Singlet-Oxygen Generation from Individual Semiconducting and Metallic Nanostructures during Near-Infrared Laser Trapping

Abstract

Photodynamic therapy has been used for several decades in the treatment of solid tumors through the optical generation of chemically reactive singlet-oxygen molecules ( 1 O 2 ). Recently, nanoscale metallic and semiconducting materials have been reported to act as photosensitizing agents with additional diagnostic and therapeutic functionality. To date there have been no reports of observing the generation of singlet-oxygen at the level of single nanostructures, particularly at near-infrared (NIR) wavelengths. Here we demonstrate that NIR laser tweezers can be used to observe the formation of singlet oxygen produced from individual silicon and gold nanowires via use of a commercially available reporting dye. The laser trap also induces two-photon photoexcitation of the dye following a chemical reaction with singlet oxygen. Corresponding two-photon emission spectra confirms the generation of singlet oxygen from individual silicon nanowires at room temperature (30 °C), suggesting a range of applications for investigating semiconducting and metallic nanoscale materials for solid tumor photoablation.

Direct 1O2 optical excitation: A tool for redox biology

“…organ or whole animal), and it usually happens that good two-photon absorbing PSs have other undesirable biological constrains, like inadequate cellular uptake. A very recent development of non-linear absorption-sensitized 1 O 2 generation is the pulsed excitation of metal or semiconductor nanoparticles, leading to the so-called hot-electron excitation [50] , [51] . Briefly, a very short laser pulse (femtoseconds) excites a small population of electrons in the nanoparticle by plasmon resonance.…”

Recovery of hexagonal Si-IV nanowires from extreme GPa pressure

“…A silicon wafer with <111> orientation, doped with boron to a resistivity of 11 Ω cm, was immersed in a solution of 1:1 volume ratio of 10 M HF:0.04 M AgNO 3 for 3 hours. The etched wafer was then immersed in a 1:1 volume ratio solution of 30% (v/v) NH 4 OH:28% (v/v) H 2 O 2 which has been shown to remove any residual silver particles [24]. The resulting nanowire array was sonicated to suspend the nanowires in deionized H 2 O.…”

High-Resolution Photonic Force Microscopy Based on Sharp Nanofabricated Tips

“…Moreover, the chemical stability of the crystal prevents the formation of reactive molecules, as observed in trapped semiconductor and metallic nanoparticles. 31 Our OT setup is shown in Figure 1 d and is described in detail in the Supporting Information . Briefly, a stabilized infrared laser beam of 20–60 mW power is focused by a 1.2 NA microscope objective into a flow cell containing the sample to scan.…”

“…Also, due to the torque imposed by the laser linear polarization on the birefringent medium, the x -cut quartz particle cannot rotate about its geometrical axis (the particle can rotate about its main axis if the laser polarization is circular or if the linear polarization is set in rotation). , This constrains all the degrees of freedom ( x , y , z and two angles, Figure c) of the trapped particle. Moreover, the chemical stability of the crystal prevents the formation of reactive molecules, as observed in trapped semiconductor and metallic nanoparticles . Our OT setup is shown in Figure d and is described in detail in the Supporting Information.…”