Latest ArticlesRuPt/AC bimetallic catalysts were prepared by two-step incipient impregnation method and evaluated in the hydrogenation of phthalates. According to the characterization results, well dispersed RuPt bimetallic nanoparticles were formed on the catalyst, and the strong interaction between the two metals resulted in the formation of RuPt alloy. It was found that Ru can donate electrons to Pt on RuPt alloy nanoparticles, leading to the formation of electron-deficient Ru which significantly promotes the hydrogenation rate of dioctyl phthalate and improves the selectivity of dioctyl di-2-ethylhexylcyclohexane-1, 4-dicarboxylate by accelerating the further hydrogenation of intermediate products. The bimetallic RuPt catalyst also presented excellent stability and versatility in the hydrogenation of phthalates, demonstrating its prospective future in the hydrogenation of aromatic ring contained compounds.
Multi-bond network (MBN) hydrogels contain hierarchical dynamic bonds with different bond association energy as energy dissipation units, enabling super-tough mechanical properties. In this work, we copolymerize a protonated 2-ureido-4[1H]-pyrimidone (UPy)-contained monomer with acrylic acid in HCl solution. After removing excess HCl, UPy motifs are deprotonated and from dimers, thus generating an UPy-contained MBN hydrogel. The obtained MBN hydrogels (75 wt% water content) exhibit super-tough mechanical properties (0.39 MPa to 2.51 MPa tensile strength), with tremendous amount of energy (1.68 MJ/m3 to 11.1 MJ/m3) dissipated by the dissociation of UPy dimers. The introduction of ionic bonds can further improve the mechanical properties. Moreover, owing to their dynamic nature, both UPy dimers and ionic bonds can re-associate after being dissociated, resulting in excellent self-recovery ability (around 90% recovery efficiency within only 1 h). The excellent self-recovery ability mainly originates from the re-association of UPy dimers based on the high dimerization constant of UPy motifs.
Flat and crystalline materials with exceptional nonlinear optical (NLO) properties are highly desirable for their potential applications in integrated NLO photonic devices. Graphdiyne (GD), a new two-dimensional (2D) carbon allotrope, has recently evoked burgeoning research attention by virtue of its tunable bandgap along with a high carrier mobility and extended π-conjugation compared with most conventional optical materials. Here, we experimentally probe the third-order nonlinear optical response of GD dispersed in several common solvents (alcohols) using a femtosecond Z-scan technique. The measured nonlinear optical refractive index is in the order of ~10-8 cm2/W, which is approximately one order of magnitude higher than that of most 2D materials. In particular, we find that different NLO responses can be observed from GD when dispersed in different solvents, with the strongest NLO response when dispersed in 1-propanol. It is proposed that some intrinsic properties of the solvents, such as the polarity and viscosity, could influence the NLO response of GD materials. Our experimental results confirm the assumptions on the NLO behavior in GD and demonstrate its great potential for future generations of Kerr-effect-based NLO materials and devices.
The donor: acceptor (D: A) blend ratio plays a very important role in affecting the progress of charge transfer and energy transfer in bulk heterojunction (BHJ) organic solar cells (OSCs). The proper D: A blend ratio can provide maximized D/A interfacial area for exciton dissociation and appropriate domain size of the exciton diffusion length, which is beneficial to obtain high-performance OSCs. Here, we comprehensively investigated the relationship between various D: A blend ratios and the charge transfer and energy transfer mechanisms in OSCs based on PBDB-T and non-fullerene acceptor IT-M. Based on various D: A blend ratios, it was found that the ratio of components is a key factor to suppress the formation of triplet states and recombination energy losses. Rational D: A blend ratios can provide appropriate donor/accepter surface for charge transfer which has been powerfully verified by various detailed experimental results from the time-resolved fluorescence measurement and transient absorption (TA) spectroscopy. Optimized coherence length and crystallinity are verified by grazing incident wide-angle X-ray scattering (GIWAXS) measurements. The results are beneficial to comprehend the effects of various D: A blend ratios on charge transfer and energy transfer dynamics and provides constructive suggestions for rationally designing new materials and feedback for photovoltaic performance optimization in non-fullerene OSCs
Carbon nanotubes (CNTs), as one-dimensional nanomaterials, show great potential in energy conversion and storage due to their efficient electrical conductivity and mass transfer. However, the security risks, time-consuming and high cost of the preparation process hinder its further application. Here, we develop that a negative pressure rather than a following gas environment can promote the generation of cobalt and nitrogen co-doped CNTs (Co/N-CNTs) by using cobalt zeolitic imidazolate framework (ZIF-67) as a precursor, in which the negative pressure plays a key role in adjusting the size of cobalt nanoparticles and stimulating the rearragement of carbon atoms for forming CNTs. Importantly, the obtained Co/N-CNTs, with high content of pyridinic nitrogen and abundant graphitized structure, exhibit superior catalytic activity for oxygen reduction reaction (ORR) with half-wave potential (E1/2) of 0.85 V and durability in terms of the minimum current loss (2%) after the 30, 000 s test. Our development provides a new pathway for large-scale and cost-effective preparation of metal-doped CNTs for various applications.
Stimulus responsive materials can provide a variety of desirable properties in one equipment unit, such as optoelectronic devices, data communications, actuators, memories, sensors and capacitors. However, it remains a large challenge to design such stimulus responsive materials, especially functional materials having both dielectric switch and second harmonic generation (SHG). Here, a new stimuli-responsive switchable material [(CH3)3N(CH2)2Cl]2[Mn(SCN)4(H2O)2] was discovered as a potential second-harmonic generation (SHG) dielectric switch. It is worth noting that it has SHG characteristics before and after undergoing reversible high-temperature phase transitions. In this work, we successfully refined the tetramethylammonium cation to obtain a quasi-spherical cation, which is tetramethylchloroethyl-amine (TMCEM) cation. By substituting H with a halogen, the increased steric hindrance of the molecular makes energy barrier increased, resulting in the reversible high-temperature phase transition. At the same time, the interactions of quasi-spherical cations and [Mn(SCN)4(H2O)2]2- anions affect a non-centrosymmetric structure to induce the SHG effect. These findings provide a new approach to design novel functional switch materials.
Since graphene-based materials have shown great potential in many fields, it is important to explore ultrafast and high-efficient methods to synthesize reduced graphene oxide (rGO) using inexpensive reducing agents under mild conditions. Here, we reported a novel method for the ultrafast chemical reduction of graphene oxide (GO) at room temperature using sodium borohydride (NaBH4), sodium molybdate (Na2MoO4) and hydrochloric acid (HCl). The reduction was carried out within 2 min. A series of characterization results revealed that the obtained reduced graphene oxide has higher reduction degree than that synthesized by NaBH4 alone at high temperature. Moreover, rGO electrode based on the present reducing method exhibited a superior specific capacitance of 139.8 F/g at a current density of 1 A/g, indicating that it can be used as electrode materials for supercapacitors.
Water-soluble thermoresponsive polymers present either upper critical solution temperature (UCST) or lower critical solution temperature (LCST) depending on the location of their miscibility range with water at high temperatures or at low temperatures. Compared with LCST polymers, the water-soluble UCST polymers are still less explored until now. In this work three copolymers of P(AAm-co-GAA) were synthesized by copolymerizing two acrylamide monomers, acrylamide (AAm) and acrylamide functionalized with natural glycyrrhetinic acid (GAA), using reversible addition-fragmentation chain transfer (RAFT) polymerization. These copolymers exhibited the typical UCST thermoresponsive behavior, and their phase transition temperatures could be easily tuned to around 37 ℃ for potential biological applications. Moreover, the UCST of P(AAm-co-GAA) can be adjusted not only by the content of glycyrrhetinic acid (GA) and polymer concentrations, but also by the host-guest interactions between GA and cyclodextrins (β- and γ-CD). The suitable value of UCST and the biocompatible nature of GA and CDs may endow these copolymers with practical applications in biomedical chemistry
Proppant is a key material in the hydraulic fracturing process, which has been widely used in unconventional oil exploitation. Normal proppants are easy to sedimentate and accumulate at the entrance of shale fracture, which will block the diversion of water, oil and gas. Coated proppants (CPs) are fabricated by coating resin on normal ceramic proppants through a simple method, which is dramatically enhanced the supporting properties in shale fracture and easy to scale up. Compared with uncoated ceramic proppants, the self-suspension ability of CPs is ~11 times higher, which are able to migrate and distribute farther and deeper inside the fracture. At the same time, Coating enhanced the 23.7% of adhesive force in maximum, which makes the CPs easier to adhere on the fracture surface to supportthe shale fracture. Besides, the liquid conductivity of CPs is 60% higher than uncoated ceramic proppants at 13.6 MPa pressure. This method is expected to fabricated varieties of proppantsfor shale fracture supporting to improve the exploration of unconventional oil and gas resources.
Two isostructural Ni(Ⅱ)/Co(Ⅱ)-based metal-organic frameworks (MOFs), namely {[M3(L)2(bpb)3(H2O)4]·2DMF·2H2O}n [M = Ni (HL-5, HL is short for Hui-Ling Liu); M = Co (HL-6); H3L = 2', 6'-dimethyl-[1, 1'-biphenyl]-3, 4', 5-tricarboxylic acid; bpb = 1, 4-bis(pyrid-4-yl)benzene], have been hydrothermally syn-thesized and structurally characterized. Both HL-5 and HL-6, which have the same three-interpenetrated 3D pillared-layer framework with sqc306 type topology, present good selective methyl orange (MO) adsorption over rhodamine B (RhB). Moreover, the catalytic CO2 cycloaddition properties with epoxides of the two MOFs have also been studied at ambient pressure and temperature.
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