Micro-Raman and FTIR Spectroscopic Observation on the Phase Transitions of MnSO4 Droplets and Ionic Interactions between Mn2+ and SO42−

Manganese Sulfate Nanocomposites Fabricated by Hot-Melt Extrusion for Chemodynamic Therapy of Colorectal Cancer

The development of metal salts-based nanocomposites is highly desired for the Fenton or Fenton-like reaction-based chemodynamic therapy of cancer. Manganese sulfate (MnSO₄)-dispersed nanoparticles (NPs) were fabricated with a hot-melt extrusion (HME) system for the chemodynamic therapy of colorectal cancer in this study. MnSO₄ was homogeneously distributed in polyethylene glycol (PEG) 6000 (as a hydrophilic polymer) with the aid of surfactants (Span 80 and Tween 80) by HME processing. Nano-size distribution was achieved after dispersing the pulverized extrudate of MnSO₄-based composite in the aqueous media. The distribution of MnSO₄ in HME extrudate and the interactions between MnSO₄ and pharmaceutical additives were elucidated by Fourier-transform infrared, X-ray diffractometry, X-ray photoelectron spectroscopy, and scanning electron microscopy analyses. Hydroxyl radical generation efficiency by the Fenton-like chemistry capability of Mn²⁺ ion was also confirmed by catalytic assays. By using the intrinsic H₂O₂ in cancer cells, MnSO₄ NPs provided an elevated cellular reactive oxygen species level, apoptosis induction capability, and antiproliferation efficiency. The designed HME-processed MnSO₄ formulation can be efficiently used for the chemodynamic therapy of colorectal cancer.

Boosting the Areal Capacity of Titanium-Manganese Single Flow Battery by Fe2+ /Fe3+ Redox Mediator

Aqueous manganese-based flow batteries (AMFBs) have attracted great attention due to the advantages of low cost and environmental friendliness. Extending the cycle life of AMFBs has long been a challenging theme. The titanium-manganese single-flow batteries (TMSFB) are promising due to their special structure and electrolyte composition. However, TMSFB with high areal capacity faces capacity decay for unknown reasons. In this work, the capacity decay mechanism (accumulation and growth of MnO₂ ) is clarified by a homemade in situ microscope system. Given that, a redox mediator of Fe²⁺ /Fe³⁺ is specially designed to boost the areal capacity of TMSFB without side reaction. The directional promoting principle of the Fe²⁺ /Fe³⁺ is elaborated in detail. Fe²⁺ chemically reacts with the residual MnO₂ to form Fe³⁺ , which is reduced to Fe²⁺ by the electrochemical reaction. And then Fe²⁺ continues reacting with MnO₂ until MnO₂ is consumed completely. As a result, the TMSFB with the areal capacity of ≈55 mA h cm^-2 can stably operate at a current density of 40 mA cm^-2 , which is the highest areal capacity reported in aqueous manganese-based batteries. This work provides a new strategy for boosting the capacity of manganese-based batteries, shedding light on the improvement of other deposition-type batteries.

Coordination with zirconium: A facile approach to improve the mechanical properties and thermostability of gelatin hydrogel

The poor mechanical property and thermostability restricted applications of gelatin hydrogel. Herein, a facile and inexpensive approach of immerging cooling induced gelatin hydrogels into Zr(SO₄)₂ dilute solution was applied to overcome these shortages. After this treatment, the micropores in hydrogel decreased to tens of microns while the water content slightly decreased. XPS results revealed that the coordination bonds formed between amino or carboxyl groups of gelatins and Zr⁴⁺. After immerging in 0.06 M Zr⁴⁺ solution, mechanical tests showed that the elastic modulus, compressive modulus and compressive strength of hydrogel were about 400, 1192 and 476 kPa, respectively, which were approximate 100, 11 and 5 times larger than those of pure gelatin. The DSC data indicated that the thermoreversible temperature of triple helix structure in gelatin was improved from about 30 °C to 55 °C. More importantly, the rheological temperature sweep test revealed that hydrogels with 0.06 M Zr⁴⁺ treatment can maintain the hydrogel state without melting even at 80 °C. CCK-8 tests and Calcein-AM/PI double-stain experiments demonstrated Zr⁴⁺ coordination was non-cytotoxic. These promising data indicated this nontoxic method was efficient and had potential to fabricate gelatin related materials for further application.

Reunderstanding the Reaction Mechanism of Aqueous Zn-Mn Batteries with Sulfate Electrolytes: Role of the Zinc Sulfate Hydroxide

Rechargeable aqueous Zn-Mn batteries have garnered extensive attention for next-generation high-safety energy storage. However, the charge-storage chemistry of Zn-Mn batteries remains controversial. Prevailing mechanisms include conversion reaction and cation (de)intercalation in mild acid or neutral electrolytes, and a MnO₂ /Mn²⁺ dissolution-deposition reaction in strong acidic electrolytes. Herein, a Zn₄ SO₄ ·(OH)₆ ·xH₂ O (ZSH)-assisted deposition-dissolution model is proposed to elucidate the reaction mechanism and capacity origin in Zn-Mn batteries based on mild acidic sulfate electrolytes. In this new model, the reversible capacity originates from a reversible conversion reaction between ZSH and Zn_x MnO(OH)₂ nanosheets in which the MnO₂ initiates the formation of ZSH but contributes negligibly to the apparent capacity. The role of ZSH in this new model is confirmed by a series of operando characterizations and by constructing Zn batteries using other cathode materials (including ZSH, ZnO, MgO, and CaO). This research may refresh the understanding of the most promising Zn-Mn batteries and guide the design of high-capacity aqueous Zn batteries.

Role of Sulfur Trioxide (SO3) in Gas-Phase Elemental Mercury Immobilization by Mineral Sulfide

Mineral sulfide based sorbents were superior alternatives to traditional activated carbons for elemental mercury (Hg⁰) immobilization in industrial flue gas. A systematical study concerning the influence of sulfur trioxide (SO₃) on Hg⁰ adsorption over a nanosized copper sulfide (Nano-CuS) was for the first time conducted. SO₃ was found to significantly inhibit the Hg⁰ removal over Nano-CuS partially because SO₃ oxidized the reduced sulfur species (sulfide) with high affinity to mercury to its oxidized sulfur species (sulfate). Moreover, a brand new "oxidation-reduction" mechanism that led to a simultaneous oxidation of sulfide and reduction of mercury on the immobilized mercury sulfide (HgS) was responsible for the inhibitory effect. Even though the released Hg⁰ from the reduction of mercury in HgS could be oxidized by SO₃ into its sulfate form (HgSO₄) and recaptured by the sorbent, the "oxidation-reduction" mechanism still compromised the Hg⁰ capture performance of the Nano-CuS because HgSO₄ deposited on the sorbent surface could be easily leached out when environmentally exposed. These new insights into the role of SO₃ in Hg⁰ capture over Nano-CuS can help to determine possible solutions and facilitate the application of mineral sulfide sorbents as outstanding alternatives to activated carbons for Hg⁰ immobilization in industrial flue gas.

A Facile Method for Batch Preparation of Electrochemically Reduced Graphene Oxide

The electrochemical reduction of graphene oxide (GO) is an environmentally friendly and energy-saving method for improving the characteristics of GO. However, GO films must be coated on the cathode electrode in advance when usingthis technique. Thus, the formed electrochemically reduced GO (ERGO) films can be used only as sensing or conductive materials in devices because mass production of the flakes is not possible. Therefore, this study proposes a facile electrochemical reduction technique. In this technique, GO flakes can be directly used as reduced materials, and no GO films are required in advance. A 0.1 M phosphate buffered saline solution was used as the electrolyte, which is a highly safe chemical agent. Experimental results revealed that the as-prepared GO flakes were electrochemically reduced to form ERGO flakes by using a -10 V bias for 8 h. The ratio of the D-band and G-band feature peaks was increased from 0.86 to 1.12, as revealed by Raman spectroscopy, the π-π stacking interaction operating between the ERGO and GO has been revealed by UV-Vis absorption spectroscopy, and the C⁻O ratio was increased from 2.02 to 2.56, as indicated by X-ray photoelectron spectroscopy. The electrical conductivity of the ERGO film (3.83 × 10^-1 S·cm^-1) was considerably better than that of the GO film (7.92 × 10^-4 S·cm^-1). These results demonstrate that the proposed electrochemical reduction technique can provide high-quality ERGO flakes and that it has potential for large-scale production.

Elucidating "screw dislocation"-driven film formation of sodium thiosulphate with complex hierarchical molecular assembly

Sodium thiosulphate (Na₂S₂O₃) films were synthesized on carbon steel substrates through solution deposition, and a film formation growth mechanism is delineated in detail herein. Dislocation-driven film formation took place at the lower concentration of Na₂S₂O₃ (0.1 M) studied, where screw dislocation loops were identified. Interestingly, we observed the co-existence of screw dislocation spiral loops and hierarchically-ordered molecular assembly in the film, and showed the importance of hierarchical morphology in the origin of screw dislocation. The screw dislocation loops were, however, distorted at the higher studied concentration of Na₂S₂O₃ (0.5 M), and no hierarchical structures were formed. The mechanisms of film formation are discussed in detail and provide new insights into our understanding regarding morphology of the hierarchical molecular assembly, screw dislocation loop formation, and the role of chemical elements for their development. The main crystalline and amorphous phases in the surface films were identified as pyrite/mackinawite and magnetite. As sodium thiosulphate is widely used for energy, corrosion inhibition, nanoparticle synthesis and catalysis applications, the knowledge generated in this study is applicable to the fields of corrosion, materials science, materials chemistry and metallurgy.

Novel nanoporous MnOx (x=∼1.75) sorbent for the removal of SO2 and NH3 made from MnC2O4·2H2O

In this work, nanoporous manganese oxides (MnOx) were prepared by thermal decomposition of MnC2O4·2H2O at 225°C for 6h in air. The manganese oxalate dihydrate precipitate was made from manganese sulfate and ammonium oxalate during ultrasonication and stirring. The physical properties of the oxalate precursors and the resulting MnOx samples were characterized with SEM, TGA-DSC, FTIR and powder XRD. The specific surface areas and porosity of MnOx were studied by single-point BET and multi-point N2 adsorption-desorption measurements. The amorphous MnOx from oxalate prepared by sonication showed a specific surface area as large as 499.7m(2)/g. Dynamic SO2 and NH3 flow tests indicated that the adsorption capacity of MnOx, especially for SO2, can be increased by increased surface area. Compared to the best Mn3O4-impregnated activated carbon adsorbent, nanoporous MnOx could remove approximately three times as much SO2 and a comparable amount of NH3 per gram of adsorbent. This could lead to respirators of lower weight and smaller size which will be attractive to users.

Microscopic study of the corrosion behaviour of mild steel in ionic liquids for CO2 capture applications

Exposure of mild steel to ionic liquids (IL) results in two main types of degradation that may be significantly limited by addition of molybdate without affecting the IL's CO₂ capture performance.

Micro-Raman observation on the HPO4(2-) association structures in an individual dipotassium hydrogen phosphate (K2HPO4) droplet

A single K(2)HPO(4) droplet with size of ∼50 μm on a Teflon substrate was forced to enter into the supersaturated state by decreasing the relative humidity (RH), allowing accurate control over the concentration of the solute within a droplet of a nanogram. The K(2)HPO(4) solutions from dilute (0.1-1.0 mol·L(-1) bulk) to concentrated state (a droplet from RH 98.2% to 25.1%) were studied through micro-Raman spectroscopy in the spectral region of about 200-4000 cm(-1). The area ratio between the water stretching band to the sum of the ν(1)-PO(3), ν(2)-POH, and ν(4)-PO(3) bands of the HPO(4)(2-) at various RHs was used to describe the dehydration behavior of a microsized single K(2)HPO(4) droplet in dehumidifying process. The peak position of the v(1)-PO(3) band for the 1 mol·L(-1) bulk solution appeared at 991 cm(-1) and moved to 986 cm(-1) at 98.2% RH, to 978 cm(-1) at 70.2% RH, and then to 964 cm(-1) at 30.0% RH for a droplet, accompanying an increase of the full width at half-height (fwhh) of this peak from 16.3 to 17.2, 22.2, and then to 24.2 cm(-1), indicating transition of the HPO(4)(2-) anions from monomers to dimers/trimers/oligomers and then to polyanions with chain structures in the K(2)HPO(4) solutions. After 25.1% RH, the solid was proved to be K(2)HPO(4)·3H(2)O according to the Raman spectral features. Furthermore, the O-H stretching envelope of a K(2)HPO(4) droplet showed that the intensity ratios of the strong hydrogen bonding component (3255 cm(-1)) to the weak one (3417 cm(-1)) and the cage-like water (2925 cm(-1)) to the weak one (3417 cm(-1)) were sensitive to the HPO(4)(2-) association structures, which can be used to understand the effects of dimers/trimers/oligomers and chain structures of the HPO(4)(2-) associations on the hydrogen bonding of water molecules.

High-quality thin graphene films from fast electrochemical exfoliation

Flexible and ultratransparent conductors based on graphene sheets have been considered as one promising candidate for replacing currently used indium tin oxide films that are unlikely to satisfy future needs due to their increasing cost and losses in conductivity on bending. Here we demonstrate a simple and fast electrochemical method to exfoliate graphite into thin graphene sheets, mainly AB-stacked bilayered graphene with a large lateral size (several to several tens of micrometers). The electrical properties of these exfoliated sheets are readily superior to commonly used reduced graphene oxide, which preparation typically requires many steps including oxidation of graphite and high temperature reduction. These graphene sheets dissolve in dimethyl formamide (DMF), and they can self-aggregate at air-DMF interfaces after adding water as an antisolvent due to their strong surface hydrophobicity. Interestingly, the continuous films obtained exhibit ultratransparency (∼96% transmittance), and their sheet resistance is <1k Ω/sq after a simple HNO3 treatment, superior to those based on reduced graphene oxide or graphene sheets by other exfoliation methods. Raman and STM characterizations corroborate that the graphene sheets exfoliated by our electrochemical method preserve the intrinsic structure of graphene.