Nicolet nexus

A gold substrate was cleaned for 10 min in piranha solution (v/v 70% H₂SO₄/30% H₂O₂), rinsed with distilled water, and dried with a flow of argon gas. The gold substrate was immersed in an ethanolic solution of MUA (1 mM) for 18 h to form the self-assembled monolayers (SAMs) terminating in negatively charged carboxylate. The SAM-coated substrate was incubated in a 150-mM aqueous NaCl solution of MNP@PDADMACs (0.1 mg mL⁻¹) for 5 min, and, after washing with aqueous sodium phosphate-buffered (PB, 50 mM, pH 5.8) solution, immersed for 10 min in the 100-mM silicic acid derivative solution that had been prepared by stirring an HCl solution (1 mM) of TMOS (1 M) at room temperature for 20 min and adding the resulting solution to a PB solution with 1:9 (v/v) ratio. The cycle of MNP deposition and bioinspired silicification was repeated with the predetermined number from 1 to 7. The substrate was washed with a PB solution after each step. IR spectra were recorded with an FT-IR spectrometer (Thermo Nicolet Nexus).

All reagents of commercial quality were used without further purification. The purity of the compounds was determined by elemental analysis and verified to be ≥95%. NMR spectra were recorded at 25°C on a Bruker Avance 400 FT spectrophotometer. The attenuated total reflectance IR spectra were recorded by means of a Nicolet-Nexus (Thermo Fisher) spectrophotometer by using a diamond crystal plate in the range of 4000–400 cm^-1. Elemental analyses were performed by using a FlashEA 1112 series CHNS/O analyzer (Thermo Fisher) with gas-chromatographic separation. Electrospray mass spectral analyses (ESI-MS) were performed with an electrospray ionization (ESI) time-of-flight Micromass 4LCZ spectrometer. MS spectra were acquired in positive EI mode by means of a direct exposure probe mounting on the tip of a Re-filament with a DSQII Thermo Fisher apparatus, equipped with a single quadrupole analyzer.

A FTIR spectrometer (Nicolet Nexus, Thermo Scientific, Loughborough, UK) was employed to determine the infrared spectra of pure HA, BDDE, and synthesized HA-BDDE hydrogels. Spectra were recorded using KBr pellets in the 400–4000 cm⁻¹ range at a 4 cm⁻¹ resolution and 32 scans/spectrum.

All digital photographs in this paper were taken by iPhone 12 and maintained at a certain lighting intensity. The structure of the precursors was analyzed using a UV–Vis spectrometer model Lamdba, Perkin Elmer, Waltham, MA, USA. The groups of products were analyzed using an infrared spectrometer (400–4000 cm⁻¹) of Nicolet Nexus model of Thermo Fisher Scientific, Waltham, MA, USA. The particle size and potential of the products were measured using a Zetasizer Ultra model dynamic light dispersometer from Malvern Instruments Ltd., UK. The surface morphology of the synthesized and modified products was observed using a Tecnai G2 F20 type field emission transmission electron microscope from FEI, Hillsboro, OR, USA. The crystal shape of the products was tested using a D8 Advance type X-ray diffractometer from Brucker Technology GmbH, Saarbrucken, Germany. The chemical compositions of the synthesized products were analyzed using an X-ray photoelectron spectrometer model ESCALAB250Xi from Thermo Fisher Scientific, USA. The magnetic properties of the synthesized products were tested at room temperature using a vibrating sample magnetometer model 7404 from LakeShore, LA, USA. The reflectance spectra of the MRPCs were collected using a fiber optic spectrometer model ATP2000P from OPTISCO, Xiamen, China.