Enhancement of visible-light-driven photoresponse of Mn/ZnO system: photogenerated charge transfer properties and photocatalytic activity

The synergistic degradation of pollutants in water by photocatalysis and PMS activation

In recent years, the synergistic degradation of water pollutants through advanced oxidation technology has emerged as a prominent research area due to its integration of various advanced oxidation technologies. The combined utilization of peroxymonosulfate (PMS) activation technology and photocatalysis demonstrates mild and nontoxic characteristics, enabling the degradation of water pollutants across a wide pH range. Moreover, this approach reduces the efficiency of electron hole recombination, broadens the catalyst's light response range, facilitates electron transfer of PMS, and ultimately improves its photocatalytic performance. The paper reviews the current research status of photocatalytic technology and PMS activation technology, respectively, while highlighting the advancements achieved through the integration of photocatalytic synergetic PMS activation technology for water pollutant degradation. Furthermore, this review delves into the mechanisms involving both free radicals and nonradicals in the reaction process and presents a promising prospect for future development in water treatment technology. PRACTITIONER POINTS: Degradation of water pollutants by photocatalysis and PMS synergistic action has emerged. Synergism can enhance the generation of free radicals. This technology can provide theoretical support for actual wastewater treatment.

Improving the Photocatalytic Performance of Porous Ceria under Visible Light Illumination via Mn Incorporation

Porous cerium oxide (ceria) nanoparticles were prepared with and without manganese (Mn) by using the flash combustion technique. Samples with different loadings (Ce/Mn ratio ranged from 100 to 10) were prepared by using a one-step process and water only as a solvent. Moreover, citric acid was utilized as a fuel in an aqueous medium, and the overall synthesis mixture was dried at 100 °C overnight and then calcinated at 550 °C for 3 h. The obtained final solid product was characterized by inductively coupled plasma (ICP), X-ray powder diffraction (XRD), diffuse reflectance ultraviolet-visible spectroscopy (DR-UV-Vis), and scanning electron microscopy (SEM), which was coupled with Energy Dispersive X-Ray Analysis (EDX), high resolution transmission electron microscopy (HR-TEM), and photoluminescence (PL) analysis. The characterization data showed that Mn ions were totally incorporated into the framework of ceria up to the applied loading. Under visible light illumination, the photocatalytic activity of the prepared samples was tested in the decolorization reaction of methyl green (MG) dye (wavelength greater than 425 nm). The results showed that increasing Mn content improved the photocatalytic activity of ceria. The sample with a Ce/Mn ratio of 10 performed 1.8 times better than bare porous ceria. Finally, the reusability of the best-performing sample was investigated in four consecutive runs without treatment, and slight deactivation was monitored after the fourth run.

Engineering of anatase/rutile TiO2 heterophase junction via in-situ phase transformation for enhanced photocatalytic hydrogen evolution

Constructing effective interphase boundary is one of the efficient approaches for improving photocatalytic performances of semiconductor materials. In this work, an anatase/rutile-TiO₂ (AR-TiO₂) heterophase junction with appropriate carbon content was successfully fabricated via an in-situ phase transformation process. The phase transformation started from the inner core of the nanoparticles and the area of phase interface between anatase and rutile was carefully controlled by regulating the activation temperature. The well-established type-II band alignment between two TiO₂ phases with residual carbon as additional charge transfer intermediary which significantly improved the light-harvesting and photoinduced electron-hole pair separation. As a result, the optimal AR-TiO₂-550 catalyst (without adding commonly used Pt as co-catalyst) remarkably enhanced photocatalytic H₂ generation (201 μmol h^-1 g^-1), which was about 12-fold to that of P25. The AR-TiO₂-550 heterophase junction also showed long-term stability under simulated solar light irradiation. This research provides a new phase engineering route for developing high-efficient photocatalysts.

A phosphorescence resonance energy transfer-based "off-on" long afterglow aptasensor for cadmium detection in food samples

Cadmium contamination is a severe food safety risk for human health. Herein, a long afterglow "off-on" phosphorescent aptasensor was developed based on phosphorescence resonance energy transfer (PRET) for the detection of Cd²⁺ in complex samples which minimizes the interference of background fluorescence. In this scheme, initially the phosphorescence of Cd²⁺-binding aptamer conjugated long afterglow nanoparticles (Zn₂GeO₄:Mn) was quenched by black hole quencher 1 (BHQ₁) modified complementary DNA. Upon encountering of Cd²⁺, the aptamer interacted with Cd²⁺ and the complementary DNA with BHQ₁ was released, leading to phosphorescence recovery. The content of Cd²⁺ could be quantified by the intensity of phosphorescence recovery with 100 μs gate time (which eliminated the sample autofluorescence) with a linear relationship between 0.5 and 50 μg L^-1 and a limit of detection (LOD) of 0.35 μg L^-1. This method was successfully demonstrated for Cd²⁺ detection in drinking water and yesso scallop samples. The "off-on" phosphorescent aptasensor based on PRET of long afterglow nanomaterials could be an effective tool for Cd²⁺ detection in food samples.

Semiconductors as Effective Electrodes for Dye Sensitized Solar Cell Applications

As proficient photovoltaic devices, dye-sensitized solar cells (DSSCs) have received considerable consideration in recent years. In order to accomplish advanced solar-to-electricity efficiency and increase long-term functioning stability, improvements in the configuration structure of DSSCs are essential, as is an understanding of their elementary principles. This work discusses the application of different semiconductor constituents designed for effective DSSCs. The main parameters crucial to fabrication of DSSC electrodes in nano-porous semiconductor structures are high surface area and large pore size. Different inorganic semiconductor materials are used to load sensitizer dyes, which absorb a lot of light and induce high photocurrent for efficient DSSCs. The first section of the review covers energy sources, photovoltaics, and the benefits of solar cells in daily life, while the second part includes the various types of semiconductors applied in DSSC applications. The final section provides a brief review of future perspectives for DSSCs and a survey of semiconductor materials proposed for solar cell applications.

Manganese-deposited iron oxide promotes tumor-responsive ferroptosis that synergizes the apoptosis of cisplatin

Background: Ferroptosis is a form of iron-dependent programmed cell death that differs from apoptosis with regards to both mechanism and cell morphology. Therefore, ferroptotic-based cancer therapy has shown significant potential to overcome the weaknesses of conventional therapeutics mediated by apoptosis pathways. Effective ferroptosis can be induced by the intracellular Fenton reaction that is dependent on the adequate supply of iron ions and H2O2 in cells. However, these are often insufficient due to intrinsic cellular regulation. Methods: In this study, we designed a cisplatin prodrug-loaded manganese-deposited iron oxide nanoplatform (Pt-FMO) to trigger intracellular cascade reactions that lead to generation of reactive oxygen species (ROS) to enhance ferroptotic effect. The Pt-FMO causes the tumor microenvironment responsive to release manganese, iron ions and Pt-drugs. As manganese is an element that is able to catalyze the Fenton reaction more effectively than iron, coupled with the Pt-drugs that can promote generation of H2O2 in cells, the Pt-FMO is expected to significantly strengthen catalysis of the Fenton reaction, which favors the ferroptotic effect. Moreover, the Pt-drugs will eventually function as cisplatin. Thus, Pt-FMO is an ideal candidate for tumor ferroptotic combined with apoptotic treatment. Results:In vivo results demonstrated that, at a dosage of only 8.89% Pt content, Pt-FMO is able to achieve a similar treatment effect as cisplatin. Hence, Pt-FMO exhibited significantly lower systemic toxicity compared to cisplatin. Additionally, Pt-FMO exhibits effective T2 -weighted MRI enhancement for tumor imaging. Conclusion: The Pt-FMO nanoplatform is designed to introduce mutual beneficial cascade reactions for promoting ferroptosis and apoptosis in combination with tumor MRI. The Pt-FMO system, which causes ferroptosis combined with apoptosis, can efficiently induce tumor cell death.

Designed Ag-decorated Mn:ZnO nanocomposite: facile synthesis, and enhanced visible light absorption and photogenerated carrier separation

A series of ZnO-based complex architectures including Mn-doped ZnO, Ag/ZnO and Ag-decorated Mn:ZnO nanocomposites were fabricated by a facile polymer network gel method. The photocatalytic performance of the as-synthesized products was evaluated by the degradation of methylene blue (MB), methyl orange (MO) and rhodamine B (RhB) under simulated sunlight irradiation. The Mn:ZnO/Ag photocatalyst achieves the superior photodegradation efficiency, which is three times higher than that of pure ZnO and two times that of the Ag/ZnO composite. Our results demonstrate that the significantly enhanced photocatalytic properties of Mn:ZnO/Ag are due to the synergetic effects of both Mn doping and Ag decoration. The possible photocatalytic mechanism of Mn:ZnO/Ag for degradation of organic dyes is proposed. The transformation from Mn3+ to Mn2+, the increase of surface defects, and the improvement of the crystal quality are the crucial factors for the enhancement of the photocatalytic properties. This study provides an effective approach to overcome the response limitation of ZnO-based photocatalysts in the visible region and realize efficient photogenerated carrier separation.

Manganese-Doped Zinc Oxide Nanostructures as Potential Scaffold for Photocatalytic and Fluorescence Sensing Applications

Herein, we report the photocatalytic and fluorescence sensing applications of manganese-doped zinc oxide nanostructures synthesized by a solution combustion technique, using zinc nitrate as an oxidizer and urea as a fuel. The synthesized Mn-doped ZnO nanostructures have been analyzed in terms of their surface morphology, phase composition, elemental analysis, and optical properties with the help of scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and UV-Visible (UV-Vis) spectroscopy. A careful observation of the SEM micrograph reveals that the synthesized material was porous and grown in very high density. Due to a well-defined porous structure, the Mn-doped ZnO nanostructures can be used for the detection of ciprofloxacin, which was found to exhibit a significantly low limit of detection (LOD) value i.e., 10.05 µM. The synthesized Mn-doped ZnO nanostructures have been further analyzed for interfering studies, which reveals that the synthesized sensor material possesses very good selectivity toward ciprofloxacin, as it detects selectively even in the presence of other molecules. The synthesized Mn-doped ZnO nanostructures have been further analyzed for the photodegradation of methyl orange (MO) dye. The experimental results reveal that Mn-doped ZnO behaves as an efficient photocatalyst. The 85% degradation of MO has been achieved in 75 min using 0.15 g of Mn-doped ZnO nanostructures. The observed results clearly confirmed that the synthesized Mn-dopedZnO nanostructures are a potential scaffold for the fabrication of sensitive and robust chemical sensors as well as an efficient photocatalyst.

Porous Mn-Doped FeP/Co3 (PO4 )2 Nanosheets as Efficient Electrocatalysts for Overall Water Splitting in a Wide pH Range

Development of highly active and stable electrocatalysts for overall water splitting is important for future renewable energy systems. In this study, porous Mn-doped FeP/Co₃ (PO₄ )₂ (PMFCP) nanosheets on carbon cloth are utilized as a highly efficient 3 D self-supported binder-free integrated electrode for the oxygen evolution and hydrogen evolution reactions (OER and HER) over a wide pH range. Specifically, overpotentials of 27, 117, 85 mV are required for the PMFCP nanosheets to attain 10 mA cm^-2 for HER in 0.5 m H₂ SO₄ , 1.0 m phosphatebuffered saline (PBS), and 1.0 m KOH, respectively. In addition to the excellent performance for HER electrocatalysis, PMFCP nanosheets were also efficient electrocatalysts for the OER. Thus, the PMFCP nanosheets can serve as anodes and cathodes for overall water splitting (OWS). The OWS working voltages to attain 10 mA cm^-2 are found to be 1.75, 1.82, and 1.61 V in acid, neutral, and alkaline electrolytes, respectively. Chronopotentiometric tests show that the PMFCP electrode can maintain its excellent pH-universal OWS activity for more than 30 000 s. This work also provides new insights into developing high-performance electrocatalysts for water splitting over a wide pH range. The improvement in electrochemical performance by introduction of Mn dopant and nano-holes offers new opportunities in the development of effective electrodes for other energy-related applications.

Insight into the photocatalytic mineralization of short chain chlorinated paraffins boosted by polydopamine and Ag nanoparticles

Short chain chlorinated paraffins (SCCPs) have attracted increasing attention recently due to their widespread occurrence and persistence in the environment, long-distance transport, and bioaccumulation and toxicity. For the sake of photocatalytic elimination of SCCPs, a kind of polydopamine (PDA) based photocatalyst, echinus-like Fe₂O₃@PDA-Ag hybrids have been synthesized via coating Fe₂O₃ with PDA by self-polymerization of dopamine and further loading silver nanoparticles by in situ reduction onto the surface of PDA shell. The photogenerated charges of Fe₂O₃@PDA-Ag hybrids exhibit long lifetime from transient photovoltage signal, which is of benefit to participate in various subsequent reaction processes before their recombination. Benefiting from the coating of PDA shell and the deposition of Ag nanoparticles, Fe₂O₃@PDA-Ag hybrids exhibit enhanced photocatalytic activity for the removel of SCCPs as investigated by the in situ Fourier transform infrared spectroscopy, 2.9 times as high as that of Fe₂O₃, due to the reactive OH radicals. The density functional theory simulation demonstrates the key mechanism of the formation of conjugate bond in the dechlorination process as well as the final product of HCl. The simulation indicates that there are no regularities for the H-abstraction but the dechlorination usually occurs in the adjacent Cl atoms next to the C with H-abstraction.

Synthesis of novel Au@Void@Nb2O5 core–shell nanocomposites with enhanced photocatalytic activity

Novel Au@Void@Nb₂O₅ core–shell nanocomposites have been fabricated through a facile sol–gel method exhibiting efficient photocatalytic performance and excellent durability.

Immobilization of TiO₂ Nanoparticles on Chlorella pyrenoidosa Cells for Enhanced Visible-Light-Driven Photocatalysis

TiO₂ nanoparticles are immobilized on chlorella cells using the hydrothermal method. The morphology, structure, and the visible-light-driven photocatalytic activity of the prepared chlorella/TiO₂ composite are investigated by various methods. The chlorella/TiO₂ composite is found to exhibit larger average sizes and higher visible-light intensities. The sensitization of the photosynthesis pigment originating from chlorella cells provides the anatase TiO₂ with higher photocatalytic activities under the visible-light irradiation. The latter is linked to the highly efficient charge separation of the electron/hole pairs. The results also suggest that the photocatalytic activity of the composite remains substantial after four cycles, suggesting a good stability.

Cobalt Phosphide Modified Titanium Oxide Nanophotocatalysts with Significantly Enhanced Photocatalytic Hydrogen Evolution from Water Splitting

Production of hydrogen from photocatalytic water splitting holds promise as an alternative energy source with superiority of cleanliness, environment friendliness, low price, and sustainability. Perfectly constructing the noble-metal-free and stable hybrid structure photocatalyst is quite essential; herein, for the first time the authors aim to use cobalt phosphide as the cocatalyst on titanium oxide to form a novel hybrid structure to enhance the utilization of the photoexcited electrons in redox reactions for improved photocatalytic H₂ evolution activity. Thus, the achieved significantly increased photocatalytic H₂ -evolution rate on the optimized CoP/TiO₂ (8350 µmol h^-1 g^-1 ) is 11 times higher than that of the pristine TiO₂ . Moreover, this work is expected to spur more insight into synthesizing such novel photofunctional systems, achieving high photocatalytic H₂ evolution activity and sufficient stability for solar-to-chemical conversion and utilization.

Large-scale synthesis of Au–WO3 porous hollow spheres and their photocatalytic properties

Uniform Au–WO₃ porous hollow spheres have been synthesized on a large-scale by a general in situ reaction. The hybrid materials exhibit excellent activity for visible-light photocatalytic degradation of organic pollutants.

Single step fabrication of CuO–MnO–2TiO2 composite thin films with improved photoelectrochemical response

CuO–MnO–2TiO₂ composite thin film having a photocurrent density of 2.21 mA cm⁻² at +0.7 V has been deposited from a homogeneous mixture of acetates of Cu and Mn and (Ti(O(CH₂)₃CH₃)₄) in the presence of trifluoroacetic acid in THF via AACVD at 550 °C.

A novel and highly efficient earth-abundant Cu3P with TiO2 "P-N" heterojunction nanophotocatalyst for hydrogen evolution from water

Semiconductor-based photocatalytic hydrogen (H₂) evolution from water is of great importance for solar-to-chemical conversion processes to boost and promote the future hydrogen economy. Here, for the first time, we demonstrate that p-Cu₃P coupled with n-TiO₂ forms a novel hybrid structure which accelerates electron-hole pair separation and transfer for improved photocatalytic H₂-evolution activity. The rate of H₂ evolution of the optimized Cu₃P/TiO₂ (7940 μmol h^-1 g^-1) is 11 times higher than that of bare TiO₂, with an apparent quantum efficiency (AQE) of 4.6%. This work may provide more insight into the synthesis of novel phosphide-based hybrid materials with high photocatalytic H₂-evolution activity and sufficient stability for solar-to-chemical conversion and utilization.

Engineered band structure for an enhanced performance on quantum dot-sensitized solar cells

A photon-to-current efficiency of 2.93% is received for the Mn-doped CdS (MCdS)-quantum dot sensitized solar cells (QDSSCs) using Mn:ZnO (MZnO) nanowire as photoanode. Hydrothermal synthesized MZnO are spin-coated on fluorine doped tin oxide (FTO) glass with P25 paste to serve as photoanode after calcinations. MCdS was deposited on the MZnO film by the successive ionic layer adsorption and reaction method. The long lived excitation energy state of Mn2+ is located inside the conduction band in the wide bandgap ZnO and under the conduction band of CdS, which increases the energetic overlap of donor and acceptor states, reducing the “loss-in-potential,” inhibiting charge recombination, and accelerating electron injection. The engineered band structure is well reflected by the electrochemical band detected using cyclic voltammetry. Cell performances are evidenced by current density-voltage (J-V) traces, diffuse reflectance spectra, transient PL spectroscopy, and incident photon to current conversion efficiency characterizations. Further coating of CdSe on MZnO/MCdS electrode expands the light absorption band of the sensitizer, an efficiency of 4.94% is received for QDSSCs.

Enhanced photovoltaic performance of dye-sensitized solar cells using a new photoelectrode material: upconversion YbF3-Ho/TiO2 nanoheterostructures

New up-conversion YbF3-Ho/TiO2 (UC/TiO2) nanoheterostructures are designed and explored as an efficient photoelectrode material to yield dye-sensitized solar cells (DSSCs) with enhanced performance. In this study, we analyze the photogenerated charge transfer properties of the UC/TiO2 nanoheterostructures via surface photovoltage (SPV) and transient photovoltage (TPV) techniques, and the interfacial dynamics of charge transfer and recombination processes in DSSCs using electrochemical impedance spectroscopy (EIS) and open circuit photovoltage decay (OCVD) techniques. It is found that these UC/TiO2 nanoheterostructures combine the upconversion function of YbF3-Ho and the semiconductive merits from TiO2. More importantly, the hetero-junction interface in the UC/TiO2 nanoheterostructures not only induces direct electron-injection from YbF3-Ho to TiO2 by utilizing near-infrared light, but also further improves the existing merits of TiO2 through facilitating the interfacial photoinduced charge separation, suppressing the photoinduced charge recombination and prolonging the lifetimes of excited electrons, which can give further improvement of the photovoltaic performances. When integrating the UC/TiO2 nanoheterostructures into DSSCs, an overall energy conversion efficiency of 8.0% is achieved. There is a 23% enhancement in the overall conversion efficiency and a 19% improvement in the photocurrent, compared to the pristine devices.

Highly efficient Ag6Si2O7/WO3 photocatalyst based on heterojunction with enhanced visible light photocatalytic activities

Ag₆Si₂O₇/WO₃ (1 : 1) heterojunction photocatalyst shows highly efficient and significant potential for photocatalytic degradation of organic contaminants under visible light irradiation.

Effect of synergic cooperation on optical and photoelectrochemical properties of CeO2–MnO composite thin films

Low-temperature (475 °C) fabrication of CeO₂–MnO composite thin films having a band gap of 2.5 eV by AACVD.

A room temperature approach for the fabrication of aligned TiO2 nanotube arrays on transparent conductive substrates

A novel room-temperature solution-approach is reported for the fabrication of highly crystallized TiO₂ nanotube arrays on transparent conductive substrates.

mpg-C3N4/anatase TiO2 with reactive {001} facets composites to enhance the photocatalytic activity of organic dye degradation

mpg-C₃N₄/anatase TiO₂ with reactive {001} facets composite shows high UV and visible photocatalytic activity for organic dye degradation.

Dilute manganese-doped ZnO nanowires for high photoelectrical performance

This study developed dilute manganese-doped ZnO (D-(Zn,Mn)O) nanowires using a low temperature hydrothermal method.

Glucose-assisted transformation of Ni-doped-ZnO@carbon to a Ni-doped-ZnO@void@SiO2 core–shell nanocomposite photocatalyst

Nanovoid core–shell structured Ni/ZnO@void@SiO₂ was obtained using the carbon layer of Ni/ZnO@C as a sacrificial template.

Efficient synthesis of bis-isoxazole ethers via 1,3-dipolar cycloaddition catalysed by Zn/Zn2+ and their antifungal activities

An efficient method was developed for synthesising isoxazoles. A series of novel bis-isoxazole ether compounds VI, VII and VIII were synthesised starting from different substituted aldehydes (I) via a 1,3-dispolar cycloaddition using Zn/Zn

Enhanced visible light photocatalytic activity in BiOCl/SnO2: heterojunction of two wide band-gap semiconductors

A series of BiOCl/SnO₂ heterojunctions exhibiting exceptional visible light photocatalytic performance has been successfully prepared using a two-step solution route.

Enhanced visible-light photocatalytic activity of active Al₂O₃/g-C₃N₄ heterojunctions synthesized via surface hydroxyl modification

Novel Al2O3/g-C3N4 heterojunction photocatalysts were fabricated through ultrasonic dispersion method. Al2O3, obtained via solution combustion, contained amorphous ingredient with lots of defect sites and was used as active component for transferring photo-induced electrons of g-C3N4. G-C3N4 was grafted surface hydroxyl groups in the presence of ammonia aqueous solution to combine with Al2O3 possessing positive charges via hydrogen bond. The XRD, SEM, element map, TEM, HRTEM, FT-IR, and XPS results indicate that these synthesized materials are two-phase hybrids of Al2O3 and g-C3N4 with interaction. The photocatalytic results for the degradation of rhodamine B (RhB) indicate that the most active heterojunction proportion is 60wt.% g-C3N4:40wt.% Al2O3, the visible light photocatalytic activity of which is 3.8 times that of a mechanical mixture. The enhanced performance is attributed to the high separation efficiency of photo-induced electrons from the LUMO of g-C3N4 injected into the defect sites of Al2O3, which is verified by photoluminescence spectroscopy (PL) and surface photovoltage (SPV) measurements. The electron paramagnetic resonance (EPR) signals and radical scavengers trapping experiments reveal holes (h(+)) and superoxide anion radical (O2(-)) are the main active species responsible for the degradation of RhB.

High quality Mn-doped (Na,K)NbO3 nanofibers for flexible piezoelectric nanogenerators

Enhanced piezoelectric and energy-harvesting characteristics of Mn-doped (Na0.5K0.5)NbO3 (NKN) nanofibers have been investigated with actual fabrication of potential flexible nanogenerators. The electrospinning process of nanofibers has been initially optimized with the proper level of chelating agent and annealing temperature. High quality nanofibers are successfully obtained only by means of a certain level of doped-Mn, which incorporates into the NKN perovskite structure and facilitates significant grain growth. A single-particle-stacked structure along the direction of fiber length becomes more evident with increasing Mn content. An XPS analysis confirms that Mn exists in multivalent states of Mn(2+)/Mn(3+). The effective piezoelectric coefficient of the nanofibers is found to be enhanced by 5 times with Mn-doping up to 3 mol % as characterized by piezoelectric force microscopy. The resultant flexible nanogenerators on PES films have exhibited ∼0.3 V output voltage and ∼50 nA output current under a bending strain.