Wavelength-switchable watt-level continuous wave near-infrared Pr3+:LiYF4 lasers pumped by an InGaN laser diode

We report a high-performance wavelength-switchable near-infrared Pr3+:LiYF4 (Pr:YLF) laser by InGaN laser diode (LD) pumping. The 895, 922, and 924 nm lasers with low emission cross sections in the Pr:YLF crystal have been successfully realized using a birefringent filter Lyot as well as designing and optimizing optical thin films and the laser resonant cavity. The maximum output powers of the 895, 922, and 924 nm lasers are 2.01, 1.92, and 1.95 W, respectively. As far as we know, these are the highest power for Pr:YLF lasers at 895, 922, and 924 nm so far. The beam quality M x2 and M y2 factors are measured to be 1.85 and 1.71 at 895 nm, 1.94 and 1.67 at 922 nm, and 1.76 and 1.60 at 924 nm, respectively. The laser output power fluctuates within ±3%. In addition, the transmittance of the Lyot is theoretically calculated to achieve laser wavelength switching. The successful realization of the wavelength-switchable watt-level continuous wave near-infrared Pr:YLF laser can provide many practical applications in biomedicine and other fields.

Biodegradation Mn-CoS@carbon di-shell nanoheterostructure with enhanced nanozyme-mediated phototherapy

The efficacy of phototherapy is dependent on intracellular O₂ concentration and NIR harvest. Here, a simple nanoplatform with nanoenzyme mediated phototherapy enhances anticancer capacity. Mn-CoS@carbon (CMS/C) di-shell hollow nanospheres (50 nm) are synthesized successfully through two-step consecutive Kirkendall process. The nanoheterostructure reveals the higher near-infrared (NIR) light absorption and photothermal conversion rate of 66.3% than pure CoS (45.5%), owing to the decreased band gap and multi-reflection of incident light in the hollow structure. And CMS/C reveals the reactive oxygen species (ROS) production and nanoenzyme activities (mimic peroxidase and catalase) that are 6 and 2 times than those of pure CoS. Furthermore, the nanoenzyme exhibits NIR-enhanced abilities to produce more OH and O₂ facilitating anticancer. In addition, it also depletes glutathione (mimicking glutathione oxidase), to disturb intracellular redox-homeostasis, boosting the increase of oxidative stress. With grafting bovine serum albumin (BSA) and drug loading, CMS/C@BSA-Dox integrated multi-therapy make the great anticancer effect in vitro and vivo. After that, the nanocomposite could be biodegraded and eliminated via urinary and feces within 14 days. Based on this work, the efficient charge-separation can be designed to reveal high performance nanoenzymes as well as photosensitizers for anticancer.

Transparent photothermal hydrogels for wound visualization and accelerated healing

Utilizing photothermal hydrogels as a wound dressing is a promising strategy to accelerate wound healing. Usually, a photothermal hydrogel has a strong light-absorbing capability, and hence its transparency can be largely sacrificed, which is unbeneficial for the visual monitoring of wound states. It remains challenging to balance the trade-off between the photothermal conversion and wound visualization for the photothermal hydrogel dressing. Herein, a composite photothermal hydrogel film with high transparency is presented for the visual monitor of the wound, which is constructed by incorporating CsxWO3 nanorods into the networks of polyacrylamide hydrogels. The composite photothermal hydrogel film exhibits high light absorption in the near-infrared region and high transmittance in the visible light region. Under 980 nm laser irradiation, the composite hydrogel can be heated up to 45 °C. In vivo animal experiment on mouse skin wound model shows that the composite hydrogel film can locally heat the skin wound to accelerate healing while maintaining more than 70% transparency to realize real-time observation of the wound. This study provides the first attempt to solve the problem of opacity in photothermal hydrogel dressings, promoting the possibility of its clinical applications.

Plasmonic Oxygen Defects in MO3- x (M = W or Mo) Nanomaterials: Synthesis, Modifications, and Biomedical Applications

Nanomedicine is a promising technology with many advantages and provides exciting opportunities for cancer diagnosis and therapy. During recent years, the newly developed oxygen-deficiency transition metal oxides MO_{3- x} (M = W or Mo) have received significant attention due to the unique optical properties, such as strong localized surface plasmon resonance (LSPR) , tunable and broad near-IR absorption, high photothermal conversion efficiency, and large X-ray attenuation coefficient. This review presents an overview of recent advances in the development of MO_{3- x} nanomaterials for biomedical applications. First, the fundamentals of the LSPR effect are introduced. Then, the preparation and modification methods of MO_{3- x} nanomaterials are summarized. In addition, the biological effects of MO_{3- x} nanomaterials are highlighted and their applications in the biomedical field are outlined. This includes imaging modalities, cancer treatment, and antibacterial capability. Finally, the prospects and challenges of MO_{3- x} and MO_{3- x} -based nanomaterial for fundamental studies and clinical applications are also discussed.

Devising Hyperthermia Dose of NIR-Irradiated Cs0.33WO3 Nanoparticles for HepG2 Hepatic Cancer Cells

Hyperthermia is one of the most patient-friendly methods to cure cancer diseases owing to its noninvasiveness, minimally induced side-effects and toxicity, and easy implementation, prompting the development of novel therapeutic methods like photothermally triggering dose system. This research herein interrogates the variables of photothermal effects of Cs0.33WO3 nanoparticles (NPs), the duration of irradiation, optical power density and NP concentration, upon HepG2 liver cancer cell line in vitro, leading to the formulation of a near-infrared (NIR)-irradiated thermal dose. Expressly, the NPs with particulate feature sizes of 120 nm were synthesized through a series of oxidation-reduction (REDOX) reaction, thermal annealing and wet-grinding processes, and the subsequent characterization of physical, compositional, optical, photothermal properties were examined using dynamic light scattering (DLS), energy-dispersive X-ray spectroscopy (EDS), scanning and tunneling electron microscopies (SEM and TEM), X-ray diffraction (XRD) and visible-near-infrared (VIS-NIR) photospectroscopy. Cytotoxicity of the NPs and its irradiation parameters were obtained for the HepG2 cells. By incubating the cells with the NPs, the state of endocytosis was verified, and the dependence of cellular survival rate on the variable parameters of photothermal dose was determined while maintaining the medium temperature of the cell-containing culture dish at human body temperature around 36.5 °C.

Constructing Cu7S4@SiO2/DOX Multifunctional Nanoplatforms for Synergistic Photothermal-Chemotherapy on Melanoma Tumors

The integration of photothermal therapy and chemotherapy has been recognized to be an efficient strategy through the instant thermally ablation and long-term chemical inhibition, thus achieving high therapeutical effect. In the present work, we designed and prepared Cu₇S₄@SiO₂/DOX nanocomposites and used them as efficient nanoplatforms for synergistic photothermal-chemo therapy on melanoma tumors. The Cu₇S₄@SiO₂/DOX was constructed by firstly synthesizing Cu₇S₄ nanocrystals, then in situ growing SiO₂ shell on the surface of Cu₇S₄ nanocrystals, and finally loading DOX within SiO₂ shell. The Cu₇S₄@SiO₂/DOX was composed of Cu₇S₄ core as the photothermal transducer, SiO₂ shell as DOX carrier and DOX as the model of anticancer drug. Once exposed to a 1064 nm laser, the Cu₇S₄@SiO₂/DOX could simultaneous generate heat for photothermal therapy and accelerate the DOX release. When the Cu₇S₄@SiO₂/DOX was injected into the center of tumor, the tumor exhibit rapid temperature elevation once exposed to the NIR laser and the tumor growth is significantly inhibited through the synergistic photothermal-chemo therapy, in comparison to the limited therapeutical effect of photothermal therapy or chemotherapy alone. Therefore, the Cu₇S₄@SiO₂/DOX with photothermal-chemo function can be used as excellent nanoplatforms for treating solid tumor with high theoretical effect.

Facile synthesis of urchin-like CsxWO3 particles with improved transparent thermal insulation using bacterial cellulose as a template

Urchin-like Cs_xWO₃ particles were synthesized using bacterial cellulose (BC) as a template by the hydrothermal method. The effects of the BC addition amount on the morphology, W⁵⁺ content and transparent thermal insulation of Cs_xWO₃ were studied. It has been confirmed that abnormal growth of Cs_xWO₃ rods was greatly reduced after introduction of BC into the precursor solution. Moreover, introduction of BC into the precursor solution could significantly improve the transparent thermal insulation properties of the Cs_xWO₃ film. In particular, when the BC amount was appropriate, the prepared Cs_xWO₃ film exhibited better visible transparency, with the visible light transmittance (T_Vis) more than 60%. In addition, the urchin-like particles could be transformed into small size nanorods after H₂ heat-treatment, exhibiting excellent visible light transparency and thermal insulation performance. In particular, it has been proved that the 20BC-HT-Cs_xWO₃ film exhibits excellent thermal insulation performance, and shows broad application prospects in the field of solar heat filters and energy-saving window glass.

Urchin-like Cs_xWO₃ particles were synthesized using bacterial cellulose (BC) as a template by the hydrothermal method. The BC could greatly reduce the abnormal growth of Cs_xWO₃ rods and improve the transparent heat-insulation properties of Cs_xWO₃ film.

Spectrally Selective Smart Window with High Near-Infrared Light Shielding and Controllable Visible Light Transmittance

Smart windows with high near-infrared (NIR) light shielding and controllable visible light transmittance are highly sought after for cooling energy saving in buildings. Herein, we present a rationally designed spectrally selective smart window which is capable of shielding 96.2% of the NIR irradiation from 800 to 2500 nm and at the same time permitting acceptable visible light (78.2% before and 45.3% after its optical switching) for indoor daylighting. The smart window synergistically integrates the highly selective and effective NIR absorption based photothermal conversion of cesium tungsten bronze (Cs _xWO₃) with the transparent thermoresponsive poly( N-isopropyl acrylamide) (PNIPAM) microgel-polyacrylamide (PAM) hydrogel. Optical switching of the smart window is a direct result of the phase transition of PAM-PNIPAM hydrogel, which in turn is induced by the photothermal effect of Cs _xWO₃ under sunlight irradiation. The smart window exhibits fast optical switching, shows long-term operational stability, and can be made highly flexible. Under the experimental conditions in this work, the indoor temperature with the smart window is ∼21 °C lower than that with a regular single-layered glass window under one sun irradiation. The smart window design in this work is meaningful for further development of effective smart windows for energy saving in the build environment.

Melt Electrospun Reduced Tungsten Oxide /Polylactic Acid Fiber Membranes as a Photothermal Material for Light-Driven Interfacial Water Evaporation

The development of efficient photothermal materials is the most important issue in solar water evaporation. In this work, melt electrospun reduced tungsten oxide/polylactic acid (WO_2.72/PLA) fiber membranes were successfully prepared with improved near-infrared (NIR) photothermal conversion properties owing to strong NIR photoabsorption by the metal oxide. WO_2.72 powder nanoparticles were incorporated into PLA matrix by melt processing, following which the composites were extruded into wires using a single screw extruder. Subsequently, fiber membranes were prepared from the extruded wire of the WO_2.72/PLA composite by melt electrospinning, which is a cost-effective technique that can produce fiber membranes without the addition of environmentally unfriendly chemicals. The melt electrospun WO_2.72/PLA fiber membranes, floatable on water due to surface hydrophobicity, were systematically designed for, and applied to, vapor generation based on the interfacial concept of solar heating. With the photothermal WO_2.72/PLA fiber membrane containing 7 wt % WO_2.72 nanoparticles, the water evaporation efficiency was reached 81.39%, which is higher than that for the pure PLA fiber membrane and bulk water. Thus, this work contributes to the development of novel photothermal fiber membranes in order to enhance light-driven water evaporation performance for potential applications in the fields of water treatment and desalination.

Highly Efficient Near Infrared Photothermal Conversion Properties of Reduced Tungsten Oxide/Polyurethane Nanocomposites

In this work, novel WO3-x/polyurethane (PU) nanocomposites were prepared by ball milling followed by stirring using a planetary mixer/de-aerator. The effects of phase transformation (WO₃ → WO2.8 → WO2.72) and different weight fractions of tungsten oxide on the optical performance, photothermal conversion, and thermal properties of the prepared nanocomposites were examined. It was found that the nanocomposites exhibited strong photoabsorption in the entire near-infrared (NIR) region of 780-2500 nm and excellent photothermal conversion properties. This is because the particle size of WO3-x was greatly reduced by ball milling and they were well-dispersed in the polyurethane matrix. The higher concentration of oxygen vacancies in WO3-x contribute to the efficient absorption of NIR light and its conversion into thermal energy. In particular, WO2.72/PU nanocomposites showed strong NIR light absorption of ca. 92%, high photothermal conversion, and better thermal conductivity and absorptivity than other WO₃/PU nanocomposites. Furthermore, when the nanocomposite with 7 wt % concentration of WO2.72 nanoparticles was irradiated with infrared light, the temperature of the nanocomposite increased rapidly and stabilized at 120 °C after 5 min. This temperature is 52 °C higher than that achieved by pure PU. These nanocomposites are suitable functional materials for solar collectors, smart coatings, and energy-saving applications.

PEGylated (NH4)xWO3 nanorods as efficient and stable multifunctional nanoagents for simultaneous CT imaging and photothermal therapy of tumor

The simultaneous imaging and photothermal therapy of tumors have attracted much attention, and a prerequisite is to obtain multifunctional nanomaterials. Ideally, one kind of nanoparticles with single component can be used as both imaging agent and photothermal agent. Herein, we have developed the PEGylated (NH₄)_xWO₃ (denoted as (NH₄)_xWO₃-PEG) nanorods as multifunctional nanoparticles with single semiconductor component. (NH₄)_xWO₃-PEG nanorods with about 30nm diameter and length of several hundred nanometers have been obtained through a solvothermal synthesis-PEGylation two-step route. Under the irradiation of 980-nm laser with intensity of 0.72Wcm^-2, aqueous dispersion of (NH₄)_xWO₃-PEG nanorods (0.67-5.44mmol/L) displays high elevation (17.6-34.5°C) of temperature in 400s, accompanied by an excellent long-term photothermal stability. Furthermore, (NH₄)_xWO₃-PEG nanorods exhibit as high as 6 times X-ray attenuation ability compared to that of the clinically used iodine-based X-ray computed tomography (CT) contrast agent (Iopromide). More importantly, after PBS solution of (NH₄)_xWO₃-PEG nanorods is injected into the tumor of mice, the tumor can be effectively detected by CT imaging. Moreover, cancer cells in vivo can be further destroyed by the photothermal effects of (NH₄)_xWO₃-PEG nanorods, under the irradiation of 980-nm laser with the safe intensity of 0.72Wcm^-2 for 10min. Therefore, (NH₄)_xWO₃-PEG nanorods can be used as a new kind of stable and efficient multifunctional nanoagent with single component for simultaneous CT imaging and photothermal therapy of tumor.

Strategies to Improve Cancer Photothermal Therapy Mediated by Nanomaterials

The deployment of hyperthermia-based treatments for cancer therapy has captured the attention of different researchers worldwide. In particular, the application of light-responsive nanomaterials to mediate hyperthermia has revealed promising results in several pre-clinical assays. Unlike conventional therapies, these nanostructures can display a preferential tumor accumulation and thus mediate, upon irradiation with near-infrared light, a selective hyperthermic effect with temporal resolution. Different types of nanomaterials such as those based on gold, carbon, copper, molybdenum, tungsten, iron, palladium and conjugated polymers have been used for this photothermal modality. This progress report summarizes the different strategies that have been applied so far for increasing the efficacy of the photothermal therapeutic effect mediated by nanomaterials, namely those that improve the accumulation of nanomaterials in tumors (e.g. by changing the corona composition or through the functionalization with targeting ligands), increase nanomaterials' intrinsic capacity to generate photoinduced heat (e.g. by synthesizing new nanomaterials or assembling nanostructures) or by optimizing the parameters related to the laser light used in the irradiation process (e.g. by modulating the radiation wavelength). Overall, the development of new strategies or the optimization and combination of the existing ones will surely give a major contribution for the application of nanomaterials in cancer PTT.

NIR-laser-triggered smart full-polymer nanogels for synergic photothermal-/chemo-therapy of tumors

Full-polymer smart nanogels (PNA–CS–PPy–DOX) have been developed. They exhibit excellent photothermal and drug-release abilities for the synergic therapy of tumors.

Synthesis of CuS nanoplate-containing PDMS film with excellent near-infrared shielding properties

CuS nanoplates have been developed as a near-infrared (NIR) shielding agent, and the corresponding flexible CuS/PDMS composite film can transmit visible light (400–780 nm) but efficiently block NIR light (780–2500 nm).

Synthesis of polypyrrole nanoparticles for constructing full-polymer UV/NIR-shielding film

Polypyrrole (PPy) nanoparticles with diameter of ∼50 nm are synthesized, and the corresponding flexible PPy–polyacrylic acid (PAA) full-polymer films can transmit visible light but efficiently block UV/NIR light.