Electron-hole Separation Research Articles

Research progress on ZnO/MoS2/rGO ternary photocatalysts

Energy shortages and environmental pollution have become one of the important global issues, and semiconductor photocatalytic technology is considered one of the most effective means to solve these problems. As a new and efficient green material, ZnO has attracted wide attention. ZnO is widely used in the field of photocatalysis due to its non-toxicity, low cost, environmental friendliness, adjustable band gap, high electron density, and chemical stability. However, the recombination of photogenerated charge carriers in ZnO hinders its practical application and lowers the utilization efficiency of visible light. On the other hand, molybdenum disulfide/reduced graphene oxide (MoS2/rGO), as a binary non-precious metal co-catalyst, has a larger specific surface area, suitable band gap width, and visible light response capability compared to a single-phase graphene co-catalyst. Therefore, introducing the MoS2/rGO co-catalyst into the ZnO system can provide more active sites, reduce the probability of photogenerated charge carrier recombination, and improve the utilization efficiency of visible light. In this review, we summarize the hydrothermal synthesis methods for preparing this highly demanded nanocomposite material, including one-step and stepwise methods. Subsequently, we elaborate on the mechanism of enhancing light absorption and achieving efficient electron-hole separation behavior in the ternary system heterojunction structure during the photocatalytic process. Due to its significant advantages, this ternary system heterojunction structure has been widely applied in the field of photocatalysis, including applications such as pollutant degradation, sterilization, and water splitting.

Acid modification on ZnIn2S4 with sulfur vacancy for highly efficient photocatalytic reduction of Cr(VI)

Anion vacancies caused by acid treatment over photocatalysts have significant influences on photocatalytic processes. In this study, the ZnIn2S4 (denoted as ZIS) nanoflower samples were synthesized using a one-step hydrothermal process and then impregnated with different amounts of nitric acid solutions. The gathered samples were characterized using XRD, SEM, XPS, BET, and EPR, and their photocatalytic reduction activity of Cr(VI) was also studied. Owing to defect structures, the removal of Cr(VI) of sulfur-rich vacancies ZIS-NA-3 reached nearly 100% within 90 min under simulated solar light, which was about 3 times greater than that of the original ZIS. In summary, this study confirmed that nitric acid treatment could form a defect state on the surface of catalysts, enhancing the light absorption range and improving the electron-hole pair separation efficiency. Furthermore, the stability and recycling of the ZIS-NA-3 catalysts were evaluated. This work offered a simple surface modification technique for constructing high-activity photocatalysts so as to achieve the purpose of removal from polluted wastewater containing Cr(VI).

Enhanced selectivity of novel sea urchin-like h-/m-WO3 hetero nanoflowers for highly sensitive detection of ammonia by double filtration method

Real-time monitoring of toxic gases and breath markers can be performed by metal oxide semiconductor-based chemo-resistive gas sensors due to their simple structures, low cost, and faster and better recovery and response. Due to the effective electron-hole separation, tuning the development of phase junctions of the metal oxide is an efficient method for improving their gas sensing properties. In this study, two distinct hydrothermal methods were used to synthesize h-/m-WO3 hetero-nanoflowers. In the first method, L-Cysteine was used to facilitate the formation of phase junctions between h-WO3 and m-WO3 nanostructures, whereas Thiourea was used in the second. Various characterisation approaches validated the hexagonal-monoclinic phase junction development in the nanoflowers. The sensing material fabricated using Thiourea with a concentration of 0.01M performed better than other sensors. At 350°C, the selected sample displayed outstanding ammonia sensing capacity with the experimental detection limit of 1 ppm (response=3.33). The theoretical detection limit is determined to be 27 ppb. The selectivity of the sensor towards NH3 over H2S and acetone is increased by combining the devices with a double filtration setup. The effectiveness of the selected h-/m-WO3 sensor for diagnosing kidney dysfunction was evaluated by analyzing simulated breath samples.

A covalent organic framework integrating photocatalytic center and electron reservoir for photocatalytic CO2 reduction to HCOOH

Direct and efficient photocatalytic conversion of CO2 into fuels and high value-added chemicals under sunlight is of great significance in alleviating the energy crisis and environmental issues. Covalent organic frameworks (COFs) have attracted much attention in the photocatalytic field as materials that can be pre-designed on demand. Taking advantage of the pre-designable properties of COFs materials, the integration of organic building blocks with photocatalytic activity and photoelectron-resident properties into frameworks can improve the electron-hole separation efficiency and photocatalytic performance. Here, we report a newly designed COF (COF-TVBT-N) with triazine and alkenyl groups that can be used as a photocatalyst to accomplish the photoreduction of CO2 to HCOOH under simulated sunlight without the assistance of metal sites and photosensitizers. Furthermore, we unambiguously reveal that the photocatalytic active center in COF-TVBT-N is TVBT through the combination of experiments and theoretical calculations. DFT calculations suggest that the adsorption of H near the active center is beneficial for the adsorption and photoreduction of CO2 in this photocatalytic system. The photoexcitation process and photocatalytic CO2 reduction mechanism of COF-TVBT-N are also reasonably deduced based on DFT calculations. This work provides ideas for the design of COFs as photocatalysts for CO2 reduction and gives insights into the mechanism of CO2 conversion to HCOOH.

Narrow Bandgap Schottky Heterojunction Sonosensitizer with High Electron-Hole Separation Boosted Sonodynamic Therapy in Bladder Cancer.

Sonodynamic therapy (SDT) is applied to bladder cancer (BC) given its advantages of high depth of tissue penetration and nontoxicity due to the unique anatomical location of the bladder near the abdominal surface. However, low electron-hole separation efficiency and wide bandgap of sonosensitizers limit the effectiveness of SDT. This study aims to develop a TiO2-Ru-PEG Schottky heterojunction sonosensitizer with high electron-hole separation and narrow bandgap for SDT in BC. Density functional theory (DFT) calculations and experiments collectively demonstrate that the bandgap of TiO2-Ru-PEG is reduced due to the Schottky heterojunction with the characteristic of crystalline-amorphous interface formed by the deposition of ruthenium (Ru) within the shell layer of TiO2. Thanks to the enhancement of oxygen adsorption and the efficient separation of electron-hole pairs, TiO2-Ru-PEG promotes the generation of reactive oxygen species (ROS) under ultrasound (US) irradiation, resulting in cell cycle arrest and apoptosis of bladder tumor cells. The in vivo results prove that TiO2-Ru-PEG boosted the subcutaneous and orthotopic bladder tumor models while exhibiting good safety. This study adopts the ruthenium complex for optimizing sonosensitizers, contributing to the progress of SDT improvement strategies and presenting a paradigm for BC therapy.

Peroxymonosulfate enhanced photocatalytic degradation of organic dye by metal-free TpTt-COF under visible light irradiation

Recently, the activation of persulfate (PDS) by non-metallic photocatalysts under visible light has attracted significant interest in applications in environmental remediation. This study presents a pioneering investigation into the combined application of the TpTt-COF and PMS for visible light degradation of organic dyes. Synthesized orange TpTt-COF monomers exhibit exceptional crystallinity, a 2D structure, and notable stability in harsh conditions. The broad visible light absorption around a wavelength of 708 nm. The TpTt-COF emerges as a promising candidate for photocatalytic dye degradation. The study addresses high charge recombination in the TpTt-COF, highlighting the crucial role of its electron donor and acceptor for the PMS activation. Comparative analyses against traditional photocatalytic materials, such as the metal-free carbon-based material g-C3N4 and transition metal-containing TiO2, demonstrate TpTt-COF's superior performance, generating diverse free radicals. In simulated experiments, the TpTt-COF's degradation rate surpasses PMS-combined g-C3N4 by 13.9 times. and 1.6 times higher than the TpTt-COF alone. Remarkably, the TpTt-COF maintains high activity under harsh environments. Investigations into the degradation mechanism and the TpTt-COF's reusability reveal its efficiency and stability. Under visible light, TpTt-COF facilitates efficient electron–hole separation. Combining the TpTt-COF with PMS produces various radicals, ensuring effective separation and a synergistic effect. Radical quenching experiments confirm the pivotal role of O2-· radicals, while ·OH and SO4-· radicals intensify the degradation. After five cycles, TpTt-COF maintains an impressive 83.2% degradation efficiency. This study introduces an efficient photocatalytic system mediated by PMS and valuable insights into governing mechanisms for organic pollutant degradation in water environments.

Synthesis of rare earth MOF/CZS materials derived from aromatic tetracarboxylic acids and photocatalytic hydrogen production

With the increasing urgency of clean energy, photocatalytic hydrogen production serves as a sustainable hydrogen manufacturing method to improve the increasing scarcity of fossil fuels and environmental pollution. Herein, Cd0.2Zn0.8S (CZS)-modified Metal-Organic Framework (MOF) composites Pr–NO2–TPTC/CZS were successfully prepared through the reaction of Pr3+, aromatic tetracarboxylic acid, and Cd0.2Zn0.8S nanoparticles. Pr–NO2–TPTC/CZS composite materials exhibited enhanced photolysis performance compared to pure Pr–NO2–TPTC and Cd0.2Zn0.8S materials. With the decrease of Cd0.2Zn0.8S in Pr–NO2–TPTC/CZS composites, the photocatalytic performance of the synthesized composites is constantly improved. Pr–NO2–TPTC/CZS (1:1) photocatalyst exhibited excellent hydrogen evolution performance, with a hydrogen production capacity of 6321 μmol g−1 h−1. Photoluminescence spectroscopy (PL), photocurrent-time test (I-t), and electrochemical impedance spectroscopy (EIS) confirmed that the heterojunction interface formed between Pr–NO2–TPTC and CZS promoted electron-hole separation and transfer. Electron paramagnetic resonance (EPR) indicated that CZS-modified Pr–NO2–TPTC can promote the production of ·OH and ·O2− in the system, thereby increasing the photocatalytic hydrogen production performance. This work provides an effective solution for photocatalytic hydrogen production and a potential method for solving the energy crisis and environmental pollution.

Enhanced Fenton-like process over Z-scheme MoO3 surface decorated with Fe2O3 under visible light

Photocatalysts consisting of Z-scheme heterojunctions are commonly used in wastewater treatment due to their exceptional reactivity in photocatalysis and highly efficient visible-light utilization. In this work, Fe2O3-decorated MoO3 rods were synthesized through a two-step method and their photodegradation of methylene blue (MB) was evaluated. The Fe2O3/MoO3 rods were characterized by XRD, SEM, micro-Raman, XPS, UV–Vis DRS, and PL to investigate their structural, morphological, and optical properties. The results indicate that the photodegradation efficiency of Fe2O3/MoO3 improved through a reduction in the gap energy and persistence of a 1D hexagonal prism structure. The degradation rate of MB was enhanced from 31.7 to 91.5% after irradiation for 180 min owing to electron–hole separation and Fenton-like process. Formation of the OH radical is a key factor in the photodegradation reaction and with the addition of H2O2 the efficiency can further improve via a Fenton-like mechanism. Furthermore, the Z-scheme mechanism concurrently delineated. The Fe2O3/MoO3 rod composites were also found to retain high photocatalytic efficiency after being reused five times, which may be useful for future applications.

Layered double hydroxides derived prussian blue analogue nanocage confining NiCoP nanoparticles as efficient bifunctional electrocatalyst

Designing novel electrocatalysts with excellent catalytic activity for efficient water splitting is necessary to achieve the large-scale H2/O2 production from renewable resources. In this study, a facile hydrothermal method followed by low-temperature phosphorylation treatment was employed to fabricate a nanocage of prussian blue analogue encapsulating NiCoP nanoparticles (NiCoP@PBA), which was derived from the layered double hydroxide precursor. As a bifunctional non-precious metal electrocatalyst, NiCoP@PBA demonstrates superior performance in KOH electrolyte water splitting, with overpotentials of 59 mV for electrocatalytic hydrogen evolution reaction (HER) and 263 mV for oxygen evolution reaction (OER) at 10 mA cm−2. The catalyst also exhibits low Tafel slopes of 54 mV dec−1 for HER and 120 mV dec−1 for OER, reflecting efficient charge transfer kinetics. DFT simulations show that the Co–N moieties at the heterogeneous interface of NiCoP@PBA can optimize the surface electron distribution and energy states, thus facilitating efficient electron-hole pair separation, significantly enhancing catalytic activity for both HER and OER process, and significantly extending the electrocatalyst's service life. Our approach can be extended to more non-precious metal electrocatalysts, which is significant for the design of efficient bifunctional water splitting electrocatalysts.

2D Copper–Porphyrin Metal–Organic Framework Nanosheet‐Photosensitized TiO2 for Efficiently Broadband Light‐Driven Conversion of CO2 to CH4

The effective utilization of light is crucial in the use of the solar energy for CO2 conversion into valuable fuels and chemicals, in which improving the photocatalytic materials’ capacity to absorb light is a key. Herein, a 2D copper–porphyrin metal−organic framework (MOF)‐photosensitized titania, TiO2/Zn–CuTCPP, is reported, which can absorb wide range of light and photoreduce CO2 with high efficiency under full spectrum irradiation. Fluorescence spectral analysis elucidates the relationship between the photocatalytic activity and the electron–hole separation efficiency. In addition, mechanistic information obtained from electron paramagnetic resonance and in situ infrared analyses demonstrates that the presence of Cu–N4 site in the MOF structure is conducive to the generation of hydrogen free radicals (•H), which plays a key role in the formation of intermediates, thus facilitating the hydrogenation in the reaction process. Consequently, TiO2/Zn–CuTCPP significantly enhances the photocatalytic conversion of CO2 into CH4 with a yield 14 times higher than that of P25.

NH2-UiO-66 modification BiOBr enhancement photoreduction CO2 to CO

As a typical semiconductor catalyst, BiOBr has an advisable bandgap, superior light absorption properties, and a unique laminated structure. However, the slow electron-hole separation rate results in poor CO2 reduction performance. To enhance the photocatalytic efficiency of BiOBr, this study constructs BiOBr heterojunctions with Lewis basic groups by loading NH2-UiO-66 on BiOBr. The BiOBr/NH2-UiO-66 heterojunction have been built and possess stronger light response, larger specific surface area and electron-hole separation efficiency compared to pure BiOBr and NH2-UiO-66. The optimal BiOBr/NH2-UiO-66 displays that the CO yield is 9.19 μmol g-1h−1, which is 4 times higher than pure BiOBr.

BiOCl/BiOBr composites for efficient photocatalytic carbon dioxide reduction

BiOBr (BOB) photocatalysts have low photocatalytic CO2 reduction performance due to their low electron-hole pair separation efficiency. To improve this problem, BiOCl (BOCl) is used as a co-catalyst. BOCl is loaded into BOB to form BiOCl/BiOBr (BOCl/BOB) type Ⅰ heterojunction, which enhances the photocatalytic CO2 reduction performance of BOB by promoting the separation of photogenerated electrons and holes. The results of TPR and PL experiments show that the 20% BOCl/BOB composites have the highest photogenerated carrier separation rate, and the results of CO2 reduction experiments show that 20% BOCl/BOB composites have the best photocatalytic CO2 reduction performance of 7.353 μmolg−1h−1, which is 3.22 and 1.99 times higher than pure BOB and BOCl, respectively. This work provides an effective reference for the development of modified photocatalysts.

Tumour microenvironment-responded Fe-doped carbon dots-sensitized cubic Cu2O for Z-scheme heterojunction-enhanced sono-chemodynamic synergistic tumor therapy

The efficacy of electron-hole separation in a single sonosensitizer and the complexities of the tumor microenvironment (TME) present significant challenges to the effectiveness of sonodynamic therapy (SDT). Designing efficient sonosensitizers to enhance electron-hole separation and alleviate TME resistance is crucial yet challenging. Herein, we introduce a novel Z-scheme heterojunctions (HJs) sonosensitizer using Fe-doped carbon dots (CDs) as auxiliary semiconductors to sensitize cubic Cu2O (Fe-CDs@Cu2O) for the first time. Fe-CDs@Cu2O demonstrated enhanced SDT effects due to improved electron-hole separation. Additionally, the introduction of Fe ions in CDs synergistically enhances Fenton-like reactions with Cu ions in Cu2O, resulting in enhanced chemodynamic therapy (CDT) effects. Moreover, Fe-CDs@Cu2O exhibited rapid glutathione (GSH) depletion, effectively mitigating TME resistance. With high rates of 1O2 and OH generated by Fe-CDs@Cu2O, coupled with strong GSH depletion, single drug injection and ultrasound (US) irradiation effectively eliminate tumors. This innovative heterojunction sonosensitizer offers a promising pathway for clinical anti-tumor treatment.

Effects of surface property on loading octaaza bis-α-diimine Ni complex, charge separation, and H2 production activity of MnS@ZnS photocatalysts

The MnS@ZnS photocatalyst was prepared using a microwave-assisted solvothermal method. Then, the octaaza bis-α-diimine Ni complex was loaded to prepare a composite photocatalyst. The adsorption of metal complex on photocatalyst depends on the anchoring groups of the Ni complex and the colloidal surface charge of the photocatalyst. The effects of the zeta potential of MnS and MnS@ZnS photocatalysts on the loading of Ni complex, separation of photogenerated carriers, and activity of Ni complex-modified composite photocatalysts were studied. The loading of NiC complex in photocatalysts was analyzed by Raman spectra, TEM line scan, mapping images, and total reflection x-ray fluorescence spectrometer. MnS@ZnS photocatalyst exhibits negative zeta potential that provides a strong electrostatic attraction force between photocatalysts and the Ni complex (Columb attraction), leading to increased Ni complex loading. MnS@ZnS/Ni complex exhibits better photocatalytic activity than MnS/Ni complex. Loading the Ni complex facilitates the photosensitization of photocatalysts, resulting in improved light absorbance. Besides, the electron-hole separation was further improved because the Ni complex acted as a redox mediator, enabling the transfer of electrons from MnS@ZnS to the Ni complex. The H2 production activity of MnS@ZnS/Ni complex photocatalyst reaches 3997 μmol h−1g−1, which is 1.72 times the pristine MnS.

Engineering NH2-Cu-NH2 Triple-atom Sites in Defective MOFs for Selective Overall Photoreduction of CO2 into CH3COCH3.

Selective photoreduction of CO2 to multicarbon products, is an important but challenging task, due to high CO2 activation barriers and insufficient catalytic sites for C-C coupling. Herein, a defect engineering strategy for incorporating copper sites into the connected nodes of defective metal-organic framework UiO-66-NH2 for selective overall photo-reduction of CO2 into acetone. The Cu2+ site in well-modified CuN2O2 units served as a trapping site to capture electrons via efficient electron-hole separation, forming the active Cu+ site for CO2 reduction. Two NH2 groups in CuN2O2 unit adsorb CO2 and cooperated with copper ion to functionalize as a triple atom catalytic site, each interacting with one CO2 molecule to strengthen the binding of *CO intermediate to the catalytic site. The deoxygenated *CO attached to the Cu site interacted with *CH3 fixed at one amino group to form the key intermediate CO*-CH3, which interacted with the third reduction intermediate on another amino group to produce acetone. Our photocatalyst realizes efficient overall CO2 reduction to C3 product acetone CH3COCH3 with an evolution rate of 70.9 μmol gcat -1 h-1 and a selectivity up to 97 % without any adducts, offering a promising avenue for designing triple-atomic sites to producing C3 product from photosynthesis with water.

Dynamic Ag-mediated electron transfer confined ZnO nanorods for boosted photocatalytic bacterial disinfection

Infectious diseases, particularly bacterial infections, pose a global crisis with significant impacts on public health and economic stability due to the emergence of multi-drug resistance and limitations in existing therapeutic options. The present study focused on the development of photocatalytic disinfectant and silver-decorated hexagonal zinc oxide nanorods (Ag/ZnO NRs) were fabricated through an ultrasonic-assisted solvothermal method, and investigated for the photocatalytic inactivation on E. coli. The morphological, structural, and optical characteristics of the fabricated Ag/ZnO NRs were systematically studied through various analytical techniques. Here, 3%Ag/ZnO NRs showed 96.9% inactivation of E. coli within 120 min of visible light irradiation. The excellent inactivation efficiency of the photocatalyst could be attributed to the higher charge carrier mobility, efficient electron-hole pair separation, and highvisible light harvesting ability. The Schottky heterojunction was proposed as a possible mechanism for the photoinactivation of E. coli. Further, the impacts of different dosages of nanocomposites (NCs) and varying pH on bacterial inactivation were studied under visible light exposure. The reusability and stability of the NCs were investigatedfor 6 consecutive cycles of photoinactivation and it showed excellent efficiency (91.16%) of the photocatalyst for prolonged usage. The real-time application was assessed using reclaimed wastewaterand the influence on the organic matter was determined using COD analysis. The proposed study offers a significant point reference for the practical application of photocatalysis forthe inactivation of antibiotic-resistant microbes present in water bodies and environmental wastewater.

A signal amplification strategy based on hexametaphosphate-stabilized BiVO4@CdS heterojunction with Mg2+-modulated surface charge for CEA detection

An ultrasensitive sensor with excellent photoelectrochemical (PEC) properties was developed based on the combination of electrostatic interactions between the hexametaphosphate (HMP)-coated BiVO4@CdS novel photoelectric material and the electron donor. Compared with the conventional BiVO4@CdS photoactive material, the HMP-modified BiVO4@CdS not only increases the stability, but also utilizes the electrostatic interactions between the negative charge carried by the phosphate group and the electron donor, which results to a significant increase in the photoelectric conversion ability after Mg2+ incubation. Specifically, carcinoembryonic antigen (CEA)-targeted immunorecognition was combined with MgCO3 antibody labelling inspired by the ability of HMP to complex with Mg2+. The released Mg2+ from the MgCO3 tag could neutralize the negative charge on the surface of BiVO4@CdS-HMP, and the electrostatic repulsion with the electron donor was suppressed, accelerating the electron transfer, and thus improving the electron-hole separation efficiency. A sensitive detection capability was demonstrated with CEA as the model target. Featuring a wide linear detection range with a detection limit as low as 60 fg/mL, this work provides a fresh perspective on the development of high-performance PEC biosensors.

Sonochemical fabrication of S-scheme Bi2O2CO3/g-C3N4 heterojunction for enhanced photocatalytic destruction of rhodamine B and tetracycline pollutants under natural solar radiations

Photocatalysis is a promising low cost green technology to efficiently mineralize refractory contaminants from wastewater. In this novel research, S-scheme Bi2O2CO3/g-C3N4 heterojunctions containing (0-25) wt % Bi2O2CO3 were sonochemically fabricated for mitigation of hazardous rhodamine B dye and tetracycline antibiotic under sunlight radiations of 900 W power. The physicochemical properties of the solid specimen were explored by photoluminescence [PL], diffuse reflectance spectrum [DRS], X-ray diffraction [XRD], Mapping, high resolution transmission electron microscope [HRTEM], selected area electron diffraction [SAED], N2–adsorption–desorption isotherms and X–ray photoelectron spectroscopy [XPS] techniques. As elucidated by HRTEM analysis, 15 wt% of spherical Bi2O2CO3 nanoparticles of 12 nm size were deposited on g-C3N4 of 40 m2/g surface area at nearly equidistant from each other. The point of zero charge of g-C3N4 sheets was shifted from pHPZC 6.2 to pHPZC 4.8 with incorporation of 15 wt % Bi2O2CO3 revealing the production of negatively charged surface that strongly destructed cationic rhodamine B dye. The rate of photocatalytic degradation of rhodamine B dye for heterojunction containing 15 wt% Bi2O2CO3 was 0.0168 min−1 which is three fold higher than that of pristine g-C3N4 nanosheets. The radical scavengers experimental results revealed that superoxide radicals and positive holes are the main reactive species in the degradation process. The exceptional photocatalytic reactivity emerged from construction of S-scheme heterojunction with auspicious electron-hole pair separation and transportation electron-hole pairs and significant redox power.

Modulating interface internal electric field for efficient charge separation in Co3O4/M-TiO2 p-n junction

The practical application of photocatalysis in water purification is restricted by the high electron-hole recombination efficiency. Herein, a Co3O4/M-TiO2 p-n composite catalyst with internal electric field (IEF) modulation was constructed. Because of the large number of oxygen vacancies (OVs) within Co3O4/M-TiO2, which could redistribute extra electrons to adjacent Co sites through the strong electron absorption effect of Co. Consequently, the charge distribution at the interface of Co3O4/M-TiO2 have been changed, forming positive and negative charge regions on M-TiO2 and Co3O4, respectively. Compared with Co3O4/P25, the amount of OVs in Co3O4/M-TiO2 is significantly increased, making the charge distribution at the interface more uneven and resulting in a significantly increased IEF intensity of Co3O4/M-TiO2 by 1.9 times. A series of photoelectric chemical experiments showed that driven by powerful IEF, the photogenerated electron-hole separation efficiency of Co3O4/M-TiO2 is significantly improved. In the photocatalysis-peroxymonosulfate (PMS) oxidation coupling system, Co3O4/M-TiO2 achieved high efficiency degradation of tetracycline hydrochloride (93.6 %) within 30 min, and a synergistic degradation mechanism of photocatalysis and PMS oxidation was proposed. This study provides a novel perspective on the construction of heterojunctions possessing strong internal electric fields.

Single Atom Catalysts Remodel Tumor Microenvironment for Augmented Sonodynamic Immunotherapy.

The immunosuppressive tumor microenvironment (TME) is a huge hurdle in immunotherapy. Sono-immunotherapy is a new treatment modality that can reverse immunosuppressive TME, but the sonodynamic effects are compromised by overexpressed glutathione (GSH) and hypoxia in the TME. Herein, this work reports a new sono-immunotherapy strategy using Pdδ+ single atom catalysts to enhance positive sonodynamic responses to the immunosuppressive and sono-suppressive TME. To demonstrate this technique, this work employs rich and reductive Ti vacancies in Ti3-xC2Ty nanosheets to construct the atomically dispersed Pd-C3 single atom catalysts (SAC) with Pd content up to 2.5 wt% (PdSA/Ti3-xC2Ty). Compared with Pd nanoparticle loaded Ti3-xC2Ty, PdSA/Ti3-xC2Ty single-atom enzyme showed augmented sonodynamic effects that are ascribed to SAC facilitated electron-hole separation, rapid depletion of overexpressed GSH by ultrasound (US) excited holes, and catalytic decomposition of endogenous H2O2 for relieving hypoxia. Importantly, the sono-immunotherapy strategy can boost abscopal antitumor immune responses by driving maturation of dendritic cells and polarization of tumor-associated macrophages into the antitumoral M1 phenotype. Bilateral tumor models demonstrate the complete eradication of localized tumors and enhance metastatic regression. Th strategy highlights the potential of single-atom catalysts for robust sono-immunotherapy by remodeling the tumor microenvironment.