Formaldehyde Ambient-Temperature Decomposition over Pd/Mn3O4-MnO Driven by Active Sites' Self-Tandem Catalysis.

The widespread presence of formaldehyde (HCHO) pollutant has aroused significant environmental and health concerns. The catalytic oxidation of HCHO into CO2 and H2O at ambient temperature is regarded as one of the most efficacious and environmentally friendly approaches; to achieve this, however, accelerating the intermediate formate species formation and decomposition remains an ongoing obstacle. Herein, a unique tandem catalytic system with outstanding performance in low-temperature HCHO oxidation is proposed on well-structured Pd/Mn3O4-MnO catalysts possessing bifunctional catalytic centers. Notably, the optimized tandem catalyst achieves complete oxidation of 100 ppm of HCHO at just 18 °C, much better than the Pd/Mn3O4 (30%) and Pd/MnO (27%) counterparts as well as other physical tandem catalysts. The operando analyses and physical tandem investigations reveal that HCHO is primarily activated to gaseous HCOOH on the surface of Pd/Mn3O4 and subsequently converted to H2CO3 on the Pd/MnO component for deep decomposition. Theoretical studies disclose that Pd/Mn3O4 exhibits a favorable reaction energy barrier for the HCHO → HCOOH step compared to Pd/MnO; while conversely, the HCOOH → H2CO3 step is more facilely accomplished over Pd/MnO. Furthermore, the nanoscale intimacy between two components enhances the mobility of lattice oxygen, thereby facilitating interfacial reconstruction and promoting interaction between active sites of Pd/Mn3O4 and Pd/MnO in local vicinity, which further benefits sustained HCHO tandem catalytic oxidation. The tandem catalysis demonstrated in this work provides a generalizable platform for the future design of well-defined functional catalysts for oxidation reactions.

Atomically precise AuxAg25-x nanoclusters with a modulated interstitial Au-Ag microenvironment for enhanced visible-light-driven photocatalytic hydrogen evolution.

Herein, we report the study of atomically precise AuxAg25-x nanoclusters (NCs) toward photocatalytic hydrogen evolution. The incorporation of Au atoms into Ag25 NCs not only narrowed the HOMO-LUMO gaps but also created an interstitial Au-Ag microenvironment, which promoted the photogenerated charge carrier utilization and optimized the reaction dynamics.

Size transformation of Au nanoclusters for enhanced photocatalytic hydrogen generation: Interaction behavior at nanocluster/semiconductor interface.

Recently, atomically precise metal nanoclusters (NCs) become a new class of photosensitizer for light energy conversion in metal-cluster-sensitized semiconductor (MCSS) system. However, fundamental understanding for the suitable combination of NCs and semiconductor is still unclear. Aside from aspects of light harvesting, energy level alignment and catalytic activity, interfacial interaction behavior at NCs/semiconductor interface is also crucial due to its important influence in charge transportation. In this work, the interface interaction between Au NCs and TiO2 is examined by precise transformation of Au NCs from Au22(SG)18 to Au18(SG)14, as well as its effect on photocatalytic hydrogen production activity. From the optical, charge transport and solid-states spectroscopy analyses, it is able to display that precisely tuning the number of core atoms from Au22(SG)18 to Au18(SG)14 results in the strong interface interaction between Au NCs and TiO2, reflecting in high difference of work function and modified surface band bending of TiO2, therefore promoting the injection of electrons from NCs to TiO2 and reducing interfacial charges recombination. As a result, Au18(SG)14/TiO2 shows higher hydrogen generation rate than Au22(SG)18/TiO2 under light irradiation. This work would provide new insights into rational combination of metal NCs with semiconductor and highlights the overlooked effect of interfacial interaction behavior on light energy conversion.

[Analysis of Heavy Metal Pollution Characteristics and Potential Ecological Risks of Surface Sediments in Dongjiang Lake].

To understand the pollution characteristics, spatial distribution characteristics, potential ecological risks, and sources of heavy metals in surface sediments of Dongjiang Lake, 12 surface sediment samples were collected from Dongjiang Lake. The contents of 20 heavy metals including Li, Be, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, As, Se, Rb, Sr, Ag, Cd, Cs, Ba, Pb, and U were analyzed in this study. The geo-accumulation index method and potential risk index method were used to evaluate the pollution degree and potential risks of heavy metals in sediments, and the correlation analysis and principal component analysis were used to trace the source of the primary heavy metals. The results showed that the average contents of ω(Cd)(2.25 mg·kg-1) and ω(As)(80.80 mg·kg-1) in heavy metals of Dongjiang Lake sediments were 21.2 times and 5.5 times the background value (0.11 mg·kg-1 and 14.7 mg·kg-1) of Hunan province. The overall spatial distribution of heavy metals was in the order of South>North>Central. The evaluation by the geo-accumulation index method showed that Cd was at the heavy pollution level, As and Se were at the moderate pollution level, Ag and Ga were at the light pollution level, and the other heavy metals were below the pollution standard. The evaluation by the potential risk index showed that all the surface sediments of Dongjiang Lake were at the high-risk level. The main environmental risk factor was Cd, which had an extremely high risk; the second was As, which had a medium risk; and the remaining heavy metals had no ecological risk.

[Distribution Characteristics and Ecological and Health Risk Assessment of Phthalic Acid Esters in Surface Water of Qiandao Lake, China].

In order to reveal the pollution and risk level of phthalic acid esters (PAEs) in Qiandao Lake, six types of PAEs in 17 sampling points (in Qiandao Lake and its inflowing rivers) in dry and wet seasons were detected. The results showed that six types of PAEs were detected in both dry and wet seasons, with the concentrations of 0.98-5.33 µg·L-1 (average concentration 2.63 µg·L-1) in the dry season and 3.22-17.88 µg·L-1 (average concentration 7.99 µg·L-1) in the wet season. In terms of the detection rate and concentration of each monomer PAEs, DiBP, DBP, and DEHP were the main PAEs components in the water body. The measured value of DBP at 10 sampling points and its average mass concentration in the wet season were higher than the national standard (3 µg·L-1). Principal component analysis indicated that the main sources of PAEs were personal care products, plastics, and domestic waste. The pollution level of PAEs in Qiandao Lake was at a high level at home and abroad. The health risk assessment results in Qiandao Lake showed that the non-carcinogenic risk index of PAEs in the study area was less than 1, which would not produce non-carcinogenic risks to the human body. The carcinogenic risk index of children exceeded 10-6 at some points, indicating that it may pose carcinogenic risks to children, to which more attention should be paid.

Secondary Phosphine Oxide Functionalized Gold Clusters and Their Application in Photoelectrocatalytic Hydrogenation Reactions.

Ligands in ligand-protected metal clusters play a crucial role, not only because of their interaction with the metal core, but also because of the functionality they provide to the cluster. Here, we report the utilization of secondary phosphine oxide (SPO), as a new family of functional ligands, for the preparation of an undecagold cluster Au11-SPO. Different from the commonly used phosphine ligand (i.e., triphenylphosphine, TPP), the SPOs in Au11-SPO work as electron-withdrawing anionic ligands. While coordinating to gold via the phosphorus atom, the SPO ligand keeps its O atom available to act as a nucleophile. Upon photoexcitation, the clusters are found to inject holes into p-type semiconductors (here, bismuth oxide is used as a model), sensitizing the p-type semiconductor in a different way compared to the photosensitization of a n-type semiconductor. Furthermore, the Au11-SPO/Bi2O3 photocathode exhibits a much higher activity toward the hydrogenation of benzaldehyde than a TPP-protected Au11-sensitized Bi2O3 photocathode. Control experiments and density functional theory studies point to the crucial role of the cooperation between gold and the SPO ligands on the selectivity toward the hydrogenation of the C═O group in benzaldehyde.

[Local injection of BTX-A prevents iatrogenic anterior urethral stricture in rabbits].

OBJECTIVE: To investigate the preventive effect of local injection of botulinum toxin type A (BTX-A) against iatrogenic anterior urethral stricture (IAUS) in New Zealand male rabbits. METHODS: Sixteen adult New Zealand male rabbits were randomly divided into an experimental and a control group of equal number. The model of IAUS was established in the rabbits by incision of the ventral urethra of the penile segment and electrocoagulation of the urethral mucosa. The rabbits of the experimental group were injected with 10 U of BTX-A solution and those of the control group with 1.0 ml of normal saline into the electrocoagulated submucosa of the urethra. At 30 days after modeling, retrograde urethrography was performed and the scarred urethral tissue harvested for HE and Masson staining. RESULTS: No systemic symptoms of botulinum toxin poisoning were observed in either group of the rabbits. Retrograde urethrography showed statistically significant differences between the control and experimental groups in the diameter of the urethra (ï¼»0.15 ± 0.08ï¼½ vs ï¼»0.50 ± 0.23ï¼½ cm, P < 0.05) and the stenosis ratio (3.68 ± 1.22 vs 1.29 ± 0.15, P < 0.05). Urethrography revealed obvious hyperplasia and contracture of urethral scar with high bulge and narrow urethral cavity, while HE and Masson staining exhibited absence or discontinuity of the urethral epithelium, submucosal fibrosis with infiltration of a large number of fibroblasts, and hyperplasia and thickening of collagen fibers (blue) in the control group. All the changes above were slight and the urethral epithelium was continuous in the experimental group. CONCLUSIONS: Local injection of BTX-A reduced the incidence of iatrogenic anterior urethral stricture after iatrogenic acute heat injury in New Zealand male rabbits.

Insights into Charge Transfer at an Atomically Precise Nanocluster/Semiconductor Interface.

The deposition of an atomically precise nanocluster, for example, Ag44 (SR)30 , onto a large-band-gap semiconductor such as TiO2 allows a clear interface to be obtained to study charge transfer at the interface. Changing the light source from visible light to simulated sunlight led to a three orders of magnitude enhancement in the photocatalytic H2 generation, with the H2 production rate reaching 7.4 mmol h-1 gcatalyst -1 . This is five times higher than that of TiO2 modified with Ag nanoparticles and even comparable to that of TiO2 modified with Pt nanoparticles under similar conditions. Energy band alignment and transient absorption spectroscopy reveal that the role of the metal clusters is different from that of both organometallic complexes and plasmonic nanoparticles: A type II heterojunction charge-transfer route is achieved under UV/Vis irradiation, with the cluster serving as a small-band-gap semiconductor. This results in the clusters acting as co-catalysts rather than merely photosensitizers.

Facile Synthesis of a Porous ZnO Nanorod Array with Enhanced Photocatalysis for Photoelectrochemical Water Splitting Application.

Highly efficient and effective porous ZnO nanorod arrays were fabricated by annealing ZnO nanorod arrays grown on a substrate using a simple hydrothermal method. The annealing had a positive effect on the nanorod morphology, structure and optical properties. The porosity was closely related to the annealing temperature. After heating at 450 °C, pores appeared on the nanorods. It was demonstrated that the porosity could be exploited to improve the visible light absorption of ZnO and reduce the bandgap from 3.11 eV to 2.99 eV. A combination of improved charge separation and transport of the heat-treated ZnO thus led to an increase in the photoelectrochemical properties. At an irradiation intensity of 100 mW/cm-2, the photocurrent density of the porous nanorod array was approximately 1.3 mA cm-2 at 1.2 V versus Ag/AgCl, which was five times higher than that of the ZnO nanorods. These results revealed the synthesis of promising porous ZnO nanorods for photoelectrochemical applications.

Multi-functional photocatalytic fuel cell for simultaneous removal of organic pollutant and chromium (VI) accompanied with electricity production.

It is of significant importance to realize the efficient wastewater treatment and energy recovery. This study presents a multi-functional photocatalytic fuel cell (PFC), which could reductively treat Cr(VI) contaminant and oxidatively degrade organic pollutant simultaneously along with electricity production in an economical strategy. TiO2 nanotube arrays (TNA) and graphite were used as photoanode and cathode in two separated chambers, respectively. The optimized PFC with open circuit voltage of 1.06 V, maximum power density of 1 W m-2 and short circuit current density of 3.7 A m-2 can be obtained by increasing Cr(VI) concentration and decreasing pH values in catholyte. Under optimized PFC conditions, more photogenerated electrons will be transferred to cathode for Cr(VI) reduction, and accelerating electron-hole separation in the photoanode, then facilitating the oxidation of organic pollutants on anode. More than 96.8% removal efficiency for 6.8 mM Cr(VI) with a cathodic efficiency of 95.1% can be achieved within 6 h. Methylene blue (MB), an organic model pollutant, is totally decolorized on photoanode, which is significantly improved compare to photocatalysis (61.5% removal efficiency). The stable cycle operation of this economical PFC has obtained owing to the stable and low cost materials of both photoanode and cathode. This work may provide an efficient and economical method to simultaneously remove two types of pollutants with electricity harvested in one cell.

A new family of dinuclear lanthanide complexes constructed from an 8-hydroxyquinoline Schiff base and ß-diketone: magnetic properties and near-infrared luminescence.

Six phenoxo-O bridged dinuclear lanthanide(iii) complexes have been assembled utilizing the 2-[(4-nitrophenyl)imino]methyl-8-hydroxyquinoline (HL) and dibenzoylmethane (Hdbm) ligands: [Ln2(dbm)4L2] (Ln = Nd (1), Eu (2), Gd (3), Tb (4), Dy (5) and Er (6)). Complexes 1 and 6 exhibit the characteristic emission peaks of the corresponding Nd3+ and Er3+ ions, respectively. Meanwhile, the excitation wavelength (470 nm) for complex 1 is located in the visible-light region, confirming a practical application value. The studies on magnetic properties reveal that complex 3 features a magnetocaloric effect with a magnetic entropy change of -ΔSm = 14.36 J kg-1 K-1 at 4 K for ΔH = 7 T. What's more, the dynamic magnetic studies for complex 5 show that it exhibits slow magnetic relaxation behavior, typical of SMM behavior, resulting in an energy barrier of ΔE/kB = 75 K with the pre-exponential factor τ0 = 2.2 × 10-7 s. Meanwhile, this research demonstrates that the magnetic properties can be modulated by regulating the electron-donating/withdrawing effects of the substituents on the ligands.

Atomically Precise Bimetallic Nanoclusters as Photosensitizers in Photoelectrochemical Cells.

The atomically precise bimetallic nanocluster (NC), Au24 Ag20 (PhCC)20 (SPy)4 Cl2 (1) (Py=pyridine), was employed for the first time as a stable photosensitizer for photoelectrochemical applications. The sensitization of TiO2 nanotube arrays (TNA) with 1 greatly enhances the light-harvesting ability of the composite because 1 shows a high molar extinction coefficient (ϵ) in the UV/Vis region. Compared to a more standard Au25 (SG)18 -TNA (2-TNA; SG=glutathione) composite, 1-TNA shows a much better stability under illumination in both neutral and basic conditions. The precise composition of the photosensitizers enables a direct comparison of the sensitization ability between 1 and 2. With the same cluster loading, the photocurrent produced by 1-TNA is 15 times larger than that of 2-TNA. The superior performance of 1-TNA over 2-TNA is attributed not only to the higher light absorption ability of 1 but also to the higher charge-separation efficiency. Besides, a ligand effect on the stability of the photoelectrode and charge-transfer between the NCs and the semiconductor is revealed. This work paves the way to study the role of metal nanoclusters as photosensitizers at the atomic level, which is essential for the design of better material for light energy conversion.

Sequential recovery of copper and nickel from wastewater without net energy input.

A novel bioelectrochemical system (BES) was designed to recover copper and nickel from wastewater sequentially. The BES has two chambers separated by a bipolar membrane and two cathodes. Firstly, the copper ions were reduced on a graphite cathode with electricity output, and then with an additional bias-potential applied, the nickel ions were recovered sequentially on a copper sheet with electricity input. In this design, nickel and copper can be recovered and separated sequentially on two cathodes. By adjusting the molar ratio of copper and nickel ions to 2.99:1 in wastewater, 1.40 mmol Cu²âº could be recovered with 143.78 J electricity outputs, while 50.68 J electricity was input for 0.32 mmol nickel reduction. The total energy output of copper recovery was far more than the electricity input of nickel reduction. The present technology provides a potential method for heavy metal ion separation and recovery.