Bioinspired nanodevice based on the folic acid/titanium dioxide system

Poprzez chemisorpcję kwasu foliowego na powierzchni dwutlenku tytanu otrzymano nowe nanomateriały bioinspirowane. Chromofor organiczny jest połączony kowalencyjnie z powierzchnią półprzewodnika za pośrednictwem grup karboksylanowych łańcucha glutaminianowego. Geometria i struktura elektronowa chromofora zostały dokładnie określone za pomocą obliczeń techniką DFT. Badania fotoelektrochemiczne wykazały silną fotosensybilizację półprzewodnika na światło widzialne. Fotoelektrody zbudowane z dwutlenku tytanu modyfikowanego kwasem foliowym generują fotoprądy w zakresie 300-600 nm. Ponadto stwierdzono, że kierunek fotoprądu (anodowy lub katodowy) może być zmieniony poprzez zmianę polaryzacji podłoża przewodzącego. Pomiary fotoelektrochemiczne uzupełnione badaniami spektroskopowymi pozwalają na określenie machenizmu przełączenia fotoprądu. Fotoelektrody zbudowane z materiału hybrydowego mogą pozwolić naudowę przełączników optoelektronicznych i bardziej złożonych układów logicznych.A new bioinspired nanomaterial has been obtained by chemisorption of folic acid onto nanocrystalline titanium dioxide. The organic chromophore is linked with the semiconductor surface via the glutamate chain and anchored with the carboxylate group. The geometry and electronic structure of the chromophore was studied in detail with DFT. Photoelectrochemical studies revealed photosensitization of the new material towards visible light. The photoelectrodes composed of the folic acid/titanium dioxide hybrid material generated photocurrent over a 300-600-nm window. Moreover, the direction of the photocurrent could be changed from anodic to cathodic and vice versa by application of the appropriate photoelectrode potential. Photoelectrochemical and spectroscopic studies allowed the elucidation of the mechanism of photocurrent switching. Photoelectrodes composed of folate-modified titanium dioxide may serve as a simple model of optoelectronic switches and may constitute the basis for molecular photoelectronic devices

Photosensitization and photocurrent switching in carminic acid/titanium dioxide hybrid material

New photoactive material is obtained by chemisorption of carminic acid onto nanocrystalline titanium dioxide. Organic chromophore is anchored at the semiconductor surface via the neighboring carboxylate and phenolate groups; the anchorage is strengthened by formation of the six-membered chelate ring. Photoelectrochemical studies reveal strong photosensitization of the new material toward visible light: The photoelectrodes comprised of carminic acid−titanium dioxide hybrid material generate photocurrent within 300−650 nm window. Moreover, the direction of the photocurrent can be changed from anodic to cathodic and vice versa by application of appropriate photoelectrode potential, changes in electrolyte composition, and incident light wavelength. Geometry, electronic structure, and the photophysics of the neat chromophore and its model complex with TiIV oxo-species are studied in detail using the density functional theory method. Photoelectrochemical and spectroscopic studies supplemented with quantum-chemical modeling allow elucidation of photocurrent switching mechanism. The carminic acid−titanium dioxide material constitutes an efficient platform for light harvesting antennae, optoelectronic switches, and other optoelectronic devices

The Effect of Tillage Systems and Weed Control Methods on the Yield and Quality of Spelt Grain (Triticum aestivum ssp. spelta L.)

The aim of this three-year field experiment was to determine how simplified (reduced) pre-planting tillage and different weed control methods impact the yield and selected quality parameters of spelt grain (Triticum aestivum ssp. spelta L.). Conventional tillage and three variants of reduced tillage (RT) were tested. The second experimental variable (weed control) had three variants: mechanical weed control (M), combined mechanical + chemical treatment at full herbicide rate (MC 100%), and combined mechanical + chemical treatment at 25%-reduced herbicide rate (MC 75%). The mechanical method consisted of harrowing the wheat crop in the fall and spring. The results showed that the wheat yields obtained under reduced pre-planting tillage were comparable to those under conventional tillage. However, the grain quality parameters proved to be worse under the reduced tillage regimes. Herbicide applications, both at full and reduced rates, significantly improved grain quality parameters and yields compared with mechanical-only weed control. In particular, the herbicide-treated crops boasted higher values of thousand-kernel weight and grain weight per ear

Mechanistic studies of the hydrolysis of p-nitrophenyl sulfate catalyzed by arylsulfatase from Helix pomatia

The kinetics of the hydrolysis of small aryl substrate p-nitrophenyl sulfate (p-NPS) catalyzed by arylsulfatase from Helix pomatia was studied at a wide range of temperatures as well as at ambient and elevated pressures. The employed kinetic assay techniques allow for the determination of activation entropy ([image omitted]), activation enthalpy ([image omitted]), as well as activation volume ([image omitted]) which suggested associative interchange character of the sulfate ester hydrolysis. The pH dependence obtained for catalytic parameters suggests that two protonation/deprotonation reactions can occur and the optimum pH for the catalytic activity was also detected