2.1. Materials

For the synthesis and functionalization process, MWCNTs and GO were provided by the Van de Graff Laboratory, Department of Physics PUC-RIO, Rio de Janeiro, Brazil. Zinc Menthol-Phthalocyanine was provided by the Federal University of São Carlos, São Carlos, Brazil; Fe(SO₄), H₂SO₄·7H₂O from MERCK, Rio de Janeiro, Brazil; NH₄OH, 14.8N and N,N Dimethylformamide from Fisher Scientific, Princeton, NJ, USA; Fe₂(SO₄)₃·H₂O from Fisher Scientific. HNO₃ from the Fermont, Monterrey, Mexico; saline solution Fisiol UB (pH = 7) from Lamosan, Quito, Ecuador and Tween80 from La casa del Químico, Quito, Ecuador.

For VCL/PEGDA hydrogel synthesis by emulsion polymerization, the following reagents were used. N-vinylcaprolactam (VCL; Sigma Aldrich, Darmstadt, Germany, 98%), and Poly(ethylene glycol) diacrylate (PEGDA; Sigma Aldrich, Mn 250), the initiator ammonium persulfate (APS; FMC Corporation, Philadelphia, PA, USA, >99%), the emulsifier sodium dodecyl sulfate (SDS; STEOL^®CS-230 Stepan, Northbrook, IL, USA) and a buffer of sodium hydrogen carbonate (Sigma Aldrich, ≥99.7%) were used as provided.

Characterizations of MNPs-MWCNTs and MNPs-GO were carried out by FT-IR spectroscopy analysis in a JASCO FT/IR-4100 spectrometer, JASCO International Co., Ltd., Tokyo, Japan. ES (wavenumber range 7800 to 350 cm⁻¹, resolution of 0.7 cm⁻¹) and Raman spectroscopy analysis in a HORIBA Raman spectrometer LabRAM HR Evolution (Horiba, Kyoto, Japan), where the samples were excited with a 2.33 eV (532 nm).

Magnetization (M) measurements were carried out using a Quantum Design Versalab VSM, Quantum Design, Darmstadt, Germany. FR, magnetometer in the temperature range between −210 and +60 °C with applied magnetic fields, μ₀H, up to 3 T.

Stability over time of the PS magnetic nanocomposites was characterized by UV-VIS spectroscopy analysis at a wavelength range of 280 to 780 nm (resolution better than 1.8 Å), using a UV-VIS Spectrophotometer model Evolution 220 from Thermo Fisher Scientific, Waltham, MA, USA. DPBF photobleaching and thermic studies were carried out with homemade equipment using an LED red light at 635 nm, 65.5 mW·cm⁻². A DPBF photobleaching study was characterized in a UV-VIS Specord 210 Plus. XRD analysis was performed on a PANalytical brand EMPYREAN Diffractometer (Malvern Panalytical, Malvern, UK) operating in a θ–2θ configuration (Bragg-Brentano geometry) equipped with a copper X-ray tube (Kα radiation λ = 1.54056 Å) at 45 kV and 40 mA.