In hydrothermal synthesis of Pd, Cu(ii) and NaCl enhance yield of 1D nanostructures, which can be optically manipulated in water.

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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We demonstrate that NIR laser-tweezers can be used to induce and observe the formation of singlet-oxygen produced from individual silicon and gold nanowires via use of a commercially available reporting dye and 2-photon photoexcitation. OCIS codes: 350.4855, 260.5130.Singlet oxygen reacts with a range of proteins, lipids, and nucleic acids in vivo to prevent angiogenesis within and metastasis from solid tumors [1]. In this process (known as photodynamic therapy), visible light is typically absorbed by an intermediate photosensitizing molecule (e.g., Photofrin [2]) to create electronic excited states that then transfer their energy to 3 O 2 molecules, converting them to 1 O 2 through a triplet-triplet annihilation process. However, solid materials such as silicon have also been shown to generate singlet oxygen [3].Silicon nanowires are synthesized from p-type silicon wafers using metal assisted chemical etching (MACE) with silver as the active etching metal [4]. High-angle annular dark field transmission electron microscopy (HAADF TEM) was used to confirm the presence of silver domains on SiNWs following their synthesis (Fig. 1a). TEM imaging also confirms that the silver nanocrystals can be removed following an aqueous etching step that dissolves silver (Fig. 1b). Given that metallic nanocrystals [5] have recently been demonstrated to generate singlet oxygen, it must be implicitly ruled out that there is no residual silver to interfere with the experimental measurements. Neutron activation analysis (NAA) is a sensitive measure of metallic elemental composition and was used to analyze the residual amount of silver both with and without the silver-etch. The distinct gamma-ray emission from the 110 Ag isotope decay was used to identify and quantify the silver concentration in the SiNWs. Before silver etching, the Ag concentration is measured to be 291 ppm, whereas after silver etching the amount of Ag is below the detection limits of NAA (<100 parts per trillion).The surface of silicon nanowires following MACE in hydrofluoric acid is expected to be hydrogen terminated, however the metal-etching step is highly oxidative and may also oxidize the surface of silicon nanowires. Fouriertransform infrared absorption spectroscopy on silicon nanowires following the silver-etching step reveals the presence of a silicon dioxide passivation layer that is also confirmed by oxygen k-edge scanning transmission x-ray absorption microscopy. Atom-probe tomography measurements on silicon nanowires further confirm the absence of silver in the bulk of the nanowires following the silver etch, as well as the presence of a surface oxide layer.Laser trapping of individual nanowires was performed using a custom instrument. A 975 nm laser is expanded to overfill the back aperture of a 100x oil immersion objective (NA=1.25) and then focused into a chamber with an