Various orientation assemblies of isophthalic acid modified ZnO nanoflowers using double-solvent technique and DMF-concentration depended photocatalytic performance

Three isophthalic acid modified ZnO nanoflowers were prepared by double-solvent technique. These nanoflowers can be formed by various orientation assemblies of building units via different growth modes, planes and directions of nanorods. When the amount of N,N-dimethylformamide (DMF) increases, the specific surface area, photocurrent and charge transfer efficiency of samples increase, while the average grain size and pore radius decrease. These changes are favourable for the improvement of surface active points and the enhancement of photocatalytic degradation rate of the samples. Comparing to S1 and S2, S3 possesses the highest photocatalytic activity, and degrades about 83.082% of tetracycline (TC) within 35 min, and 93.026% of salicylic acid (SA) within 180 min, respectively. DMF mainly acts as a solvent and a nucleation inhibitor. The increase of the DMF concentration decreases nucleation rate, leads to secondary nucleation and growth and different space assembly, which significantly enhance photocatalytic activity of samples. In addition, the photocatalytic mechanisms and assembly processes were proposed.