A method for easy and fast regeneration of aqueous periodate solutions from dialdehyde cellulose (DAC) production by ozone treatment is presented, along with a direct and reliable simultaneous quantification of iodate and periodate by reversed-phase HPLC. The influence of iodate and ozone concentration, solution pH, and reaction time on the regeneration efficiency was studied, as well as the reaction kinetics. Regeneration of spent periodate solutions by ozone was successfully performed in alkaline medium, which favors the formation of free (.) OH radicals, as supported by the addition of radical scavengers and quantum mechanical calculations. At pH 13 and an ozone concentration of approximately 150 mg L(-1) , periodate was completely regenerated from a 100 mm solution of iodate within 1 h at room temperature. A cyclic process of cellulose oxidation and subsequent regeneration of spent periodate with 90 % efficiency has been developed. So far, commercial applications of DAC have been hampered by difficulties in reusing the costly periodate. This work overcomes this hurdle and presents a highly efficient, clean, and low-cost protocol for the preparation of DAC with integrated periodate recycling, with the possibility of scaling the process up.
Herein we investigate the feasibility of detecting photo-induced surface stress changes using the deflection response of cantilevers. For this purpose, silicon microcantilevers have been functionalised with spiropyran photochromic molecules, using both a monolayer and a polymeric brushes approach. Upon ultraviolet light irradiation, the spiropyran unit is converted to the merocyanine form due to the photo-induced cleavage of the C spiro -O bond. The two forms of the molecule have dramatically different charge, polarity and molecular conformations. This makes spiropyrans an ideal system to study the correlation between photo-induced molecular changes and corresponding changes in surface stress. Our investigations include monitoring the changes in static cantilever deflection, and consequently, surface stress of the spiropyran functionalised cantilevers on exposure to ultraviolet light. Cantilever deflection data reveals that ultraviolet induced conformational changes in the spiropyran moiety cause a change in compressive surface 2 stress and this varies with the type of functionalisation method implemented. The change in surface stress response from the spiropyran polymer brushes functionalised cantilevers gives an average surface stress change of 98 Nm -1 (n = 8) while the spiropyran monolayer coated cantilevers have an average surface stress change of about 446 Nm -1 (n = 24) upon irradiation with UV light.
Here we investigate the feasibility of detecting the photo-reversible inter-conversion between the two thermodynamically stable states of the photochromic molecule spiropyran, using silicon microcantilever sensors. The merging of microcantilever technology and spiropyran photochromic brushes for the first time, offers a good route for the pairing of a sensitive transducer with a sensing surface which can be optically controlled. Photo-induced switching between the spiropyran isomers has been tracked through changes in surface stress of the cantilever that can be detected by monitoring the cantilever deflection.
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