Monodisperse State Research Articles

Solution-processed ZnO quantum dot thin films with low solvent residues and ultra-flat surfaces

ZnO quantum dots are considered a desirable material for the electron transport layer (ETL) in thin-film optoelectronic devices, determining their efficiency and stability. Solution-processed ZnO quantum dot films are fascinating due to the potential for low-cost manufacture of large-area devices and the compatibility with flexible substrates. However, eliminating solvent residues from solution-derived ZnO films remains a challenge, as their presence can significantly impact the efficiency and performance of the devices. Herein, we reported a straightforward and controllable strategy to overcome the above problem, aiming to achieve low solvent residues and ultra-flat ZnO films. Methanol, with its low boiling point and high relative evaporation rate, is utilized as a dispersing solvent for ZnO quantum dots, the resulting thin films exhibit low solvent residue, as confirmed by TGA and NMR analyses. Moreover, we achieved a stable monodisperse state of ZnO quantum dots in methanol solvent for three months by a simple temperature control method. The ZnO film prepared using a low-temperature spin-coating technique demonstrates extremely low surface roughness (RMS less than 1 nm).

Optimization of surface filtration to enhance wafer uniformity by removing large particle in ceria slurry

Owing to the limitations of scaling down, the development of complex structures for chip design is progressing in the semiconductor industry. As a result, the chemical mechanical polishing (CMP) process has become essential for the precise control of micro-level steps and for maintaining surface uniformity between layers during the stacking process. Structural management and improved performance of the consumables used in CMP processes are required. In particular, controlling the abrasive particles in the slurry that directly contact the wafer surface is crucial. Large particles within the slurry can occur scratches and cause non-uniformity in the polishing process, thus the particle size distribution of the slurry must be regulated. In this study, two types of filtration systems were constructed to determine the optimal conditions for CMP of ceria slurry. Depth filtration effectively removes particles through a cake layer formation mechanism but has limitations in achieving a consistent pore size within the fiber layer. Consequently, separation efficiency for particle sizes is relatively low. In contrast, surface filtration consisting of a single membrane demonstrates a consistent correlation between pore size and the size of the filtered particles, resulting in high particle removal efficiency. The pore size capable of removing large particles without active particle loss was 200 nm. After evaluating slurry productivity and filter-induced agglomeration, 0.8 L per minute (LPM) was identified as the optimal flow rate. Additionally, after filtration at 0.8 LPM, the maximum reduction in removal rates was relatively small at 272.54 Å/min due to decreased edge removal rates. However, by removing large particles to implement a monodisperse state, an improvement in uniformity of 17.11 % was achieved. Therefore, the CMP performance can be enhanced using surface filtration to control the particle size distribution (PSD).

Porous liquids assisted in-situ generated Co-LDH@MOF heterostructure with abundant defects for flame retardant and mechanical enhancement in polyurea composites

Preventing aggregation and inducing homogeneous dispersion of flame retardant nanofillers is critical to enhance the fire safety and mechanical properties of nanocomposites. Although chemical modifications are commonly used to improve the filler’s compatibility with the polymer chain, such methods are often cumbersome and limited. Herein, porous liquids (PLs) with flame retardant function were constructed in which porous defect-Co-LDH@ZIF-67 (d-LDH@ZIF) heterostructure particles were converted into liquid materials by electrostatic interaction with a large-volume solvent. This is also the first report of PLs in the field of flame retardant. Specifically, the d-LDH@ZIF heterostructure was designed by defect engineering and in situ growth strategy to compensate for the low catalytic activity and specific surface area of Co-LDH, and to serve as a rigid porous framework for PLs. Numerous cobalt/oxygen vacancies and lattice defects in the d-LDH@ZIF heterostructure have also been proven to confer higher flame retardancy relative to Co-LDH. d-LDH@ZIF porous liquids (PLs-d-L@Z) presents favorable liquid characteristics and achieves a monodisperse state in the polyurea matrix. The limiting oxygen index of polyurea composites blended with 20 wt% PLs-d-L@Z (3 wt% d-LDH@ZIF content) can be increased to 24.2 % and pass the V-0 rating in the UL-94 test. Moreover, the peak of heat release rate, total heat release, and total smoke production are reduced by around 40.4, 27.0, and 39.9 %, respectively, compared to neat polyurea. Emphatically, the PLs-modified polyurea composites exhibit significantly improved mechanical and impact resistance properties, as well as favorable chemical resistance. This strategy of liquefying solid flame retardant fillers will open an avenue to the design of functional nanomaterials for fire safety and other potential applications.

Structure elucidation of a multi-modular recombinant endoglucanase, AtGH9C-CBM3A-CBM3B from Acetivibrio thermocellus ATCC 27405 and its substrate binding analysis

Cellulases from GH9 family show endo-, exo- or processive endocellulase activity, but the reason behind the variation is unclear. A GH9 recombinant endoglucanase, AtGH9C-CBM3A-CBM3B from Acetivibrio thermocellus was structurally characterized for conformation, binding and dynamics assessment. Modeled AtGH9C-CBM3A-CBM3B depicted (α/α)6-barrel structure with Asp98, Asp101 and Glu489 acting as catalytic triad. CD results revealed 25.2 % α-helix, 18.4 % β-sheet and rest 56.4 % of random coils, corroborating with predictions from PSIPRED and SOPMA. MD simulation of AtGH9C-CBM3A-CBM3B bound cellotetraose showed structural stability and global compactness with lowered RMSD values (1.5 nm) as compared with only AtGH9C-CBM3A-CBM3B (1.8 nm) for 200 ns. Higher fluctuation in RMSF values in far-positioned CBM3B pointed to its redundancy in substrate binding. Docking studies showed maximum binding with cellotetraose (ΔG = −5.05 kcal/mol), with reduced affinity towards ligands with degree of polymerization (DP) lower (DP < 4) or higher than 4 (DP > 4). Processivity index displayed the enzyme to be processive with loop 3 (342–379 aa) possibly blocking the non-reducing end of cellulose chain, resulting in cellotetraose release. SAXS analysis of AtGH9C-CBM3A-CBM3B at 5 mg/mL displayed monodispersed state with fist-and-elbow shape in solution. Negative zeta potential of −24 mV at 5 mg/mL indicated stability and free from aggregation.

Facet-dependent dispersion and aggregation of aqueous hematite nanoparticles.

Nanoparticle aggregates in solution controls surface reactivity and function. Complete dispersion often requires additive sorbents to impart a net repulsive interaction between particles. Facet engineering of nanocrystals offers an alternative approach to produce monodisperse suspensions simply based on facet-specific interaction with solvent molecules. Here, we measure the dispersion/aggregation of three morphologies of hematite (α-Fe2O3) nanoparticles in varied aqueous solutions using ex situ electron microscopy and in situ small-angle x-ray scattering. We demonstrate a unique tendency of (104) hematite nanoparticles to maintain a monodisperse state across a wide range of solution conditions not observed with (001)- and (116)-dominated particles. Density functional theory calculations reveal an inert, densely hydrogen-bonded first water layer on the (104) facet that favors interparticle dispersion. Results validate the notion that nanoparticle dispersions can be controlled through morphology for specific solvents, which may help in the development of various nanoparticle applications that rely on their interfacial area to be highly accessible in stable suspensions.

Enhanced optical properties of lead-free double perovskite Cs2AgBiBr6 nanocrystals by doping of Na ions

Lead free double perovskite nanocrystals is an ideal alternate considering its nontoxic and stable property comparing with their counterpart lead halide perovskite NCs. A simple solution synthesis strategy was used to prepare lead-free double perovskite Cs2AgBiBr6 nanocrystals (NCs) doped with Na ions, resulting in NCs with a monodisperse state, homogeneous morphology, and good crystallinity. By adjusting the amount of Na+ doping, the band gap of the NCs was significantly increased from 2.57 eV to 3.00 eV. Furthermore, the relatively low value of photoluminescence quantum yield (PLQY) in the original Cs2AgBiBr6 NCs (∼0.5%) was increased to about 8.5% when doped with 60% Na+. Additionally, the exciton lifetime of the NCs was extended to 16.15 ns compared to the original 2 ns. As a result, the doping of Na + significantly enhanced the PLQY of Cs2AgBiBr6 NCs, indicating their potential value for use in optoelectronic devices.

The ceria – Germania solid oxide hydrogen storage hollow porous nanoparticles

The combination of high specific surface area and high porosity content as diffusion routes for adsorption/desorption in monodispersed solid state mixed oxide ceramic nanosized hollow porous particles enabled high hydrogen storage capacity with promising platform for controlled gas molecules delivery. The synthesized thin-walled nanoparticles were characterized for crystallinity, bond structure, morphology, and surface activity/adsorption profiles. The optimum molar ratio mixture of equal parts ceria and germania in hollow porous nanoparticles stored up to 7.8 wt% with specific surface area near 6100 m2/g and about 2 cm3/g volume content of 2.9 Å pores. The maximum discharge capacity of ∼5600 mAh/g after 12 cycles of this mesoporous structure provided a considerable storage performance and reversibility at ambient conditions. The structure dependency of storage was attributed to structural characteristics in CeO4 - GeO6 polyhedras and alterations between oxidation states in ceria.

Effect of cations on the improvement of material removal rate of silicon wafer in chemical mechanical polishing

For obtaining a sub-nanometer surface, the material removal rate (MRR) is usually very low. It is challenging to achieve sub-nanometer surface with high MRR. To overcome this challenge, in this work, different cations are considered to improve the MRR during CMP for silicon (Si) wafer. When the concentration of NH4+ ions is 125 mmol/L, the MRR of Si wafer reaches 1687 Å/min, increasing 107.8 % compared with the controlled group. It is noted that nanometer silica abrasives remain at a good monodisperse state in CMP. The surface roughness Sa after CMP on a Si wafer is 0.744 nm under a measurement area of 868 × 868 µm2. COF data and X-ray photoelectron spectroscopy indicate that NH4+ ions reduce the electrostatic repulsion between silica nanoparticles and Si, whilst accelerating chemical reactions between Si and developed slurry. This work suggests a novel approach to fabricating sub-nanometer surface of Si wafer with high MRR, which is beneficial for the potential use in semiconductor and microelectronics industries.

Efficient secretory production of proline/alanine/serine (PAS) biopolymers in Corynebacterium glutamicum yielding a monodisperse biological alternative to polyethylene glycol (PEG)

BackgroundPAS biopolymers are recombinant polypeptides comprising the small uncharged l-amino acids Pro, Ala and/or Ser which resemble the widely used poly-ethylene glycol (PEG) in terms of pronounced hydrophilicity. Likewise, their random chain behaviour in physiological solution results in a strongly expanded hydrodynamic volume. Thus, apart from their use as fusion partner for biopharmaceuticals to achieve prolonged half-life in vivo, PAS biopolymers appear attractive as substitute for PEG—or other poorly degradable chemical polymers—in many areas. As a prerequisite for the wide application of PAS biopolymers at affordable cost, we have established their highly efficient biotechnological production in Corynebacterium glutamicum serving as a well characterized bacterial host organism.ResultsUsing the CspA signal sequence, we have secreted two representative PAS biopolymers as polypeptides with ~ 600 and ~ 1200 amino acid residues, respectively. Both PAS biopolymers were purified from the culture supernatant by means of a simple downstream process in a truly monodisperse state as evidenced by ESI–MS. Yields after purification were up to ≥ 4 g per liter culture, with potential for further increase by strain optimization as well as fermentation and bioprocess development. Beyond direct application as hydrocolloids or to exploit their rheological properties, such PAS biopolymers are suitable for site-specific chemical conjugation with pharmacologically active molecules via their unique terminal amino or carboxyl groups. To enable the specific activation of the carboxylate, without interference by the free amino group, we generated a blocked N-terminus for the PAS(1200) polypeptide simply by introducing an N-terminal Gln residue which, after processing of the signal peptide, was cyclised to a chemically inert pyroglutamyl group upon acid treatment. The fact that PAS biopolymers are genetically encoded offers further conjugation strategies via incorporation of amino acids with reactive side chains (e.g., Cys, Lys, Glu/Asp) at defined positions.ConclusionsOur new PAS expression platform using Corynex® technology opens the way to applications of PASylation® technology in multiple areas such as the pharmaceutical industry, cosmetics and food technology.

Multifunctionality and mechanism of processivity of family GH5 endoglucanase, RfGH5_4 from Ruminococcus flavefaciens on lignocellulosic polymers

Multifunctional endoglucanase, RfGH5_4 from Ruminococcus flavefaciens showed (β/α)8-TIM barrel structure by homology modeling. Glu168 and Glu292 residues acted as general acid and base during catalysis. Circular Dichroism results, 40.83 % α-helices, 13.84 % β-strands and 45 % random turns-coils for RfGH5_4 corroborated with predictions by PSIPRED and SOPMA. Molecular Dynamic simulation of RfGH5_4 for 100 ns showed RMSD, 0.71 nm while for RfGH5_4-Cellopentaose complex was 0.55 nm, confirming that the binding of cellulosic ligand stabilizes its structural fold. RfGH5_4 showed strong affinity towards cellulosic ligands having higher degree of polymerization such as cellohexaose (−11.70 kcal/mol) and cellodecaose (−12.64 kcal/mol). Interestingly, complex hemicellulosic ligands such as XLLG of xyloglucan also showed higher affinity (−13.2 kcal/mol) and accommodated at RfGH5_4 active-site. Its catalytic cleft was broad enough to accommodate and hydrolyse various cellulosic and hemicellulosic ligands like XLLG of xyloglucan setting the basis of multifunctionality of RfGH5_4. Loops L2, L3 and L4 having Trp58 formed barrier at active-site of RfGH5_4 were responsible for processivity. RfGH5_4 showed monodispersed state at 2.5 mg/mL and a rattle-toy shape by SAXS. Zeta potential, −16 mV of RfGH5_4 indicated its higher stability. Multifunctional RfGH5_4 endoglucanase could be beneficial for generation lignocellulosic bioethanol and in health, prebiotic and food sector.

Bi-Mn diatomic interaction on SOD zeolite substrate promotes electrochemical methanol oxidation

The strategy of diatomic synergy is applied to the in-situ synthesis of electrode catalyst material for methanol fuel cells. During the one-pot synthesis in hydrothermal conditions, the doped Bi and Mn atoms are highly dispersed on and immobilized into the SOD zeolite cage structure as nanocrystals with trace amounts to form the novel Bi/Mn/SOD composite catalyst. The as-synthesized Bi and Mn NPs were confined in a rigid SOD nano-cage to maintain the stability and catalytic activity of the monodisperse state. Several key problems to be solved in methanol fuel cell applications are its energy density, catalytic efficiency, stability, and cost. Through the combined action of Mn and Bi, the composite electrode performed high activity in the methanol oxidation reaction (MOR) with a high current density of 45.9 mA cm−2 without precious metal and with high stability in 10 M methanol without any catalyst poisoning.

Dual isolated bimetal single-atom catalysts for tumor ROS cycle and parallel catalytic therapy

The application of emerging nanocatalytic drugs in tumor therapy mainly depends on reactive oxygen species (ROS) production in tumors. However, current nanocatalysts have drawbacks such as catalytic inefficiency and high toxicity. Herein, we designed a paradigm of synergy and “division of labor” bimetallic dual active sites single-atom catalyst (SAC) combined with ROS circulation and parallel catalytic therapy for efficient tumor therapy. Both Fe and Co atoms were isolated in the N-doped carbon material with a sharp-angled dodecahedron in a monodisperse state to form an independent bimetallic non-alloy structured atom pair (FeCo-DIA/NC). FeCo-DIA/NC synergistically initiates both Fenton and Fenton-like reactions, directly and simultaneously catalyzing H2O2 and O2 into ROS, including hydroxyl radicals (•OH), superoxide ions (O2•−), and singlet oxygen (1O2). The above ROS are further converted into H2O2 in the acid tumor microenvironment (TME), forming a “ROS Cycle” for highly efficient tumor inhibition. FeCo-DIA/NC exhibits higher activity for Fenton and Fenton-like reactions than single-atom Fe dispersed on N-doped carbon material (Fe-SIA/NC) and single-atom Co dispersed on N-doped carbon material (Co-SIA/NC). The in vitro and in vivo results show that the FeCo-DIA/NC catalyst significantly induces cell apoptosis and inhibits tumor growth. Furthermore, extremely low metal concentrations and high therapeutic effects were achieved simultaneously in FeCo-DIA/NC, highlighting the promising clinical potential. This bimetallic dual-active site monodisperse catalyst provides an important example for applying SACs in the biomedical field, moreover, the highly effective and parallel catalytic “ROS Cycle” provides an opportunity to design nanocatalysts for oncology.

Nano-AgCu Alloy on Wood Surface for Mold Resistance.

The mold infection of wood reduces the quality of its surface and potentially endangers human health. One category of the most popular mold inhibitors on the market is water-soluble fungicides. However, easy leaching due to ionic forms is a problem, which reduces the effectiveness of their antimicrobial action, as well as causing environmental pollution. Interestingly, nanometer-sized sterilizing agents present strong permeability and highly fungicidal behavior, and they are not easily leached, due to the unique nanoscale effect, and they have become alternative candidates as marketable anti-mold agents for wood protection. In this study, we first designed and explored a nanoscale alloy (nano silver–copper alloy, nano-AgCu) to treat wood surfaces for mold growth resistance. The results showed that three molds, i.e., Aspergillus niger, Penicillium citrinum and Trichoderma viride, mainly grew on the surface of wood within a depth of 100 μm; and that the nano-AgCu alloy with a particle size of ~15 nm presented improved retention and anti-mold efficiency at a nanomaterial concentration on the wood surface. Its leaching rate increased non-linearly with the increase in nano-AgCu retention and then it showed a gradually decreasing trend. When the concentration reached 1000 mg/L, the nano-AgCu alloy uniformly distributed on the wood surface in a monodispersed state and exhibited a lower retention of 0.342 g/m2, with an anti-mold efficiency of more than 75% and a leaching rate of only 7.678%. Such results positioned 1000 mg/L as the toxic threshold concentration of nano-AgCu against the three molds. This study can provide a scientific basis for the analysis of the anti-mold mechanisms of nano-AgCu alloy on wood surfaces and guide the application of nano-metal alloy materials in the field of wood antimicrobials.

Reduced graphene oxide-Mn3O4 composites as effective electron acceptors for hybrid polymer-based solar cells

In this work, reduced graphene oxide (rGO)-Mn3O4 composites with different weight ratios were prepared by solvothermal method. The Mn3O4 nanoparticles were distributed on the rGO sheets in a monodispersed state and at the same time GO sheets were reduced to rGO sheets. Furthermore, rGO-Mn3O4 composites were employed as electron acceptors for hybrid polymer-based solar cells. The distribution of Mn3O4 nanoparticles on graphene sheets imposes a remarkable effect on device performance. It is demonstrated that the hybrid polymer-based solar cells based on blend of poly(1-methoxy-4-(2-ethylhexyloxy)-p-phenylene vinylene) and rGO-Mn3O4 composite with weight ration of rGO/Mn3O4 (1:1) exhibited a peak power conversion efficiency of 1.04%, which was 5-fold higher than that of the counterpart devices of MEH-PPV/rGO sheets.

Coassembled Chitosan-Hyaluronic Acid Nanoparticles as a Theranostic Agent Targeting Alzheimer's β-Amyloid.

β-Amyloid (Aβ) fibrillogenesis is closely associated with the pathogenesis of Alzheimer's disease (AD), so detection and inhibition of Aβ aggregation are of significance for the theranostics of AD. In this work, the coassembled nanoparticles of chitosan and hyaluronic acid cross-linked with glutaraldehyde (CHG NPs) were found to work as a theranostic agent for imaging/probing and inhibition of Aβ fibrillization both in vitro and in vivo. The biomass-based CHG NPs of high stability exhibited a wide range of excitation/emission wavelengths and showed binding affinity toward Aβ aggregates, especially for soluble Aβ oligomers. CHG NPs displayed weak emission in the monodispersed state, while they remarkably emitted increased red fluorescence upon interacting with Aβ oligomers and fibrils, showing high sensitivity with a detection limit of 0.1 nM. By comparing the different fluorescence responses of CHG NPs and Thioflavin T to Aβ aggregation, the Aβ oligomerization rate during nucleation can be determined. Moreover, the fluorescence recognition behavior of CHG NPs was selective. CHG NPs specifically bind to negatively charged amyloid aggregates but not to positively charged amyloids and negatively charged soluble proteins. Such enhancement in fluorescence emission is attributed to the clustering-triggered emission effect of CHG NPs after interaction with Aβ aggregates via various electronic conjugations and hydrogen bonding, electrostatic, and hydrophobic interactions. Besides fluorescent imaging/probing, CHG NPs over 360 μg/mL could almost completely inhibit the formation of Aβ fibrils, exhibiting the capability of regulating Aβ aggregation. In-vivo assays with Caenorhabditis elegans CL2006 demonstrated the potency of CHG NPs as an effective theranostic nanoagent for imaging Aβ plaques and inhibiting Aβ deposition. The findings proved the potential of CHG NPs for development as a potent agent for the diagnosis and treatment of AD.

The aggregation of Aspergillus spores and the impact on their inactivation by chlorine-based disinfectants

The formation of fungal biofilm goes through some different states, including monodisperse state, aggregated state, germinated state, hyphal and biofilm. The aggregation of spores is a primary step of fungal biofilm development in aquatic systems. Previous studies on the inactivation of fungi were mostly performed in the monodisperse state of fungal spores and biofilm state, however, the inactivation of aggregated fungal spores is still unclear. In this study, the aggregated characteristics of fungal spores (Aspergillus fumigatus and Aspergillus flavus) at different pH values were firstly studied, and the inactivation efficiency of fungal spores at different aggregation degree by chlorine-based disinfectants was also clarified. The results showed that the aggregation degree of Aspergillus fumigatus was the highest at pH 9.0 while it was the lowest at pH 5.0. Aggregation between fungal spores was mainly mediated by occasional adhesin–adhesin interactions and electrostatic interactions. Compared with monodisperse spores, fungal spores were more resistant to chlorine-based disinfectants with the increase of spore aggregation degree. The inactivation rate constants of Aspergillus fumigatus at 30% and 63% aggregation degree were 1.5- and 4-folds lower than that of monodisperse spores, respectively. The lower proportion of membrane damage and higher intracellular reactive oxygen species level for aggregated spores than monodisperse spores was observed according to the flow cytometric results after chlorine-based disinfectants treatment. The reasons for the lower inactivation efficiency of aggregated spores are as following: the protection of outer layer spores and signals between aggregates lead to the increase of resistance for aggregated spores. This study is meaningful for the control of the fungal spores at different states in water.

Low-Triggering-Potential Electrochemiluminescence from Surface-Confined CuInS2@ZnS Nanocrystals and their Biosensing Applications.

Electrochemiluminescence (ECL) of low triggering potential is strongly anticipated for ECL assays with less inherent electrochemical interference and improved long-term stability of the working electrode. Herein, effects of the thiol capping agents and the states of luminophores, i.e., the thiol-capped CuInS2@ZnS nanocrystals (CuInS2@ZnS-Thiol), on the ECL triggering potential of CuInS2@ZnS-Thiol/N2H4·H2O were explored on the Au working electrode. The thiol capping agent of glutathione (GSH) not only enabled CuInS2@ZnS-Thiol/N2H4·H2O with the stronger oxidative-reduction ECL than other thiol capping agents but also demonstrated the largest shift for the ECL triggering potential of CuInS2@ZnS-Thiol/N2H4·H2O upon changing the luminophores from the monodispersed state to the surface-confined state. CuInS2@ZnS-GSH/N2H4·H2O exhibited an efficient oxidative-reduction ECL around 0.78 V (vs Ag/AgCl) with CuInS2@ZnS-GSH of the monodispersed state. Upon employing CuInS2@ZnS-GSH as the ECL tag and immobilizing them onto the Au working electrode, the oxidative-reduction ECL of CuInS2@ZnS-GSH/N2H4·H2O was lowered to 0.32 V (vs Ag/AgCl), which was about 0.88 V lower than that of traditional Ru(bpy)32+/TPrA (typically ∼1.2 V, vs Ag/AgCl). The ECL of the CuInS2@ZnS-GSH/N2H4·H2O system with the luminophore of both monodispersed and surface-confined states was spectrally identical to each other, indicating that this surface-confining strategy exhibited negligible effect on the excited state for the ECL of CuInS2@ZnS-GSH. A surface-confined ECL sensor around 0.32 V was fabricated with CuInS2@ZnS-GSH as a luminophore, which could sensitively and selectively determine the K-RAS gene from 1 to 500 pM with a limit of detection at 0.5 pmol L-1 (S/N = 3).

Ratiometric fluorescent sensing of ethanol based on copper nanoclusters with tunable dual emission

Copper nanoclusters (Cu NCs) have attracted a surge of interest in fluorescent sensors as their outstanding physicochemical and optical properties. However, most of the reports have focused on single-signal fluorescent sensors, which are susceptible to background interferences and affect accuracy of the results. Herein, we constructed a facile ratiometric fluorescent sensor for monitoring ethanol based on Cu NCs with tunable dual emission. Polyvinylpyrrolidone (PVP)-modified Cu NCs were simply prepared in water, which exhibit ratiometric dual emission, including a strong green emission at 520 nm and a weak blue emission at 450 nm. The PVP-Cu NCs in water with strong green emission display monodisperse state due to the formation of hydration shell around Cu NCs. In ethanol where the hydration shell is destructed, Cu NCs tend to aggregate and show strong blue emission. This emission shift might attribute to the enhancement of Cu–Cu metallophilic interaction with the aggregation of Cu NCs, which induces the excited-state level increasing. Thus, a ratiometric fluorescent probe for ethanol based on the PVP-Cu NCs is fabricated, which possesses rapid response (<1 min), and realize full-range detection from 0 to 100%. In addition, this ratiometric probe is successfully applied to determine the alcohol strength of alcohol beverages, demonstrating the great potential in practical application.

Control Over Protein Multimerization Induced by Water-Soluble Porphyrins

Interactions between charged porphyrins and complimentary or similarly charged proteins provide important models systems for studies of electron transfer processes, artificial photosynthesis, and control of protein-protein interactions. Typically, the experimental results are analyzed and discussed assuming that the proteins exist in a monodisperse state. However, combined small- and wide-angle X-ray scattering experiments revealed the formation of multimers with a wide range of complex sizes. Binding interactions were explored using wild-type and 12 mutants of PpcA, a 3-heme c-type cytochrome from Geobacter sulfurreducens, with several anionic water-soluble derivatives of tetraphenylporphyrin.

Novel Mo-V Oxide Catalysts with Nanospheres as Templates for the Selective Oxidation of Acrolein to Acrylic Acid

Novel Mo-V-PMMA and Mo-V-PS catalysts are prepared by addition of hard polymethyl methacrylate (PMMA) and polystyrene (PS) nanospheres into Mo/V compounds in the preparation process, respectively. The catalytic tests in selective oxidation of acrolein reveal that Mo-V-PMMA catalyst shows very high acrolein conversion (99.1%) and the yield of acrylic acid (90.7%). The BET, DLS, SAXS, XRD, XPS, H2-TPR and NH3-TPD measurements reveal that the addition of PMMA and PS nanospheres causes the obvious changes of porous structure, crystal phases composition and chemical properties of catalysts. These differences between Mo-V-PMMA and Mo-V-PS catalysts are attributed to the totally different “real” nano–environment during heat treatment in the high–concentration component mixture. PS nanospheres are in a state of adhesion or agglomeration or not uniformly distributed in the active component solution, while PMMA nanospheres with much better hydrophilicity and monodispersed state promote Mo and V ions more easily and uniformly dispersed in the mixture. Novel Mo-V catalysts are prepared by addition of hard polymethyl methacrylate (PMMA) and polystyrene (PS) nanospheres into Mo/V mixture. Obvious changes of porous structure, crystal phases and chemical properties of catalysts are caused by the nanospheres introduction, showing very high acrolein conversion (99.1%) and the yield of acrylic acid (90.7%) in selective oxidation of acrolein.