In this study, we report soft and solvothermal methods for synthesis of zinc oxide nanoparticles (ZnO NPs). Both methods involve a precursor and are carried out at the middle low-temperature regime. The effect of different solvents on the ZnO NPs properties was studied. The nonlinear optical (NLO) response of the NPs was analyzed by the self-action of picosecond laser pulses at 1064 nm and by second harmonic generation (SHG) of a femtosecond laser pulses pump at 800 nm. The luminescence was studied within UV-visible ranges. It was shown that the NLO response efficiency significantly depends on the solvent. The obtained SHG efficiency of small (~2 nm) ZnO NPs is comparable to the one obtained for large (~150 nm) commercial ZnO NPs. The observed results are important for the application of the ZnO NPs in biolabeling.Electronic supplementary materialThe online version of this article (doi:10.1186/s11671-017-1934-y) contains supplementary material, which is available to authorized users.