2results about How to "No doping" patented technology

The preparation method and application of the material for the dimethylamine gas sensor have the following advantages that ammonium paratungstate is used as a tungsten source, the tungsten oxide material with a (020) highly exposed surface crystal phase is prepared by regulating and controlling the usage amount and the adding sequence of polyvinyl alcohol (PVA), and the material has high selectivity to dimethylamine gas. The material does not need precious metal doping, and is low in manufacturing cost, environmentally friendly, simple in synthesis route and high in repeatability. The prepared sensor is rapid in response, low in detection line (1 ppm), high in sensitivity (74) when exposed to 50 ppm dimethylamine, and excellent in selectivity and repeatability. The excellent sensing capability can be attributed to a (020) highly exposed surface crystal phase and a unique hollow bowl-shaped tungsten oxide nano spherical shell structure formed by rich porous structures. The preparation method is simply realized through spray drying and the like, so that mass production can be realized. The technology has profound market application prospects and important significance in the fields of industrial production, environment monitoring, indoor air quality monitoring, safety protection and the like and in the aspect of food quality detection.

In the existing polylactic acid production, lactide is firstly prepared from lactic acid or purchased, and then lactide is subjected to ring-opening polymerization by using a relatively expensive catalyst such as metal zinc elementary substance, so that polylactic acid is prepared in two steps. According to the scheme, food-grade zinc acetate dihydrate is used as a catalyst for catalyzing lactic acid to accelerate dehydration condensation reaction, and lactic acid obtained by fermenting lactic acid bacteria after saccharification of starch is subjected to one-step catalysis is heated, stirred and polycondensed at a proper temperature to prepare polylactic acid. The whole process is free of disordered interference reaction, and all reactant products belong to food grade, are non-toxic and harmless, and are ecological and environment-friendly. Complex and expensive instruments, equipment and reagents are not needed. Zinc acetate dihydrate is easily dissolved in a lactic acid aqueous solution, ionized zinc ions have two valence states of + 1 valence and + 2 valence, an empty electron orbital and a unique Ar 3d10 electronic structure and have strong electronegativity, the + 1 valence zinc ions lose or obtain one electron, the surfaces of the zinc ions have rich catalytic active sites, and the catalytic activity of the zinc ions is improved. In an acid environment of a lactic acid solution, zinc ions catalyze hydroxyl carboxyl contained in lactic acid molecules to accelerate transition loss of electrons with different probabilities and probabilities or shift deflection of direction, angle and the like of shared electrons, so that water molecules are formed and removed, and dehydration condensation of hydroxyl carboxyl in lactic acid molecules and between lactic acid molecules is continuously catalyzed; and carrying out polycondensation on the oligomeric lactic acid to obtain polylactic acid. Meanwhile, a small amount of intermediate lactide formed by heating and catalyzing is also subjected to ring-opening polymerization reaction to form a linear polylactic acid chain.