Chromium 3 nitrate nonahydrate

For the solid state method: zinc oxide (99.99%, Strem Chemicals, Newburyport, MA, USA), gallium oxide (99.99%, Strem Chemicals, Newburyport, MA, USA), tin oxide (99.99%, Strem Chemicals, Newburyport, MA, USA), chromium oxide (99.99%, Alfa Aesar, Karlsruhe, Germany).
For the hydrothermal method: zinc nitrate hexahydrate (>99%, Alfa Aesar, Karlsruhe, Germany), gallium oxide (99.999%, Alfa Aesar, Karlsruhe, Germany), nitric acid (35 wt%), tin chloride pentahydrate (98%, Alfa Aesar, Karlsruhe, Germany), chromium (III) nitrate nonahydrate (99.9%, Alfa Aesar, Karlsruhe, Germany), ammonia solution (30 wt%), hydrochloric acid (50 mmol L⁻¹). All the chemicals were used as received without further purification.

All chemicals were used without purification. The ammonium hydroxide solution (NH₄OH in H₂O, 30–33%), methanol (CH₃OH, 99.99%), and tetraethyl orthosilicate (TEOS, 99.99%) were obtained from Sigma‐Aldrich (Saint Louis, MO, US). Ethanol (C₂H₅OH, 99.8%) was purchased from Thermo Fisher Chemical (Waltham, Massachusetts, US). (1‐Hexadecyl) trimethyl ammonium bromide (CTAB, 98%), zinc acetate (Zn(CH₃COO)₂, 99.98%), tin(II) chloride (99%), and chromium(III) nitrate nonahydrate (Cr(NO₃)₃·9H₂O, 98.5%) were obtained from Alfa Aesar (Haverhill, MA,USA). Gallium oxide (Ga₂O₃, 99.99%) was procured from Gredmann. Nitric acid (HNO₃, 69–70%) was from J. T. Baker (Phillipsburg, NJ, USA). The Keratinocyte Serum‐Free Growth (K‐SFM) and Roswell Park Memorial Institute (RPMI 1640) media were purchased from Thermo Fisher Scientific (Waltham, Massachusetts, US) for cell seeding. The Beas2B normal lung bronchus cells used K‐SFM medium, and A549 and CL1‐5 lung cancer cells were incubated in RPMI 1640 medium. The penicillin–streptomycin–glutamine (PSG) supplement for culture media was purchased from GIBCO (Waltham, MA, USA).

Zinc nitrate hexahydrate (>99%) was purchased from Fluka. Gallium oxide (99.999%) and chromium (III) nitrate non-ahydrate (99.99%) were purchased from Alfa Aesar. (3-Aminopropyl)-triethoxysilane (99%) was obtained from Sigma-Aldrich. Dimethylformamide (>99.9%) was purchased from SDS. Alpha-methoxy-omega-N-hydroxysuccinimide poly(ethylene glycol) M_W 5.000 Dalton was bought from Iris Biotech GmbH. 1-Aminopropan-2-ol, methacryloyl chloride, tert-butanol (t-BuOH), dimethyl sulfoxide (DMSO), diethyl ether, ethyl acetate, acetone, methanol (MeOH), dimethylacetamide (DMA), dichloromethane (DCM), 2,2′azobis(isobutyronitrile) (AIBN), 4-cyano-4-(ethylthiocarbonothioylthio) pentanoic acid, 2-thiazoline-2-thiol, N-ethyl-N′-(3-dimethyl aminopropyl)carbodiimide hydrochloride were purchased from Merck-Sigma-Aldrich (Germany). Azo initiator V-70 was purchased from Wako Chemicals (Japan).