Effect of Fe and Zn co-doping on LiCoPO4 cathode materials for High-Voltage Lithium-Ion batteries

Lithium cobalt phosphate (LiCoPO4) has great potential to be developed as a cathode material for lithium-ion batteries (LIBs) due to its structural stability and higher voltage platform with a high theoretical energy density. However, the relatively low diffusion of lithium ions still needs to be improved. In this work, Fe and Zn co-doped LiCoPO4: LiCo0.9-xFe0.1ZnxPO4/C is utilized to enhance the battery performance of LiCoPO4. The electrochemical properties of LiCo0.85Fe0.1Zn0.05PO4/C demonstrated an initial capacity of 118 mAh/g, with 93.4 % capacity retention at 1C after 100 cycles, and a good capacity of 87 mAh/g remained under a high current density of 10C. In addition, the diffusion rate of Li ions was investigated, proving the improvement of the materials with doping. The impedance results also showed a smaller resistance of the doped materials. Furthermore, operando X-ray diffraction displayed a good reversibility of the structural transformation, corresponding to cycling stability. This work provided studies of both the electrochemical properties and structural transformation of Fe and Zn co-doped LiCoPO4, which showed that 10 % Fe and 5 % Zn co-doping enhanced the electrochemical performance of LiCoPO4 as a cathode material in LIBs.

Tailoring competitive adsorption sites of hydroxide ion to enhance urea oxidation-assisted hydrogen production

Alloys with bimetallic electron modulation effect are promising catalysts for the electrooxidation of urea. However, the side reaction oxygen evolution reaction (OER) originating from the competitive adsorption of OH- and urea severely limited the urea oxidation reaction (UOR) activity on the alloy catalysts. This work successfully constructs the defect-rich NiCo alloy with lattice strain (PMo-NiCo/NF) by rapid pyrolysis and co-doping. By taking advantage of the compressive strain, the d-band center of NiCo is shifted downward, inhibiting OH- from adsorbing on the NiCo site and avoiding the detrimental OER. Meanwhile, the oxygenophilic P/Mo tailored specific adsorption sites to adsorb OH- preferentially, which further released the NiCo sites to ensure the enriched adsorption of urea, thus improving the UOR efficiency. As a result, PMo-NiCo/NF only requires 1.27 V and -57 mV to drive a current density of ±10 mA cm-2 for UOR and hydrogen evolution reaction (HER), respectively. With the guidance of this work, reactant competing adsorption sites could be tailored for effective electrocatalytic performance.

A band gap and photoluminescence properties engineering in BaO semiconductor for ultraviolet (UV) photodetector applications: A comprehensive role of co-doping

We report on ultra-violet (UV) photodetectors based on BaO nanoparticles by the detailed investigation of band gap and photoluminescence properties. The BaO nanomaterials were fabricated by the modified sol-gel technique. The innovation of co-doping can modulate the photoluminescence or sensing properties by narrowing the band gap related to enhancing the high carrier concentration, higher electronic lifetime, and low carriers recombination. It is investigated that the BaO nanoparticles with co-doping reveals a highly reduced band gap and exceptional photoluminescence properties as compared to the pristine BaO nanoparticles due to hindering carrier,s recombination for Ultra-violet (UV) photodetectors. The optical studies revealed that the addition of co-dopants in BaO host material creates new energy sites, so the band gap declines up to 1.31 eV as compared to that of pristine BaO (1.36 eV). The photoluminescence properties recorded with photoluminescence (PL) spectroscopy were recorded which revealed the decrease in PL intensity due to the hindering of carriers recombination with the addition of co-dopant metal ions. Furthermore, the inclusion of co-dopant metals results in an improvement in electrical conductivity because of a decline in carrier recombination, according to an I-V characteristic study. This factor contributes to enhance the photoluminescence properties of BaO which, in turn, contributes to enhance the sensing capability of the photodetector device. These obtained features modify optoelectronic properties are far superior as compared to that of previously reported literature on BaO nanomaterials, and the synthesized BaO semiconductor material becomes a potential candidate for efficient use in the ultraviolet (UV) photodetectors device applications.

Effect of Tb3+ and Ce3+ Co-doping on the Structure and Photoluminescence Properties of Hexagonal Boron Nitride Phosphors

In the paper, we have successfully prepared hexagonal boron nitride (h-BN:Tb3+, Ce3+) phosphors with melamine as the nitrogen source. The X-ray powder diffraction patterns confirm that the sample possesses a hexagonal crystal structure within the P 6 ¯ m2 space group. It is interesting that the co-doping combination of Tb3+ and Ce3+ can markedly enhance the threshold concentration of doped activators within the limited solid solution of h-BN phosphors. Under 302 nm excitation, the h-BN:Ce3+ phosphors exhibit broadband blue light emission at 406 nm. In h-BN:Tb3+, Ce3+ phosphors, the co-doping of Ce3+ not only ensures high phase purity but also results in strong green light emission. The energy transfer efficiency from Ce3+ to Tb3+ is about 55%. The fluorescence lifetime increases with the increase of Ce3+ and Tb3+ concentration, and the fluorescence lifetime of h-BN:0.025Tb3+, 0.05Ce3+ phosphor reached 2.087 ms. Additionally, the h-BN:0.025Tb3+, 0.05Ce3+ phosphor exhibits excellent thermal performance with an activation energy value of 0.2825 eV. Moreover, the photoluminescence quantum yield of the sample exceeds 52%. Therefore, the h-BN:Tb3+, Ce3+ samples can be used as green phosphors for solid state lighting and fluorescent labeling.

Polar electric field-modulated peroxymonosulfate selective activation for removal of organic contaminants via non-radical electron transfer process

Nonradical electron transfer process (ETP) in peroxomonosulfate (PMS) based advanced oxidation processes (AOPs) is regarded promising for selective degradation of organic contaminants in water, however, the subjective modulation strategy and the definitive mechanistic elucidation of ETP are still lacking. Herein, we proposed a heretofore unreported yet efficient ETP indution approach by construction of polar electrical field on biochar via nonmetallic elements co-doping. Physicochemical characterizations and density functional theory (DFT) calculations verified the electronegativity difference among boron, nitrogen, and sulfur elements bestowed robust local electric fields on biochar surface (BC-BNS), which effectively enhanced the adsorption complexation and charge transfer between biochar and PMS. Compared to the other single-doped or co-doped biochar, BC-BNS exhibited superior catalytic performance of PMS activation for degradation of atrazine (ATZ) (kobs=0.036 min-1), as well as various kinds of electron-rich organics. The remarkable catalytic degradation capacity was further verified in various aqueous matrices and background factors, representing the excellent selectivity. Analysis of contribution from reactive oxygen species and electrochemical testing together substantiated the role of polar electric fields in facilitating the modulation from singlet oxygen (1O2) to ETP as a prevailing mechanism. DFT calculations and apparent interactions revealed the dissociation of S-O bond was thermodynamically favored within this potent localized electric field, which further induced the cleavage of OO bond and ultimately promoted the dual electron transfer between ATZ and PMS. The superiority of BC-BNS/PMS system was further validated with the low ecotoxicity caused by enhanced dechlorination, the low energy consumption, and the long-term effectiveness. The novel modulation principle and atomic-level mechanism exploration gave suggestions for advancing ETP-dominated AOP to remove recalcitrant contaminants during water treatment and restoration.

Mg/Li@GCN as highly active visible light responding 2D photocatalyst for wastewater remediation application

In this study, a highly visible light responding 2D photocatalytic material has been prepared and analysed for its potential for photodegradation of organic pollutants. The pristine GCN has been co-doped with Mg/Li using the facile synthesis route. The prepared photocatalytic materials were then analysed using characterisation techniques like X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, diffuse reflectance spectra (DRS) and photoluminescence spectroscopy (PL) analysis. The prepared samples were analysed for photocatalytic degradation analysis towards methylene blue dye. The apparent rate constant value increased up to 5.4 times in the case of the GCNML (0.5,2) sample in comparison to GCNP. In addition, the GCNML (0.5,2) sample was also analysed for degradation of crystal violet (CV) (97% in 80 min), rose bengal (RB) (84% in 120 min) and methyl orange (MO) (45% in 120 min) dyes. The result obtained from the study confirmed that GCNML (0.5,2) can act as a potential photocatalyst for wastewater remediation application.

Synthesis of efficient light harvesting Cr, N Co-doped TiO2 nanoparticles for enhanced visible light photocatalytic degradation of xanthene dyes; eosin yellow and rose bengal

To solve the problem of water pollution, using environment friendly and cost effective method in short time is the need of hour. In this work, chromium (Cr) and nitrogen (N) co-doped TiO2 nanoparticles were synthesized and were used for the photocatalytic degradation of dyes under visible light. The synergistic effect of metal and non-metal co-dopants added would result in appropriate reduction of band gap {from 3.2 eV of TiO2 to 2.67 eV}, decrease in recombination rate of charge carriers by trapping electrons and holes, and in better light harvesting capacity. Nanoparticles were synthesized by sol-gel method and characterized using ultraviolet-visible (UV-VIS) spectroscopy, fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), zeta potential, X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) analysis, field emission scanning electron microscopy (FE-SEM), and RAMAN spectroscopy. Eosin yellow (EY) and rose bengal (RB) were subjected to photocatalytic degradation under solar light to check the photocatalytic activity of the synthesized nanoparticles. Effects of dye concentration, the concentration of nanoparticles, time, and pH were investigated to optimize the parameters. The results obtained were remarkable for 20 ppm EY solution took 10 min using 1 gL-1 NPs at pH 3 and 10 ppm RB solution took 5 min using 0.75 gL-1 NPs at pH 5.78 (original pH) for complete degradation. Kinetics studies were also performed and both dyes followed pseudo-second-order kinetics with R2 values 0.99312 and 0.99712 for EY and RB, respectively. The study of degraded products was conducted using high-performance liquid chromatography (HPLC) hyphenated with electron spray ionization mass spectroscopy (ESI-MS) (LC-MS) and possible degradation pathways were made for both dyes. A reusability test was also performed showing the efficiency of the particles was up to 88% after 3 cycles of use. These notable results can be attributed to the efficient removal of organic pollutants using the proposed dopants in this study.

Photocatalytic degradation of metronidazole and oxytetracycline by novel l-Arginine (C, N codoped)-TiO2/g-C3N4: RSM optimization, photodegradation mechanism, biodegradability evaluation

Removal of Metronidazole (MNZ) and Oxytetracycline (OTC) from wastewater by the prepared (C, N codoped)-TiO₂/g-C₃N₄ (Graphitic carbon nitride) was examined. l-Arginine (C, N codoped)-TiO₂ and l-Arginine (C, N codoped)-TiO₂/g-C₃N₄ photocatalysts were successfully synthesized through the sol-gel method, and optimal ratio of l-arginine:TiO₂, as well as l-arginine/TiO₂:g-C₃N₄, was determined by a kinetic study of photodegradation process. The maximum photocatalytic removal rate (0.065 min^-1 for MNZ removal) was observed using 1% l-Arginine-TiO₂/g-C₃N₄ (1:1) under visible light illumination, 2.2 and 6.5 times greater than those of 1% l-Arginine-TiO₂ and pure TiO₂, respectively. l-Arginine (1%)-TiO₂/g-C₃N₄ (1:1) (co-doped-TCN) was investigated using X-ray diffraction analysis (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray (EDX), Photo-luminescence (PL), and Differential Reflectance Spectroscopy (DRS) as the best-performing photocatalyst. Response surface methodology (RSM) was used to study the effect of co-doped-TCN dosage (0.5-1.0 g/L), pH of simulated wastewater (4-10), initial concentration of MNZ and OTC (50-100 mg/L), and irradiation time (30-90 min for MNZ and 20-40 min for OTC) on removal efficiency of the antibiotics. Also, their optimum values were determined by RSM. The treated pharmaceutical wastewater showed high biodegradability features with 5-day biological oxygen demand/chemical oxygen demand (BOD₅/COD) of 0.51 and 0.46 after 40 and 100 min reaction for OTC and MNZ, respectively. The order of reactive species responsible for the photodegradation of pollutants was •O₂^─> •OH > h⁺>¹O₂. The effect of inorganic anions showed that all anions decreased the removal efficiency of both antibiotics in order of NO₃^─> Cl^─ >SO₄^2─>HPO₄^2─ >HCO₃^─ for MNZ and NO₃^─> SO₄^2─ > Cl^─ >HPO₄^2─ >HCO₃^─ for OTC. Also, introducing different oxidants improved the photocatalytic removal efficiency with the order of H₂O₂>K₂S₂O₈> KBrO₃.

C, F co-doping Ag/TiO2 with visible light photocatalytic performance toward degrading Rhodamine B

The organic pollutants in industrial wastewater continuously endanger human health. Therefore, effective treatment of organic pollutants is very urgent. Photocatalytic degradation technology is an excellent solution to remove it. TiO₂ photocatalysts are easy to prepare and have high catalytic activity, unfortunately, TiO₂ only absorbs ultraviolet light limiting its utilization of visible light. In this study, a facile environmentally friendly synthesis of Ag-coated on micro-wrinkled TiO₂-based catalysts in order to extend the absorption of Visible light. Firstly, a fluorinated titanium dioxide precursor was prepared by a one-step solvothermal method, and the precursor was calcined at high temperature in a nitrogen atmosphere to form a carbon dopant, and then a surface silver-deposited carbon/fluorine co-doped TiO₂ photocatalyst C/F-Ag-TiO₂ was prepared by a hydrothermal method The results showed that the Ag was coated on the wrinkled TiO₂ layer and C/F-Ag-TiO₂ photocatalyst was synthetized successfully. Benefit from the synergistic effect of doped carbon and fluorine atoms in combination with the quantum size effect of the surface silver nanoparticles, the band gap energy of C/F-Ag-TiO₂ (2.56 eV) is obviously lower than anatase (3.2eV). The photocatalyst achieved an impressive degradation rate of 84.2% for Rhodamine B in 4 h, with a degradation rate constant of 0.367 h^-1, which was 17 times higher than that of P25 under visible light. Therefore, the C/F-Ag-TiO₂ composite is a promising candidate as a highly efficient photocatalyst for environmental remediation.

Bi(Ⅲ) and Ce(Ⅳ) functionalized carbon nitride photocatalyst for antibiotic degradation: Synthesis, toxicity, and mechanism investigations

Graphite-phase carbon nitride (g-C₃N₄) has shown great potential for antibiotic wastewater treatment due to its unique electronic structure and corresponding to visible light. In this study, a series of Bi/Ce/g-C₃N₄ photocatalysts with different doping amount were developed by direct calcination method for Rhodamine B and sulfamethoxazole photocatalytic degradation. The experiment result shows that the photocatalytic performance of Bi/Ce/g-C₃N₄ catalysts were better than that of single component samples. Under the optimal experimental conditions, the degradation rates of RhB (20 min) and SMX (120 min) by 3Bi/Ce/g-C₃N₄ reached 98.3% and 70.5%, respectively. The theoretical calculation results of DFT show that after Bi and Ce doping modification, the band-gap width of g-C₃N₄ is reduced to 1.215 eV and carrier migration rate is greatly improved. The enhanced photocatalytic activity was mainly attributed to the capture of electrons after doping modification, which inhibition of photogenerated carriers recombination and reduced the gap width. The cyclic treatment experiment of sulfamethoxazole showed that Bi/Ce/g-C₃N₄ catalysts had good stability. Ecosar evaluation and leaching toxicity test showed that Bi/Ce/g-C₃N₄ can be safely used for wastewater treatment. This study provides a perfect strategy for modifying g-C₃N₄ and a new way to improve the photocatalytic performance.

Lithium and phosphorus-functionalized graphitic carbon nitride monolayer for efficient hydrogen storage: A DFT study

We have explored the consequence of lithium and phosphorous functionalization on the graphitic carbon nitride (g-C₃N₄) monolayer for hydrogen storage using density functional theory. Both pristine and Li and P decorated g-C₃N₄ show a semiconductor nature. The substantial overlap between the s orbital of Li and the p orbital of nitrogen near the Fermi level shows the binding between Li and the g-C₃N₄. The repositioning of HOMO and LUMO is noticed in the Li and P decorated g-C₃N₄. The Bader charge analysis indicates the charge allocation from the Li and P atom to the g-C₃N₄, which results in the adsorption of H₂ by electrostatic interaction. The hydrogen storage capacity of 5.78 wt% is obtained after functionalizing Li and P into the g-C₃N₄. The obtained adsorption energies for the H₂ adsorption and the H₂ desorption temperature confirm that Li and P functionalized g-C₃N₄ is a fascinating candidate for the reversible loading of H₂ at ambient conditions.

Codoping g-C3N4 with boron and graphene quantum dots: Enhancement of charge transfer for ultrasensitive and selective photoelectrochemical detection of dopamine

The development of superior photoelectrochemical (PEC) sensors for biosensing has become a major objective of PEC research. However, conventional PEC-active materials are typically constrained by a weak photocurrent response owing to their limited surface-active sites and high electron-hole recombination rate. Here, a boron and graphene quantum dots codoped g-C₃N₄ (named GBCN) as PEC sensor for highly sensitive dopamine (DA) detection was fabricated. GBCN exhibited the greatest photocurrent response and PEC activity compared to free g-C₃N₄ and g-C₃N₄ doped with boron. The proposed PEC sensor for DA determination exhibited a broad linear range (0.001-800 μM) and a low detection limit (0.96 nM). In particular, a sensitivity up to 10.3771 μA/μM/cm² was seen in the case of GBCN. The high PEC activity can be attributed to the following factors: (1) the boron and graphene quantum dots co-doping significantly increased the specific surface area of g-C₃N₄, providing more adsorption sites for DA; (2) the dopants extended the absorption intensity of g-C₃N₄, red-shifting the absorption from 470 to 540 nm; and (3) the synergism of boron and graphene quantum dots efficiently boosted the photogenerated electrons migration from the conduction band of g-C₃N₄ to graphene quantum dots, facilitating charge separation. In addition, GBCN also exhibited good anti-interference ability and stability. This research may shed light on the creation of a highly sensitive and selective PEC platform for detecting biomolecules.

Design of Ti-Pt Co-doped α-Fe2O3 photoanodes for enhanced performance of photoelectrochemical water splitting

This study demonstrates Ti and Pt co-doping can synergistically improve the PEC performance of the α-Fe₂O₃ photoanode. By varying the doping methods, the sample with in-situ Ti ex-situ Pt doping (Ti_i-Pt_e) exhibits the best performance. It demonstrates that Ti doping in bulk facilities charge separation and Pt doping on the surface further accelerates charge transfer. In contrast, Ti doping on the surface inhibits charge separation, and Pt doping in bulk hinders charge separation and transfer. HCl treatment is used to minimize the onset potential further, while it is favorable for the ex-situ doped α-Fe₂O₃, which is more efficient on Ti_e than the Pt_e-doped ones. On the ex-situ Ti-doped α-Fe₂O₃ after HCl treatment, anatase TiO₂ is probed, suggesting that Ti-O bonds accumulate when Fe-O bonds are partly removed, which enhances the charge transfer in surface states. Unfortunately, HCl treatment also induces lattice defects that are adverse to charge transport, inhibiting the performance of in-situ doped α-Fe₂O₃ and excessively treated ex-situ doped ones. Coupled with methanol solvothermal treatment and NiOOH/FeOOH cocatalysts loading, the optimized Ti-Pt/Fe₂O₃ photoanode exhibits an impressive photocurrent density of 2.81 mA cm^-2 at 1.23 V vs. RHE and a low onset potential of 0.60 V vs. RHE.

Al and Ta co-doped LLZO as active filler with enhanced Li+conductivity for PVDF-HFP composite solid-state electrolyte

Battery safety calls for solid state batteries and how to prepare solid electrolytes with excellent performance are of significant importance. In this study, hybrid solid electrolytes combined with organic PVDF-HFP and inorganic active fillers are studied. The modified active fillers of Li_7-x-3yAl_yLa₃Zr_2-xTa_xO₁₂are obtained by co-element doping with Al and Ta when LLZO is synthesized by calcination. And an high room temperature ionic conductivity of 5.357 × 10^-4S cm^-1is exhibited by ATLLZO ceramic sheet. The composite solid electrolyte PVDF-HFP/LiTFSI/ATLLZO (PHL-ATLLZO) is prepared by solution casting method, and its electrochemical properties are investigated. The results show that when the contents of lithium salt LiTFSI and active filler ATLLZO are controlled at 40 wt% and 10%, respectively, the ionic conductivity of the resulting composite solid electrolyte is as high as 2.686 × 10^-4S cm^-1at room temperature, and a wide electrochemical window of 4.75 V is exhibited. The LiFePO₄/PHL-ATLLZO/Li all-solid-state battery assembled based on the composite solid-state electrolyte exhibits excellent cycling stability at room temperature. The cell assembled by casting the composite solid-state electrolyte on the cathode surface shows a discharge specific capacity of 134.3 mAh g^-1and 96.2% capacity retention after 100 cycles at 0.2 C. The prepared composite solid-state electrolyte demonstrates excellent electrochemical performance.

Novel La3+/Sm3+ co-doped Bi5O7I with efficient visible-light photocatalytic activity for advanced treatment of wastewater: Internal mechanism, TC degradation pathway, and toxicity analysis

Controlling semiconductor photocatalysts by doping rare-earth ions is an effective strategy to improve photocatalytic performance. Simple solvothermal and calcination methods were used to prepare La³⁺ and Sm³⁺ modified Bi₅O₇I nanomaterials. Some characterizations such as XRD, XPS, SEM, TEM, UV-vis, etc. were carried out to explore its structural composition and photoelectrochemical properties. The photocatalytic activity was investigated by simulating the degradation of TC and RhB under visible-light irradiation. The degradation results showed that the photocatalytic efficiency of 4S4L-Bi₅O₇I was the best among the samples with the 100% degradation rate of TC (Tetracycline hydrochloride) and 93% of RhB (Rhodamine B). The capture experiment and ESR test proved that the active substances that play a role in the photocatalytic degradation of pollutants were ·O₂^-, ¹O₂ and h⁺, and on this basis, the possible degradation mechanism was proposed. The final results showed that La/Sm co-doping expanded the light absorption range of Bi₅O₇I and improved the charge separation efficiency and the specific surface area. Besides, the surface defects were formed on the surface of Bi₅O₇I due to ion-doping, which could catch e^- to promote the separation and transfer of carriers and improve the photocatalytic activity. LC-MS was used to analyze the possible degradation pathways of TC. And the toxicity of TC was also analyzed via T.E.S.T and Toxtree. The results showed comprehensive toxicity of TC was decreased by 4S4L-Bi₅O₇I so that the overall water pollution was reduced. This work can provide a reference for the subsequent development of bismuth-based photocatalysts.

Embedding Co in perovskite MoO3 for superior catalytic oxidation of refractory organic pollutants with peroxymonosulfate

A cobalt (Co)-doped perovskite molybdenum trioxide (α-MoO₃) catalyst (Co-MO) was synthesized by a facile pyrolysis strategy and used for degrading various organic contaminants via peroxymonosulfate (PMS) activation. The doped Co was inserted in the inter space between the octahedron [MoO₆], facilitating the growth of the α-MoO₃ crystal on the [010] direction. This unique structure accelerated the activation of PMS as the Co-MO could function as a carrier for electron transfer to facilitate the Co(II)/Co(III) cycle in the Co-MO/PMS system. As a result, the Co-MO/PMS system showed noticeable activity for removing 100% bisphenol A (BPA) under a broad conditions within 30 min. The radical quenching test and electron paramagnetic resonance analysis revealed that singlet oxygen (¹O₂) was the main active species for BPA degradation in the Co-MO/PMS system, while free radicals, such as O₂^•-, SO₄^•- and •OH, were also produced as the intermediate species. Furthermore, the carrier mechanism may enable the Co-MO/PMS system maintain relatively high performance during repeat use, and also excellent adaptability was revealed by the well function in various water matrices and high activity in degrading various refractory organic pollutants. Our findings pave a useful avenue for the rational design of novel cobalt-doped catalysts with high catalytic performance toward wide environmental applications.

Energy-levels well-matched direct Z-scheme ZnNiNdO/CdS heterojunction for elimination of diverse pollutants from wastewater and microbial disinfection

Energy-levels well-matched direct Z-scheme ZnNiNdO/CdS heterojunction was successfully fabricated using facile co-precipitation and ultra-sonication techniques and characterized with XRD, FTIR, Raman, PL, UV-vis, and FE-SEM. The XRD diffractograms confirmed the co-doping of Ni-Nd in ZnO and the formation of heterostructured nanocomposite. FTIR and Raman data showed the presence of metal-oxygen vibration and optical phonon modes of ZnO and CdS. FE-SEM images exhibited the network type morphology. The energy bandgap was redshifted by co-doping (3.37-2.9 eV) and was further reduced (2.6 eV) by making a composite with CdS. The ZnNiNdO/CdS catalyst degraded 99.7, 49, 96.6, 98.6, and 98.6% methylene blue (MB), p-nitroaniline (P-Nitro), methyl orange (MO), methyl red (MR), and rhodamine B (RhB) dyes under 50 min sunlight irradiation. Moreover, ZnNiNdO/CdS showed intense inhibition activity towards Staphylococcus aureus, Escherichia coli, Proteus vulgaris, and Pseudomonas aeruginosa bacterial strains with maximum inhibition zone diameters 30, 33, 27, and 31 mm, respectively. The synergistic effects arising from band alignment can lead to efficient vectorial charge separation, transportation, and lower recombination of photoinduced charge carriers, ultimately boosting photocatalytic and antibacterial performance. The ZnNiNdO/CdS photocatalyst has higher stability up to the 7th cycle towards MB dye with ~ 5% deficit in degradation efficiency. The higher generation of superoxide and hydroxyl radical was confirmed by species trapping experiments responsible for photodegradation of dyes molecules. Furthermore, the results showed that the photocatalytic and antibacterial performance of pristine ZnO can be enhanced by co-doping and tuning energy bandgap.

Fabrication, application, and mechanism of metal and heteroatom co-doped biochar composites (MHBCs) for the removal of contaminants in water: A review

The potential risk of various contaminants in water has recently attracted public attention. Biochars and modified biochars have been widely developed for environmental remediation. Metal and heteroatom co-doped biochar composites (MHBCs) quickly caught the interest of researchers with more active sites and higher affinity for contaminants compared to single-doped biochar by metal or heteroatoms. This study provides a comprehensive review of MHBCs in wastewater decontamination. Firstly, the main fabrication methods of MHBCs were external doping and internal doping, with external doping being the most common. Secondly, the applications of MHBCs as adsorbents and catalysts in water treatment were introduced emphatically, which mainly included the removal of metals, antibiotics, dyes, pesticides, phenols, and other organic contaminants. Thirdly, the removal mechanisms of contaminants by MHBCs were deeply discussed in adsorption, oxidation and reduction, and degradation. Furthermore, the influencing factors for the removal of contaminants by MHBCs were also summarized, including the physicochemical properties of MHBCs, and environmental variables of pH and co-existing substance. Finally, futural challenges of MHBCs are proposed in the leaching toxicity of metal from MHBCs, the choice of heteroatoms on the fabrication for MHBCs, and the application in the composite system and soil remediation.

Efficient Electrooxidation of 5-Hydroxymethylfurfural Using Co-Doped Ni3 S2 Catalyst: Promising for H2 Production under Industrial-Level Current Density

Replacing oxygen evolution reaction (OER) by electrooxidations of organic compounds has been considered as a promising approach to enhance the energy conversion efficiency of the electrolytic water splitting proces. Developing efficient electrocatalysts with low potentials and high current densities is crucial for the large-scale productions of H₂ and other value-added chemicals. Herein, non-noble metal electrocatalysts Co-doped Ni₃ S₂ self-supported on a Ni foam (NF) substrate are prepared and used as catalysts for 5-hydroxymethylfurfural (HMF) oxidation reaction (HMFOR) under alkaline aqueous conditions. For HMFOR, the Co_0.4 NiS@NF electode achieves an extremely low onset potential of 0.9 V versus reversible hydrogen electrode (RHE) and records a large current density of 497 mA cm^-2 at 1.45 V versus RHE for HMFOR. During the HMFOR-assisted H₂ production, the yield rates of 2,5-furandicarboxylic acid (FDCA) and H₂ in a 10 mL electrolyte containing 10 × 10^-3 M HMF are 330.4 µmol cm^-2 h^-1 and 1000 µmol cm^-2 h^-1 , respectively. The Co_0.4 NiS@NF electrocatalyst displays a good cycling durability toward HMFOR and can be used for the electrooxidation of other biomass-derived chemicals. The findings present a facile route based on heteroatom doping to fabricate high-performance catalyses that can facilitate the industrial-level H₂ production by coupling the conventional HER cathodic processes with HMFOR.

Environmental photochemistry with Sn/F simultaneously doped TiO2 nanoparticles: UV and visible light induced degradation of thiazine dye

Environmental route such as degradation of toxic dyes can be improved through photochemical activity such as light driven photocatalytic degradation. Herein, fluorine and tin simultaneously doped TiO₂ nanoparticles were synthesized and characterized. The formation of anatase phase in synthesized samples and the reduction in the crystallite size of doped TiO₂ was confirmed from XRD results. The existence of O-Ti-O stretching vibration in pure and co-doped TiO₂ confirmed from FTIR results. Optical studies reveal that the band gap of co-doped TiO₂ is increased and hence it was concluded that the particle size of co-doped TiO₂ is reduced compared with as-synthesized TiO₂. The morphologies of TiO₂ changed significantly with doping of fluorine and tin. It reveals majority of the particles are hexagons, pentagons and ellipse shaped and some of them are spheres with a mean particle size of 31.17 nm. PL studies showed the reduction in intensity for Sn-F/TiO₂ accredited to the lesser recombination rate of electron-hole pair under UV light irradiation. Thus tin and fluorine doped TiO₂ could be considered as a good candidate for photocatalytic activity. The photocatalytic activity of TiO₂ and Sn-F/TiO₂ nanoparticles was analyzed separately through the degradation of methylene blue (MB) under visible and UV light irradiation. The use of Sn and F ions in the synthesis of TiO₂ are revealed not only create small sized nanoparticles but these water soluble nanoparticles have very good antibacterial and antifungal action by inhibiting the growth of bacteria and fungus.

Exploring the Influence of Synthesis Parameters on the Optical Properties for Various CeO2 NPs

Cerium oxide (CeO₂) nanoparticles were synthesized with a chemical precipitation method in different experimental conditions using cerium nitrate hexahydrate (Ce(NO₃)₃·6H₂O) as a precursor, modifying the solution pH, the reaction time, and Co atoms as dopants, in order to tune the band gap energy values of the prepared samples. The physical characteristics of the synthesized ceria nanoparticles were evaluated by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis analyses and photoluminescence measurements. XRD data revealed a pure cubic fluorite structure of CeO₂ NPs, the estimation of crystallite sizes by Scherrer’s formula indicates the formation of crystals with dimensions between 11.24 and 21.65 nm. All samples contain nearly spherical CeO₂ nanoparticles, as well as cubic, rhomboidal, triangular, or polyhedral nanoparticles that can be identified by TEM images. The optical investigation of CeO₂ samples revealed that the band gap energy values are between 3.18 eV and 2.85 eV, and, after doping with Co atoms, the E_g of samples decreased to about 2.0 eV. In this study, we managed to obtain CeO₂ NPs with E_g under 3.0 eV by only modifying the synthesis parameters. In addition, by doping with Co ions, the band gap energy value was lowered to 2.0 eV. This aspect leads to promising results that provide an encouraging approach for future photocatalytic investigations.

Photocatalytic degradation of organic synthetic dyes and textile dyeing waste water by Al and F co-doped TiO2 nanoparticles

Textile wastewater threatens people health by alluring diseases and revealing public existing close to the waste to the dangerous products within. Because waste causes a risk to the environment and people, waste management making is the main challenge of the municipal world. Environmental process such as toxic dye degradation can be stepped up through photochemical process such as visible light induced catalytic degradation. Here, the successful synthesis of co-doping of Al and F into TiO₂ nanoparticles (Al-F∕TiO₂ NPs) by solid state reaction method comprising different proportions of co-dopants is evaluated for the applications of degrading organic synthetic dyes and textile dyeing waste water. Influence of co-dopants was studied in their optical, structural, compositional, morphological and vibrational properties. The average crystallite size of Al-F∕TiO₂ NPs was found as 15 nm.FTIR and UV-vis spectrum confirmed F and Al atoms were incorporated into the TiO₂ lattice.The absorption edges slightly moved to shorter wavelength by increasing level of dopants and this specifies the control of optical absorption of TiO₂ by the incorporation of F and Al³⁺ ions.The EDS spectrum indicates the purity of the samples. The highest zone of inhibition for the prepared nanoparticles over Staphylococcus aureus reached to 22 mm. The rate constant (k_app) value of MB, MO and textile waste water is 0.0138/min, 0.0174/min and 0.0139/min for the prepared nanoparticles respectively. The study of photocatalytic degradation of visible light assisted MB, MO and real textile waste water by Al-F∕TiO₂ NPs revealed that the prepared nanoparticles act as ideal catalyst by tuning the concentration of co-dopants in TiO₂.

Design of nitrogen-phosphorus-doped biochar and its lead adsorption performance

The surface properties of the adsorbents and the acidic environment have an influence effect on Pb adsorption. In order to further improve the adsorption performance of biochar, we herein reported an effective method to synthesize high-adsorbed biochar by co-doping with nitrogen and phosphorus. After atom doping, the N/P co-doped biochar (NP-BC) showed the enhanced adsorption capacity for lead ion (Pb²⁺). The adsorption kinetics, isotherm, pH value, and influencing factors were studied. The results show that the synthesized NP-BC has high Pb²⁺ adsorption capacity in aqueous solution, and can be maintained with various environmental interference factors including pH, natural organic matter, and other metal ions. High adsorption performance shows that the material may be well used to remove Pb²⁺ in various water bodies. Various characterization experiments prove that surface properties contribute to Pb²⁺ adsorption, and the high performance of NP-BC is mainly due to the surface complexation between functional groups and Pb²⁺. This work demonstrates that the surface functional groups of biochar are critical to the development of high-performance heavy metal adsorbents.

Effects of nitrogen/bismuth-doping on the photocatalyst composite of carbon dots/titanium dioxide nanoparticles (CDs/TNP) for enhanced visible light-driven removal of diclofenac

The present work demonstrates the coupling of titanium dioxide, TiO₂ nanoparticles (TNP) with N-doped, Bi-doped, and N-Bi co-doped rice husk-derived carbon dots (CDs) via a facile dispersion method, forming respective photocatalyst composites of CDs/TNP, N-CDs/TNP, Bi-CDs/TNP and N-Bi-CDs/TNP. Characterization analyzes verified the successful incorporation of respective CDs samples into TNP, forming photocatalyst composite with narrowed band gap and quenched photoluminescence intensity. Photocatalytic activity of TNP and the respective composites was investigated for photodegradation of diclofenac (DCF) under both simulated sunlight and natural sunlight irradiation. The as-prepared N-Bi-CDs/TNP composite showed the best photocatalytic performance among all composites, able to completely degrade 5 ppm of DCF within 60 min and 180 min under both types of visible light irradiation, respectively. The N-Bi-CDs/TNP composite also showed a TOC removal efficiency up to 87.63%. N-Bi-CDs, worked as photosensitizer and electron reservoir, contributed to the outstanding photocatalytic activity of N-Bi-CDs/TNP, whereby the recombination was prolonged and light absorption was shifted towards the visible light region. Furthermore, the composite of N-Bi-CDs/TNP also demonstrated good stability and reusability over repeated degradation cycles. The photodegradation of DCF resulted into several intermediates, which were identified from LC-MS analysis. The present work could provide an insight on the application of heteroatoms doped and co-doped carbon dots in semiconductor oxide as high performance photocatalysts.

Paracetamol degradation via electrocatalysis with B and N co-doped reduced graphene oxide: Insight into the mechanism on catalyst surface and in solution

This paper presents the use of B and N co-doped reduced graphene oxide (BN-GN) as an electrode for paracetamol electrochemical degradation. The reaction mechanism, focused on active sites in the atom level and dominant radical species generated through the reaction, was analyzed by characterization, density functional theory (DFT) calculation, quenching experiments, and electron paramagnetic resonance analysis. The characterization results indicated that the introduction of N and B functionalities into GN improved catalytic activity due to the generation of new surface defects, active sites, and improvement of conductivity. Results of experiments and DFT showed that co-doping of B and N greatly improved the catalytic activity, and the B atoms in C-N-B groups were identified as main active sites. The main active substances of BN-GN generated in the electrocatalytic oxidation of paracetamol in the solution were O₂^•- and active chlorine. The influence of O₂^•- and active chlorine on the efficiency/path of catalytic oxidation and the proposed mechanism were also determined for paracetamol degradation. This study provides an in-depth understanding of the mechanism of BN-GN catalysis and suggests possibilities for practical applications.

Biomass-derived N,S co-doped 3D multichannel carbon supported Au@Pd@Pt catalysts for oxygen reduction

A beancurd-derived mesoporous carbon (NSC) was prepared by an environmentally friendly procedure, and then it was investigated as Au@Pd@Pt core-shell catalysts support (Au@Pd@Pt-NSC) for oxygen reduction reaction (ORR). The Au@Pd@Pt-NSC (E_1/2 = 0.91 V) has a marginally negative ORR half-wave potential compared with other materials, in particular Pt/C (E_1/2 = 0.87 V) and Au@Pd@Pt-C (E_1/2 = 0.81 V). The specific and mass activities of the Au@Pd@Pt-NSC were 5 and 13 times higher than the commercial a Pt/C catalyst. After 20000 cycles of rapid durability test, the Au@Pd@Pt-NSC sample showed a loss of just 4.9% compared with the initial ECSA area, which can be attributed to the favorable interaction between Au@Pd@Pt and NSC. These results can be considered of environmental relevance and high potential applicability.

Structural, FTIR spectra and optical properties of pure and co-doped Zn1-x-y Fe x M y O ceramics with (M = Cu, Ni) for plastic deformation and optoelectronic applications

We report here a considered novel study on the structural, FTIR spectra and optical properties of pure and co-doped Zn0.90-x Fe0.1M x O with ((M = Cu, Ni and (x = 0.00, 0.10) and (0.00 < y < 0.20)) at different sintering temperatures T s (T s  = 850 °C for series I and 1000 °C series II). Although the ZnO wurtzite structure is conformed for all samples, some secondary lines with little intensity are formed. But the number of these lines is higher for series I than for series II. The (c/a) value and U-parameter are almost constant for all samples, while Zn-O bond length L is slightly increased. The porosity and crystallite size are decreased by Fe, and also for (Fe + Cu) samples, and their values for series I are lower than for series II. The residual stress is tensile for most samples. Interestingly, the Young's, rigid and bulk modulus, Poisson's ratio and Debye temperature, obtained from FTIR analysis, are increased by Fe addition with a further increase for Fe + Ni) samples for both series. A ductile nature is obtained for pure, Fe and (Fe + Cu) samples; whereas a brittle nature is approved for (Fe + Ni) samples. On the other hand, the energy gap (E g ), residual lattice dielectric constant (ε L ) and carrier density N are increased by Fe addition, followed by a further increase for (Fe + Cu) samples, while the vice is versa for the inter-atomic distance R. For example, E g was increased from 3.153 eV for pure ZnO to 3.974 eV for (Fe + Cu) samples (i.e., 0.821 eV more), while it was decreased to 2.851 eV for (Fe + Ni) samples (i.e., 0.302 eV less). A direct behavior is obtained between E g and both elastic modulus (Y, β), lattice and micro strains (ε L , ε m ), dislocation density (δ), residual stress (σ) and carrier density N, whereas a reverse behavior is obtained between E g and both crystallite size (D), porosity (PS) and inter-atomic distance (R) . These results are explained in terms of the generated blocked states of the conduction band as indicated by the Burstein Moss effect. These novel findings reveal that the co-doping has intense ZnO and moderate metal oxide modes in the ZnO matrix structure, which makes ZnO co-doped with (Fe + Cu) more suitable for gas sensors and optoelectronic devices. In contrast, ZnO co-doped with (Fe + Ni) samples is strongly recommended for altering plastic deformation. To our knowledge, the present investigation can be considered the first study and probably has never been discussed elsewhere, which highlights the present investigation.

Insights into the co-doping effect of Fe3+ and Zr4+ on the anti-K performance of CeTiOx catalyst for NH3-SCR reaction

A novel K-resistant Fe³⁺ and Zr⁴⁺ co-doped CeTiO_x catalyst was first prepared by co-precipitation method for the ammonia-selective catalytic reduction (NH₃-SCR) of NO_x. On the premise of retaining the outstanding catalytic activity of CeTiO_x catalyst, Fe³⁺ and Zr⁴⁺ co-doping efficiently improves its K-resistance with superior NO_x conversion up to 84% after K-poisoning. Specially, the grain growth during the second calcination after K poisoning is successfully inhibited by Fe³⁺ and Zr⁴⁺ co-doping. Consequently, the large specific surface area with increased acid sites and efficiently retained reducibility over K-poisoned FeZrCeTiO_x catalyst are realized, which prompt NH₃ activation and NO oxidation, further benefit NH₃-SCR. Besides, NH₃-SCR reaction over CeTiO_x and FeZrCeTiO_x catalysts follows a possible L-H mechanism, and K-poisoning makes no change to it. Finally, a reasonable anti-K poisoning mechanism of FeZrCeTiO_x catalyst is proposed: the excellent K-resistance is attributed to part of Fe and Zr are sacrificed to form Fe-O-K and Zr-O-K species protecting the active site Ce-O-Ti from K-poisoning, as well as the additional reducibility and surface acidity brought from Fe-O species with Zr prompting its uniform distribution.

Visible light assisted photocatalytic degradation of commercial dyes and waste water by Sn-F co-doped titanium dioxide nanoparticles with potential antimicrobial application

The disintegration of natural water sources signals out the scarcity of adam's ale and will be hurdle for the human physical state. So it is necessary to decrease waste loads and hence pressure on the ecology for the sustainability of fishery and dye industry. Herein, TiO₂ nanoparticles doped with Sn and F are synthesized and the influence of simultaneous doping on the optical, surface morphological, structural, photocatalytic and antibacterial activities are investigated. Doping of TiO₂ with Sn and F suppress the growth of both anatase and rutile phase because of the dissimilar boundaries. All the prepared doped and undoped samples are found to possess tetragonal structure. The influence of F and Sn in TiO₂ lattice is recognized with the XRD and FT-IR spectra of the prepared particles The size of the obtained nanoparticles decreases as increasing concentration of F and Sn. TiO₂ is showing the presence of spherical and ellipsoidal nanoparticles whereas doped samples showing nanobulk, pentagons and rods. The absorption edge of the doped samples are blue shifted with increasing concentration of dopants indicates the control of optical absorption property of TiO_2. The visible light assisted photocatalytic degradation of fish processing waste water by doped and undoped samples are found to be established as 0.0076/min and 0.0071/min respectively. Visible light assisted degradation of commercially available dyes and fish processing waste water is assessed. Methyl blue showed enhanced photocatalytic activity under visible light irradiation compared to Methyl orange. It is observed that all the prepared particles show good antimicrobial activity against Staphylococcus aureus.

Structural morphology and nonlinear behavior of pure and co-doped Zn1-x-yFexMyO varistors with (M = Cu, Ni)

We report here structural morphology and nonlinear behavior of pure and co-doped Zn_0.90-xFe_0.1M_xO with (M = Cu, Ni and (x = 0.00, 0.10) and (0.00 ≤ y ≤ 0.20)) at different sintering temperatures (T _s = 850 and 1000 °C). It is found that the co-doping of ZnO by (Fe + Cu) or (Fe + Ni) up to 0.30 does not deform the well-known wurtzite structure of ZnO, as well as pure and 0.1 of Fe-doped ZnO. The SEM micrographs did not show any secondary phases at the boundaries of grains as compared to ZnO, the average grain size is decreased for Fe and (Fe + Cu) samples, while it is increased for (Fe + Ni) samples. The nonlinear coefficient α and breakdown field E _B are generally increased by 0.1 of Fe addition, but they are shifted to lower values as T _s increases for all samples. Furthermore, they are gradually increased/decreased to higher/lower values for (Fe + Cu/Fe + Ni) samples up to 0.30 of co-doping content. The values of α and E _B are increased from 30.06, 2115.38 V/cm for ZnO at 850 °C to 50.07, 5012 V/cm by (0.1Fe + 0.2Cu) co-doping, and from 23.53, 1956.52 V/cm to 45.58, 4750 V/cm at 1000 °C, while they are, respectively, decreased by (0.1Fe + 0.2Ni) to 13.19, 312 V/cm and 11.85, 172.42 V/cm. Similar behavior was generally obtained for nonlinear conductivity σ _L and height of potential barrier φ_B, whereas the vice is versa for the behavior of leakage current J _k and residual voltage K _r. Our results are discussed in terms of the comparative participation between the effects of co-doping of (Fe + Cu) and (Fe + Ni) to ZnO for supporting the potential barrier as compared to individual doping by Fe, Cu and Ni. This study perhaps recommended these samples for optoelectronic and ferromagnetic investigation after COVID-19 is over.

Enhanced electrochemical properties of Ni-rich layered cathode materials via Mg2+ and Ti4+co-doping for lithium-ion batteries

To optimize the electrochemical performance of Ni-rich cathode materials, the 0.005 mol of Mg²⁺ and 0.005 mol of Ti⁴⁺co-doping LiNi_0.83Co_0.11Mn_0.06O₂ composite powders, labeled as NCM-11, are successfully prepared by being calcinated at 750 °C for 15 h following by an appropriate post-treatment, which are confirmed by XRD, EDS and XPS. The results suggest that NCM-11 presents a well-ordered layered structure with a low Li⁺/Ni²⁺ mixing degree of 1.46% and Mg²⁺ and Ti⁴⁺ ions are uniformly distributed across the lattice. The cell assembled with NCM-11 can deliver an initial discharge specific capacity of 194.2 mAh g^-1 and retain a discharge specific capacity of 163.0 mAh g^-1 after 100cycles at 2.0C at 25 °C. Furthermore, it still maintains a discharge specific capacity of 166.7 mAh g^-1 after 100cycles at 2.0C at 60 °C. More importantly, it also exhibits a higher discharge specific capacity of about 150.7 mAh g^-1 even at 5.0C. Those superior electrochemical performance can be mainly ascribed to the synergistic effect of Mg²⁺ and Ti⁴⁺co-doping, in which Mg²⁺ ions can occupy the Li⁺ layer to act as pillar ions and Ti⁴⁺ ions can occupy the transition metal ions layer to enlarge the interplane spacing. Thus, the heterovalent cations co-doping strategy can be considered as a simple and practical method to improve the electrochemical performance of Ni-rich layered cathode materials for lithium-ion batteries.

Ultrahigh-response hydrogen sensor based on PdO/NiO co-doped In2O3 nanotubes

Hydrogen can be regarded as an ideal type of secondary energy considering its potential for achieving renewable and sustainable development due to water being its sole combustion product and its possible production by solar energy-based water electrolysis. Monitoring the presence and concentration of hydrogen during production, transportation, and application requires a hydrogen gas sensor with high response, high selectivity, and fast response and recovery times. In an attempt to meet these requirements, NiO and PdO are used in the co-doping of In₂O₃ nanotubes by subsequent electrospinning and impregnation under UV irradiation. The fabricated hydrogen gas sensor demonstrates an ultrahigh response of 487.52, a fast response time of 1 s and high selectivity at an operating temperature of 160 °C, which characteristics are superior to reported monometal-doped hydrogen sensors. The remarkable gas sensing performance could be attributed to the synergistic effect of the resistance modulation, the chemical sensitization of PdO, and the catalytic effect of NiO. This study demonstrates that co-doping of PdO and NiO on In₂O₃ nanotubes is an effective way to improve hydrogen sensing characteristics more effectively than doping with PdO or NiO alone, and provides a potential application for the fast and accurate detection of hydrogen.

The role of band structure in Co- and Fe-co-doped Ba0.5Sr0.5Zr0.1Y0.1O3-δ perovskite semiconductor to design an electrochemical aptasensing platform: application in label-free detection of ochratoxin A using voltammetry

Nanocomposites can offer a platform to conjugate biorecognition features of aptamer with unique size-dependent properties of a given material, which can autoprobe the binding event based on their electroactive characteristics. Herein, we design electroactive switchable aptamer probes based on co-doped single-phase semiconducting materials employing the cyclic voltammetry method to record the current signal at each step of electrochemical characterization. To do so, we utilized a facile hydrothermal method assisted by co-precipitation method such as Co-Fe-co-doped Ba_0.5Sr_0.5Zr_0.1Y_0.1O_3-δ (CF-BSZY) and tuned the alignment of the energy band structure of the material to amplify the output of the electrochemical signal. At various steps, changes occurred in the electrochemical properties at the surface of CF-BSZY. The binding of the ssDNA with prepared materials enhances the current signal by the interaction with the target (ochratoxin A (OTA)) depressing the current signal and facilitating the construction of a novel design of electrochemical aptasensor. As a proof of concept, an electrochemical aptasensor for the detection of ochratoxin A (OTA) in rice samples has been developed. The electrochemical aptasensor provides a limit of detection (LOD) of 0.00012 μM (0.12 nM), with a linear range from 0.000247 to 0.74 μM and sound OTA recovery in real samples. The developed aptasensor is simply designed and is free of oligonucleotide labeling or decorative nanoparticle modifications. The proposed mechanism is generic in principle with the potential to translate any type of aptamer and target binding event into a detectable signal; hence, it can be largely applied to various bioreceptor recognition phenomena for subsequent applications.

Hydrothermal Cobalt Doping of Titanium Dioxide Nanotubes towards Photoanode Activity Enhancement

Doping and modification of TiO2 nanotubes were carried out using the hydrothermal method. The introduction of small amounts of cobalt (0.1 at %) into the structure of anatase caused an increase in the absorption of light in the visible spectrum, changes in the position of the flat band potential, a decrease in the threshold potential of water oxidation in the dark, and a significant increase in the anode photocurrent. The material was characterized by the SEM, EDX, and XRD methods, Raman spectroscopy, XPS, and UV-Vis reflectance measurements. Electrochemical measurement was used along with a number of electrochemical methods: chronoamperometry, electrochemical impedance spectroscopy, cyclic voltammetry, and linear sweep voltammetry in dark conditions and under solar light illumination. Improved photoelectrocatalytic activity of cobalt-doped TiO2 nanotubes is achieved mainly due to its regular nanostructure and real surface area increase, as well as improved visible light absorption for an appropriate dopant concentration.

Improved photocatalyst: Elimination of triazine herbicides by novel phosphorus and boron co-doping graphite carbon nitride

A non-metallic and low-cost novel phosphorus and boron co-doping graphite carbon nitride (PB-g-C₃N₄) photocatalyst was prepared by a facile thermal copolymerization of urea with B₂O₃ and (NH₄)₂·HPO₄. The novel PB-g-C₃N₄ exhibited excellent optical and electrical properties and the photocatalytic elimination efficiency for atrazine (AT, can make feminization of male frogs in the wild, and even induce reproductive cancers in humans.) has been greatly improved compared with the pristine g-C₃N₄. The results of characterization techniques indicate that the introduced B and P atoms most probably to substitute for sp²-hybridized C atoms in triazine rings. O₂^- and h⁺ are the dominant active species to induce the elimination of AT demonstrated by the radical-trapping experiments. And a possible elimination pathway is proposed according to the detected main intermediates. In addition, PB-g-C₃N₄ was applied to the simultaneous photocatalytic elimination of 9 triazine herbicides, and the effects of different initial concentrations, pH, fulvic acid (FA) and ion species on their elimination effects were studied. And it was proved that the photocatalytic performance of PB-g-C₃N₄ did not significant decrease after 4 times of reuse.

Solar oxidation of toluene over Co doped nano-catalyst

Cobalt (Co) co-doped TiO₂ photo-catalysis were synthesized, characterized and tested toward solar photocatalytic oxidation of toluene (TOL). A multi-technique approach was used to characterize and relate the photo-catalytic property to photo-oxidation performance. Adding Co to TiO₂ significantly changed crystal size and surface morphology (surface area, pore-volume, and pore size), reduced the bandgap energy of TiO₂ and improved the solar photo-oxidation of TOL. Up to 96.5% of TOL conversion (%TN_conv) was achieved by using Co-TiO₂ compared with 28.5% with naked TiO₂. The maximum %TN_conv was achieved at high hydraulic retention time (HRT) ≥ 100 s, Co content in the photo-catalyst of 5 wt% and relative humidity (%RH) of 50%. The mechanism of TOL solar oxidation was related to the concentration of OH• and •O₂^-. radicals produced from the generated electrons and holes on the surface of Co-TiO₂. The products formed during the photo-catalytic oxidation of TOL were mainly CO₂ and water, and minor concentration of benzene and benzaldehyde. Overall, the Co-TiO₂ could be used as a potential photo-catalyst for the oxidation of toluene in gas-phase streams on an industrial scale.

Nitrogen, sulfur and oxygen co-doped carbon-armored Co/Co9S8 rods (Co/Co9S8@N-S-O-C) as efficient activator of peroxymonosulfate for sulfamethoxazole degradation

In this study, nitrogen, sulfur and oxygen co-doped carbon armored cobalt sulfide (Co/Co₉S₈@N-S-O-C) composite was synthesized, characterized and used to activate peroxymonosulfate (PMS) for the degradation of sulfamethoxazole (SMX). SMX (0.04 mM) can be completely degraded within 20 min in the presence of 0.8 mM PMS and 0.1 g/L Co/Co₉S₈@N-S-O-C composite. The first-order kinetics constant of SMX degradation was 0.307 min^-1, and the mineralization of SMX was 30.1 %. The Quenching experiments of the free radicals and the identification of degradation products demonstrated that sulfate radicals played a dominant role in SMX degradation. The degradation rate of SMX increased with temperature, and activation energy was calculated to be 48.6 kJ/mol. The degradation rate of SMX increased firstly then decreased with increase of pH. Chloridion and humic acid decreased the degradation rate of SMX no matter what their initial concentration was. The effect of carbonate on SMX degradation depended on its initial concentration. Co/Co₉S₈@N-S-O-C composite showed good stability, the removal efficiency of SMX was 98.4 % in the fifth experiment. Based on the characterization results of the catalyst before and after use, it was concluded that cobalt, sulfur, pyridnic N and graphitic N were responsible for PMS activation.

Supramolecular self-assembly synthesis of noble-metal-free (C, Ce) co-doped g-C3N4 with porous structure for highly efficient photocatalytic degradation of organic pollutants

Developing inexpensive and stable photocatalysts without noble metals, yet remarkably enhancing the photocatalytic activities, is highly needed. Here, a novel carbon and cerium co-doped porous g-C₃N₄ (C/Ce-CN) has been successfully prepared through thermal polymerization of the supramolecular aggregation. The morphologies, chemical structures, optical and photoelectrochemical properties of the synthesized photocatalysts were analyzed via a series of characterization measurements. Experimental results indicated that C/Ce-CN showed remarkably enhanced photocatalytic activity of TC and RhB degradation, which is about 2.6 and 2.4 times higher than that of pristine CN, and it also exhibited a good stability. Compared with bare CN, the enhanced performance of C/Ce-CN is mainly attributed to the stronger utilization rate of visible light, the rapider charge transfer rate, the longer lifetime of carriers and the larger surface specific area. The main intermediates in degradation process of antibiotics were tested by the HPLC-MS. Finally, the possible photocatalytic degradation pathways and mechanisms were proposed.

Photocatalytic activity and antibacterial behavior of TiO2 coatings co-doped with copper and nitrogen via sol-gel method

The sol-gel process is used to prepare photocatalytic coatings with antibacterial properties. Also, doping with metallic or non-metallic elements has an impact on the antibacterial and photocatalytic activity of these coatings. Although there are many studies in this field, the effect of co-doping with Cu and N and their concentrations on the antibacterial properties of TiO₂ coatings against the E. coli and S. aureus bacteria has not been studied. In the present investigation, the sol-gel method was employed to deposit both undoped and Cu-N co-doped TiO₂ photocatalytic coatings on glass surface, which are expected to degrade bacterial and chemical contaminants in water while exposed to visible sunlight wavelengths. Before the coating process, an appropriate heat treatment was applied on the samples and the quality of coatings, band gap energy, and also photocatalytic and antibacterial properties were evaluated. Results showed that, in the presence of dopants, the band gap become narrower and the absorption spectrum is transferred from the ultraviolet to the visible light range. Also, it was demonstrated that, under the visible light radiation, all of the co-doped samples show higher photocatalytic activity than the undoped ones. Meanwhile, the antibacterial characteristics of TiO₂ coatings was enhanced by increasing the dopant concentration when exposing to sunlight.

Strong Valence Electrons Dependent and Logical Relations of Elemental Impurities in 2D Binary Semiconductor: a Case of GeP3 Monolayer from Ab Initio Studies

Using first-principle calculations within density functional theory, we investigate the electronic property and stability of substitutionally doped 2D GeP₃ monolayer with dopants from group III to VI. The conducting properties are found to be dramatically modified by both the doping sites and the number of valence electrons of dopants. Specifically, substitution on Ge site exhibits metal-semiconductor oscillations as a function of the number of valence electrons of dopants, while such oscillations are totally reversed when substitution on P site. Moreover, we also study the case of co-doping in GeP₃, showing that co-doping can produce a logical "AND" phenomenon, that is, the conducting properties of co-doped GeP₃ can be deduced via a simple logical relation according to the results of single doping. Finally, we investigate the formation energy of dopants and find that the electron-hole and hole-hole co-doped systems are much more energetically favorable due to the Coulomb attraction. Our findings not only present a comprehensive understanding of 2D doping phenomenon, but also propose an intriguing route to tune the electronic properties of 2D binary semiconductors.

Hierarchical Cobalt-Doped Molybdenum-Nickel Nitride Nanowires as Multifunctional Electrocatalysts

Herein, we demonstrate hierarchically porous Co-doped MoNi nitride nanowires for multifunctional electrocatalysts. After the Co incorporation for water electrolysis and zinc-air systems, the active surface area is enhanced, whereas the charge-transfer and mass-transfer resistances are reduced significantly. Due to the dual modulation in the electric conductivity and active surface area induced by the Co-doping, the hierarchically porous trimetal nitrides show high activity and good stability for the hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction. The two-electrode electrolyzer assembled by the bifunctional electrocatalysts can deliver 10 mA cm^-2 at a voltage of merely 1.57 V, compared to the best reported electrocatalysts. Meanwhile, two all-solid-state zinc-air batteries in series can power more than 50 red light-emitting diodes and the two-electrode electrolyzer catalyzed by the multifunctional electrocatalysts with excellent operation stability.

Enhancing high-rate and elevated-temperature properties of Ni-Mg co-doped LiMn2O4 cathodes for Li-ion batteries

The improvements of cyclability and rate capability of lithium ion batteries with spinel LiMn₂O₄ as cathode are imperative demands for the large-scale practical applications. Herein, a nickel (Ni) and magnesium (Mg) co-doping strategy was employed to synthesize LiNi_0.03Mg_0.05Mn_1.92O₄ cathode material via a facile solid-state combustion approach. The effects of the Ni-Mg co-doping on crystalline structure, micromorphology and electrochemical behaviors of the as-prepared LiNi_0.03Mg_0.05Mn_1.92O₄ are investigated by a series of physico-chemical characterizations and performance tests at high-rate and elevated-temperature. The resultant LiNi_0.03Mg_0.05Mn_1.92O₄ has the intrinsic spinel structure with no any impurities, and exhibits an elevated average valence of manganese in comparison to the pristine LiMn₂O₄. Owing to the Ni and Mg dual-doped merits, the LiNi_0.03Mg_0.05Mn_1.92O₄ sample demonstrates a robust spinel structure and high first discharge specific capacity of 112.3 mAh g^-1, whilst undergoing a long cycling of 1000 cycles at 1 C. At a high current rate of 20 C, the capacity of 91.2 mAh g^-1 with an excellent retention of 77% is obtained after 1000 cycles. Even at 10 C under 55 °C, an excellent capacity of 97.6 mAh g^-1 is also delivered. These results offer a new opportunity for developing high-performance lithium ion batteries with respect to the Ni-Mg co-doping strategy.

Synthesis and characterization of Ag2O/B2O3/TiO2 ternary nanocomposites for photocatalytic mineralization of local dyeing wastewater under artificial and natural sunlight irradiation

In this work, Ag₂O/B₂O₃/TiO₂ ternary nanocomposite was synthesized by a combination of green and precipitation method involving mixing of different concentrations of silver nitrate, boric acid, and titanium (IV) isopropoxide precursor with Plumeria acuminate leaf extract. The extract was obtained by boiling the mixture of distilled water and the powdered leaves in a beaker for few minutes followed by filtration. The microstructure, morphology, chemical composition, surface area, phase structure, and optical properties of the various prepared nanomaterials were determined by HRTEM, HRSEM, UV-Vis/DRS, BET, XRD, and XPS. The photocatalytic potential of TiO₂ nanoparticles and Ag₂O/B₂O₃/TiO₂ nanocomposites to degrade local dyeing wastewater under artificial and natural sunlight irradiation was investigated. The extent of degradation of the organic pollutants was measured using chemical oxygen demand (COD) and total organic carbon (TOC) as indicator parameters. The XRD pattern of Ag₂O/B₂O₃/TiO₂ nanocomposites revealed that the formation of pure anatase TiO₂ phase and the addition of both silver and boron precursors did not influenced the phase structure of the nanocomposites. The oxidation states of +1 and +3 for both Ag and B on the surface of Ag₂O/B₂O₃/TiO₂ nanocomposites were confirmed by XPS. Optical characterization of the sample revealed reduction of band gap energy from 2.6 to 2.0 eV for TiO₂ and Ag₂O/B₂O₃/TiO₂, respectively. The Ag₂O/B₂O_3/TiO₂ nanocomposites demonstrated excellent photocatalytic activity under natural sunlight and artificial light than mono and binary oxide systems with TOC and COD degradation efficiencies of 86.11% and 75.69%, respectively. The kinetics of degradation of organic dyes in the wastewater followed the order of Langmuir-Hinshelwood pseudo-first-order > Freundlich > Zero > Parabolic diffusion model. The coupling effect of Ag₂O and B₂O₃ onto TiO₂ framework was responsible for the enhanced photochemical stability of the nanocomposites even after five repeated cycles.

Photocatalytic degradation of local dyeing wastewater by iodine-phosphorus co-doped tungsten trioxide nanocomposites under natural sunlight irradiation

In the present work, one-step green synthesis of WO₃ based on the interaction of ammonium paratungstate and Spondias mombin leaves extract is reported. Different concentrations of iodine and phosphorus in the range of (2%, 5% and 10%) were firstly incorporated into the prepared WO₃ nanoparticles to obtain Iodine doped and Phosphorus doped WO₃ nanoparticles respectively. Subsequently, iodine and phosphorus co-doped WO₃ nanocomposites was prepared using a wet impregnation method followed by calcination at high temperature. The nanomaterials were characterized by HRSEM, HRTEM, BET, UV-Visible, EDS, XRD and XPS. The photo-oxidation of dyeing wastewater by the synthesized WO₃ nanomaterials were tested and assessed using Total organic carbon (TOC) and Chemical oxygen demand (COD) as indicator parameters. XRD and HRSEM analysis demonstrated the formation of only monoclinic phase of WO₃ irrespective of the dopants. The UV-Visible diffuse reflectance spectroscopy showed the band gap energy of 2.61 eV for undoped WO₃ and 2.02 eV for I-P co-doped WO₃ nanocomposites. The surface area of I-P co-doped WO₃ (416.18 m²/g) was higher than the undoped WO₃ (352.49 m²/g). The XPS demonstrated interstitial and substitution of oxygen (O^2-) vacancies in WO₃ by I^- and P³⁺ and formed I-P-WO(_3-x). The I-P co-doped WO₃ exhibited higher catalytic activities (93.4% TOC, 95.1% COD) than the undoped (54.9% TOC, 79.2% COD) due to the synergistic effects between the two dopants. The experimental data better fitted to pseudo-second order than first order and pseudo-first order model. This study demonstrated the enhanced photocatalytic performance of I-P co-doped WO₃ nanocomposites under sunlight.

Enhanced Electrochemical Performances of Cobalt-Doped Li₂MoO₃ Cathode Materials

Co-doped Li₂MoO₃ was successfully synthesized via a solid phase method. The impacts of Co-doping on Li₂MoO₃ have been analyzed by X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR) measurements. The results show that an appropriate amount of Co ions can be introduced into the Li₂MoO₃ lattices, and they can reduce the particle sizes of the cathode materials. Electrochemical tests reveal that Co-doping can significantly improve the electrochemical performances of the Li₂MoO₃ materials. Li₂Mo_0.90Co_0.10O₃ presents a first-discharge capacity of 220 mAh·g⁻¹, with a capacity retention of 63.6% after 50 cycles at 5 mA·g⁻¹, which is much better than the pristine samples (181 mAh·g⁻¹, 47.5%). The enhanced electrochemical performances could be due to the enhancement of the structural stability, and the reduction in impedance, due to the Co-doping.

Efficient visible-light-driven hydrogen evolution and Cr(VI) reduction over porous P and Mo co-doped g-C3N4 with feeble N vacancies photocatalyst

Developing highly efficient and inexpensive photocatalysts without noble metals, yet remarkably enhancing hydrogen production and Cr(VI) reduction activity, is highly needed. Here, the effective photocatalytic H₂ evolution under visible light from an Eosin Y (EY)-sensitized (P, Mo)-g-C₃N_x system by avoiding any noble metal co-catalyst is reported by the first time. Meanwhile, the optimized sample also displays the excellent performance in photocatalytic hexavalent chromium (Cr(VI)) reduction. In addition, this composite exhibits delectable stability for photocatalytic activities, no significant decay of activity is being observed after 16h reaction for photocatalytic H₂ evolution (8h for Cr(VI) reduction). It is believed that this work will open up a new route for fabricating high-performance and inexpensive photocatalysts for hydrogen production and Cr(VI) reduction.

Fluorescence resonance energy transfer of CaF2: Eu2+, Tb3+ applied to dye-sensitized solar cells

CaF₂: Eu²⁺, Tb³⁺ introduced into dye-sensitized solar cells (DSSCs) were studied to examine the influence of luminescent materials on photoanodes using a simple method. The emission spectra of CaF₂: Eu²⁺, Tb³⁺ included the blue light of Eu²⁺ (4f → 5d) at 430 nm and green emission of Tb³⁺ (⁵D₄ → ⁷F₅) at 542 nm under the monitoring wavelengths at 398 nm, which matched well the absorption range of the N719 dye in DSSCs. Energy transfer (ET) was verified between Eu²⁺ and Tb³⁺ ions and the efficiency of ET found to increase with Tb³⁺ concentration. Both the fluorescence resonance and luminescence-mediated ETs between phosphor and N719 dye were observed as the main contribution in improving photocurrent and power conversion efficiency (PCE) of these DSSCs. The PCE of DSSCs doped with phosphors was greatly increased by 5.16, to 43.3%, which was comparable to cells made of pure TiO₂ photoanodes. Moreover, CaF₂: Eu²⁺, Tb³⁺ enlarged the surface area of TiO₂ photonaodes, which helped the adsorption performance of the TiO₂ film.

Graphitic carbon nitride based nanocomposites for the photocatalysis of organic contaminants under visible irradiation: Progress, limitations and future directions

Graphitic carbon nitride (g-C₃N₄) has drawn great attention recently because of its visible light response, suitable energy band gap, good redox ability, and metal-free nature. g-C₃N₄ can absorb visible light directly, therefore has better photocatalytic ability under solar irradiation and is more energy-efficient than TiO₂. However, pure g-C₃N₄ still has the drawbacks of insufficient light absorption, small surface area and fast recombination of photogenerated electron and hole pairs. This review summarizes the recent progress in the development of g-C₃N₄ nanocomposites to photodegrade organic contaminants in water. Element doping especially by potassium has been reported to be an efficient method to promote the degradation efficacy. In addition, compound doping improves photodegradation performance of g-C₃N₄, especially Ag₃PO₄-g-C₃N₄ which can completely degrade 10mgL^-1 of methyl orange under visible light irradiation in 5min, with the rate constant (k) as high as 0.236min^-1. Moreover, co-doping enhances the photodegradation rate of multiple contaminants while immobilization significantly improves catalyst stability. Most of g-C₃N₄ composites possess high reusability enabling their practical applications in wastewater treatment. Furthermore, environmental conditions such as solution pH, reaction temperature, dissolved oxygen, and dissolved organic matter all have important effects on the photocatalytic ability of g-C₃N₄ photocatalyst. Future work should focus on the synthesis of innovative g-C₃N₄ nanocomposites for the efficient removal of organic contaminants in water and wastewater.

Effect of catalyst calcination temperature in the visible light photocatalytic oxidation of gaseous formaldehyde by multi-element doped titanium dioxide

The present study investigates the influence of calcination temperature on the properties and photoactivity of multi-element doped TiO₂. The photocatalysts were prepared by incorporating silver (Ag), fluorine (F), nitrogen (N), and tungsten (W) into the TiO₂ structure via the sol-gel method. Spectroscopic techniques were used to elucidate the correlation between the structural and optical properties of the doped photocatalyst and its photoactivity. XRD results showed that the mean crystallite size increased for undoped photocatalysts and decreased for the doped photocatalysts when calcination was done at higher temperatures. UV-Vis spectra showed that the absorption cut-off wavelength shifted towards the visible light region for the as-synthesized photocatalysts and band gap narrowing was attributed to multi-element doping and calcination. FTIR spectra results showed the shifting of OH-bending absorption bands towards increasing wave numbers. The activity of the photocatalysts was evaluated in terms of gaseous formaldehyde removal under visible light irradiation. The highest photocatalytic removal of gaseous formaldehyde was found at 88%. The study confirms the effectiveness of multi-element doped TiO₂ to remove gaseous formaldehyde in air by visible light photocatalysis and the results have a lot of potential to extend the application to other organic air contaminants.

Cu and Zr surface sites in the photocatalytic activity of TiO2 nanoparticles

The rate of methylene blue and terephthalic acid degradation assisted with double metal-modified catalyst (0.1 mol% Cu and 1.0 mol% Zr) was enhanced as compared with single metal-modified catalysts (0.1, 0.5 mol% Cu and 1.0 mol% Zr). The wet impregnation method was used for copper and zirconium modification of the surface of Aeroxide P25 TiO₂ particles. Simultaneous loading of both metals on the surface of P25 leads to an increased specific surface area of the obtained material despite negative Cu influence. The tendency of stabilization and agglomerate size rising with the time for Cu and Zr-modified catalysts were traced by dynamic light scattering (DLS) measurements. The observed optical characteristics suggest that Cu compensated the broadening of band gap caused by Zr loading. Crystal structure of obtained photocatalysts was explored by XRD; morphological data and particle size were obtained by SEM. EDX was used for Zr and Cu content determination. Cu K-edge extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) analytical techniques were used to investigate the local Cu neighbourhood in the samples and to identify copper coordination and valence state of copper species in the synthesized nanocomposites.