Libra 200fe electron microscope

The ultraviolet-visible (UV-Vis) absorption spectra of gold colloid were recorded on a UV-1800 spectrophotometer (Shimadzu (Kyoto, Japan)) with a spectral resolution of 1 nm. The spectra were measured at room temperature in a quartz cell with optical pathway of 1 cm.
Transmission electron microscopy (TEM) images of gold nanoparticles before and after shell coating were taken on a Libra 200FE electron microscope (Zeiss (Jena, Germany)) with an accelerating voltage of 200 kV. The colloid was applied dropwise (10 μL) onto the surface of carbon films, after which the samples were placed in a dark place for the solvent evaporation in air. TEM images were recorded from three random areas of each sample. Energy dispersive X-ray (EDX) spectra were measured with a X-Max Silicon Drift Detector (SDD) detector (Oxford Instruments Inc. (Abingdon, Oxfordshire, UK)). The line profiles for Si Kα, O Kα and Au Lα signals were recorded for nanotags coated by silica.

All chemicals were purchased from Sigma-Aldrich, Acros Organics, Merck, VWR or TCI and used without further purification if not stated otherwise. UV–vis absorbance measurements were performed with a V-770 double beam spectrophotometer (JASCO) at 25 °C. Samples for spectroscopic measurements were prepared in disposable 1 mL semi-micro PMMA cuvettes (BRAND). Transmission electron microscopy was performed using a Titan Themis G3 300 TEM (FEI) operating at 300 kV or a Libra 200 FE electron microscope (Zeiss) operating at 200 kV. The ζ-potential measurements were carried out on a Nano ZS Zetasizer (Malvern Instruments) at 25 °C and samples were prepared in disposable DTS 1060 capillary cells (Malvern Instruments). The syntheses of the tCD and tTEG can be found in Supporting Information File 1.