| Liquid colloidal photonic crystals are special colloidal assembly structures founded in colloidal solutions,usually with a solvent-filled,non-contact,close-packed structure.The liquid colloidal crystals have the characteristics of fluidity,mesostability,reversible assembly,etc.They are easy to produce sensitive optical response under weak stimulation,and thus have broad application prospects in the fields of photonic crystal sensors and structural color display devices.However,there are few researches on the efficient synthesis methods of liquid colloidal crystals,and there are several key problems to be solved in the preparation process,such as the driving force of spontaneous precipitation of colloids,the assembly efficiency of colloidal crystals with high crystallinity,etc.,which seriously limits the research and application of related materials.In order to solve the above scientific problems,we have developed a new synthetic method for the preparation of liquid colloidal photonic crystals based on colloid superabsorbent precipitation driven by electric field.The charged colloidal particles are electrophoretically enriched in the direction of the oppositely charged electrode under the action of an electric field,and the increasing electrostatic repulsion which is continuously enhanced as the colloidal particle spacing is reduced prevents the colloidal from coalescing and settling,thereby efficiently producing a highly concentrated and non-agglomerated colloid.And then the colloidal particles spontaneously precipitates and self-assembles into a liquid colloidal crystal.Studies have shown that the electric field driven method is based on the general behavior of colloidal particles electrophoresis in dielectric solvents,and there is no special requirement for the chemical composition of colloidal particles and solvents.Therefore,electric field driven colloidal supersaturated precipitation method is a universal method for preparing liquid colloidal crystals.Using this method,we have successfully prepared a dozen liquid colloidal crystal systems with bright structural colors such as SiO2 / EtOH,CeO2 / PC and PS / EG.We can greatly improved the efficiency of the preparation process which is driven by electric field by selecting colloidal dilute solution with appropriate polarity,viscosity and concentration,and optimizing the electrode spacing,operating voltage,electric field action time,and electrode material.Using the strategy of replenishing solvent and colloidal powders step by step,we have also achieved the continuous preparation of liquid colloidal crystals,which can reduce the use of reagents and increasing the yield of liquid colloidal crystals.During the preparation process,we find that liquid colloidal crystals have a sensitive response to changes in the physicochemical environment of the system,so we use liquid photonic crystals to construct sensors that are sensitive to glucose.In the past work,the researchers mainly grafted the glucose recognition group into the photonic crystal gel structure and detected the concentration of the glucose solution by the change of the photonic crystal structure and optical properties caused by the swelling and contraction of the gel.In our work,liquid photonic crystals,which have a liquid state,facilitate the introduction and dispersion of the recognition group and the detected substances.By optimizing the concentration of colloidal particles and the amount of PBA in the concentrated solution,we constructed PBA functionalized liquid photonic crystals with different detection ranges and detection sensitivities.At the same time,we established a working curve between the wavelength change of the reflection spectrum of the liquid photonic crystal and the glucose concentration,through which the concentration of the unknown glucose can be obtained.A large number of experimental data and systematic studies have shown that PBA functionalized liquid photonic crystals have reliability and stability for the specific recognition of glucose. |
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