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Preparation of graded‐index optical microcavities based on porous silicon is demonstrated, and chemical modifications for obtaining improved stability under alkaline conditions are studied. Four surface modification methods for stabilizing the samples are examined, and the effects on the optical properties are verified. Two different thermal carbonization treatments resulting in hydrophilic and hydrophobic surfaces are employed. In addition, modification with undecylenic acid is performed on as‐prepared and thermally hydrocarbonized porous silicon surfaces. Stability and sensing capabilities of the modified samples are examined by subjecting them to different concentrations of methylamine and trimethylamine vapors. Vapor induced changes in the reflectance spectra are used for evaluating sensitivity and stability. Sensitivity towards ethanol vapor is also measured in order to compare the sensitivity to a normal organic solvent. The results show that the two carbonization treatments and the undecylenic acid functionalization of the hydrocarbonized surface result in greatly improved stability. In contrast, derivatization of as‐prepared porous silicon with undecylenic acid does not protect the surface sufficiently against oxidation under the highly basic conditions produced by the amine vapors. Surface chemistry is also shown to have a large effect on sensitivity towards the examined vapors. X‐ray photoelectron spectroscopy was used to assess changes in elemental composition of sample surface. The results suggest that thermally promoted addition of undecylenic acid on hydrocarbonized porous silicon is an effective method for producing highly stable optical structures with a carboxyl group functionalization.

Sorption of Co(II) on the biogenic Mn oxide produced by a Paraconiothyrium sp.-like strain was investigated. The biogenic Mn oxide, which was characterized to be poorly crystalline birnessite (Na4Mn(III) 6Mn(IV) 8O27 ·9H2O) bearing Mn(III) and Mn(IV) in the structure, showed approximately 6.0-fold higher efficiency for Co(II) sorption than a synthetic Mn oxide. XP-spectra of Co 2p for the biogenic and synthetic Mn oxides after Co(II) sorption indicate that Co was immobilized as Co(III) on the surface of Mn oxides, clearly suggesting that redox reaction occurs between Co(II) ions and each Mn oxides. The Co(II) ions would be initially sorbed on the vacant sites of the surface of biogenic Mn oxide, and then oxidized to Co(III) by neighbor Mn(III/IV) atoms to release Mn(II). For the synthetic Mn oxide, release of Mn(II) was negligibly small because the oxidant is only Mn(IV) in ramsdellite (γ-MnO2). The Mn(II) release from the biogenic Mn oxide during Co(II) adsorption would be not only from weakly bounded Mn(II), but also from redox reaction between Mn(III/IV) and Co(II) ions.

Slurry phase alkylation of biphenyl with propene was carried out using H-mordenite (HM) catalysts with Si/O2Al2O3 ratios of 10, 15, and 20. The HM(10) catalyst exhibited low selectivity for 4,4′-diisopropylbiphenyl (4,4′-DIPB) production compared with the HM (20) catalyst. When the external acid sites were posioned by treatment with tributylphosphite, however, HM (10) became the most selective catalyst for 4,4′-DIPB production. The high selectivity of HM (10) was related to its low activity for isomerization of 4,4′-DIPB. Propene was selectively consumed by alkylation on HM (10), while undesirable side reactions of propene occurred on HM (20). These results are understood by taking acid strength into consideration.