Rm2000

Characterization of the crystal structures of minerals in NWA 8003 was performed by obtaining their Raman spectra and Electron Backscatter Diffraction (EBSD) patterns, and comparing these with the spectra and patterns in datasets. Raman spectra were measured with the laser micro-Raman spectrometer Renishaw RM2000 at Nanjing University. A microscope was used to focus the excitation laser beam of 514 nm (Ar⁺ laser) on the target phases. The sample was excited by a laser power of ~5 mW, using a spot size of ~2–3 μm. The Raman spectra baselines were reduced by using the OPUS software (version 3.1). The minerals’ EBSD patterns were obtained using an Oxford EBSD detector attached to a JEOL 7000F FEG-SEM at Hokkaido University, at an accelerating voltage of 20 kV and an incident beam current of 4 nA. Before analysis, the sample was vibro-polished and carbon-coated. The experimental EBSD patterns were indexed using the Aztec software with structures from both the HKL dataset and a dataset from the Mineralogical Society of America. The Aztec software automatically suggests indexing solutions ranked by the lowest ‘mean angular deviation’ (MAD) as a ‘goodness of fit’. MAD values of <1 are considered desirable for accurate solutions.

Raman spectra of the bimetallic nanoparticles deposited on aluminum plate were measured at different points of the dried sample by using a Renishaw RM2000 micro-Raman instrument equipped with a diode laser emitting at 785 nm. Sample irradiation was accomplished by using the 50× microscope objective of a Leica Microscope DMLM. The backscattered Raman signal was fed into the monochromator through 40 μm slits and detected by an air-cooled CCD (2.5 cm⁻¹ per pixel) filtered by a double holographic Notch filters system. Spectra were calibrated with respect to a silicon wafer at 520 cm⁻¹.
SERS spectra of 10⁻⁴ M 2,2′-bipyridine (Sigma-Aldrich, St. Louis, Missouri (USA), 99% purity) in bimetallic colloid were obtained after addition of 10⁻² M NaCl (Sigma-Aldrich, St. Louis, Missouri (USA), 99.999% purity) in order to increase the SERS enhancement without compromising the colloidal stability. The 647.1 nm line of a Kripton ion laser and a Jobin-Yvon HG2S monochromator equipped with a cooled RCA-C31034A photomultiplier were used. A defocused laser beam with 100 mW power was employed for impairing thermal effects. Power density measurements were made using a power meter instrument (model 362; Scientech, Boulder, CO, USA) giving ∼5% accuracy in the 300–1000 nm spectral range.

The samples were characterised via scanning electron microscopy (SEM, Quanta FEG 250), transmission electron microscopy (TEM, Tecnai G2 F20), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT, Spectrum 100 FT-IR), and Raman spectroscopy (Renishaw RM2000). The crystallinity of the sample was investigated by X-ray diffraction (XRD, BRUKER D8 ADVANCE), whereas the Brunauer–Emmett–Teller (BET) surface area (Micromeritics ASAP2020), pore volume, and pore size were characterised using nitrogen adsorption at liquid nitrogen temperatures, and via X-ray photoelectron spectroscopy (XPS, Thermo SCIENTIFIC ESCALAB 250Xi).

Raman measurements were performed at room temperature on RENISHAW RM2000 micro-Raman apparatus (Pianezza, Italy) with a 785 nm laser as excitation source unless otherwise stated in the text. The relatively lower photon energy of the 785 nm laser was chosen to avoid thermal degradation of the protein. We used a 50× objective with accumulation times of 30 s per spectrum and a 70 µW power on the sample. The accumulation times and the laser power were the same for all Raman measurements.
SERS measurements were performed directly on AgNC/NS and GO-AgNC/NS coated QMC sensors after monitoring the adsorption of native Hen egg-white lysozyme (HWL-N) or fibrillar Hen egg-white lysozyme (HWL-F).
In the case of SERS measurements on glass substrates coated with GO-AgNC/NS layers, the coated slides were immersed in HWL-N or HWL-F solution for two hours to ensure that adsorption equilibrium was reached, then repeatedly rinsed with buffer and dried under nitrogen flux before each SERS measurement.

RhB with analytically purity was used as the probe molecule to study the SERS activities of the mullite nanowhisker array. Before the SERS measurement, a 2 mL droplet of the RhB aqueous solution was dropped on each of the mullite nanowhisker array substrates which were subsequently dried at 50°C for 30 min. The solution diffused on the surface to be a spot with 0.4 cm in diameter. The SERS measurements were carried out in the center of the droplet at room temperature by a microscopic confocal Raman spectrometer(RM2000, Renishaw PLC, England) using a charge-coupled device (CCD) detector with a resolution of 1 cm⁻¹. The laser beam power was 4.7 mW and the laser beam diameter was 5 mm. Excitation wavelength of 632.8 nm (according to the previous literature11 (link)), scan time of 30 s, field lens of 20 times and accumulation of 4 times were applied. The SERS mapping measurements were carried out in the center of the droplet by a microscopic confocal Raman spectrometer (LabRAM HR Evolution, HORIBA Jobin Yvon, France) using a charge-coupled device (CCD) detector with a resolution of 0.65 cm⁻¹.