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Graphitic carbon nitride (g-C3N4 or GCN) shows promise in photocatalytic water splitting, despite facing the challenge of rapid electron–hole recombination. In this study, we investigated the influence of boron/oxygen codoping on the photocatalytic performance of GCN systems for hydrogen generation. First-principles calculations and nonadiabatic molecular dynamics (NAMD) simulations were employed to reveal that the recombination time of photogenerated carriers could be increased by 16% to 64% in the codoped systems compared to the pristine GCN. The time-dependent density functional theory (TDDFT) scheme was utilized to select energy windows and initiate dynamics in cluster models of B/O co-doped heptazine with water molecules. Notably, we observed efficient direct photodissociation of hydrogen atoms from water molecules within 60 fs and proton hops within the hydrogen-bonded network within 80 fs in the co-doped system, diverging from the previously proposed mechanism for pristine heptazine in NAMD simulations. This discovery underscores the significant role of faster proton-coupled electron transfer (PCET) reactions and rapid radiationless relaxation in achieving high photocatalytic efficiency in water splitting. Our work enhances the understanding of the internal mechanism of highly efficient photocatalysts for water splitting and provides a new design strategy for doped GCN. [ABSTRACT FROM AUTHOR]

Understanding how the electronic state of transition metal atoms can influence molecular adsorption on a substrate is of great importance for many applications. Choosing NH3 as a model molecule, its adsorption behavior on defected SnS2 monolayers is investigated. The number of valence electrons n is controlled by decorating the monolayer with different transition metal atoms, ranging from Sc to Zn. Density-Functional Theory based calculations show that the adsorption energy of NH3 molecules oscillates with n and shows a clear odd–even pattern. There is also a mirror symmetry of the adsorption energies for large and low electron numbers. This unique behavior is mainly governed by the oxidation state of the TM ions. We trace back the observed trends of the adsorption energy to the orbital symmetries and ligand effects which affect the interaction between the 3σ orbitals (NH3) and the 3d orbitals of the transition metals. This result unravels the role which the spin state of TM ions plays in different crystal fields for the adsorption behavior of molecules. This new understanding of the role of the electronic structure on molecular adsorption can be useful for the design of high efficiency nanodevices in areas such as sensing and photocatalysis. [ABSTRACT FROM AUTHOR]

Two-dimensional material-supported single metal atom catalysts have been extensively studied and proved effective in electrocatalytic reactions in recent years. In this work, we systematically investigate the OER catalytic properties of single metal atoms supported by the NiN2 monolayer. Several typical transition metals with high single atom catalytic activity, such as Fe, Co, Ru, Rh, Pd, Ir, and Pt, were selected as catalytic active sites. The energy calculations show that transition metal atoms (Fe, Co, Ru, Rh, Pd, Ir, and Pt) are easily embedded in the NiN2 monolayer with Ni vacancies due to the negative binding energy. The calculated OER overpotentials of Fe, Co, Ru, Rh, Pd, Ir and Pt embedded NiN2 monolayers are 0.92 V, 0.47 V, 1.13 V, 0.66 V, 1.25 V, 0.28 V, and 0.94 V, respectively. Compared to the 0.57 V OER overpotential of typical OER noble metal catalysts IrO2, Co@NiN2 and Ir@NiN2 exhibit high OER catalytic activity due to lower overpotential, especially for Ir@NiN2. The high catalytic activity of the Ir embedded NiN2 monolayer can be explained well by the d-band center model. It is found that the adsorption strength of the embedded TM atoms with intermediates follows a linear relationship with their d-band centers. Besides, the overpotential of the Ir embedded NiN2 monolayer can be further reduced to 0.24 V under −2% biaxial strain. Such findings are expected to be employed in more two-dimensional material-supported single metal atom catalyzed reactions. [ABSTRACT FROM AUTHOR]

Over the past few decades, molecular machines have been extensively studied, since they are composed of single molecules for functional materials capable of responding to external stimuli, enabling motion at scales ranging from the microscopic to the macroscopic level within molecular aggregates. This advancement holds the potential to efficiently transform external resources into mechanical movement, achieved through precise control of conformational changes in stimuli-responsive materials. However, the underlying mechanism that links microscopic and macroscopic motions remains unclear, demanding computational development associated with simulating the construction of molecular machines from single molecules. This bottleneck has impeded the design of more efficient functional materials. Advancements in theoretical simulations have successfully been developed in various computational models to unveil the operational mechanisms of stimulus-responsive molecular machines, which could help us reduce the costs in experimental trial-and-error procedures. It opens doors to the computer-aided design of innovative functional materials. In this perspective, we have reviewed theoretical approaches employed in simulating dynamic processes involving conformational changes in molecular machines, spanning different scales and environmental conditions. In addition, we have highlighted current challenges and anticipated future trends in the collective control of aggregates within molecular machines. Our goal is to provide a comprehensive overview of recent theoretical advancements in the field of molecular machines, offering valuable insights for the design of novel smart materials. [ABSTRACT FROM AUTHOR]

Ensuring food safety is a critical concern for the development and well-being of humanity, as foodborne illnesses caused by foodborne bacteria have increasingly become a major public health concern worldwide. Traditional food safety monitoring systems are expensive and time-consuming, relying heavily on specialized equipment and operations. Therefore, there is an urgent need to develop low-cost, user-friendly and highly sensitive biosensors for detecting foodborne bacteria. In recent years, the combination of nanomaterials with optical biosensors has provided a prospective future platform for the detection of foodborne bacteria. By harnessing the unique properties of nanomaterials, such as their high surface area-to-volume ratio and exceptional sensitivity, in tandem with the precision of optical biosensing techniques, a new prospect has opened up for the rapid and accurate identification of potential bacterial contaminants in food. This review focuses on recent advances and new trends of nanomaterial-based biosensors for the detection of foodborne pathogens, which mainly include noble metal nanoparticles (NMPs), metal organic frameworks (MOFs), graphene nanomaterials, quantum dot (QD) nanomaterials, upconversion fluorescent nanomaterials (UCNPs) and carbon dots (CDs). Additionally, we summarized the research progress of color indicators, nanozymes, natural enzyme vectors and fluorescent dye biosensors, focusing on the advantages and disadvantages of nanomaterial-based biosensors and their development prospects. This review provides an outlook on future technological directions and potential applications to help identify the most promising areas of development in this field. [ABSTRACT FROM AUTHOR]

Two triplet excitons are generated through an ultrafast photophysical process, namely singlet fission (SF), providing a solution for efficient solar energy usage. In this work, we provide an effective guideline for designing SF materials by adjusting the planarity in cyclopentadithiophene (CPDT) derivatives. A practical strategy is proposed for tuning the quinoidal-biradical resonance structures by varying the electron push–pull groups of CPDTs for SF. The localized, delocalized, and intermediate charge-transfer excited configurations are predicted in the singlet excited state via computational simulations, which is further confirmed by ultrafast spectroscopy. Deduced from the potential energy surfaces in the low-lying excited states and transient absorption, the delocalized excited state is formed in 2.1 ps via postulated intramolecular SF in a polar solvent, followed by the ultrafast formation of the free triplet state with a lifetime of 6.8 ps. In comparison with different cross-conjugated chromophores, it is found that the increase in the charge separation could enhance the triplet-pair generation for iSF. We expect that by introducing symmetry-breaking modifications in the electronic configurations and adjusting the separation between the push–pull groups of CPDTs, it should be possible to prolong the duration of the free triplet state by preventing recombination within the triplet-pair excited configuration. [ABSTRACT FROM AUTHOR]

Designing p–n junctions without introducing foreign atoms has attracted considerable attention, especially as far as high carrier concentrations are concerned. Here, we systematically investigate the structural and electronic properties of polar GaN/MoSSe by first-principles calculations. The diversity of GaN and MoSSe structures and their polarization leads to versatile heterostructures with different electronic behaviors. Particularly, the band alignment can be effectively modified from type-I or type-II to type-III, forming a self-doped p–n junction. Interestingly, the carrier concentration in self-doped p–n junctions is large (>3.48 × 1012 cm−2). This unique behavior is mainly attributed to the charge redistribution and intrinsic electric field induced by polarization, leading to a shift of the band edge positions and induction of the quantum Stark effect. This work provides a perspective for regulating vdW heterostructures and shows possibilities for designing self-doped p–n semiconductors for low-power and multi-functional device applications. [ABSTRACT FROM AUTHOR]

Z-scheme van der Waals heterojunctions are very attractive photocatalysts attributed to their excellent reduction and oxidation abilities. In this paper, we designed InN/XS2 (X = Zr, Hf) heterojunctions and explored their electronic structure properties, photocatalytic performance, and light absorption systematically using first-principles calculations. We found that the valence-band maximum (VBM) and conduction-band minimum (CBM) of the InN/XS2 (X = Zr, Hf) heterojunctions are contributed by InN and XS2, respectively. Photo-generated carriers transferring along the Z-path can accelerate the recombination of interlayer electron–hole pairs. Therefore, the photogenerated electrons in the CBM of the InN layer can be maintained making the hydrogen evolution reaction occur continuously, while photogenerated holes in the VBM of the Ti2CO2 layer make the oxygen evolution reaction occur continuously. The band edge positions of heterojunctions can straddle the required water redox potentials, while pristine InN and XS2 (X = Zr, Hf) can only be used for photocatalytic hydrogen evolution or oxygen evolution, respectively. Furthermore, the HER barriers can be tuned by transition metal doping. With Cr doping, the hydrogen evolution reaction (HER) barriers decrease to −0.12 for InN/ZrS2 and −0.05 eV for InN/HfS2, very close to the optimal value (0 eV). In addition, the optical absorption coefficient is as high as 105 cm−1 in the visible and ultraviolet regions. Therefore, the InN/XS2 (X = Zr, Hf) heterojunctions are expected to be excellent photocatalysts for water splitting. [ABSTRACT FROM AUTHOR]

Low activity and poor product selectivity of CO2 reduction have seriously hampered its further practical application. Introducing p-block atoms to the catalyst is regarded as a promising strategy due to the versatility of p orbitals and diversity of p-block elements. Here, we systematically studied the influence of p-block atom X (X = C, N, O, S, and Se) on CO2 catalytic properties on a Sn(200) surface by first-principles calculation. Our work shows that all the p-block atoms are relative stable with Ef in the range of −5.11 to −3.59 eV. Further calculation demonstrates that the diversity of the p-block atoms results in unique CO2 electrocatalytic activity and product selectivity. Interestingly, the p-block C atom shows bi-functional activity to form two-electron products HCOOH and CO, with the corresponding energy barriers remarkably low at about 0.19 eV and 0.28 eV. In particular, the p-block S(Se) atom appears to have striking HCOOH selectivity, with the energy barrier to form HCOOH only a quarter of that to form the CO product. This unusual behavior is mainly attributed to the adsorption strength and frontier orbital interaction between the p-block atom and intermediates. These findings can effectively provide a valuable insight into the design of highly efficient CO2 electrocatalyst. [ABSTRACT FROM AUTHOR]

Designing photocatalysts with suitable band alignment and considerable carrier mobility is extremely important. Here, by means of first-principles calculation, we systematically investigated the structural, photoelectronic, and carrier mobility behavior of the two-dimensional Janus MoSSe/WSSe superlattice. The results show that both armchair-type (AN-SL) and zigzag-type (ZN-SL) superlattices are relatively stable with negative Ef values in the range of −2.35 to −1.16 eV. Band gap and band edge position calculations demonstrate that these superlattices are completely suitable for water splitting by visible light. Particularly, the interface contact of the superlattice can be spontaneously changed from type-I to type-II when N > 4, facilitating separation of photogenerated carriers. Furthermore, the hole carrier mobility (μh) in AN-SL can be effectively regulated from 1200 to 2200 cm2 V−1 s−1, much larger than that of the isolated components. Interestingly, the disparity of hole/electron carrier mobility is remarkably large with an approximately 20-fold difference, showing the potential in prohibiting the recombination of photogenerated carriers. This unique behavior is further illustrated by the relaxation times of carriers, where the lifetime of hole carriers is about 7 times larger than that of electron carriers. These findings suggest that forming a Janus superlattice is a promising approach for regulating the photoelectronic properties of semiconductors, providing a promising way to design high efficiency photocatalysts. [ABSTRACT FROM AUTHOR]

Microencapsulated core–shell structures have proven to be an effective means for realizing high-enthalpy and shape-stabilized phase change materials (PCMs), but the low heat and shear resistance of the shell material seriously restrict their practical application in functional materials. Here, leak-free and shape-stabilized PCMs were fabricated by a strategy of confinement of phase change media via capillary adsorption on synthetic radial spherical silica (RSSiO2) scaffolds. The organic and inorganic components exchange the traditional core–shell positions, forming a new phase change composite with an inorganic material as the core layer. It not only endowed this composite with high-temperature regulation ability but also its enthalpy value was stabilized at 96.0 J g−1 after the heat treatment process. More importantly, its heat-resistant stability was significantly improved, reaching above 300–350 °C. This indicates that the core structure of inorganic RSSiO2 could not merely solve the inherent defects of conventional microcapsules but provides higher thermal stability as well, which is expected to be applied in high-temperature melt fiber spinning and electrical thermal management of devices. [ABSTRACT FROM AUTHOR]

The Schottky barrier height (ESBH) is a crucial factor in determining the transport properties of semiconductor materials and it directly regulates the carrier mobility in opto-electronics devices. In principle, van der Waals (vdW) Janus heterostructures offer an appealing avenue for controlling the ESBH. However, the underlying atomistic mechanisms are far from understood conclusively, which prompts further research in the topic. To this end, here we carry out an extensive first-principles study of the electronic properties and ESHB of several vdW Janus MXY/graphene (M = Mo, W; X, Y = S, Se, Te) heterostructures. The results of the simulations show that by changing the composition and geometry of the heterostructure's interface, it is possible to control its electrical contact, and thence electron transport properties, from ohmic to Schottky with up to a factor seven variation in the ESBH. Detailed analysis of the simulations enables rationalization of this highly attractive property on the basis of the interplay between the permanent dipole moment of the Janus MXY sheet and the induced one due to interfacial charge redistribution at the MXY/Gr interface. Such an interplay is shown to be highly effective in altering the electrostatic potential difference across the vdW Janus heterostructure, determining its ESBH, and thence Schottky (ohmic) contact type. These computational findings contribute guidelines to control the electrical contacts in Janus heterostructures towards the rational design of electrical contacts in nanoscale devices. [ABSTRACT FROM AUTHOR]

The ever-increasing fossil fuel consumption and portable electronic device proliferation have caused numerous environmental challenges in terms of producing massive carbon dioxide (CO2) emissions and end-of-life wastes. Incorporating naturally abundant resources into the recyclable and renewable battery components at the design stage has, therefore, become essential. Cellulose (CC) is an attractive raw material for eco-friendly solid/gel polymer electrolytes. However, they suffer from unsatisfactory ionic conductivity due to the narrow spacing between the molecular chains originating from the strong inherent inter- and intra-molecular hydrogen bonds. Herein, we propose a strategy to achieve highly conductive cellulose by bedecking the CC with CO2via its ionization (CC-CO2), which breaks the inherent inter- and intra-molecular hydrogen bonds. Upon being employed as quasi-solid-electrolytes for Zn–air batteries (ZABs), the CO2-decorated CC with substantially enhanced conductivity can effectively impede the CO2 poisoning of the electrolyte and Zn dendrite formation, endowing the fabricated ZABs with promoted electrochemical performance and stability even in a CO2-rich atmosphere. The spent CC-CO2 and all chemicals used for the ionization can be facilely and efficiently recycled. Moreover, the CC-CO2 can be degraded to CO2 and glucose on demand. The strategy here sheds light on integrating CO2 utilization with bio-derived materials for renewable energy storage systems to meet sustainability targets. [ABSTRACT FROM AUTHOR]

Charge-carrier mobility is a determining factor of the transport properties of semiconductor materials and is strongly related to the optoelectronic performance of nanoscale devices. Here, we investigate the electronic properties and charge carrier mobility of monolayer Janus MoSSe nanoribbons by means of first-principles simulations coupled with deformation potential theory. These simulations indicate that zigzag nanoribbons are metallic. Conversely, armchair nanoribbons are semiconducting and show oscillations in the calculated band gap as a function of edge-width according to the 3p < 3p + 1 < 3p + 2 rule, with p being the integer number of repeat units along the non-periodic direction of the nanoribbon. Although the charge-carrier mobility of armchair nanoribbons oscillates with the edge-width, its magnitude is comparable to its two-dimensional sheet counterpart. A robust room-temperature carrier mobility is calculated for 3.5 nm armchair nanoribbons with values ranging from 50 cm2 V−1 s−1 to 250 cm2 V−1 s−1 for electrons (e) and holes (h), respectively. A comparison of these values with the results for periodic flat sheet (e: 73.8 cm2 V−1 s−1; h: 157.2 cm2 V−1 s−1) reveals enhanced (suppressed) hole (electron) mobility in the Janus MoSSe nanoribbons. This is in contrast to what was previously found for MoS2 nanoribbons, namely larger mobility for electrons in comparison with holes. These differences are rationalized on the basis of the different structures, edge electronic states and deformation potentials present in the MoSSe nanoribbons. The present results provide the guidelines for the structural and electronic engineering of MoSSe nanoribbon edges towards tailored electron transport properties. [ABSTRACT FROM AUTHOR]

In this work, we report a comparative study of the interfacial properties of fcc-Al/L12-Al3M (M = Sc, Ti, V, Y, Zr, Nb) from first-principles calculations. It is found that the fcc-Al(111)/L12-Al3Nb(111) interface is energetically favorable because of its negative interfacial energy (−0.225 J m−2), whereas the interfacial energies of the other five interfaces are positive. Despite their thermodynamically unfavorable characteristics, the stabilities of the formed interfaces are ranked in the order fcc-Al(111)/L12-Al3Nb(111) > fcc-Al(111)/L12-Al3Ti(111) > fcc-Al(111)/L12-Al3Zr(111) > fcc-Al(111)/L12-Al3Sc(111) > fcc-Al(111)/L12-Al3V(111) > fcc-Al(111)/L12-Al3Y(111). Moreover, the computed generalized stacking fault energy curves revealed that the (111)[11−2] slip system is preferred over the (111)[10−1] slip system under external stresses for all six interfaces. Based on the Rice ratio criterion, the interface slips also energetically favor the generation of stacking faults instead of cleavage for these interface systems; this finding implied that these interfaces did not greatly influence the plastic deformation behavior of aluminum. Furthermore, the derived bulk elastic properties indicate that fcc-Al, L12-Al3Nb, and L12-Al3V tend to present ductile behavior, while L12-Al3Zr, L12-Al3Ti, L12-Al3Y, and L12-Al3Sc are found to be brittle compounds. Nevertheless, all of these intermetallics can strengthen the aluminum matrix without losing much plasticity to provide a higher elastic modulus than aluminum along with the ductile interface nature of fcc-Al(111)/L12-A13M(111). [ABSTRACT FROM AUTHOR]

The conversion of CO2 to value-added chemicals represents an attractive approach for CO2 utilization. Formate and methanol are sustainably valuable fuels and chemical feedstocks. However, the CO2 reduction reaction (CO2RR) suffers from unsatisfactory activity, low faradaic efficiency (FE) and inadequate durability. In this study, ultrathin bismuth nanosheets (NSs) and Bi NSs grown on nitrogen-doped ordered mesoporous carbon (OMC-N) are prepared from in situ transformation of atomic-thick Bi2O2Se and Bi2O2Se/OMC-N. Bi NSs enable efficient formate production with a large current density (51 mA cm−2 at −1.0 VRHE) and excellent selectivity (FE ≈ 90%). Interestingly, Bi NSs/OMC-N catalyzes the conversion of CO2 to formate and methanol simultaneously with maximum FEformate (70%) and FEmethanol (67%), and long-term stability (35 h). The composition produces 9.15 and 8.00 μmol cm−2 h−1 for formate and methanol at −0.67 VRHE, respectively, and methyl formate could be further prepared from the above products. Moreover, the generated Bi NSs achieve 288 mA cm−2 at −0.61 VRHE within a flow cell. Theoretical studies reveal that the activity for methanol is rationalized as the outcome of abundant pyridinic-N sites that stabilize the *COOH intermediate. Our study unveils the potential of hierarchical Bi NSs/OMC-N for an efficient and stable CO2RR to produce chemical feedstocks. [ABSTRACT FROM AUTHOR]

Photoreduction of molecular CO2 by solar light into added-value fuels or chemical feedstocks is an appealing strategy to simultaneously overcome environmental problems and energy challenges. However, multiple reaction steps and a large number of possible products have significantly hindered the development of highly selective catalysts capable of delivering CO2 conversion with high efficiency. Recently, several strategies associated with different conversion mechanisms have been proposed to improve the activity and product selectivity of CO2 photocatalysts. These are based on development of low dimensional nanomaterials, defect or facet engineering, design of tailored heterostructures, and carrier conductivity enhancement. In spite of impressive progress in the field, real-world applications are yet to be delivered. To sustain further research in this promising field, here we provide a short frontier of recent advances in activity and selectivity of CO2 reduction photocatalysts, together with a critical discussion of further avenues of research in this field. [ABSTRACT FROM AUTHOR]

Conductive polymer composites (CPCs) with segregated structures can achieve excellent electrical conductivity with low conductive filler, however, the weak interfacial adhesion always impairs their mechanical performance and limits the practical applications. Herein, we developed a carbon nanotube (CNT)/thermoplastic polyurethane (TPU) composite containing a novel co-continuous segregated structure, with a highly continuous TPU region and highly continuous CNT network among the interfaces of the TPU region, via the utilization of a 3D printed TPU skeleton. The electrical conductivity and mechanical performance were simultaneously improved. The co-continuous segregated CNT/TPU composite with only 4.0 wt% CNT achieves a superb electrical conductivity of 46.7 S m−1, which is 83% higher than that for the CNT/TPU composite with a conventional segregated structure. The tensile strength and the elongation at break of the co-continuous segregated CNT/TPU composite are 18.1 MPa and 281%, exhibiting 389% and 1238% enhancements in comparison to 3.7 MPa and 21% for the conventional segregated structure. Our work reveals a new methodology, i.e., the construction of a co-continuous segregated structure with a highly continuous polymer region and highly continuous conductive networks composed of interfacial distributed conductive fillers, to address the trade-off between electrically conductive performance and mechanical performance in CPCs, which can be extended to almost all other 3D-printed continuous polymer skeletons and even other 3D continuous polymer matrices (e.g., melt spun or mechanically woven 3D fabric). [ABSTRACT FROM AUTHOR]

A stretchable carbon nanotube (CNT)/thermoplastic polyurethane (TPU) composite with an enhanced segregated structure was developed for use as an electrically driven heater. The segregated conductive networks can be repaired after multiple processing cycles, endowing the CNT/TPU composite with highly reliable electrical heating performance. The steady-state maximum temperature (TMAX) of the composite maintains a high retention of 95.2% even after the tenth cycle of processing, while the TMAX value for the CNT/TPU composite with a segregated structure suffers a 68.3% decrease after the second cycle of processing. Moreover, the enhanced segregated structure composite (ESSC) exhibits a tensile strength of 23.8 MPa and an elongation at break of 419.9%, which are almost doubled in comparison to the segregated structure composite (SSC); also, it meets the requirements for practical application as an electrically driven heater (EDH). The ESSC is capable of accommodating repeated heating and a large amount of strain and bending in a completely reversible fashion, thereby proving outstanding durability. This was proven by its application as a wearable electrical heater for personal heating management. This ESSC can facilitate an electrically driven heater with segregated networks for application in integrated flexible devices. [ABSTRACT FROM AUTHOR]

The TiO2–Pt–water interface is of great relevance in photocatalysis where Pt is widely used as a co-catalyst for enhancing hydrogen evolution in aqueous TiO2. Using ab initio molecular dynamics, we investigated this interface focusing on Pt single atoms supported on anatase TiO2(101) in a water environment. Based on recent experiments showing a broad distribution of Pt coordination sites in TiO2, we examined six distinct single-Pt supported species with different nominal Pt oxidation states, namely: Pt, PtOH, and PtO2 species adsorbed on the stoichiometric surface; Pt adsorbed at a surface oxygen vacancy (Ov); and Pt substituting a surface Ti cation (PtTi), both without and with an accompanying Ov (PtTi + Ov). As found for the pristine anatase surface, interfacial water remained intact in the presence of a nearly neutral Pt adatom within the time duration of our simulations (∼15 ps). Similarly, no (or only temporary) water dissociation was observed at the PtTi + Ov and PtO2 interfaces, due to the formation of very stable planar Pt coordination structures that interact only weakly with water. In contrast, water dissociated with OH− (H+) on the Pt atom when this substituted a surface Ti (oxygen) ion as well as on PtOH. The significant proton affinity of Pt atoms at surface oxygen vacancies suggests that negatively charged Pt species are particularly efficient at catalyzing hydrogen evolution in aqueous TiO2. [ABSTRACT FROM AUTHOR]

An appropriate band structure and effective carrier separation are very important for the performance of a solar photocatalyst. In this paper, based on first-principles calculations, it was predicted that blue phosphorene (BlueP) and a C2N monolayer can form a promising metal-free type-II heterojunction. The electronic structure of the BlueP/C2N heterojunction facilitated the overall water splitting reactions well. The projected band structure showed that the conduction band edge was contributed by C2N and the valence band edge was dominated by BlueP. Under the combination of the driving force of the band offset and the built-in electric field between the two layers, the photo-generated electrons and holes were transferred spontaneously to the conduction band of C2N and the valence band of BlueP, respectively. An effective carrier separation in the heterostructure was thus achieved. More notably, the obtained light absorption of the BlueP/C2N junction showed an obvious red-shift, which greatly extended the area of light adsorption to the visible light region. We further proposed that strain could also be used to modulate the band gap and the band edge positions of the heterojunction. Our results not only provide a theoretical design, but also reveal the fundamental separation mechanism of the photo-generated carriers in the BlueP/C2N heterojunction. [ABSTRACT FROM AUTHOR]

White-light-emitting Ag, Mn: Zn–Ga–S/ZnS quantum dots (QDs) with a gratifying photoluminescence (PL) quantum yield (QY) of up to 90% were prepared, and shown to be ultra-stable, maintaining a high PL intensity at 300 °C or for 32 h of UV illumination. These QDs were employed in a white QD-LED displaying a color rendering index (CRI) of 72 and maximum current efficiency of 0.22 cd A−1. [ABSTRACT FROM AUTHOR]

The major challenges faced by magnetic–luminescent bi-functional nanoparticles include poor luminescence intensity and severe magnetic–luminescence quenching. Introduction of an intermediate layer with localized surface plasmon resonance (LSPR) effects in magnetic–luminescent bi-functional nanoparticles plays a major role in solving these challenges. Herein, a fascinating process of plasmonic energy conversion in Fe3O4@WO3@GdF3:Eu3+ heterostructures, which can enhance the luminescence by LSPR effects of WO3, is demonstrated. It is proposed that the LSPR of WO3 is the primary reason for the enhanced luminescence of Fe3O4@GdF3:Eu3+. Moreover, saturation magnetization did not significantly decline on introducing WO3 with LSPR effect. This research conclusion can solve the problems faced by magnetic–luminescent bimodal imaging materials and promote the application of this type of composite materials in tumor therapy and optical confocal microscopy technology. [ABSTRACT FROM AUTHOR]

Optimized white light emitting Ag,Mn:Zn–In–S quantum dots (QDs) were synthesized via a simple, scalable, reproducible, and low-cost one-pot non-injection synthetic approach. After coating a thick ZnS shell (∼12 monolayers) on the core QDs, high photoluminescence (PL) quantum yield (QY) up to 76% was achieved and high emission efficiency was retained even when the initially oil-soluble QDs were transferred into aqueous media by ligand replacement. Moreover, both thermal stability and photostability of thick shell-Ag,Mn:Zn–In–S/ZnS QDs were significantly enhanced as compared with those of Ag,Mn:Zn–In–S core QDs due to the suppressed surface defects resulting from the passivation of the dense ZnS layers. White quantum dot light-emitting diodes (QD-LEDs) were fabricated using thick shell Ag,Mn:Zn–In–S/ZnS QDs as single QDs emitter, showing good performance with maximum current efficiency of 1.86 cd A−1 corresponding to external quantum efficiency (EQE) of 0.82% at a current density of 0.065 mA cm−2, color rendering indices (CRI) of 83, Commission International d’Eclairage (CIE) coordinates of (0.344, 0.393) and correlated color temperature (CCT) of 5156 K. [ABSTRACT FROM AUTHOR]

Graphene films are considered promising electromagnetic interference (EMI) shielding materials in view of high electrical conductivity, light weight, and flexibility. Nevertheless, pristine graphene films exhibit only modest mechanical performance because of the weak interfaces between graphene nanosheets. We have developed an advanced graphene film that integrates excellent EMI shielding performance with improved mechanical performance, by intercalating calcium alginate (CA) molecules into reduced graphene oxide (rGO) nanosheets. The rGO/CA film exhibits an EMI shielding effectiveness (EMI SE) of 25.7 dB at only 12 μm thickness, and the corresponding specific EMI SE is 2142 dB mm−1, which is far superior to previously reported EMI shielding materials. Importantly, the rGO/CA film achieves an excellent tensile strength of 118.0 MPa and a toughness of 4.6 MJ m−3, which is 102% and 130% higher than those of the rGO film. Such significant enhancement is attributed to the synergistic interfacial interactions of hydrogen bonding between CA and rGO nanosheets and ionic bonding between calcium ions and rGO nanosheets. Moreover, the rGO/CA film shows a high EMI shielding reliability (96% EMI SE retention even after 5000 folding cycles). Its features make the rGO/CA film highly attractive for EMI shielding applications, especially in aircraft, aerospace, and next-generation flexible electronics. [ABSTRACT FROM AUTHOR]

We have used two-photon photoemission (2PPE) spectroscopy and first-principles density functional theory calculations to investigate the electronic structure and photoabsorption of the reduced anatase TiO2(101) and rutile TiO2(110) surfaces. 2PPE measurements on anatase (101) show an excited resonance induced by reduced Ti3+ species centered around 2.5 eV above the Fermi level (EF). While this state is similar to that observed on the rutile (110) surface, the intensity of the 2PPE peak is much weaker. The computed oscillator strengths of the transitions from the occupied gap states to the empty states in the conduction band show peaks between 2.0 and 3.0 eV above the conduction band minimum (CBM) on both surfaces, confirming the presence of empty Ti3+ resonances at these energies. Although the crystal field environment of Ti ions is octahedral in both rutile and anatase, Ti3+ ions exhibit distinct d orbital splittings due to different distortions of the TiO6 units. This affects the directions of the transition dipoles from the gap states to the conduction band, explaining the polarization dependence of the 2PPE signal in the two materials. Our results also show that the Ti3+ induced states in the band gap are shallower in anatase than in rutile. The d → d transitions from the occupied gap states to the empty Ti3+ excited states in anatase can occur at energies well below 3 eV, consistent with the observed visible-light photocatalytic activity of Ti3+ self-doped anatase. [ABSTRACT FROM AUTHOR]

Asymmetrical etching of nanoparticles was achieved by employing interface-confined galvanic replacement reactions. Interfacial Ag nanocubes, nanowires and nanospheres were fabricated into symmetry-reduced cubic, trough-like and spherical nanocups, respectively. The formation of nanocups is attributed to in situ local nanomasking and selective etching of interfacial nanoparticles at the single-nanoparticle level. [ABSTRACT FROM AUTHOR]

A 3D inorganic–organic hybridized skeleton cadmium borate [Cden][B5O8(OH)] (1) (en = ethylenediamine) has been solvothermally synthesized. By calcining it, specific shape carbon dots (C-dots) with abundant free radicals were observed. In addition, C-dots in the ethanol phase exhibited variable photoluminescence and showed rare turn on or off effects to Cr3+ ions and CdSe/ZnS quantum dots, but only a turn on effect to Cs+ ions and a turn off effect to CsPbBr3 quantum dots. [ABSTRACT FROM AUTHOR]

Herein, we report a new series of ultra-stable Cd-free Ag:Zn–Ga–S/ZnS quantum dots (QDs) with an overall short emission wavelength tunable from 370 to 540 nm via a facile one-pot non-injection method. The highest PL quantum yield of the resultant core/shell QDs could be up to 85%, and the exceptional luminescence could be maintained not only at 300 °C but also after phase transfer. [ABSTRACT FROM AUTHOR]

Recent studies have unveiled the unique osteogenesis and angiogenesis abilities of akermanite. However, such bioceramics rarely fit well into irregularly shaped bony cavities (such as bone defects and the maxillary sinus). In this study, an injectable hydrogel SAG system containing sodium alginate, akermanite and glutamate was prepared and evaluated in such defects. Cell proliferation experiments showed that except for stoste, the other extracts showed no cytotoxicity at various concentrations. In addition, the gene expression of Runx2 (runt-related transcription factor-2), BMP-2 (bone morphogenetic protein-2), ALP (alkaline phosphatase), and BSP (bone sialoprotein) and the activity of ALP were significantly higher in human bone marrow stromal cells (hBMSCs) cultured with 1/2 hydrogel extracts containing 66.9 ppm calcium ions, 23.8 ppm magnesium ions and 33.5 ppm silicon ions compared to those in hBMSCs cultured with the control medium, which indicated that the hydrogel extracts could stimulate the osteogenic differentiation of hBMSCs. Further experiments revealed that the ERK signaling pathway was engaged in osteogenic differentiation as early as 15 minutes after incubation with the hydrogel extracts. In addition, hBMSCs incubated in half-diluted extracts exhibited an almost doubled migration ability compared with the hBMSCs in the control group. More specifically, compared to the control group, hBMSCs cultured with 1/2 hydrogel extracts showed a 7% increase and a 10-fold increase in the protein and gene levels of CXCR4 (C-X-C chemokine receptor type 4), respectively. In vivo tests demonstrated that the bone formation rate of SAG hydrogels injected alone was similar to that of its counterpart seeded with BMSCs, reaching 24% at three months after operation. Therefore, it could be concluded that SAG hydrogels contribute to bone regeneration by not only promoting osteogenic differentiation but also by enhancing the recruitment of BMSCs to defect sites, making the injectable SAG hydrogels competent for the regeneration of irregular bony cavities. [ABSTRACT FROM AUTHOR]

Transition metal chalcogenides have attracted considerable attention for the further development of nanoscale devices, however low carrier mobility seriously prevents its further application. Here, the first-principles calculations are used to explore the structural, electronic, and carrier mobility properties of few layer Janus MoSSe in different types of stacking. The result shows that AC-stacking is the most favored stacking regardless of combination mode. Besides the band gap regulation, the dipole moment perpendicular to the x–y plane can be effectively modified through varying of the combination mode and thickness of few layers, which is further evidenced by the plane electrostatic potential energy difference between the two sides. Furthermore, the carrier mobility in these Janus structures can be greatly affected by the dipole and thickness. Although the carrier mobility in monolayer MoSSe is relatively low, the bilayer or trilayer structures have a quite high electron carrier mobility of 1194 cm2 V−1 s−1 and hole carrier mobility of 5894 cm2 V−1 s−1, mainly determined by the deformation potential. The results presented here show that the few layer Janus MoSSe has a potential in designing electronic devices or photocatalysts such as for water splitting with the intrinsic built-in electronic field. [ABSTRACT FROM AUTHOR]

We developed a facile noninjection synthetic method to prepare white light-emitting Cd-free thick shell Cu,Mn:Zn–In–S/ZnS quantum dots (QDs) with high stability. Based on systematic research on the relationship between shell thickness and QD stability, it was demonstrated that overcoating thick ZnS passivation layers (∼7.9 monolayers) onto a Cu,Mn:Zn–In–S core could improve the photoluminescence quantum yield (PL QY) substantially up to 75% and the high PL QY could be maintained after the initial oil-soluble QDs were transferred into aqueous media via ligand exchange. The PL lifetime of thick shell Cu,Mn:Zn–In–S/ZnS QDs increased remarkably by 30-fold (from 0.13 μs to 3.50 μs). Also, the prominent thermally and photochemically stable properties of the resultant thick shell QDs have been ascertained. Moreover, gram-scale white emission Cu,Mn:Zn–In–S/ZnS QDs could be prepared in a single batch reaction via the noninjection synthetic approach. In addition, the as-obtained white emissive Cu,Mn:Zn–In–S/ZnS QDs could be employed in white quantum dot light-emitting diode (QD-LED) devices and have shown good performance with a lower turn-on voltage of 5.7 V and color rendering indexes (CRI) as high as 85, indicating that Cu,Mn:Zn–In–S/ZnS QDs could be a potential candidate in QD-based lighting or solid-state lighting as a single color-converting material. [ABSTRACT FROM AUTHOR]

Bismuth oxyhalides (BiOX, X = Cl, Br, and I) are a new family of promising photocatalysts. BiOCl and BiOBr possess large band gaps and weak absorption in visible light regions, which limit their applications. Although the band gap of BiOI is suitable to absorb most of the visible light, its redox capability is very weak. In this work, the doping and strain effects on the electronic structures and optical properties of BiOCl are explored using first principle calculations. The results show that doping in BiOCl, especially co-doping of Sb and I atoms, can obviously decrease the band gaps along with enhancing the optical absorption coefficients of pristine BiOCl because of the electronegativity difference between Sb/I atoms and Bi/Cl atoms. Meanwhile the band gap of BiOCl can be tuned under strain. This work offers potential strategies to enhance BiOCl absorption coefficients in the visible light region and its photocatalyst activity. [ABSTRACT FROM AUTHOR]

A UiO-66 analog was synthesized in 100 s using water-assisted grinding. The linker solubility suggested that tetrafluorobenzene-1,4-dicarboxylic acid was the best linker. Zr–metal–organic framework nanocrystals displayed good topologies and hydrophobicities, and high water/thermal stabilities. The less amorphous complex led to higher porosities and pore volumes with a 60 min grinding time. [ABSTRACT FROM AUTHOR]

Surfaces modified with a functional molecular monolayer are essential for the fabrication of nano-scale electronics or machines with novel physical, chemical, and/or biological properties. Theoretical simulation based on advanced quantum chemical and classical models is at present a necessary tool in the development, design, and understanding of the interfacial nanostructure. The nanoscale surface morphology, growth processes, and functions are controlled by not only the electronic structures (molecular energy levels, dipole moments, polarizabilities, and optical properties) of building units but also the subtle balance between intermolecular and interfacial interactions. The switchable surfaces are also constructed by introducing stimuli-responsive units like azobenzene derivatives. To bridge the gap between experiments and theoretical models, opportunities and challenges for future development of modelling of ferroelectricity, entropy, and chemical reactions of surface-supported monolayers are also addressed. Theoretical simulations will allow us to obtain important and detailed information about the structure and dynamics of monolayer modified interfaces, which will guide the rational design and optimization of dynamic interfaces to meet challenges of controlling optical, electrical, and biological functions. [ABSTRACT FROM AUTHOR]

Transition metal oxides (TMOs) have attracted extensive research attention as promising anode materials for lithium ion batteries due to their high theoretical capacities. However, their applications have been hindered by their poor electronic conductivity and drastic volume change in the reversible conversion reaction. Here three-dimensional NiO ultrathin nanosheets were grown on the composites of N-doped carbon nanotubes (N-CNTs) and Ni foam by chemical vapor deposition and electrochemical deposition methods, and the 3D Ni foam/N-CNT/NiO nanosheet electrode thus obtained exhibits larger capacity, better cycling stability, superior rate capability and higher ionic conductivity. The first-principles calculations suggest that N-doping can improve the interaction between NiO and N-CNTs, which can facilitate fast electron hopping from N-CNTs to NiO to enhance the electronic conductivity. The results indicate that the introduction of N-doped carbon nanotubes can greatly improve the electrochemical performance of NiO. The understanding between N-CNTs and NiO can be extended to the preparation of N-CNTs coated with other high-performance electrode materials for energy-storage devices. [ABSTRACT FROM AUTHOR]

Osseointegration remains a major clinical challenge in osteoporotic patients. Strontium (Sr) has been shown to be a significant therapy to favor bone growth by both increasing new bone formation and reducing bone resorption. In this study, we attempt to chemically functionalize Ti implants by micro-arc oxidation, alkali treatment and ion exchange. This functionalized Ti surface possessed a hierarchical topography with Sr incorporation, which can release Sr ions at a slow rate. To our knowledge, this work is the first to use this type of Sr-doped Ti surface to address osteoporotic bone mesenchymal stem cells (BMSCs) in the dual directions of bone regeneration, bone formation and bone resorption. The modified surface was demonstrated to remarkably enhance the adhesion, spreading, and osteogenic differentiation of BMSCs in vitro. The effect of the wash-out solution from various groups on osteoporotic BMSCs was also investigated. The Sr-doped group can improve the ALP activity and osteogenic gene expression. Moreover, the Sr-doped group and the wash-out solution show the most inhibition in osteoclast formation and maturation. Furthermore, the increased bioactivity of the hierarchical structure was also confirmed with the ovariectomized rat femur model in vivo. The outcome of fluorescence labeling, histology and histomorphometric analysis demonstrated a significant promotion of osseointegration in ovariectomized rats. Altogether, the experimental data indicate that the fabrication of a Sr-doped hierarchical Ti surface is a meaningful attempt to incorporate the Sr nutrient element into Ti-based implants, and it is expected to be exploited in developing better osseointegration for osteoporotic patients. [ABSTRACT FROM AUTHOR]

Graphite may be viewed as a low-surface-energy carbon allotrope with little layer–layer interaction. Other low-surface-energy allotropes but with much stronger layer–layer interaction may also exist. Here, we report a first-principles prediction for one of the known carbon allotropes, bcc-C6 (a body centered carbon allotrope with six atoms per primitive unit), that should have exceptionally low-surface energy and little size dependence down to only a couple layer thickness. This unique property may explain the existence of the relatively-high-energy bcc-C6 during growth. The electronic properties of the bcc-C6 thin layers can also be intriguing: the (111), (110), and (001) thin layers have direct band gap, indirect band gap, and metallic character, respectively. The refrained chemical reactivity of the thin layers does not disappear after cleaving, as lithium-doped (Li-doped) 3-layers (111) has a noticeably increased binding energy of H2 molecules with a maximum storage capacity of 10.8 wt%. [ABSTRACT FROM AUTHOR]

Silver nanowires (AgNWs) with high aspect ratio are usually prepared via complicated multi-step procedures or by a relatively tedious polyol method with the assistance of Xa−/O2 (Xa− represents the halide ion or sulfion) etching. In this paper, silver nanowires with both a high aspect ratio of 800–1600 and high purity were prepared via a simple, cost-effective, high-yield and eco-friendly method without the introduction of external halides or sulfides. Embedding the as-prepared silver nanowires beneath the surface of the poly(dimethylsiloxane) (PDMS) substrate, novel stretchable AgNW/PDMS electrodes with superior comprehensive performances were fabricated. The resulting AgNW/PDMS electrodes show high optoelectronic performance. Without annealing, transparent conductive films with both high conductivity and transmittance, Rs = 14 Ω□−1, T = 90% and Rs = 9 Ω□−1, T = 81% were fabricated, respectively. To the best of our knowledge, they are among the best AgNW/PDMS electrodes in terms of transparency and electrical conductivity. The transparent electrodes also possess excellent electromechanical performance and stretchability (no obvious changes in sheet resistance with strain up to 20%). What is more, the conductive layer of the as-prepared electrodes shows strong adhesion to the substrates, demonstrating their superior durability. They also show high flexibility, good chemical stability and high uniformity. [ABSTRACT FROM AUTHOR]