Enhanced thermal effect of plasmonic nanostructures confined in discoidal porous silicon particles.

The design of plasmonic nanostructures could have many exciting applications since it enhances or provides valuable control over efficient energy conversion. A three-dimensional (3D) space is a realistic hotspot matrix harvesting a wide conversion that has been shown in zero-dimensional nanoparticles, one-dimensional linear structures, or two-dimensional films. A novel 3D plasmonic nanostructure platform consisting of plasmonic metal nanoparticles in discoidal porous silicon particles is used in this study. Plasmonic gold nanoparticles are anchored inside the discoidal porous silicon (DPS) particles by reduction synthesis. The novel plasmonic nanostructures can tailor the plasmon band and overcome the instability of photothermal materials. The "trapping well" for the anchored nanoparticles in 3D space can result in a huge change of plasmonic band of metal nanoparticles to the near-IR region in a novel 3D geometry. A multifunctional scaffold, Au-DPS particle, composed of doxorubicin conjugated to poly-(l-glutamic acid) (pDOX), was developed for combinatorial chemo-photothermal cancer therapy. The therapeutic efficacy was examined in treatment of the A549 cell line under near-IR laser irradiation. The highly efficient photothermal conversion can also be demonstrated in the laser desorption/ionization time-of-flight mass spectrometry detection analysis. The limit of detection was obviously improved in the detection of angiotensin II, P14R, and ACTH fragments 18-39 peptides. Overall, we envision that Au-DPS particles may be used in ultrasensitive theranostics in the future.