Methods The samples were grown employing an Au-assisted VLS process. Si(100) substrates were functionalised with 0.1% poly-L-lysine solution SB202190 (PLL) and coated with colloidal 5-nm-diameter Au nanoparticles. A solid precursor was placed in the AZD3965 centre of
a Nabertherm B180 horizontal tube furnace (Lilienthal, Germany) at atmospheric pressure and at a constant N2 flow rate of 150 standard cubic centimetres (sccm). Prior to growth, the tube was flushed several times by pumping with a membrane pump and readmitting dry nitrogen. The furnace was ramped to the desired temperature over 1 h and then held constant for 1 h, before being allowed to cool down to room temperature. The substrates were placed downstream from the precursor. By adjusting the position, substrate temperatures between 150°C and 550°C can be set for a chosen centre temperature of 585°C. SEM and EDS measurements were carried out on as-grown samples. For TEM measurements, nanowires were scraped from the substrate and placed onto a carbon support film on a copper grid. For tapping-mode AFM measurements, the nanowires were transferred onto a clean Si substrate in a frozen drop of DI water. X-ray powder diffraction data were measured on beamline I15 at the Diamond Light Source in Didcot, Oxfordshire, England. A pre-focused monochromatic beam (E=37.06 keV) was collimated with a 30 – μm pinhole. The sample material
was removed from the as-grown substrate using a micro-chisel and placed onto the culet of a PLX 4720 single crystal diamond (as used in diamond anvil cell experiments). In this way, diffraction patterns free of substrate contributions can be recorded. At these energies, there is little absorption by diamond and the diamond background scattering and Bragg contributions are easily identified. Powder diffraction patterns Ribose-5-phosphate isomerase were recorded using a PerkinElmer detector (Waltham, MA, USA), integrated using Fit-2D and analysed using PowderCell.
Raman spectroscopy was carried out on a Horiba T64000 Raman spectrometer system (Kyoto, Japan) in combination with a 632.8 -nm He-Ne laser at 1 mW. The beam was focussed onto the substrate through a microscope with a ×100 objective lens to allow for the study of individual nanowires. The backscattered signal was dispersed by a triple grating spectrometer with a spectral resolution of 1 cm −1. The polarisation of the light was parallel to the nanowire axis to maximise the intensity. All measurements were carried out at room temperature. The spectrometer was calibrated using a Ne standard. Results and discussion The morphology and composition of the synthesised nanostructures depend strongly on the substrate temperature. SEM micrographs of samples grown at substrate temperatures of 480°C, 506°C, and 545°C are shown in Figure 1 together with the composition of the grown structures.