Adaptive Cavitation Ultrasonication for Large-Scale Preparation of Porous Silicon Nanoparticles

Porous silicon nanoparticles (pSiNPs) are of increased interest for use in drug delivery systems, as catalysts, and as biomedical imaging agents. The most common synthesis of pSiNPs involves electrochemical anodization of a silicon wafer, followed by ultrasonic fracture of the resulting mesoporous film to form well-defined nanoparticles. A major source of loss in this process is the ultrasonic fracture step. This work presents a method of synthesizing gram-scale quantities of pSiNPs with high yield and high reproducibility using an ultrasonic bath equipped with a sample rotation stage and a refrigerator (4 °C) and a higher ultrasound frequency with power delivered in a pulsed modality compared with the static ultrasound “cleaning baths” commonly used for this purpose. The optimal processing conditions are determined by adjusting the pSi film mass, solvent volume, and iteration number of on/off cycles used in sonication. The approach provides pSiNPs with a narrow size distribution (∼170 nm, PDI = 0.149), higher yields (59%), and an approximately 12-fold reduction in the total processing time, allowing the preparation of gram-scale quantities of pSiNPs from single-crystal silicon wafers with high reproducibility in a single 24 h process. The performance of the produced pSiNPs is validated in a drug delivery application in which loading and release of the anthracycline drug doxorubicin are compared with pSiNPs prepared in a conventional cleaning bath ultrasonicator.