Application of sensitive hydrogels in chemical and pH sensors

In the present work, pH-sensitive poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) blends as well as hydrogels based on poly(N-isopropylacrylamide) (PNIPAAm), which are sensitive to organic solvent concentration in aqueous solutions, were used in silicon micromachined sensors. A sensitivity of approximately 15 mV/pH was obtained for a pH sensor with a 50 μm thick PVA/PAA hydrogel layer in a pH range above the acid exponent of acrylic acid (pK_a=4.7). The output voltage versus pH-value characteristics and the long-term signal stability of hydrogel-based sensors were investigated and the measurement conditions necessary for high signal reproducibility were determined. The influence of the preparation conditions of the hydrogel films on the sensitivity and response time of the chemical and pH sensors is discussed.     

ChemInform Abstract: The Extended Stability Range of Phosphorus Allotropes.

A complete stability range of known and new crystalline allotropes of phosphorus including recently discovered tubular modifications and not‐yet‐known crystal structures of [P₁₂] nanorods, and not‐yet‐isolated [P₁₄] nanorods is given using quantum chemical DFT calculations.