He ne laser

The single-particle SERS measurement was conducted using a Raman microscope (Ntegra, NT- MDT) equipped with an inverted optical microscope (IX 73, Olympus). A dichroic mirror directs the excitation laser beam into an oil-immersion objective (UPlanSApo, 100×, 1.4 numerical aperture), which focuses the beam to a diffraction-limited spot (~2 μm) on the upper surface of the cover glass slip. Photomultiplier tube images were obtained using a piezoelectric x, y sample scanner to identify nanoparticles. For attaching Raman reporter on the entire surface of nanostructures, we added the Raman reporter into solution including the resulting nanostructures and kept the solution at 30 °C during 3 h. After centrifugation twice, we can remove the extra amount of Raman reporter in solution and get the concentrated solution of nanostructure. Then, we dropped the solution on the cover glass and removed the droplet using blow gun after 5 min. The SERS spectra were acquired with 633 nm laser (He–Ne laser, Thorlabs) excitation for 10 s. The signals were obtained by a CCD detector (1024 × 256 pixels; Peltier; cooled to −70 °C, Andor Newton DU920P BEX2-DD). After analysis, FESEM images of the samples were obtained after Pt layer deposition using an Ar plasma sputter-coater (Cressington 108 auto) with a current level of 30 mA for 60 s on a slide glass.

The PCS measurements were performed on a custom-built fixed-angle setup (scattering angle $\theta$ : 60°) utilizing a He–Ne Laser (wavelength $\lambda =632.8$ nm, 21 mW, Thorlabs, Newton, MA, USA) and two photomultipliers (ALV/SO-SIPD, ALV-GmbH, Langen, Germany) in a pseudo-cross-correlation configuration. The signal was correlated with an ALV-6010 multiple-tau correlator (ALV GmbH, Langen, Germany). Subsequently, the intensity–time correlation functions were converted to the field–time correlation function $g^1\left(t\right)$ and analyzed using the CONTIN software [62 (link)]. However, an analysis using a second-order cumulant function also leads to the same result within the exp. precision. The temperature was controlled via a thermostat (Phoenix II, Thermo Fisher Scientific, Waltham, MA, USA together with Haake C25P, Thermo Fisher Scientific, Waltham, MA, USA), and the sample was equilibrated for 25 min inside the decaline-filled refractive index matching bath. For each temperature, 5 consecutive measurements were performed. The obtained mean relaxation rates $\Gamma$ of the $g^1\left(t\right)$ functions were converted to the hydrodynamic radius by
$R_h=\frac{k_{B}T}{6\pi \eta \frac{\Gamma }{q^2}}.$ Here, $k_B$ is the Boltzmann constant, $\eta$ the solvent viscosity (water), T the temperature in Kelvin, and $q=\frac{4\pi n}{\lambda }sin\frac{\theta }{2}$ the magnitude of the scattering vector. n is the refractive index of the solvent.

To evaluate the structural properties of the InN NCs, we employed HR-XRD by means of a MRD Xpert system from Panalytical (Panalytical, Malvern, Worcestershire, UK), which has a Cu $\alpha$ radiation in an open detector configuration. The surface morphology was analyzed by using a JEOL JSM-7401F SEM (JEOL, Akishima, Tokyo, Japan). The nanocolumns were additionally studied by HR-TEM images, obtained in a Jeol JEM 2010 (JEOL, Akishima, Tokyo, Japan) operating at $200\mathrm{kV}$ , where NCs were peeled off from the substrates and mounted on holey carbon-coated copper grids. Micro-structural properties were studied by micro-Raman spectroscopy (NT-MDT, Integra Spectra, Zelenograd, Moscow, Russia) at room temperature in a backscattering configuration employing the $632\mathrm{nm}$ line of a He–Ne laser (Thorlabs Inc, Newton, NJ, USA).