Unraveling the potential-dependent structure evolution in CuO for electrocatalytic biomass valorization.

Electrocatalytic oxidation of renewable biomass (such as glucose) into high-value-added chemicals provides an effective approach to achieving carbon neutrality. CuO-derived materials are among the most promising electrocatalysts for biomass electrooxidation, but the identification of their active sites under electrochemical conditions remains elusive. Herein, we report a potential-dependent structure evolution over CuO in the glucose oxidation reaction (GOR). Through systematic electrochemical and spectroscopic characterizations, we unveil that CuO undergoes Cu2+/Cu+ and Cu3+/Cu2+ redox processes at increased potentials with successive generation of Cu(OH)2 and CuOOH as the active phases. In addition, these two structures have distinct activities in the GOR, with Cu(OH)2 being favorable for aldehyde oxidation, and CuOOH showed faster kinetics in carbon-carbon cleavage and alcohol/aldehyde oxidation. This work deepens our understanding of the dynamic reconstruction of Cu-based catalysts under electrochemical conditions and may guide rational material design for biomass valorization.

Identification of Active Sites Formed on Cobalt Oxyhydroxide in Glucose Electrooxidation.

Transition-metal-based oxyhydroxides are efficient catalysts in biomass electrooxidation towards fossil-fuel-free production of valuable chemicals. However, identification of active sites remains elusive. Herein, using cobalt oxyhydroxide (CoOOH) as the archetype and the electrocatalyzed glucose oxidation reaction (GOR) as the model reaction, we track dynamic transformation of the electronic and atomic structure of the catalyst using a suite of operando and ex situ techniques. We reveal that two types of reducible Co3+ -oxo species are afforded for the GOR, including adsorbed hydroxyl on Co3+ ion (µ1 -OH-Co3+ ) and di-Co3+ -bridged lattice oxygen (µ2 -O-Co3+ ). Moreover, theoretical calculations unveil that µ1 -OH-Co3+ is responsible for oxygenation, while µ2 -O-Co3+ mainly contributes to dehydrogenation, both as key oxidative steps in glucose-to-formate transformation. This work provides a framework for mechanistic understanding of the complex near-surface chemistry of metal oxyhydroxides in biomass electrorefining.

Anion exchange behavior of MIIAl layered double hydroxides: a molecular dynamics and DFT study.

The ion exchange reaction has been extensively used in the field of synthesis of functionalized supramolecular materials such as layered double hydroxides (LDHs), ion-embedded batteries, sewage disposal and so on. In this work, the factors influencing the anion exchange behavior in the LDH gallery, such as the exchange domain, the exchange order, the driving force, and the diffusion of the anions, are investigated systematically using molecular dynamics (MD) simulations and density functional theory (DFT) methods in view of both thermodynamics and dynamics. 159 models of MIIRAl-A-LDHs (MII = Mg, Ni, Zn; R = 1.4-8, A = OH-, Cl-, Br-, NO3-, HCOO-, C6H5SO3-, CO32-, SO42-, and PO43-, respectively) are calculated. The results reveal that the anion exchange domain (interlayer distance) in LDHs is determined not only by the size and their arrangement modes of the guest anions, but also by the charges the anions carry. The relative binding energies of different anions and the Gibbs free energy changes of the anion exchange reactions in LDHs decrease in the order of PO43- > CO32- > SO42- > OH- > Cl- > Br- > HCOO- > NO3- > C6H5SO3-, which is in accordance with the experimental anion exchange order. The stronger the hydrogen bonding between the anion and the host, the larger the charge transfer, and the smaller the electronegativity of the anion, the more difficult it is for the anion to be exchanged out from LDH interlayer. In addition, for the anions with the same charges, the relative binding energy is linearly well correlated with the interlayer spacing. By analyzing the contribution of each energetic item comprising the total potential energy, it is found that the major driving force of anion exchange is the electrostatic force. The diffusion coefficient (D) along the c direction is nearly equal to zero, suggesting that the diffusion of anions occurs mainly in the ab plane of the LDH cell. It also can be inferred that when the cell parameter c < 24.0 Å, the anion exchange order is mainly determined by the thermodynamic factors, whereas when c > 24.0 Å, both the thermodynamic and the dynamic factors cast the same effect on the anion exchange behavior. This work provides an in-depth understanding of the anion exchange behavior, and is helpful guidance for the design and synthesis of functionalized guest anion intercalated LDHs and related materials using the anion-exchange method.

Correction: Manganese-based layered double hydroxide nanoparticles as highly efficient ozone decomposition catalysts with tunable valence state.

Correction for 'Manganese-based layered double hydroxide nanoparticles as highly efficient ozone decomposition catalysts with tunable valence state' by Siyu Wang et al., Nanoscale, 2020, 12, 12817-12823, DOI: 10.1039/D0NR02796K.

Manganese-based layered double hydroxide nanoparticles as highly efficient ozone decomposition catalysts with tunable valence state.

Manganese oxides are well explored effective ozone decomposition catalysts, but the accumulation of oxygen trapped on their surfaces and high valence state restrict their catalyst efficiency. Herein, we report manganese based layered double hydroxide (LDH) catalysts with different average oxidation states (AOS) of Mn. MgMnAl-LDH catalysts show large specific surface area, abundant oxygen vacancies, stable structure and excellent catalytic ozone decomposition performance. The valence state of Mn can be tuned by adjusting the metallic element ratio in the LDH matrix, and a catalyst with AOS of only 2.3 is acquired. The impacts of the valence states of Mn on the catalytic ozone decomposition process were further studied by density functional theory (DFT) calculations. It is found that the Mn2+ facilitates the desorption of generated oxygen on the surface of LDHs, while Mn3+ and Mn4+ contribute to the dissociation of adsorbed ozone.

DFT study on MgAl-layered double hydroxides with different interlayer anions: structure, anion exchange, host-guest interaction and basic sites.

The guest anions play a key role in the construction of layered double hydroxide (LDH)-based host-guest functional materials. In this work, the orientation of the interlayer species, interlayer distances, binding energies, electronic density differences and density of states of the MgnAl-LDHs (n = 1.6, 2.0, 2.6, 3.5, 5.0, and 8.0) with nine different anions (F-, Cl-, Br-, I-, OH-, NO3-, CO32-, SO42-, and PO43-) are calculated by density functional theory (DFT). The results reveal that the LDHs containing the anions with more inclined arrangement, larger size, lower charge and with a larger number of interlayer water molecules show larger interlayer distances. The higher anion charge leads to a larger binding energy for LDHs, and the order of binding energy implies that the sequence of anion exchange is PO43- > CO32- > SO42- > OH- > F- > Cl- > Br- > NO3- > I-. The interactions between interlayer species and the host layer or the interlayer water molecules are mainly derived from the electrostatic interactions. The main components of the valence band maximum (VBM) and conduction band minimum (CBM) of MgAl-LDHs are derived from p orbitals of halogen anions or the O-2p orbitals of other anions, and the Mg-2p orbital, respectively. This illustrates that the most basic sites of MgAl-LDHs are the interlayer anions rather than the hydroxyl group in the layer, while the most acidic sites are Mg in the layers. And LDHs containing anions with higher charge show stronger basicity. The calculation results agree well with the experimental findings. This work provides effective theoretical information for the design and preparation of the anion-controlled functional LDHs or related materials with prospective applications.

Upregulation of SCC-S2 in immune cells and tumor tissues of papillary thyroid carcinoma.

Studies have shown that SCC-S2 can be detected in cancer cells, but its relation with thyroid cancer remains uncertain. In the current study, we investigated SCC-S2 expression in thyroid cancer from the immune cell perspective and tumor tissue perspective. Levels of SCC-S2 in CD4+ T cells, CD8+ T cells, monocytes, natural killer (NK) T cells, tumor tissues, and adjacent noncancerous thyroid tissues were tested by real-time reverse transcription PCR and Western blot. Results revealed that mRNA and protein levels of SCC-S2 were significantly increased in peripheral CD4+ (mRNA, 1.90-fold; protein, 1.55-fold) and CD8+ T cells (mRNA, 2.37-fold; protein, 1.72-fold) but not monocytes and NKT cells in patients than in healthy donors. Further elevated mRNA level but not protein expression was observed in tumor-infiltrating CD4+ T cells, whereas both mRNA level and protein expression were further increased in tumor-infiltrating CD8+ T cells. Also, mRNA and protein levels of SCC-S2 in thyroid tissues were significantly elevated than those in adjacent noncancerous thyroid tissues. Moreover, patients with cervical lymph node metastasis presented clearly higher mRNA and protein expression of SCC-S2 compared to those without cervical lymph node metastasis (p < 0.05). These results suggest that SCC-S2 may play roles in affecting both immune cells and tumor cells in the thyroid and may indicate a novel pathway for understanding the pathogenesis of the disease.

Radioimmunoimaging with mixed monoclonal antibodies of nude mice bearing human lung adenocarcinoma xenografts.

The present study was conducted to evaluate radioimmunoimaging (RII) and in vivo distribution of mixed antibodies 99mTc-EGFR-mAb and 99mTc-CD44- mAb in nude mice bearing human lung adenocarcinoma xenografts. Single and mixed applications of the two radiolabeled monoclonal antibodies (mAbs) were compared. Direct labeling of 99mTc was applied to radiolabel the EGFR and CD44 mAbs. The properties of the radiolabeled antibodies were then characterized. RII and assessment of the distribution of the antibodies in nude mice bearing lung adenocarcinoma xenografts were achieved by applying separate and combined doses of 99mTc-EGFR-mAb and 99mTc-CD44-mAb. The labeling rates of 99mTc for EGFR-mAb and CD44-mAb were 91.5% ±3.8% and 92.3% ± 4.1% respectively, with specific activities of 2.8 and 2.9 MBq/µg, respectively, and radiochemical purities (RCP) of 96.5% and 96.2%. The radioactivity uptake of the combined application of both radiolabeled antibodies was clearly higher than with a single application of either alone. The relative values of target-to-nontarget (T/ NT) measured through the regional interest (ROI) technique were 5.59 ± 0.42 (mixed antibodies), 2.78 ±0.20 (99mTc-EGFR-mAb), and 2.28 ± 0.16 (99mTc-CD44-mAb) in the RII. The body distribution of the radiolabeled antibodies and their imaging results were basically identical. Application of the mixed antibodies with 99mTc- EGFR-mAb and 99mTc-CD44-mAb can increase the radioactivity uptake of tumor tissue, leading to more ideal target-to-nontarget ratios, and therefore superior results.