Near-infrared Light Absorption Research Articles

Photo-to-Thermal Conversion Harnessing Low-Energy Photons Renders Efficient Solar CO2 Reduction.

Efficient photocatalytic solar CO2 reduction presents a challenge because visible-to-near-infrared (NIR) low-energy photons account for over 50% of solar energy. Consequently, they are unable to instigate the high-energy reaction necessary for dissociating C═O bonds in CO2. In this study, we present a novel methodology leveraging the often-underutilized photo-to-thermal (PTT) conversion. Our unique two-dimensional (2D) carbon layer-embedded Mo2C (Mo2C-Cx) MXene catalyst in black color showcases superior near-infrared (NIR) light absorption. This enables the efficient utilization of low-energy photons via the PTT conversion mechanism, thereby dramatically enhancing the rate of CO2 photoreduction. Under concentrated sunlight, the optimal Mo2C-C0.5 catalyst achieves CO2 reduction reaction rates of 12000-15000 μmol·g-1·h-1 to CO and 1000-3200 μmol·g-1·h-1 to CH4. Notably, the catalyst delivers solar-to-carbon fuel (STF) conversion efficiencies between 0.0108% to 0.0143% and the STFavg = 0.0123%, the highest recorded values under natural sunlight conditions. This innovative approach accentuates the exploitation of low-frequency, low-energy photons for the enhancement of photocatalytic CO2 reduction.

Photothermal Depth Profiling of Gelatin-Stabilised Gold Nanorods-Trastuzumab Conjugate as a Potential Breast Cancer Photothermal Agent

AbstractGold nanorods (AuNRs) are powerful photothermal agents (PTAs) in cancer treatment due to their near-infrared laser light absorption ability. However, the cytotoxicity of AuNRs caused by the presence of cationic surfactants often used and their lack of specificity affect their application in photothermal therapy. Thus, we herein developed a bioconjugate obtained from the functionalisation of AuNRs to gelatin (Gel@AuNRs), followed by the conjugation of the as-synthesised material to a breast cancer antibody, trastuzumab (Trast-Gel@AuNRs) to address these issues. The optical and structural characterization of the as-synthesized indicated no significant changes in the optical properties of AuNRs after their functionalisation with gelatin and conjugation with the antibody. The photothermal profiling of the as-synthesised materials showed that AuNRs still have an excellent photothermal conversion efficiency (PCE) after their functionalisation (20%) and their conjugation to an antibody (19%). In addition, the In vitro photothermal depth response showed that Trast-Gel@AuNRs is a promising photothermal agent for HER2-positive breast cancer treatment. Graphical Abstract

Black Titania Janus Mesoporous Nanomotor for Enhanced Tumor Penetration and Near-Infrared Light-Triggered Photodynamic Therapy.

Thanks to their excellent photoelectric characteristics to generate cytotoxic reactive oxygen species (ROS) under the light-activation process, TiO2 nanomaterials have shown significant potential in photodynamic therapy (PDT) for solid tumors. Nevertheless, the limited penetration depth of TiO2-based photosensitizers and excitation sources (UV/visible light) for PDT remains a formidable challenge when confronted with complex tumor microenvironments (TMEs). Here, we present a H2O2-driven black TiO2 mesoporous nanomotor with near-infrared (NIR) light absorption capability and autonomous navigation ability, which effectively enhances solid tumor penetration in NIR light-triggered PDT. The nanomotor was rationally designed and fabricated based on the Janus mesoporous nanostructure, which consists of a NIR light-responsive black TiO2 nanosphere and an enzyme-modified periodic mesoporous organosilica (PMO) nanorod that wraps around the TiO2 nanosphere. The overexpressed H2O2 can drive the nanomotor in the TME under catalysis of catalase in the PMO domain. By precisely controlling the ratio of TiO2 and PMO compartments in the Janus nanostructure, TiO2&PMO nanomotors can achieve optimal self-propulsive directionality and velocity, enhancing cellular uptake and facilitating deep tumor penetration. Additionally, by the decomposition of endogenous H2O2 within solid tumors, these nanomotors can continuously supply oxygen to enable highly efficient ROS production under the NIR photocatalysis of black TiO2, leading to intensified PDT effects and effective tumor inhibition.

Coupling Gold Nanospheres into Nanochain Constructs for High-Contrast, Longitudinal Photoacoustic Imaging.

Structural parameters play a crucial role in determining the electromagnetic and thermal responses of gold nanoconstructs (GNCs) at near-infrared (NIR) wavelengths. Therefore, developing GNCs for reliable, high-contrast photoacoustic imaging has been focused on adjusting structural parameters to achieve robust NIR light absorption with photostability. In this study, we introduce an efficient photoacoustic imaging contrast agent: gold sphere chains (GSCs) consisting of plasmonically coupled gold nanospheres. The chain geometry results in enhanced photoacoustic signal generation originating from outstanding photothermal characteristics compared to traditional gold contrast agents, such as gold nanorods. Furthermore, the GSCs produce consistent photoacoustic signals at laser fluences within the limits set by the American National Standards Institute. The exceptional photoacoustic response of GSCs allows for high-contrast photoacoustic imaging over multiple imaging sessions. Finally, we demonstrate the utility of our GSCs for molecular photoacoustic cancer imaging, both in vitro and in vivo, through the integration of a tumor-targeting moiety.

Rhodium-Rhenium Alloy Nanozymes for Non-inflammatory Photothermal Therapy.

Analogous to thermal ablation techniques in clinical settings, cell necrosis induced during tumor photothermal therapy (PTT) can provoke an inflammatory response that is detrimental to the treatment of tumors. In this study, we employed a straightforward one-step liquid-phase reduction process to synthesize uniform RhRe nanozymes with an average hydrodynamic size of 41.7 nm for non-inflammatory photothermal therapy. The obtained RhRe nanozymes showed efficient near-infrared (NIR) light absorption for effective PTT, coupled with a remarkable capability to scavenge reactive oxygen species (ROS) for anti-inflammatory treatment. After laser irradiation, the 4T1 tumors were effectively ablated without obvious tumor recurrence within 14 days, along with no obvious increase in pro-inflammatory cytokine levels. Notably, these RhRe nanozymes demonstrated high biocompatibility with normal cells and tissues, both in vitro and in vivo, as evidenced by the lack of significant toxicity in female BALB/c mice treated with 10 mg/kg of RhRe nanozymes over a 14 day period. This research highlights RhRe alloy nanoparticles as bioactive nanozymes for non-inflammatory PTT in tumor therapy.

Dual-Responsive MXene-Functionalized Wool Yarn Artificial Muscles.

Fiber-based artificial muscles are promising for smart textiles capable of sensing, interacting, and adapting to environmental stimuli. However, the application of current artificial muscle-based textiles in wearable and engineering fields has largely remained a constraint due to the limited deformation, restrictive stimulation, and uncomfortable. Here, dual-responsive yarn muscles with high contractile actuation force are fabricated by incorporating a very small fraction (<1wt.%) of Ti3C2Tx MXene/cellulose nanofibers (CNF) composites into self-plied and twisted wool yarns. They can lift and lower a load exceeding 3400 times their own weight when stimulated by moisture and photothermal. Furthermore, the yarn muscles are coiled homochirally or heterochirally to produce spring-like muscles, which generated over 550% elongation or 83% contraction under the photothermal stimulation. The actuation mechanism, involving photothermal/moisture-mechanical energy conversion, is clarified by a combination of experiments and finite element simulations. Specifically, MXene/CNF composites serve as both photothermal and hygroscopic agents to accelerate water evaporation under near-infrared (NIR) light and moisture absorption from ambient air. Due to their low-cost facile fabrication, large scalable dimensions, and robust strength coupled with dual responsiveness, these soft actuators are attractive for intelligent textiles and devices such as self-adaptive textiles, soft robotics, and wearable information encryption.

A photoelectrochemical biosensor based on self-calibration platform of carbon-rich plasmonic probe with near-infrared driving signal amplification

Exploring the photochemical (PEC) method induced by low-energy light source makes great significance to achieve high stability and accurate analysis. A sensing platform driven by near-infrared (NIR) light was designed by making the biochemically encoded carbon rich plasmonic hybrid (CPH) probe, the peptide@C–Mo2C. The inherent plasmonic effect of C–Mo2C CPH can directly absorb NIR light, thus starting effective electronic-hole pairs separation. Moreover, the photothermal effect of C–Mo2C CPH also promoted the reaction yield of photothermal catalyst reaction on sensing interface to assist the PEC signal amplification. In the presence of target trypsin, it cleaves the peptides, resulting in the release of peptide@C–Mo2C probe from interface, which leads to a relative decrease in PEC signal. More importantly, a self-calibration system consisting of two independent PEC test channels attempted to eliminate the influence of background signal and baseline drift. The test channel was used to specify the recognition target, while the blank channel was used as a reference. Therefore, the signal difference between two channels was recorded, so as to obtain results with less error and higher stability. In this NIR driven PEC sensor, the carbon rich probe with direct and efficient NIR light conversion promoted the sensitivity and a self-calibration system guaranteed the stability which provided innovative thoughts for developing ingenious PEC sensor.

Complete Photooxidation of Formaldehyde to CO2 via Ni-Dual-Atom Decorated Crystalline Triazine Frameworks: A DFT Study.

Formaldehyde (CH2O) emerges as a significant air pollutant, necessitating effective strategies for its oxidation to mitigate adverse impacts on human health and the environment. Among various technologies, the photooxidation of CH2O stands out owing to its affordability, safety, and effectiveness. Nitrogen-rich crystalline triazine-based organic frameworks (CTFs) exhibit considerable potential in this domain. Nevertheless, the weak and unstable CH2O adsorption hinders the overall oxidation efficiency of CTF. To address this limitation, we incorporate single and dual Ni atoms into nitrogen-rich CTFs by density functional theory (DFT) calculations, resulting in CTF-Ni and CTF-2Ni. This strategic modification significantly enhances the adsorption capability of CH2O. Notably, this synergy between Ni dual atoms activates CH2O by strong chemical adsorption, thereby reducing the energy barrier of CH2O oxidation and achieving the complete oxidation of CH2O to CO2. Moreover, the introduction of dual-atom Ni over CTF ameliorates visible and near-infrared light absorption and facilitates photoexcited charge transfer and separation. Finally, the underlying mechanisms of complete CH2O oxidation over CTF-2Ni are proposed. This work offers novel insights into the rational design of photocatalysts for CH2O oxidation through the integration of Ni dual atoms into CTFs.

Antibacterial Polyhydroxyurethane-Gelatin Wound Dressings with In Situ-Generated Silver Nanoparticles or Hyperthermia Induced by Near-Infrared Light Absorption

Antibacterial Polyhydroxyurethane-Gelatin Wound Dressings with In Situ-Generated Silver Nanoparticles or Hyperthermia Induced by Near-Infrared Light Absorption

Graphene-decorated novel Z-scheme Bi@MOF composites promote high performance photocatalytic desulfurization

The Z-scheme photocatalyst constructed based on bismuth-based metal oxides (BMO) and metal–organic frameworks (MOF) holds significant potential for effectively degrading odorous Reduced Sulfur Compounds (RSC) due to its robust redox capabilities. However, challenges such as lattice mismatch, interface defects, and rapid recombination of photogenerated charges substantially impede the Z- scheme charge transfer in BMO@MOF photocatalysts. In this research, graphene was introduced into the BiVO4@NH2-UiO-66 system as an electron bridge and co-catalyst to reduce the interfacial transfer resistance and increase the absorption of near-infrared light, resulting in superior degradability of RSCs compared to both the individual components and BiVO4@NH2-UiO-66. The incorporated graphene not only serves as the growth substrate for BiVO4 and NH2-UiO-66 but also plays a crucial role as an electron mediator in enhancing the vectorial charge transfer from BiVO4 to NH2-UiO-66. This strengthens the Z-scheme charge transfer pathway, suppressing bulk charge recombination, increasing overall carrier density, and maintaining robust redox capabilities. Additionally, the investigation of active species and key intermediate products was conducted to explore potential degradation pathways of RSCs. This work demonstrates a novel approach in promoting photocatalytic degradation of RSCs by harnessing the synergistic effects between doping and heterogeneous structures within the photocatalyst.

An A-D-A'-D-A-Type Narrow Bandgap Electron Acceptor Based on Selenophene-Flanked Diketopyrrolopyrrole for Sensitive Near-Infrared Photodetection.

Near-infrared organic photodetectors possess great application potential in night vision, optical communication, and image sensing, but their development is limited by the lack of narrow bandgap organic semiconductors. A-D-A'-D-A-type molecules, featuring multiple intramolecular charge transfer effects, offer a robust framework for achieving near-infrared light absorption. Herein, we report a novel A-D-A'-D-A-type narrow bandgap electron acceptor named DPPSe-4Cl, which incorporates a selenophene-flanked diketopyrrolopyrrole (Se-DPP) unit as its central A' component. This molecule demonstrates exceptional near-infrared absorption properties with an absorption onset reaching 1120 nm and a low optical bandgap of 1.11 eV, owing to the strong electron-withdrawing ability and quinoidal resonance effect induced by the Se-DPP unit. By implementing a doping compensation strategy assisted by Y6 to reduce the trap density in the photoactive layer, the optimized organic photodetector based on DPPSe-4Cl exhibited efficient spectral response and remarkable sensitivity in the range of 300-1100 nm. Particularly, a specific detectivity surpassing 1012 Jones in the wavelength range of 410-1030 nm is achieved. This work offers a promising approach for developing highly sensitive visible to near-infrared broadband photodetection technology using organic semiconductors.

Indocyanine-Green-Loaded Liposomes for Photodynamic and Photothermal Therapies: Inducing Apoptosis and Ferroptosis in Cancer Cells with Implications beyond Oral Cancer.

Oral cancer represents a global health burden, necessitating novel therapeutic strategies. Photodynamic and photothermal therapies using indocyanine green (ICG) have shown promise due to their distinctive near-infrared (NIR) light absorption characteristics and FDA-approved safety profiles. This study develops ICG-loaded liposomes (Lipo-ICGs) to further explore their potential in oral cancer treatments. We synthesized and characterized the Lipo-ICGs, conducted in vitro cell culture experiments to assess cellular uptake and photodynamic/photothermal effects, and performed in vivo animal studies to evaluate their therapeutic efficacy. Quantitative cell apoptosis and gene expression variation were further characterized using flow cytometry and RNA sequencing, respectively. Lipo-ICGs demonstrated a uniform molecular weight distribution among particles. The in vitro studies showed a successful internalization of Lipo-ICGs into the cells and a significant photodynamic treatment effect. The in vivo studies confirmed the efficient delivery of Lipo-ICGs to tumor sites and successful tumor growth inhibition following photodynamic therapy. Moreover, light exposure induced a time-sensitive photothermal effect, facilitating the further release of ICG, and enhancing the treatment efficacy. RNA sequencing data showed significant changes in gene expression patterns upon Lipo-ICG treatment, suggesting the activation of apoptosis and ferroptosis pathways. The findings demonstrate the potential of Lipo-ICGs as a therapeutic tool for oral cancer management, potentially extending to other cancer types.

Collagen-Targeting Self-Assembled Nanoprobes for Multimodal Molecular Imaging and Quantification of Myocardial Fibrosis in a Rat Model of Myocardial Infarction.

Currently, inadequate early diagnostic methods hinder the prompt treatment of patients with heart failure and myocardial fibrosis. Magnetic resonance imaging is the gold standard noninvasive diagnostic method; however, its effectiveness is constrained by low resolution and challenges posed by certain patients who cannot undergo the procedure. Although enhanced computed tomography (CT) offers high resolution, challenges arise owing to the unclear differentiation between fibrotic and normal myocardial tissue. Furthermore, although echocardiography is real-time and convenient, it lacks the necessary resolution for detecting fibrotic myocardium, thus limiting its value in fibrosis detection. Inspired by the postinfarction accumulation of collagen types I and III, we developed a collagen-targeted multimodal imaging nanoplatform, CNA35-GP@NPs, comprising lipid nanoparticles (NPs), encapsulating gold nanorods (GNRs) and perfluoropentane (PFP). This platform facilitated ultrasound/photoacoustic/CT imaging of postinfarction cardiac fibrosis in a rat model of myocardial infarction (MI). The surface-modified peptide CNA35 exhibited excellent collagen fiber targeting. The strong near-infrared light absorption and substantial X-ray attenuation of the nanoplatform rendered it suitable for photoacoustic and CT imaging. In the rat model of MI, our study demonstrated that CNA35-GNR/PFP@NPs (CNA35-GP@NPs) achieved photoacoustic, ultrasound, and enhanced CT imaging of the fibrotic myocardium. Notably, the photoacoustic signal intensity positively correlated with the severity of myocardial fibrosis. Thus, this study presents a promising approach for accurately detecting and treating the fibrotic myocardium.

Coordinated carbon dots-Fe featuring synergistically enhanced peroxidase-like activity at neutral pH for specific and background-free detection of dichlorvos

Nanozyme-based assays present favorable prospects in sensitive determination of pesticides in food samples yet are constrained with little or even no catalytic activities at neutral pH, lack of selectivity, and interference by sample color. Here, a facile and novel photothermal system for rapid, specific, sensitive, and background-free detection of dichlorvos was developed based on peroxidase-like activity of coordinated carbon dots-Fe (CDs-Fe). CDs-Fe was prepared and fabricated based on the redox and coordination chemistry between CDs and Fe species. Catalytic mechanism investigations illustrate that CDs-Fe with outstanding peroxidase-like activity at neutral pH comes from the synergistic effect of •OH production and electron transfer process. More interestingly, dichlorvos can specifically complex with CDs-Fe through electrostatic attraction and π-π stacking interactions, which then cement substrates affinity and improve electron transfer efficiency to enhance the catalytic activity. Oxidized 3,3′,5,5′-tetramethylbenzidine (oxTMB) presents photothermal effect by absorption of near-infrared (808 nm) laser-driven light, which eliminates the color interference from real samples. Accordingly, a background-free photothermal strategy was established. Furthermore, a portable hydrogel kit was fabricated by embedding CDs-Fe and TMB into agarose hydrogel for on-site rapid detection of dichlorvos. A good relationship was observed in the range of 5.00–650 μg L−1 with a satisfactory detection limit at 4.85 μg L−1, and a good recovery (90.56–107.0 %) with excellent anti-interference capacity was achieved for real sample analysis. The work presents a novel nanozyme enhancement strategy for specific and background-free detecting dichlorvos in food samples.

Experimental demonstration of a Fano resonant hybrid plasmonic metasurface absorber for the O and E bands of the optical communication window

Plasmonic metasurface absorbers are capable of absorbing the incident light at wavelengths corresponding to the excitation of Fano resonant modes. Absorption of the incident light is possible because of its confinement near the edges of the plasmonic nanostructure. Confinement of light takes place because of the coupling of superradiant and subradiant modes near the edges of the plasmonic metasurface. Superradiant and subradiant modes are excited for the oblique angle incidence of transverse magnetic (TM)-polarized light. The incidence of TM-polarized light supports the excitation of surface plasmon modes at the metal–dielectric interface. For the oblique angle incidence, surface plasmon modes couple with the incident light and generate the superradiant and subradiant modes near the plasmonic metasurface. We experimentally demonstrate the absorption of near-infrared light in the O and E optical communication band by a one-dimensional (1D) hybrid plasmonic metasurface. A low-cost, and flexible, 1D hybrid plasmonic metasurface absorber (HPMA) was obtained by extracting an Ag-coated, flexible, and 1D patterned polycarbonate layer from a digital versatile disc (DVD). The DVD consists of an Ag layer sandwiched between two 1D patterned polycarbonate layers. A large-area HPMA of 3cm2 in size was fabricated for optical characterization. Control experiments on the variation of the angle of incidence of light were performed to achieve the maximum light absorption of 79%. The effect of transverse electric (TE)- and TM-polarized light on the HPMA was studied. The effect of the thickness of the polymer layer on the HPMA, and per unit change of refractive index (RIU) of the analyte medium, were also investigated. HPMA supports refractive index sensing characteristics with a maximum sensitivity of 954 nm/RIU. Electric field profiles at different incidence angles were simulated using the finite element method on COMSOL Multiphysics software to explain the underlying physics of Fano resonance. HPMA can be used to develop cost-effective photonic devices such as sensors, spectral filters, photodetectors, heat-absorbing protective photonic covers, etc.

Tailoring of Visible to Near-Infrared Active 2D MXene with Defect-Enriched Titania-Based Heterojunction Photocatalyst for Green H2 Generation.

A wide solar light absorption window and its utilization, long-term stability, and improved interfacial charge transfer are the keys to scalable and superior solar photocatalytic performance. Based on this objective, a noble metal-free composite photocatalyst is developed with conducting MXene (Ti3C2) and semiconducting cauliflower-shaped CdS and porous Cu2O. XPS, HRTEM, and ESR analyses of TiOy@Ti3C2 confirm the formation of enough defect-enriched TiOy (where y is < 2) on the surface of Ti3C2 during hydrothermal treatment, thus creating a third semiconducting site with enough oxygen vacancy. The final material, TiOy@Ti3C2/CdS/Cu2O, shows a broad absorption window from 300 to 2000 nm, covering the visible to near-infrared (NIR) range of the solar spectrum. Photocatalytic H2 generation activity is found to be 12.23 and 16.26 mmol g-1 h-1 in the binary (TiOy@Ti3C2/CdS) and tertiary composite (TiOy@Ti3C2/CdS/Cu2O), respectively, with good repeatability under visible-NIR light using lactic acid as the hole scavenger. A clear increase of efficiency by 1.53 mmol g-1 h-1 in the tertiary composite due to NIR light absorption supports the intrinsic upconversion of electrons, which will open a new prospective of solar light utilization. Decreased charge-transfer resistance from the EIS plot and a decrease in PL intensity established the improved interfacial charge separation in the tertiary composite. Compared to pure CdS, H2 generation efficiency is 29.6 times higher on the noble metal-free tertiary composite with an apparent quantum efficiency of 12.34%. Synergistic effect of defect-enriched TiOy formation, creation of proper dual p-n junction on a Ti3C2 sheet as supported by the Mott-Schottky plot, significant NIR light absorption, increased electron mobility, and charge transfer on the conductive Ti3C2 layer facilitate the drastically increased hydrogen evolution rate even after several cycles of repetition. Expectantly, the 2D MXene-based heterostructure with defect-enriched dual p-n junctions of desired interface engineering will facilitate scalable photocatalytic water splitting over a broad range of the solar spectrum.

Using Carbonized Cotton Fabric Waste to Prepare Poly(ethylene glycol) Composite Phase Change Materials with Improved Thermal Conductivity and Solar-to-Thermal Conversion.

Poly(ethylene glycol) (PEG) boasts excellent thermal energy storage capabilities but lacks efficiency in thermal conductivity and solar absorption. Simultaneously, the escalating concern surrounding the substantial volume of discarded cotton fabric underscores environmental issues. In this study, we devised composite phase change materials (PCMs) by embedding PEG into a carbon cotton material (CCM), varying PEG content from 50 to 80%, and conducted a comprehensive analysis of their thermal properties and solar-to-thermal conversion. The CCM, crafted from a waste 100% cotton towel through carbonization, provided an optimal porous structure that accommodated a significant 70% PEG content without any leakage, thanks to interactions such as surface tension, capillary forces, and interfacial hydrogen bonds. These PEG/CCM composites exhibited impressive crystallization fractions (>92%), resulting in notable thermal energy storage capacities ranging from 85.3 to 143.2 J/g as the PEG content increased from 50 to 80%. Moreover, these composites showed high thermal stability and exceptional cycling durability even after 500 melting/crystallization cycles. Notably, their thermal conductivities markedly increased to a range of 0.46-0.85 W/m·K compared to pure PEG's modest 0.24 W/m·K. Furthermore, the PEG/CCM composites substantially augmented visible and near-infrared (VIS-NIR) light absorption. Evaluation of solar-to-thermal conversion illustrated the composite's ability to efficiently convert solar energy into thermal energy, storing and subsequently releasing it through melting and crystallization processes. This study introduces a novel class of composite PCMs characterized by cost-effectiveness, outstanding thermal performance, and impressive solar-to-thermal conversion capabilities. These composite PCMs hold significant promise for large-scale solar-to-thermal energy storage applications while contributing to the sustainability of cotton waste management.

Methemoglobinemia: Case of Falsely low SpO2

Abstract Pulse oximetry is often regarded as the fifth vital sign. Based on the absorption of near-infrared light, any changes in the concentration of oxyhemoglobin influence the reading on the pulse oximeter. We present one such case of a 30-year-old lady with leprosy on multiple drug therapy that showed low SpO2 readings not associated with respiratory distress and did not improve with oxygenation. She was found to have dapsone-induced methemoglobinemia, which was reversed after 48 h of stopping the drug intake.

Near-infrared-driven upconversion nanoparticles with photocatalysts through water-splitting towards cancer treatment.

Water splitting is promising, especially for energy and environmental applications; however, there are limited studies on the link between water splitting and cancer treatment. Upconversion nanoparticles (UCNPs) can be used to convert near-infrared (NIR) light to ultraviolet (UV) or visible (Vis) light and have great potential for biomedical applications because of their profound penetration ability, theranostic approaches, low self-fluorescence background, reduced damage to biological tissue, and low toxicity. UCNPs with photocatalytic materials can enhance the photocatalytic activities that generate a shorter wavelength to increase the tissue penetration depth in the biological microenvironment under NIR light irradiation. Moreover, UCNPs with a photosensitizer can absorb NIR light and convert it into UV/vis light and emit upconverted photons, which excite the photoinitiator to create H2, O2, and/or OH˙ via water splitting processes when exposed to NIR irradiation. Therefore, combining UCNPs with intensified photocatalytic and photoinitiator materials may be a promising therapeutic approach for cancer treatment. This review provides a novel strategy for explaining the principles and mechanisms of UCNPs and NIR-driven UCNPs with photocatalytic materials through water splitting to achieve therapeutic outcomes for clinical applications. Moreover, the challenges and future perspectives of UCNP-based photocatalytic materials for water splitting for cancer treatment are discussed in this review.

First-principles study of Cs/O deposited Na&lt;sub&gt;2&lt;/sub&gt;KSb photocathode surface

Na&lt;sub&gt;2&lt;/sub&gt;KSb photocathodes have many applications in vacuum optoelectronic devices, such as photomultiplier tubes, image intensifiers, and streak image tubes for high-speed detection and imaging in extremely weak light environments, due to their advantages of high temperature resistance, small dark current, low vacuum requirement, low fabrication cost and high fabrication flexibility. In addition, this type of photocathode has important application prospect in high brightness accelerator photoinjectors. To guide the fabrication of high-sensitivity Na&lt;sub&gt;2&lt;/sub&gt;KSb photocathodes, Na&lt;sub&gt;2&lt;/sub&gt;KSb surfaces with different surface orientations and atom terminations are investigated by the first-principles calculation method based on the density functional theory to obtain the most stable and most favorable surface for electron emission. From the perspectives of surface energy, adsorption energy, and work function before and after Cs adsorption, it is revealed that the Na&lt;sub&gt;2&lt;/sub&gt;KSb (111) K surface exhibits superior surface stability and electron emission capability. Furthermore, the electronic structure and optical properties of Cs adsorption and Cs/O co-adsorption on the Na&lt;sub&gt;2&lt;/sub&gt;KSb (111) K surface under different Cs coverages are analyzed, and the mechanism of Cs/O deposition on Na&lt;sub&gt;2&lt;/sub&gt;KSb surface is studied. The adsorption energy of Cs in the Cs/O adsorption model is much larger than that in the single Cs adsorption model, indicating that the adsorption of O atoms on the Na&lt;sub&gt;2&lt;/sub&gt;KSb surface can make the adsorption of Cs atoms on the surface stronger, and thus increasing the adhesion of Cs atoms on the surface. After adsorption of Cs on the Na&lt;sub&gt;2&lt;/sub&gt;KSb (111)K surface, the surface work function only decreases by 0.02 eV, while the maximum work function decrease for the Cs/O adsorbed surface is 0.16 eV, with the Cs coverage of 2/4 ML and the O coverage of 1/4 ML. The adsorption of Cs/O atoms on the surface facilitates the charge transfer above the surface and results in charge accumulation, which can form the effective surface dipole moment. The magnitude of the surface dipole moment is directly related to the change of work function. Furthermore, through the analysis of the electronic band structure and density of states, it is found that the adsorbed Cs atoms have additional contribution to the band structure near the conduction band minimum. After the introduction of O atoms, the valence band moves up, also the bottom of the conduction band and the top of the valence band become flat. The Cs/O deposition is beneficial to increasing the absorption of near-infrared light on the Na&lt;sub&gt;2&lt;/sub&gt;KSb surface, but it will reduce the absorption of ultraviolet light and visible light, and the refractive index will also decrease. This work has a certain reference significance for understanding the optimal emission surface of Na&lt;sub&gt;2&lt;/sub&gt;KSb photocathode and the mechanism of surface Cs/O deposition.