High Oxidizability Research Articles

Engineering hierarchical TiO2/ZnIn2S4 hybrid heterostructure with synergistic interfaces: A dual-functional S-scheme photocatalyst for efficient CO2 reduction and norfloxacin degradation

The development of multifunctional photocatalysts that can harness solar energy for both environmental remediation and energy generation is a considerable challenge in achieving sustainable development. This study introduces a dual-functional S-scheme hybrid catalyst comprising hierarchical 3D flower-like ZnIn2S4 (ZIS) microspheres embedded with TiO2 (TO) nanoparticles, synthesized via a facile in situ hydrothermal process. The unique structural and compositional synergy between ZIS and TO leverages their complementary photocatalytic properties, facilitating efficient solar energy utilization, increasing specific surface area, and enhancing CO2 adsorption capabilities. The S-scheme mechanism, confirmed by in situ-irradiated X-ray photoelectron spectroscopy and electron spin resonance spectroscopy, underlying this system promotes effective separation of photoexcited charge carriers while preserving the intrinsic strong reducibility of ZIS and high oxidizability of TO. These beneficial properties of the TO/ZIS hybrid provide a robust platform for CH4 production (75.6 μmol h−1 g−1) through selective (99.6 %) CO2 reduction over competing water reduction and achieve exceptional degradation and mineralization of the persistent antibiotic norfloxacin in water, addressing both energy and environmental challenges. Furthermore, the hybrid catalyst exhibits significant stability and recyclability, maintaining high catalytic performance across multiple cycles, thereby underscoring its practical viability. This work offers a promising blueprint for developing multifunctional photocatalysts capable of addressing critical global challenges, demonstrating the potential of hierarchical nanostructures and S-scheme charge transfer mechanisms.

In vitro Antibacterial Effect Study of Plasma-Activated Saline on Mycobacterium Tuberculosis.

This study aimed to investigate the antibacterial effects of plasma-activated saline (PAS) on My-cobacterium tuberculosis (Mtb). We conducted a growth assay on 3 strains of Mtb and an antibiotic sensitivity test on 4 strains of Mtb. Both tests included groups treated with normal saline (NS), PAS, and hydrochloric acid (HCl). The test of antibiotic sensitivity consisted of parallel tests with two concentrations of bacteria suspension: 10-2 and 10-4. The selected antibiotics were rifampicin (RIF), isoniazid (INH), ethambutol (EMB), and streptomycin (SM). The number of bacteria was determined after one month of culture under different conditions. The Kruskal-Wallis test was used to analyze the differences in grouping factors at representative time points. The growth assay indicated that PAS significantly inhibited the growth of 3 strains of Mtb compared with NS and HCl treatment groups. Furthermore, except for the initial observation time point, the remaining three observation time points consistently demonstrate no significant differences between the NS group and the HCl group. The antibiotic sensitivity test of INH, SM, and RIF indicated that PAS could inhibit the growth of antibiotic-resistant Mtb, and the antibiotic sensitivity test of INH and SM with bacterial suspension concentration of 10-2 and SM with bacterial suspension concentration of 10-4 showed statistically different results. The antibiotic sensitivity test of EMB indicated that the growth of Mtb in PAS was slower than that in NS and HCl in both antibiotic-resistant and sensitive Mtb, but there was no statistical difference. The study indicates that PAS contains a significant amount of active substances and exhibits high oxidizability and an acidic pH state. The unique physicochemical properties of PAS significantly delayed the growth of Mtb, compared to the NS and the HCl. PAS not only inhibited the growth of drug-sensitive strains but also significantly enhanced the sensitivity of drug-resistant strains to anti-tuberculosis drugs, which may provide a new therapeutic strategy for the treatment of tuberculosis.

The state of natural resources of the West Kazakhstan region (1990s – early 2000s)

The purpose of the study was to analyze the state of natural resources in the West Kazakhstan region during the 1990s to the early 2000s. The ecological condition of the region’s natural resources remains one of its most pressing issues, necessitating regular monitoring. Analysis of official data sources revealed that the socio-economic development of the region coincided with the establishment and operation of large industrial and construction enterprises, leading to adverse effects on the region’s natural environment. Monitoring of arable land in areas with dark chestnut soils indicated a continued loss of humus during this period. Presence of nitrates and high permanganate oxidizability suggested the presence of organic compounds linked to the decomposition of heptyl rocket fuel. Disease patterns indicated that populations in the southern areas of the region experienced high chemical burdens alongside radiation exposure. Furthermore, the article addresses concerns regarding the state of forest resources and wildlife, with authors highlighting a significant risk of natural resource contamination by industrial waste from heavy industries in the region.

Boosting the enzymatic activity of CxxC motif-containing PDI family members.

Compounds harboring high acidity and oxidizability of thiol groups permit tuning the redox equilibrium constants of CxxC sites of members of the protein disulphide isomerase (PDI) family and thus can be used to accelerate folding processes and increase the production of native proteins by minimal loading in comparison to glutathione.

Catalytic oxidation of carbon monoxide over copper oxide with interfering gases involved for industrial buildings: An experimental and theoretical study

With the intention of thoroughly eliminating carbon monoxide (CO) from indoor environment, it is one of the most promising methods of converting it into carbon dioxide (CO2) via catalytic oxidation processes. Therefore, in this study, catalytic oxidation mechanisms of CO over copper oxide (CuO) with interfering gases involved are investigated via theoretical calculations and experimental verification, which mainly include basic catalytic oxidation processes over CuO, effects of different interfering gases and analyses of thermodynamic features. According to results, catalytic oxidation of CO over CuO can be performed in three different routes and rate-determining transition-state (TS) energy barriers vary a lot from route to route at high temperature owing to different thermal stability. In the meantime, SO2, H2O and NO are theoretically proved to affect catalytic oxidation of CO via competitive adsorption, high oxidizability and hydrogen bonds, which are accompanied with different sensitivities to changes of temperature or temperature power exponents. In experiments, it is found that impurity of lattice planes and small specific surface areas in CuO are key to restricting catalytic oxidation performances. What is more, some extra chemical reactions in experiments (e.g. SO2 + O2 + CuO → CuSO4, NO + O2 + CO → CO2 + NO) caused by interfering gases colossally affect catalytic oxidation performances of CuO. The whole study provides crucial information for indoor air purification in industrial buildings by using cheap adsorbents/catalysts.

Reviving Zn0 Dendrites to Electroactive Zn2+ by Mesoporous MXene with Active Edge Sites.

Zinc metal-based aqueous batteries (ZABs) offer a sustainable, affordable, and safe energy storage alternative to lithium, yet inevitable dendrite formation impedes their wide use, especially under long-term and high-rate cycles. How the battery can survive after dendrite formation remains an open question. Here, we pivot from conventional Zn dendrite growth suppression strategies, introducing proactive dendrite-digesting chemistry via a mesoporous Ti3C2 MXene (MesoTi3C2)-wrapped polypropylene separator. Spectroscopic characterizations and electrochemical evaluation demonstrate that MesoTi3C2, acting as an oxidant, can revive the formed dead Zn0 dendrites into electroactive Zn2+ ions through a spontaneous redox process. Density functional theory reveals that the abundant edge-Ti-O sites in our MesoTi3C2 facilitate high oxidizability and electron transfer from Zn0 dendrites compared to their in-plane counterparts. The resultant asymmetrical cell demonstrates remarkable ultralong cycle life of 2200 h at a practical current of 5 mA cm-2 with a low overpotential (<50 mV). The study reveals the unexpected edge effect of mesoporous MXenes and uncovers a new proactive dendrite-digesting chemistry to survive ZABs, albeit with inevitable dendrite formation.

LATP-coated LiNi0.8Co0.1Mn0.1O2 cathode with compatible interface with ultrathin PVDF-reinforced PEO-LLZTO electrolyte for stable solid-state lithium batteries

LiNi0.8Co0.1Mn0.1O2 (NCM811) is considered as a promising cathode for high-energy-density solid-sate Li metal battery for its high theoretical capacity. However, the high oxidizability and structural instability during charge limit its practical applications. In this work, 1% (in mass) of nanosized Li1.3Al0.3Ti1.7(PO4)3 (LATP) was coated on NCM811 to enhance its electrochemical stability with a ceramic/polymer composite electrolyte. A robust, ultrathin (11 μm) composite electrolyte film was prepared by combining poly(vinylidene fluoride) (PVDF) with polyethylene oxide (PEO)-Li6.5La3Zr1.5Ta0.5O12 (LLZTO). An in-situ polymerization process was used to enhance the interface between the PVDF/PEO-LLZTO (PPL) composite electrolyte and the LATP-coated NCM811 (LATP-NCM811). Coin-type Li|LATP-NCM811 cell with the PPL electrolyte exhibits stable cycling with an 81% capacity retention after 100 cycles at 0.5 C. Pouch-type cell was also fabricated, which can be stably cycled for 70 cycles at 0.5 C/1.0 C (80% retention), and withstand abuse tests of bending, cutting and nail penetration. This work provides an applicable method to fabricate solid-state Li metal batteries with high performance.

Study on surface quality and mechanical properties of micro-milling WE43 magnesium alloy cardiovascular stent

Traditional laser processing technique is mainly applied for cardiovascular stent manufacture, especially for materials with high mechanical properties and high melting point, while it usually produces problems such as material ablation and defects during finish machining process. Magnesium alloy, as material candidate for bioresorbable cardiovascular stent, has low melting and ignition point, high oxidizability property. Laser processing technique scarcely meets the requirements of high surface quality of magnesium alloy cardiovascular stents, this paper firstly develops a five-axis micro-milling technique to fabricate magnesium alloy cardiovascular stents. Milling orthogonal test was carried out to obtain the optimal finish machining parameters, and then a novel stent machining process was established. The processed stent has an inner diameter of 1.5 mm, a thickness of 80 μm and a length of 8 mm with a U-bend width of 100 μm and a link strut width of 70 μm, and the optimal finish processing parameters was set up with the main spindle speed of 30,000 rpm, feed speed 200 mm/min, cutting width 50 μm and cutting depth 40 μm. The dimensional accuracy and surface topography of the magnesium alloy stent were measured and characterized, and results showed that the dimensional accuracy was within 0.01 mm, and the machined stent achieved better surface quality without obvious processing defects such as pits, grooves and pores while comparing with the stent under original processing parameters. In order to evaluate the radial support performance of the stent, the radial compression and expansion experiments and simulations were conducted, respectively. Results showed that the maximum diameter error in the experiment and simulation was 13.35 %, and the radial recoiling error was 16.79 %. This work provides a potential stent manufacture technique in the development and clinical application of bioresorbable magnesium alloy stent.

Fabrication and Characterization of Botanical-Based Double-Layered Emulsion: Protection of DHA and Astaxanthin Based on Interface Remodeling.

Both DHA and astaxanthin, with multiple conjugated double bonds, are considered as health-promoting molecules. However, their utilizations into food systems are restricted due to their poor water solubility and high oxidizability, plus their certain off-smell. In this study, the interactions between perilla protein isolate (PPI) and flaxseed gum (FG) were firstly investigated using multiple spectroscopies, suggesting that hydrophobic, electrostatic force and hydrogen bonds played important roles. Additionally, double-layer emulsion was constructed by layer-by-layer deposition technology and exhibited preferable effects on masking the fishy smell of algae oil. Calcium ions also showed an improving effect on the elasticity modulus of O/W emulsions and was managed to significantly protect the stability of co-delivered astaxanthin and DHA, without additional antioxidants during storage for 21 days. The vegan system produced in this study may, therefore, be suitable for effective delivery of both ω-3 fatty acid and carotenoids for their further incorporation into food systems, such as plant-based yoghourt, etc.

Formation and evolution of secondary particulate matter during heavy haze pollution episodes in winter in a severe cold climate region of Northeast China.

The formation and evolution of sulfate (SO42-) and nitrate (NO3-) secondary contaminants under different stages of pollution episodes and different meteorological and emission conditions were compared, based on the simultaneous observation of fine particulate matter (PM2.5) and its chemical components in four heavy haze pollution episodes at 14 sampling sites in a severe cold climate region of Northeast China in winter from 2017 to 2019. The results yielded two main findings. (1) Nitrate formation during the day was mainly due to the combination of high emissions and high relative humidity (RH, 50-90%), high temperature (T, 0 to 5°C), high atmospheric oxidizability (ozone (O3) and nitrous acid (HONO) concentrations), and high ammonia (NH3) concentrations. Nitrate was formed by a gas-phase homogeneous reaction of the hydroxyl radical (OH·) with nitrogen dioxide (NO2), sulfur dioxide (SO2), and ammonia (NH3). (2) The main differences in SO42- formation between Northeast China and other regions were that the gas-phase oxidation process played an important role. This was mainly a result of the promotion of the gas-phase oxidation of SO42- due to the high oxidizing ability and the suppression of the aqueous reaction due to the low Ts in winter and low-sulfur coal emissions. Sulfate formation mostly occurred through an aqueous phase reaction in winter, but the highest yield and the fastest production capacity were produced by the gas-phase reaction.

Intensification of oxidative desulfurization by Zr(IV)-ionic liquid-HPW composite activating H2O2 system and mechanism insight

The carboxyl functionalized ionic liquid ([mim(CH2)3COOH]Cl) was prepared as a linker to combine phosphotungstic acid (HPW) and Zr(IV) ion. The obtained [mim(CH2)3COO]3PW-Zr composite acted as a heterogeneous catalyst for removing DBT from liquid fuel with H2O2 as an oxidant. As a result, [mim(CH2)3COO]3PW-Zr possessed high catalytic activity in extractive and catalytic oxidative desulfurization (ECODS). Moreover, the [mim(CH2)3COO]3PW-Zr was further exploited to grow on the surface of PEI/silica gel. And the fabricated large-grained Zr-PWIL@PEI/silica gel was used in the continuous ECODS process, and the removal of DBT could still reach more than 95% after running continuously for 16 h. More importantly, the synergistic catalytic mechanism between HPW and Zr(IV) in the ECODS process has been investigated in detail by experiments and DFT calculations. As a result, a plausible mechanism has been proposed and verified, which contains two parts: the Lewis acidic center activating H2O2 to form superoxide ion radicals (OOH), and the OOH oxidizing HPW to peroxotungstate (W(O2)n), which has a high oxidizability and stability. Thus, the effective combination of Zr(IV) and HPW active sites is a very effective strategy to promote desulfurization efficiency and utilization efficiency of H2O2. Besides, we also found the distance between the corresponding active sites of catalysts plays an essential role in ECODS reaction as it strongly influences the synergistic effect between different active sites.

Production Tests of the Don Water Purification and Disinfection Technology

One of the promising ways to reduce the content of organic pollutants in natural waters is the use of biological processes in combination with sorption on powdered activated carbon followed by membrane filtration and, as the final stage, disinfection of the obtained permeate by direct electrolysis. The paper presents the results of the efficiency of purification of the Don water, which underwent physicochemical treatment from halogen-organic contaminants in a biosorption-membrane reactor and the dependencies characterizing the disinfection of water by direct electrolysis in a flow-through membraneless electrolyzer. The studies were carried out using powdered active carbon, hollow fiber, and flat plate membranes. An oxide iridium-ruthenium titanium anode (OIRTA) was used as electrodes in a flow-through electrolyzer. As a result of processing the experimental results, the efficiency of removing not only the turbidity and color of water, but also organic substances, which cause high permanganate oxidizability and COD, has been established. The results of experimental studies have shown a high efficiency of purification and disinfection of natural water to the requirements of SanPiN. The efficiency of COD reduction was on average 41.2%, color - 57.3%, permanganate oxidizability - 33.3%.

Features of phase transformations in powder steels upon heating

At present, powder materials are used in practically all branches of industry, from medicine to aerospace technology. This is a wide range of materials ranging from constructional and instrumental materials and ending with special-purpose materials and medical implants. Powder metallurgy methods are most often used where the manufacture of products with desired properties is impossible using traditional methods: casting, stamping, etc. Heat treatment is understood as a set of operations of heating, holding at high temperatures and cooling in order to change the structure and workability of the material, improve the combination of its mechanical and physical properties without changing the shape and size of products. Heat treatment is an effective method for improving the physical and mechanical properties and wear resistance of steel. The specific features of sintered steels (porosity, structural heterogeneity, high oxidizability, etc.) make it difficult to use the technological modes of heat treatment developed for cast steels, although the main regularities of the processes occurring during heating and cooling of compact steel can be transferred to sintered materials. Heat treatment of powder steels has a number of features, primarily due to residual porosity, as well as chemical and structural heterogeneity.

Suppression of Sn2+ and Lewis acidity in SnS2/black phosphorus heterostructure for ppb-level room temperature NO2 gas sensor

The selective detection of harmful gases is of great significance to human health and air quality, triggering the need for special customizations of sensing material structure. In this study, we prepared a novel SnS2/black phosphorus (BP) two-dimensional (2D)-2D heterostructure via the in situ hydrothermal growth of SnS2 nanosheets on exfoliated BP lamellae for NO2 sensing applications. In the SnS2/BP composite, the holes with high oxidizability in p-type BP could oxidize Sn2+ into Sn4+, thus inhibiting the formation of Lewis acidic S vacancies. This Sn2+/Lewis acidity suppression of the composite was further confirmed by X-ray photoelectron spectroscopy and acidic double-layer capacitance analyses, and promoted the adsorption and detection of acidic NO2. Owing to its valence and Lewis acidity engineering, the SnS2/BP heterostructure sensor could detect trace levels of NO2 as low as 100 ppb (parts per billion) with high response, fast response/recovery, good stability, and selectivity at room temperature. The high absorption energy of NO2 (−0.74 eV), as indicated by the density functional theory calculations, suggests that NO2 was chemically adsorbed on the SnS2/BP surface, which was also evidenced by the in situ Raman spectroscopy results. This work opens up interesting opportunities for the rational design of highly efficient NO2 gas sensors through Lewis acidity modification and interface engineering.

High resolution nanoscale chemical analysis of bitumen surface microstructures

Surface microstructures of bitumen are key sites in atmospheric photo-oxidation leading to changes in the mechanical properties and finally resulting in cracking and rutting of the material. Investigations at the nanoscale remain challenging. Conventional combination of optical microscopy and spectroscopy cannot resolve the submicrostructures due to the Abbe restriction. For the first time, we report here respective surface domains, namely catana, peri and para phases, correlated to distinct molecules using combinations of atomic force microscopy with infrared spectroscopy and with correlative time of flight—secondary ion mass spectrometry. Chemical heterogeneities on the surface lead to selective oxidation due to their varying susceptibility to photo-oxidation. It was found, that highly oxidized compounds, are preferentially situated in the para phase, which are mainly asphaltenes, emphasising their high oxidizability. This is an impressive example how chemical visualization allows elucidation of the submicrostructures and explains their response to reactive oxygen species from the atmosphere.

Facile Atmospheric Generation of Water Radical Cations via TiO2‐Nanoneedle Arrays for Aromatic Hydrocarbon Detection Based on Corona Discharge

Water radical cations, (H2O)n+•, have attracted considerable attention owing to their potential practical applications in analytical chemistry, structural chemistry, radiotherapy, and radiochemistry. Recently, atmospheric pressure chemical ionization has emerged as a versatile method for direct mass spectrometric analysis. Usually, H3O+ is the major proton donor during ionization and only the pseudo molecular ion peaks, instead of molecular ions are detected. In this work, (H2O)2+• ions with high oxidizability and reactivity were generated using hydrothermally grown TiO2 nanoneedle arrays in combination with a linear ion trap mass spectrometer under low operating voltage and applied to the direct mass spectrometric analysis of a mixture of volatile aromatic hydrocarbons. (H2O)2+• ions were generated with a high absolute ion current of up to 1.07 × 105 counts/s at atmospheric pressure. Using the generated (H2O)2+• as the primary ion permitted the tandem mass spectrometric analysis of a mixed vapor sample of aromatic hydrocarbons.

Construction of phosphorus-doped carbon nitride/phosphorus and sulfur co-doped carbon nitride isotype heterojunction and their enhanced photoactivity

Photocatalysis was one of the most promising techniques for environmental remediation. Exploring photocatalysts with high efficiency, low cost and easy preparation was still an ongoing issue. In this work, phosphorus-doped carbon nitride/phosphorus and sulfur co-doped carbon nitride (P-C3N4/PS-C3N4) isotype heterojunction was prepared by a two-step calcination method. The composite displayed a sheet-like structure with a surface area of 23 m2/g. Compared with pure C3N4, band gaps of P-C3N4 and PS-C3N4 were only slightly modified during the heteroatom-doping process. Therefore, a well-matched band alignment was constructed, which not only improved the separation efficiency of photogenerated electron-hole pairs, but also well preserved the high oxidizability of holes on valance band and good reducibility of electrons on conduction band. Because of the similarity in physicochemical properties, the interface resistance between P-C3N4 and PS-C3N4 was low, which accelerated the electron transfer and prolonged the lifetime of charge carriers. Although the visible-light utilization was somewhat low in comparison with P-C3N4 and PS-C3N4, by taking advantage of above merits, P-C3N4/PS-C3N4 displayed the high photocatalytic activity in rhodamine B degradation, and the reaction rate constant was 0.183 min−1, about 8.7 and 4.0 times higher than those of P-C3N4 and PS-C3N4. Besides high catalytic activity, isotype heterojunction displayed good recyclability, since 95.3% of catalytic activity was maintained after the 5th cycle. The method presented here was facile, economic and environmentally benign, thus it was highly attractive for the application in environmental remediation.

Effective Singlet Oxygen Generation in Silica-Coated CsPbBr3 Quantum Dots through Energy Transfer for Photocatalysis.

Here, silica-coated CsPbBr3 quantum dots (QDs) were demonstrated to be effective photosensitizers for the generation of singlet oxygen (1 O2 ). The silica encapsulation improved the stability of the perovskite QDs while also preserving an excellent light-harvesting capability in the visible-light region. The appropriate exciton binding energy and dark exciton generation characteristics of perovskite QDs may be responsible for the energy transfer. The high oxidizability of 1 O2 makes the material attractive for application in decomposition of organic dyes such as methyl orange. This work provides new insight for designing excellent perovskite-based photocatalysts.

Impact of typhoon periphery on high ozone and high aerosol pollution in the Pearl River Delta region

This paper analyzes observation data in the Pearl River Delta (PRD) region from 2012 to 2013, and explores the impact of typhoon periphery on high ozone and high aerosol pollution episodes (double high episodes). Observation analysis show that severe tropical storms to severe typhoons are mainly located in the range of 10°N-30°N, 116°E-135°E when double high episodes occur. Meanwhile, obvious high temperature, low humidity, low wind speed, high actinic flux, high aerosol optical depth (AOD), and high single scattering albedo (SSA) can be observed in double high episodes.The diurnal cycle of the PM2.5 is significant in double high episodes, and the average peak concentration in the afternoon can exceed 90 μg/m3. The diurnal cycle of PM2.5 in non–double high episodes is not significant, and the average value is about 34–39 μg/m3. The ozone peak concentration in double high episodes is 81–103 ppbv, which is about 27–40 ppbv higher than that of non–double high episodes. High correlation can be found between the aerosol and ozone diurnal cycles in double high episodes, and r2 reaches 0.76. In double high episodes, black carbon, nitrate, and sea salt decrease while sulfate, ammonium, secondary organic carbon, and total PM2.5 significantly increase in the afternoon. The growth of PM2.5 in double high episodes is mainly contributed by scattered fine particles from photochemical processes and transmission. The mechanisms that control the double high episodes in the PRD are described below. Ozone and aerosol begin to accumulate under unfavorable meteorological conditions. Via local photochemical processes and external transport, the scattered aerosol increases and leads to an increase in multiple scattering and actinic radiation, which is in turn more favorable for photochemical reaction and further increases the ozone concentration. Meanwhile, high oxidizability promotes the formation of scattered aerosol, creating positive feedback. In addition, the scattered aerosol increases backscattering, which increases the photolysis rate and ozone concentration in the middle and upper boundary layer. Meanwhile, downdraft and turbulence transports high-concentration ozone to the ground.

Characteristics of 9,10-diphenylanthracene field-effect transistors obtained by exposing the silver electrodes to oxidative conditions

Organic field-effect transistors (OFETs) containing a 9,10-diphenylanthracene (DPA) layer were fabricated with oxidized silver (AgOx) electrodes, and their electrical properties were investigated. The OFET structure consisted of heavily doped n-type Si wafers (SiO2) as the gate dielectric layer, fabricated silver source–drain electrodes oxidized by ultraviolet-ozone surface treatment, and finally the DPA layer. In spite of the large ionization potential of the DPA layer (∼5.8 eV), a high mobility (∼1.1 cm2 V−1 s−1)) was measured for OFETs with a AgOx layer oxidized for 600 s, which resulted in a reduction in the contact resistance to 8.0 kΩ cm. The observed behavior was attributed to the fact that the AgOx layer with its high oxidizability contributed to hole injection by oxidizing the surface of the DPA layer. Moreover, hole injection was more strongly enhanced by the presence of Ag2O rather than AgO.