The rapid sol-gel synthesis of macroscopic quantities of nanodiamond aerogel (NDAG) is reported at standard temperature and pressure using acid-catalyzed covalent crosslinking of air-oxidized detonation nanodiamond (DND) nanocrystals. Acetonitrile acts as a polar, aprotic solvent both to form a colloidal dispersion of DND particles and to conduct acid-catalyzed polycondensation reactions between resorcinol and formaldehyde (RF) small molecule precursors. Several characterization techniques show that nanodiamond grains are connected via covalent bonding with RF molecules to form a porous, three-dimensional network. Solvent exchange into liquid carbon dioxide and subsequent supercritical drying of NDAGs are used to recover low-density (151 mg/cm 3 ), three-dimensional monolithic aerogels that exhibit surface areas in excess of 589 m 2 /g. The large accessible pore volume from the rapidly synthesized, macroscopic NDAG materials suggests a range of potential applications in catalysis, sensing, energy storage, as well as inert excipients for small-molecule pharmaceuticals.
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.
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