Hierarchical microstructured copper phosphate (HCuPO), which could accelerate water evaporation was well designed based on d–d transition of 3d electrons in Cu2+ and fabricated via a solvothermal method. A very strong vis–NIR absorption with the maximum at 808 nm was observed for the HCuPO. Upon irradiation of 808 nm NIR laser light, the HCuPO generated heat with a light-to-heat converting efficiency of 41.8%. The reason for this high efficiency was investigated and assigned to a high probability of nonradiative relaxation, which released the energy in form of heat, happened to the excited 3d electrons of Cu2+. The proposed photothermal mechanism was quite different from the surface–plasmon mechanism of other Cu-based photothermal materials. By adding HCuPO into polydimethylsiloxane (PDMS), HCuPO–PDMS composite sheets were fabricated. Due to the intrinsic hydrophobicity of PDMS matrix, the sheets were floatable on water surface and the heat generated by HCuPO was confined within water–air interface region. A much sharper temperature gradient and more rapid increase of surface temperature were observed compared with the HCuPO–water dispersion in which the HCuPO particles were dispersed in water. Porous HCuPO–PDMS sheets were fabricated in order to further accelerate water evaporation. Under 808 nm laser irradiation with power density of 1000–2000 W·m–2, water evaporation rate of salt water (3.5 wt %) was measured to be 1.13–1.85 kg·m–2·h–1 for porous floating HCuPO–PDMS, which was 2.2–3.6 times of that measured for ordinary salt water without HCuPO. By using a solar simulator as a light source, a very high solar thermal conversion efficiency of 63.6% was obtained with a power density of 1000 W·m–2, indicating that solar evaporation of salt water could be greatly enhanced by the well-designed HCuPO.

A green route to water-soluble polyaniline (PANI) using iron phosphates (FePOs) peroxidase mimic as a catalyst and H2O2 as an oxidant is presented. Polystyrene sulfonate (PSS) is used as a template to synthesize a conductive PANI-PSS complex. PANI samples were characterized by UV-Vis spectroscopy, FT-IR spectroscopy and bulk conductivity measurement. Results indicated that the conductivity of the PANI catalyzed by the FePOs peroxidase mimic greatly depends on the pH, temperature and molar ratios of H2O2 and aniline. Superior to natural horseradish peroxidase, the prepared FePOs demonstrated a robust catalytic ability and could catalyze the formation of PANI-PSS at much lower pH values of 1.5–2.6. The photothermal effect of the FePOs catalyzed PANI samples was investigated and a high light-to-heat conversion efficiency of 39.6% was obtained for the sample with a conductivity of 2.576 × 10−3 S cm−1. Excellent biocompatibility and remarkable anti-tumor effect were observed for the prepared PANI with human cervical cancer (HeLa) cells as a cell model.

Yb3+ and Er3+ co-doped Gd2O3 nanoparticles were synthesized via a simple homogeneous precipitation method followed by subsequent heat treatment. Morphology characterization results showed that these nanoparticles were almost spherical in shape with diameters of 200–400 nm. The particles were further modified by polyethylene glycol (PEG) to improve their suspensibility in water. The sintering temperature was found to greatly influence the fluorescent properties of the products. After calcination at 700–1200 °C, the Gd2O3:Yb,Er nanoparticles could emit bright up-conversion fluorescence under 980 nm near-infrared (NIR) laser light excitation. The mechanism of up-conversion fluorescence was studied in detail and a three-photon process was observed for both green and red up-conversion fluorescence of the Gd2O3:Yb,Er nanoparticles. Different from many other Yb3+,Er3+ co-doped up-conversion materials, the prepared Gd2O3:Yb,Er nanoparticles emitted much stronger red light than green light. The reason was investigated and ascribed to the presence of abundant hydroxyl groups on the surface of the nanoparticles as a result of PEGylation. The nanoparticles could be taken up by the human cervical cancer (HeLa) cells and presented low toxicity. Well-selected photodynamic therapy (PDT) drugs, methylene blue (MB) with a UV/Vis absorption maximum (λmax) of 665 nm and 5-aminolevulinic acid (5ALA) which is a precursor of the natural photosensitizer photoporphyrin IX (PpIX) with a λmax of 635 nm, were loaded onto the nanoparticles respectively to obtain Gd2O3:Yb,Er-MB and Gd2O3:Yb,Er-5ALA nanoparticles. Being up-conversion nanoparticles (UCNPs), the taken up Gd2O3:Yb,Er nanoparticles exposed to 980 nm laser light emitted red fluorescence which activated the loaded MB and PpIX, and then killed the HeLa cells via a PDT mechanism. In vitro therapeutic investigation evidenced the prominent PDT effects of Gd2O3:Yb,Er-MB and Gd2O3:Yb,Er-5ALA upon NIR light irradiation. In magnetic resonance imaging (MRI) studies, the relaxivity values obtained for Gd2O3:Yb,Er were r1 = 2.2705 M−1 s−1 and r2 = 3.0675 M−1 s−1 with a r2/r1 ratio close to 1, suggesting that it would be a good candidate as a positive MRI agent. It is expected that these particles have applications in magnetic-fluorescent bimodal imaging and NIR light-triggered PDT.

Black elemental selenium (Se), which shows peroxidase mimic activity and can catalyze the redox reaction between H2O2 and tetramethylbenzidine (TMB) was prepared by a simple method. The mimetic activity was greatly influenced by pH and temperature. The black elemental Se was used to catalyze the green synthesis of water-soluble polypyrrole (PPy) in the presence of sodium poly(styrene sulfonate) (PSS) as the template. The ultraviolet–visible (UV–vis) spectra of PPy obtained at different pH and temperature were recorded to obtain the optimum conditions. The black elemental Se catalyzed PPy can convert near-infrared (NIR) light energy to heat with a photothermal efficiency of 28.4%. After exposure to 808 nm laser light irradiation for 10 min, a remarkable antitumor effect was observed for human cervical cancer (HeLa) cells cocultured with the PPy.

Solvothermally synthesized CePO4:Tb,Gd hollow nanospheres were fabricated as a peroxidase mimic and bimodal magnetic–fluorescent imaging agent, which show potential applications in biocatalysis and bioimaging.

Novel iron phosphates microflowers which show SOD-like and peroxidase-like mimic activities were prepared, suggesting potential applications as a biocatalyst and a biosensor for H2O2.

Lanthanide-doped chitosan nanospheres (LDCNs) and lanthanide-Fe3O4-doped chitosan nanospheres (Fe3O4-LDCNs) are fabricated and show fluorescence, MRI effectiveness and desirable biocompatibility. Superior to most nanoparticles that were found retained in cytoplasmic organelles rather than the nucleus, the prepared chitosan nanospheres preferentially enter and illuminate the cell nuclei. Complexation of plasmid DNA (pDNA) to the nanospheres was accomplished via electrostatic forces between positively charged chitosan and negatively charged pDNA. Satisfactory results of the complexation indicate that the prepared chitosan nanospheres can serve as a potential fluorescent nonviral vector for pDNA delivery that can fulfill gene delivery and transfer efficiency assessment simultaneously, without an additional step of tagging fluorophores to the vectors carried out in fabrications of currently available pDNA delivery vectors.

Solvothermally synthesized CePO4:Tb,Gd hollow nanospheres were fabricated as a peroxidase mimic and bimodal magnetic–fluorescent imaging agent, which show potential applications in biocatalysis and bioimaging.

Yb3+ and Er3+ co-doped Gd2O3 nanoparticles were synthesized via a simple homogeneous precipitation method followed by subsequent heat treatment. Morphology characterization results showed that these nanoparticles were almost spherical in shape with diameters of 200–400 nm. The particles were further modified by polyethylene glycol (PEG) to improve their suspensibility in water. The sintering temperature was found to greatly influence the fluorescent properties of the products. After calcination at 700–1200 °C, the Gd2O3:Yb,Er nanoparticles could emit bright up-conversion fluorescence under 980 nm near-infrared (NIR) laser light excitation. The mechanism of up-conversion fluorescence was studied in detail and a three-photon process was observed for both green and red up-conversion fluorescence of the Gd2O3:Yb,Er nanoparticles. Different from many other Yb3+,Er3+ co-doped up-conversion materials, the prepared Gd2O3:Yb,Er nanoparticles emitted much stronger red light than green light. The reason was investigated and ascribed to the presence of abundant hydroxyl groups on the surface of the nanoparticles as a result of PEGylation. The nanoparticles could be taken up by the human cervical cancer (HeLa) cells and presented low toxicity. Well-selected photodynamic therapy (PDT) drugs, methylene blue (MB) with a UV/Vis absorption maximum (λmax) of 665 nm and 5-aminolevulinic acid (5ALA) which is a precursor of the natural photosensitizer photoporphyrin IX (PpIX) with a λmax of 635 nm, were loaded onto the nanoparticles respectively to obtain Gd2O3:Yb,Er-MB and Gd2O3:Yb,Er-5ALA nanoparticles. Being up-conversion nanoparticles (UCNPs), the taken up Gd2O3:Yb,Er nanoparticles exposed to 980 nm laser light emitted red fluorescence which activated the loaded MB and PpIX, and then killed the HeLa cells via a PDT mechanism. In vitro therapeutic investigation evidenced the prominent PDT effects of Gd2O3:Yb,Er-MB and Gd2O3:Yb,Er-5ALA upon NIR light irradiation. In magnetic resonance imaging (MRI) studies, the relaxivity values obtained for Gd2O3:Yb,Er were r1 = 2.2705 M−1 s−1 and r2 = 3.0675 M−1 s−1 with a r2/r1 ratio close to 1, suggesting that it would be a good candidate as a positive MRI agent. It is expected that these particles have applications in magnetic-fluorescent bimodal imaging and NIR light-triggered PDT.

Lanthanide-doped chitosan nanospheres (LDCNs) and lanthanide-Fe3O4-doped chitosan nanospheres (Fe3O4-LDCNs) are fabricated and show fluorescence, MRI effectiveness and desirable biocompatibility. Superior to most nanoparticles that were found retained in cytoplasmic organelles rather than the nucleus, the prepared chitosan nanospheres preferentially enter and illuminate the cell nuclei. Complexation of plasmid DNA (pDNA) to the nanospheres was accomplished via electrostatic forces between positively charged chitosan and negatively charged pDNA. Satisfactory results of the complexation indicate that the prepared chitosan nanospheres can serve as a potential fluorescent nonviral vector for pDNA delivery that can fulfill gene delivery and transfer efficiency assessment simultaneously, without an additional step of tagging fluorophores to the vectors carried out in fabrications of currently available pDNA delivery vectors.

Novel iron phosphates microflowers which show SOD-like and peroxidase-like mimic activities were prepared, suggesting potential applications as a biocatalyst and a biosensor for H2O2.