticles with graphene composites for the degradation of organic molecules and photocatalytic splitting of water under UV light. 22, 28-38 Enhanced photocatalytic activity was attributed to the synergetic effect between graphene and TiO 2 nanoparticles, because graphene acts as an excellent electron acceptor and transporter, the Ti-O-C bond open up an easy path for charge transfer which remarkably decreases the recombination of electron−hole pairs. 3 Although claiming good efficiency, many of these reports are based on usage of un-ecological UV light and suffer from low kinetics (k value). [28][29][30] Realizing the importance of efficient visible light photodegradation, there are few reportes which show enhanced photocatalytic activity of TiO 2 -GO/RGO composites under visible light. 39-42 The results and application part is...

Extracellular polymeric substances (EPS) are expected to be an important source for the formation of mineral-organic associations in soil. Because such formations affect the composition of mobile and immobile organic matter as well as the reactivity of minerals, we investigated the composition of EPS before and after adsorption to goethite. Raman measurements on EPS extracted from Bacillus subtilis distinguished four fractions rich in proteins, polysaccharides, lipids, or lipids and proteins. Scanning transmission X-ray microscopy identified three different EPS-fractions that varied in their composition in proteins, nonaromatic proteins, and polysaccharides. Reaction of EPS with goethite led to a preferential adsorption of lipids and proteins. The organic coverage was heterogeneous, consisting of ~100 × 200 nm large patches of either lipid-rich or protein-rich material. Nanoscale secondary ion mass spectrometry showed a strong S enrichment in aggregates of ~400 nm in the goethite adsorbed EPS. From our simplified model system, we learned that only a small portion (<10%) of EPS was immobilized via adsorption to goethite. This fraction formed a coating of subμm spaced protein-rich and lipid-rich domains, i.e., of two materials which will strongly differ in their reactive sites. This will finally affect further adsorption, the particle mobility and eventually also colloidal stability.

Plant diseases have a direct impact on the productivity of crops, and therefore the early detection of diseases is crucial.

We studied the formation of iron-rich particles at steeply opposing gradients of oxygen and Fe(II) within the redoxcline of an acidic lignite mine lake (pH 2.9). Particles formed had a diameter of up to 380 mm, showed high sedimentation velocity (, 2 m h 21 ), and were dominated by the iron mineral schwertmannite. Although the particles were highly colonized by microbial cells (, 10 10 cells [g dry weight] 21 ), the organic carbon content was below 11%. Bathymetry and the inflow of less acidic, Fe(II)-rich groundwater into the northern basin of the lake results in two distinct mixing regimes in the same lake. The anoxic monimolimnion of the northern basin had higher pH, Fe(II), dissolved organic carbon, and CO 2 values compared with the more central basin. Particles formed in the northern basin differed in color, were smaller, had higher organic carbon contents, but were still dominated by schwertmannite. Microcosm incubations revealed the dominance of microbial Fe(II) oxidation.