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Incorporation of earth-abundant Cu is one of the most important approaches to improve the practicability of TiO2 for photoreduction of CO2 into value-added solar fuels. However, the molecular insight on the role of Cu is complicated and far from understood. We performed a first principle calculation on the anatase (101) surface modified by a single Cu atom deposited on the surface (CuS) or doped in the lattice (CuL). It is demonstrated the CuL is clearly more stable than the CuS and could promote the formation of oxygen vacancy (Vo) greatly. The CuS plays a role of donor, while the CuL is electronically deficient and becomes a global electron trapper. If a Vo is introduced, the excess electrons would immigrate to the empty gap state of the CuL and make it half-filled in some case, which implies its metallic characters and improved conductivity; meanwhile, the formation of Ti3+ is suppressed. Judging from the adsorption energies, it is the Vo that primarily improves the adsorption of CO2 in both linear and bent states, and the CuS could hardly stabilize CO2 more, while the promotion effect of Vo could even be counteracted by the CuL due to its electronic deficiency. The reduction pathways (CO2* → CO* + O*) show that, with the assistance of the CuS, linear CO2 could directly transform into the carbonate-like geometry vertically binding to the surface, and the intermediate configuration of the bent CO2 horizontally bridging the Vo could be successfully skipped. Therefore, the barrier of the rate-determining transformation could be lowered from 0.75 to 0.39 eV. Furthermore, it is found the strong adsorption of the produced CO by the CuS might retard the smooth going of the catalytic process.

Recently, we reported the first VOx/SiO2 ethylene polymerization catalyst for making Cl-free UHMWPE, and found the dominant promotion effects of Al-/Ti-/Zr-modifications over this catalyst system (Macromol. Chem. Phys. 2017, 218, 1600443). In this work, density functional theory is applied to investigate the underlying mechanism of this remarkable promotion effect of Al-/Ti-/Zr-modifications on a molecular and atomic level. The cluster model with V(III) is found to be the most possible active site due to its lowest overall energy barrier for monomer insertion, though the process of C2H4 coordination and the subsequent formation of transition state are most energy favored for V(II) species. By modifying one of or both V-O-Si in the active model with V-O-M (M = Al, Ti, or Zr), the energy barrier for the binding of the upcoming C2H4 gets lower (particularly for Al- and Zr-modified catalysts), and the transition state also becomes more stable. Generally, the insertion process of C2H4 gets easier after support Al-/Ti-/Zr-modifications. This dominant promotion effect is partially ascribed to the more enriched positive charge distribution on or nearby the V center, and the narrower energy gap between the LUMO of model catalysts and the HOMO of C2H4 for these modified catalysts also contributes much. In addition, the decreased steric hindrance around the V center should be taken into account for the modified models as well. Furthermore, the Bronsted acidity of the catalysts is investigated by introducing a pendent hydroxyl group to the model catalysts, which has a close contact with the V center. Similar promotion effect of support modification by Al, Ti, and Zr could still be observed.

A dramatically improved, uniform distribution of commercial ultrahigh molecular weight polyethylene (UHMWPE) with high-density polyethylene (HDPE) via solution blending, rather than that of melt blending, is often apparent in experimental investigation. Recently, we demonstrated that a UHMWPE/HDPE blend created by in-reactor polymerization with a Cr/V bimetallic catalyst supported on modified silica can obtain an even better molecular chain distribution while saving energy and solution costs, even more so than experiments using a solution blend. Furthermore, by gel-spinning processing, an abundance of hierarchical, interlocking shish-kebab crystals were generated in the in-reactor polymerized blend fibers (IRBFs), exhibiting better mechanical properties than those of solution blend fibers (SBFs). The tensile strength of the IRBFs increased by about 20% under the same draw ratio, since the interlocking shish-kebab structures contributed to homogenous deformation. The two kinds of fibers exhibit high crystallinity and have a highly oriented shish-kebab structure. Compared with the SBFs, the IRBFs inclined to form longer shish features and smaller kebab sizes, and the draw process was more conducive to the transformation of kebab to shish structures. Thus, the IRBFs can obtain an excellent hierarchal network structure, benefiting more from the hot-stretching process. Our work lays a solid foundation for the efficient fabrication of high-performance UHMWPE/HDPE fibers as well as the optimization of an original polyethylene catalyst system.

Metal-peptide interactions provide plentiful resource and design principles for developing functional biomaterials and smart sensors. Pb2+, as a borderline metal ion, has versatile coordination modes. The interference from competing metal ions and endogenous chelating species greatly challenges Pb2+ analysis, especially in complicated living biosystems. Herein, a biomimetic peptide-based fluorescent sensor GSSH-2TPE was developed, starting from the structure of a naturally occurring peptide glutathione. Lewis acid-base theory was employed to guide the molecular design and tune the affinity and selectivity of the targeting performance. The integration of peptide recognition and aggregation-induced emission effect provides desirable sensing features, including specific turn-on response to Pb2+ over 18 different metal ions, rapid binding, and signal output, as well as high sensitivity with a detection limit of 1.5 nM. Mechanism investigation demonstrated the balance between the chelating groups, and the molecular configuration of the sensor contributes to the high selectivity toward Pb2+ complexation. The ion-induced supramolecular assembly lights up the bright fluorescence. The ability to image Pb2+ in living cells was exhibited with minimal interference from endogenous biothiols, no background fluorescence, and good biocompatibility. With good cell permeability, GSSH-2TPE can monitor changes in Pb2+ levels and biodistribution and thus predict possible damage pathways. Such metal-peptide interaction-based sensing systems offer tailorable platforms for designing bioanalytical tools and show great potential for studying the cell biology of metal ions in living biosystems.

This work aims to estimate the effect of interfacial carbon diffusion on the diffusion behavior of interfacial Cr element, interfacial microstructure, and tensile behavior of stainless steel (SS) composites. Here, 316L SS was selected as the clad material, and two low-alloyed steels (LASs) with different carbon contents (0.06 and 0.20 wt%) were used as the substrate. Two SS composites were prepared via vacuum hot compression in a Gleeble-3500 simulator, followed by normalization treatment. The results revealed that as the carbon content increases, the zone of the decarburized and the carburized of the composite sample become wider. The M23C6 carbides precipitated at the grain boundaries of the carburized zone of SS clad increase, and their morphology transformed from discontinuously granular to continuously lamellar. Therefore, the ultimate tensile strength (UTS) and yield strength (YS) were also increased. Simultaneously, the uniform elongation decreased from 24% to 17% due to the formation of local microcracks at the intergranular lamellar carbides.

Bimodal ultra-high-molecular-weight polyethylene (UHMWPE)/high-density polyethylene (HDPE) in-reactor blends (IRBs) are produced by the bimetallic catalysts, which are synthesized through co-supporting silylchromate and vanadium-oxide-based catalysts on silica or alumina, zirconia and titania-modified silica. After support modification, the activities of the catalysts for ethylene polymerization are substantially enhanced. The IRBs produced by the modified catalysts also contain more UHMWPE and low-molecular-weight polyethylene (LMWPE) fractions, and have much broader molecular weight distribution (MWD). The homogeneous nature of the IRBs is preliminarily confirmed by the differential scanning calorimetry melting curves, showing unique melting peak in both nascent and recrystallized states. The rheological results reflect that the viscosity of the IRBs is reduced more or less when compared with UHMWPE. The distinct elastic dominance of the IRBs is also observed, implying the UHMWPE characteristics in the IRBs. In addition, the intimate mixing of the IRBs is further verified by the similar slopes of Han curves for the polyethylene (PE) samples. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 3404–3412

Phillips catalyst (CrOx/SiO2) is one of the most famous industrial catalysts for ethylene polymerization, while VOx/SiO2 catalyst is a promising catalyst capable of making UHMWPE, which was recently developed in our group. These two catalysts were known to show completely deferent behaviors in ethylene polymerization in terms of activity, H2 response and copolymerization ability. However, a molecular insight into the mechanism is not well understood. Herein, a theoretical comparison between them via the propagation through insertion and termination through chain transfer reaction pathways is performed. The results show the transition states for olefins (ethylene, 1-butene and 1-hexene) insertion are energetically more stable in VOx/SiO2. However, the binding energies of the olefins by VOx/SiO2 is obviously lower, which results in the insertion barriers for VOx/SiO2 about 2–3 kcal mol−1 higher than those for CrOx/SiO2. As to the termination, CrOx/SiO2 is more probably to terminate via the BHE (β-H elimination to Cr center) pathway, which generally has lower barriers than those for BHT (β-H elimination to monomer) in the VOx/SiO2 system. Meanwhile, VOx/SiO2 is superior to CrOx/SiO2 in hydrogenolysis, because it is more accessible by the H2, and the reaction barrier is also much lower. The energy gap between the barriers for propagation and termination is generally smaller for CrOx/SiO2, implying its tendency to produce lower MW PE when compared with VOx/SiO2. Furthermore, for CrOx/SiO2, the insertion barriers between C2H4 and α-olefin are bigger and the promotion effect of the incorporated α-olefins on termination is more obvious, which might account for the lower incorporation efficiency for comonomer by CrOx/SiO2, despite of its lower insertion barriers.

The low-temperature-fired NiCuZn ferrites with various borosilicate glasses were prepared by the conventional solid-state reaction method. Different weight percentages of glasses such as Al2O3–B2O3–SiO2 (ABS), Na2O–Al2O3–B2O3–SiO2 (NABS), Bi2O3–B2O3–BaO–SiO2 (BBBS) were added to low-temperature-fired NiCuZn ferrites. The effects of these glasses on sintering behavior, microstructures and magnetic properties of NiCuZn ferrites were also investigated. It is found that moderate amount of borosilicate glass addition can promote the densification and improve the magnetic properties of NiCuZn ferrites due to the formation of liquid phase, but too more liquid phase formation will deteriorate the magnetic properties. In addition, results also show that addition of BBBS glass can promote best densification of NiCuZn ferrites, but improve magnetic properties worse than addition of ABS or NABS glass. By contrast, the NiCuZn ferrite sample with 0.1 wt% ABS glass can obtain best magnetic properties: μ i = 733.01 at 100 kHz, B s = 162.39 mT, B r = 86.59 mT and H c = 35.7 A m−1.

The low-temperature-fired MgCuZn ferrites with various amounts of Bi2O3 and WO3 additives were prepared by a conventional solid-state reaction method. The effects of Bi2O3 and WO3 additives on sintering behavior, microstructures and magnetic properties of MgCuZn ferrites were investigated. It is found that Bi2O3 and WO3 additives overtly improve the densification of samples through the formation of liquid phase and grains growth. Appropriate Bi2O3 and WO3 additives not only can noticeably increase the initial permeability (μ i ) and saturation flux density (B s ), but also can obviously reduce coercive field strength (H c ). However, too much additive will deteriorate the magnetic properties. The ferrite sample with 0.1 wt% Bi2O3 and 0.1 wt% WO3 shows excellent magnetic properties: μ i = 703.27 at 100 kHz, B s = 213.28 mT, B r = 117.98 mT and H c = 44.01 A m−1.

The low-temperature-fired NiCuZn ferrites with different amount of Nb2O5 and WO3 additives were prepared by solid-state reaction method. The effects of Nb2O5 and WO3 additives on sintering behavior, microstructures and magnetic properties of NiCuZn ferrites were investigated. It is found that Nb2O5 and WO3 additives overtly improve the densification of samples through grains uniformity and grains growth promotion. The appropriate Nb2O5 and WO3 additives not only can noticeably increase the initial permeability (μ i ) and saturation flux density (B s ), but also can obviously reduce the remanent flux density (B r ) and coercive field strength (H c ). However, too much additive will deteriorate the magnetic properties. By contrast, 0.2 wt% Nb2O5 and 0.5 wt% WO3 added in NiCuZn ferrites shows excellent magnetic properties: μ i = 674.81 at 100 kHz, B s = 142.48 mT, B r = 63.32 mT and H c = 31.39 A m−1.

Bi substituted YCaZrVIG ferrites, Y 2.3− x Bi x Ca 0.7 Zr 0.3 V 0.2 Fe 4.42 O 12 ( x =0.1, 0.25, 0.4, 0.5, 0.75) ferrites were prepared by conventional oxide method. The addition of Bi 2 O 3 promoted the sintering performance and lowered the sintering temperature from 1420–1230 °C. However, it also resulted in the formation of minor second phases and the decrease of grain size. With the increase of Bi concentration, the dielectric constant increases linearly and then remains unchanged. The dielectric loss decreased firstly and then increased. The saturation magnetization (4π M s ) almost retained unchanged as the Bi concentration increased except for the sample with 0.75. The coercivity ( H c ) decreased firstly and reached the minimum of 1.32 Oe at 0.25, and then rose when x >0.25, which was related to the facility of magnetic domain wall motion and magnetic moment reverse. Moderate addition of Bi also can increase the remanence ( B r ) by improving sintering process. Additionally, we got the optimum electromagnetic properties in the samples with x =0.25 at 1230 °C: RD>97%, e r =15.7, tan δ e =2.48×10 −4 , H c =1.32Oe, 4π M S =1663 Gs, B r =583.91 Gs.

Y2.6−xCa0.4+xZrxV0.2Fe4.8−xO12 (Zrx:YCaVIG) ferrite materials have been prepared by an oxide process. The phase formation and microstructure were analyzed by X-ray diffraction and scanning electron microscopy, respectively. The effects of Zr4+ substitution on phase compositions, sintering properties, microstructures and electromagnetic properties were investigated. The results indicate that all the sintered specimens with different Zr4+ contents show a single garnet structure. The addition of ZrO2 can gradually increase the lattice constant, and lower the sintering temperature and the theoretical density. With the increase of Zr4+ content, the dielectric loss (tan δe) and coercivity (Hc) decrease and then slightly increase, which is due to the variation of the microstructure. But the saturation magnetization (4πMs) shows the opposite variation compared to the former two properties. However, the dielectric constant (er) remains stable and remanence (Br) monotonically declines. Finally, the specimen of Y2.3Ca0.7Zr0.3V0.2Fe4.5O12 sintered at 1350° possesses the optimum electromagnetic properties: er=14.8, tan δe=1.35×10−3, 4πMs=1638 Gs, Br=596 Gs, Hc=0.75 Oe and ΔH (ferromagnetic resonance linewidth)=66 Oe.

Y 3 Mn x Fe 4.85- x O 12 ( x =0, 0.02, 0.04, 0.06, 0.08 and 0.1) garnet ferrites (YMnIG) were prepared by conventional solid-state reaction method in air atmosphere. The effect of Mn addition on the microstructure and electromagnetic properties of YIG were investigated by means of techniques such as X-ray diffraction, scanning electron microscopey, network analyzer, hysteresigraph, magnetic balance and electron paramagnetic resonance spectrometry. Pure garnet phase of Y 3 Fe 5 O 12 was identified for all the samples, except for minor YFeO 3 phase appearing in the sample with x =0.06. The addition of Mn showed little influence on the dielectric constant of YIG, which varied between 14.2 and 14.5. Substituting Mn n + for Fe n + in YIG decreased the total amount of Fe ions, inhibited the reduction of Fe 3+ and promoted the grain growth of garnet phase, which led to the decrease in dielectric loss and coercivity. Because the amount of Mn 3+ ions in octahedral sites increased with Mn concentration, the saturation magnetization showed a slight decrease firstly and then increased notably. The addition of Mn could also increase the remanence ratio of YIG ferrites by decreasing the magnetostriction constant γ 111 . Therefore, doping Mn into YIG ferrites with proper quantity could improve electromagnetic properties of YIG significantly. The YMnIG ferrite with x =0.08, i.e., Y 3 Mn 0.08 Fe 4.77 O 12 , showed the optimum electromagnetic properties: ɛ r =14.2, tan δ e =1.5×10 −4 , H c =36 A/m, 4π M S =192 mT, B r / B s =0.84, Δ H =6.8 KA/m.

In this work, we reported the microstructure and electromagnetic properties of a series of zirconium substituted yttrium iron garnet ferrites (YCaZrIG) with iron deficiency composition of Y 3− x Ca x Zr x Fe 4.93− x O 12 ( x = 0.1, 0.2, 0.3, and 0.4, with electrostatic balance by Ca 2+ substituted for Y 3+ ions) prepared by a solid-reaction method. The addition of ZrO 2 shows no obvious influence on the phase, density and dielectric constant of YIG ferrites. When Zr addition x ≤ 0.3, the substitution of Zr 4+ for Fe 3+ decreases the amount of Fe ions, increases the lattice parameter and enhances the grain growth of garnet phase. The solubility of zirconium in YCaZrIG ferrite was found to be approximately 0.3, above which excess ZrO 2 would lead to the precipitation of a second phase inside the YCaZrIG ferrite. This would inhibit the grain growth of garnet phase and cause an increase in the dielectric loss and coercivity. The observed reduce for saturation magnetization when x = 0.4 is possibly due to antiparallel alignment of magnetic moment of Fe 3+ in the d site caused by the decrease of a–d exchange interaction. Additionally, we got the optimum electromagnetic properties in the samples with x = 0.3: ɛ r = 14.1, tan δ e = 2.5 × 10 −4 , H c = 47 A/m, 4 πM s = 1936 × 10 −4 T , Δ H = 7.1 KA/m.

Novel vanadium-oxide-based catalysts supported on alumina, zirconia, or titania-modified silica, which are able to synthesize ultrahigh molecular weight polyethylene (UHMWPE), are successfully developed. Compared with the unmodified silica supported catalyst, the activities of the modified catalysts are substantially enhanced. By changing the polymerization temperature (Tp) from 90 to 60 °C, the molecular weight of the produced UHMWPE can be easily regulated from 2 × 106 to more than 6 × 106 g mol−1. It is the first time that chloride-free nonsingle site catalysts have been developed to synthesize UHMWPE within such a broad range of Tp. Catalyst characterization by NH3-temperature-programmed desorption and pyridine-Fourier transform infrared spectroscopy reveals that the modified catalysts have increased acidity derived from both Lewis and Bronsted acid sites. The X-ray photoelectron spectroscopy characterization indicates that the vanadium on the modified catalysts is more electron deficient. Thus, the acidity of the catalysts and the electronic state of the vanadium play a critical role in determining the activity of the vanadium active sites for ethylene polymerization.

The construction of molecularly imprinted polymers on magnetic nanoparticles gives access to smart materials with dual functions of target recognition and magnetic separation. In this study, the superparamagnetic surface-molecularly imprinted nanoparticles were prepared via surface-initiated reversible addition-fragmentation chain transfer (RAFT) polymerization using ofloxacin (OFX) as template for the separation of fluoroquinolones (FQs). Benefiting from the living/controlled nature of RAFT reaction, distinct core-shell structure was successfully constructed. The highly uniform nanoscale MIP layer was homogeneously grafted on the surface of RAFT agent TTCA modified Fe3O4@SiO2 nanoparticles, which favors the fast mass transfer and rapid binding kinetics. The target binding assays demonstrate the desirable adsorption capacity and imprinting efficiency of Fe3O4@MIP. High selectivity of Fe3O4@MIP toward FQs (ofloxacin, pefloxacin, enrofloxacin, norfloxacin, and gatifloxacin) was exhibited by competitive binding assay. The Fe3O4@MIP nanoparticles were successfully applied for the direct enrichment of five FQs from human urine. The spiked human urine samples were determined and the recoveries ranging from 83.1 to 103.1% were obtained with RSD of 0.8-8.2% (n = 3). This work provides a versatile approach for the fabrication of well-defined MIP on nanomaterials for the analysis of complicated biosystems.

A novel quartz crystal microbalance (QCM) sensor for rapid, highly selective and sensitive detection of copper ions was developed. As a signal amplifier, gold nanoparticles (Au NPs) were self-assembled onto the surface of the sensor. A simple dip-and-dry method enabled the whole detection procedure to be accomplished within 20 min. High selectivity of the sensor towards copper ions is demonstrated by both individual and coexisting assays with interference ions. This gold nanoparticle mediated amplification allowed a detection limit down to 3.1 μM. Together with good repeatability and regeneration, the QCM sensor was also applied to the analysis of copper contamination in drinking water. This work provides a flexible method for fabricating QCM sensors for the analysis of important small molecules in environmental and biological samples.