The Porosity Sensor Based On The Liquid Photonic Crystals

Porous material have been widely used in chemical industry,environmental protection,medical engineering and many other fields due to their high porosity,tunable pore size,good absorbability,selective permeability,which is indispensable functional material for national production and economic construction.The properties of porous material in specific applications are determined by pore structure such as pore volume,pore distribution,surface area,so the measurement of pore structure is an indispensable technology in various application.Generally,the gas adsorption method and mercury intrusion has been accepted as a standard method for a long time,there are still unsatisfactory aspects including the time-consuming process and consumption of liquid nitrogen or mercury which is both harmful for people and environment,so a high-efficient,encomic,environmental and new characterization method is urgent to be developed.In many smart materials,responsive photonic crystal?PC?is intrinsically suitable for different sensors because of its tunable crystal structure and optical signal.In this paper,a new liquid photonic crystal based technology is proposed to determine the pore structure.Supersaturated SiO₂ collodial solution could precipitate spontaneously to form liquid colloidal photonic crystals.When it is mixed with porous substance,part of the solvent will be absorbed into the porous pores,which leads to the shrinkage of the precipitated photonic crystal lattice and blue shift of reflection peaks.The woking curves for moespore and total pore volume are bulit according to the positive relationship between the unit mass reflection change???/m?and pore volume?V?,the negative relationship between the average absorption temperature?Ta?and the pore diameter?D?.Therefore,the pore volume and diameter of unknown mesporous SiO₂ material could be measured successfully through the liquid photonic crystals method.Same as the above-mentioned method,we bulid the working curve for macropore according to the the negative relationship between saturated absorption temperature?Ts?and the pore diameter?d?.Consequently,the pore diameters of unknown hierarchically porous silica could be measured through the woking curves for mesopore and macropore.Compared to the traditional methods,the liquid PC method provides a convenient,efficient,eco-friendly and low-cost solution for porosity measurement,which could be a useful supplement to the current methods no matter in lab research or industrial application.