Stacking Of Nanosheets Research Articles

Rearrangement of cellulose molecular chains in situ for stabilizing two-dimensional nanochannels

Two-dimensional (2D) nanochannels originating from ordered stacking of nanosheets exhibit great potential in osmotic energy harvest, which provides a promising way to address the increasing energy crisis. Although polymer nanorods have unique advantages in constructing and adjusting 2D nanochannels, the stability of these nanochannels still faces great challenges. Herein, cellulose nanocrystal (CNC) nanorods are intercalated between graphene oxide (GO) nanosheets to construct 2D sub-nanochannels. Ordered sub-nanochannel structures are first formed through a vacuum assisted self-assembly of CNC and GO. A facile strategy involving the rearrangement of cellulose molecular chains in situ is subsequently employed to stabilize the dimensions and arrangement of the sub-nanochannels. After the rearrangement, the mechanical properties and water stability of the sample are greatly enhanced due to the increased dynamic hydrogen bond network, and tensile strength and strain at break are increased by 88.7% and 472.2%, respectively. Additionally, the prepared membrane exhibits a power density of 0.49 W m-2 under a 50-fold salinity gradient with a long-term stability and could be further improved to 0.75 W m-2 by reducing the ion transport distance. The photo-thermal conversion property of the membrane could also benefit the osmotic power generation. Our work opens new insights into stabilizing the dimensions and arrangement of 2D nanochannels constructed by nanorods and nanosheets for commercial osmotic power generation.

Chirality Engineering of Nanostructured Copper Oxide for Enhancing Oxygen Evolution from Water Electrolysis.

The exploration of a new conceptual strategy for improving the oxygen evolution reaction (OER) of earth-abundant electrocatalysts is critical. In this study, chiral copper oxide nanoflower is explored by a self-assembly method. The characterization suggests the chiral structure originates from the crystal plane-level helical stack of the secondary nanosheets. Of note, the assembly illustrates a record-high degree of spin polarization of 96%, indicating the ideal alignment of electron spin. Moreover, density function theory calculations show the chiral structure reducing the reaction energy barrier (REB) while switching the potential-determining step from *O→*OOH to *OH→*O. Together with the enhanced electrochemical active surface area and accelerated charge transfer, the production of ground-state triplet O2 is improved via a spin-forbidden route that involves the singlet H2O/OH•. Consequently, the chiral nanoflower shows a overpotential of 308mV at 10mA cm-2 and a Tafel slope of 93.5mV dec-1, which is even superior to the commercial RuO2 (310mV, 101mV dec-1). This study presents a new strategy for improving the OER activity by simultaneously enhancing electronic properties and lowering the REB of an non-noble electrocatalyst via chirality engineering.

Corn stalk decorated with magnetic graphene oxide as an efficient adsorbent for the removal of cationic dye from wastewater

In this study, an in situ immersion loading method is employed to introduce graphene oxide (GO) nanosheets and hollow copper ferrite nanospheres into the ordered porous structure of alkali-activated corn stalk (CS). This approach facilitates the construction of a novel magnetic three-dimensional composite sponge (GO/CS/CuFe2O4) utilized for the efficient removal of methylene blue (MB) and malachite green (MG) dyes from wastewater samples. In this hybrid adsorbent, the stacking of GO nanosheets is inhibited due to the ordered porous structure of CS, based on which GO nanosheets are well immobilized and dispersed. In addition, the hollow CuFe2O4 nanospheres and GO nanosheets support each other, further reducing the accumulation of GO, and increasing the specific surface area of the adsorbent. The engineered morphology of GO/CS/CuFe2O4 sponges supports the maximum exposure of the active adsorption sites to the dye solution, promoting the adsorption process. Microscopy and surface analyses show that GO/CS/CuFe2O4 sponges have a rich pore structure with the specific surface area of 289.85 m2·g−1, more than 17 times higher than that of CS, significantly improving their adsorption performance for MB and MG. The maximum adsorption capacity of GO/CS/CuFe2O4 for MB and MG is as high as 243.65 and 231.53 mg/g, respectively, superior to those of many other biomass-based adsorbents. The dye adsorption performance of GO/CS/CuFe2O4 can be well described by the Langmuir adsorption isotherm and pseudo-second-order kinetic model, suggesting the existence of strong monolayer chemisorption. The FTIR and X-ray photoelectron spectroscopy (XPS) analyses show that the dye removal mechanisms observed mainly includ π-π interactions, hydrogen bonding, electrostatic interactions and pore filling. In addition, GO/CS/CuFe2O4 sponges exhibit an excellent magnetic behavior (Ms = 49.52 emu/g), enabling the adsorbent to be recycled by the application of a magnetic field. The adsorption capacities of the adsorbent for MB and MG remain 88.6 % and 90.2 % of the initial adsorption capacity, respectively, even after 10 regeneration cycles, showing its excellent reusability performance. Finally, GO/CS/CuFe2O4 is applied for the removal of MB and MG from real aqueous environments comprising the seawater, tap water and wastewater treatment plant effluent, and the removal rates are observed to be over 90 % of that achieved in deionized water. This study provides new concepts for the sustainable utilization of agricultural waste and natural structure of plants to purify dye containing wastewater.

Unveiling the potential: Asymmetric supercapacitors with conductive polymers/Ti3C2Tx/Ni3S4 electrodes deliver high energy densities

Ti3C2Tx is considered a promising electrode material for supercapacitors due to its fast electronic properties, excellent hydrophilicity and mechanical properties. However, severe Ti3C2Tx nanosheet stacking reduces the exposed active sites and hinders the ion diffusion of Ti3C2Tx, leading to poor electrochemical performance. Here, we report a strategy for doping of Ti3C2Tx, in which the Ni3S4 and conducting polymer (CP) were selected as doping agent for Ti3C2Tx, and it is expected that metal sulfide and CP can overcome the defects of Ti3C2Tx. In this work, the conducting polymers were as polyaniline (PANI), polypyrrole (PPY) and poly(3,4-ethylenedioxythiophene) (PEDOT). As a result, the prepared composites exhibit superior multiplicative capacity with a capacitance of 2502 F g-1 (PANI/Ti3C2Tx/Ni3S4), 2440 F g-1 (PPY/Ti3C2Tx/Ni3S4), and 2620 F g-1 (PEDOT/Ti3C2Tx/Ni3S4), respectively. In addition, CP/Ti3C2Tx/Ni3S4// AC asymmetric supercapacitors were assembled with energy densities of 60.2 (PANI/Ti3C2Tx/Ni3S4), 86.7 (PPY/Ti3C2Tx/Ni3S4), and 53.4 (PEDOT/Ti3C2Tx//Ni3S4) Wh kg-1 at 1,500 W kg-1, respectively. This work develops a simple way to prepare the porous Ti3C2Tx film for supercapacitors with excellent electrochemical performance.

MoS2/NiO heterocatalyst featuring stacking Structures, oxygen Vacancies, and hydrophilic Interfaces for hydrogen production via urea electrolysis

Two-dimensional nano-MoS2 holds remarkable potential for widespread use in hydrogen evolution reaction (HER) applications owing to its high catalytic activity, abundant availability, and low cost. However, its electrocatalytic performance is significantly lower than that of Pt-based catalysts necessitating strategies to improve its catalytic activity. We developed an effective strategy for enhancing the HER performance of MoS2 based on the synergistic effect of oxygen vacancies (Ov), heterostructures, and interfacial wettability. In particular, highly graphitized wood-based carbon (GWC) was used as a platform to prepare a hydrophilic/aerophobic MoS2@Ov-NiO-GWC heterocatalyst featuring nanosheet stacking and containing abundant Ov. Consequently, a current density of 10 mA cm−2 and an overpotential of only 77 mV were achieved in a 1 M KOH electrolyte using the prepared catalyst; notably, the overpotential increase was only 1.2 % after continuous operation for 90 h. Density functional theory calculations showed that coupling MoS2 with the Ov-NiO heterointerface increased the exposure of the MoS2 active sites on the heterointerface and accelerated the electron transfer between NiO and the MoS2 interface, considerably enhancing the HER performance. Moreover, an overall urea electrolysis cell assembled using this heterocatalyst demonstrated excellent hydrogen production activity and durability, with current densities of 10 and 100 mA cm−2 at cell voltages of only 1.33 and 1.46 V, respectively. Even after continuous operation for 75 h at a current density of 100 mA cm−2, the cell exhibited a voltage retention rate of 92.8 %. These results demonstrate the potential of this nano-heterocatalyst to efficiently produce hydrogen via overall urea electrolysis.

Boosting Zinc‐Ion Storage Capability in Longitudinally Aligned MXene Arrays with Microchannel Architecture

AbstractFlexible Zn2+ ion hybrid capacitors (ZHCs) will play a crucial role in developing next‐generation wearable products, which demand portability, durability, and environmental adaptability. To further meet these requirements, Ti3C2Tx MXene with exceptional conductivity and robust mechanical properties can be utilized as cathodes, except for challenges such as the dense stacking of Ti3C2Tx nanosheets. In this study, a novel MXene cathode architecture has been developed with the facilitation of an ice template, which creates longitudinally aligned Ti3C2Tx arrays with microchannels. The introduction of hydrochloric acid to the Ti3C2Tx slurry induces a crumpled morphology, increasing active sites and enhancing ion transport with expanded interlayer spacing. Interestingly, experimental results and COMSOL simulations verify that the cathode structure also has effective impacts on the Zn anode with a weakened ion concentration gradient and suppressed dendrite formation. Consequently, the ZHCs exhibit enhanced electrochemical performance with excellent rate performance and long‐term cycling stability (enduring over 50 000 cycles at 5 A g−1) and further deliver a reliable low‐temperature operation by applying an anti‐freezing electrolyte. Moreover, flexible ZHCs assembled with gel electrolytes demonstrate excellent flexibility, improved rate performance, and mechanical stability, making them well‐suited for flexible electronics that power flexible LED panels.

Flexible all-solid-state asymmetric supercapacitor based on Ti3C2Tx MXene/graphene/carbon nanotubes

As the emerging 2D materials, MXenes have been regarded as promising electrode materials in supercapacitor as power supply for wearable and portable electronic devices due to their metallic conductivity, hydrophilic feature, abundant functional groups, and large theoretical specific surface area etc. The capacity and rate capability of MXene-based electrodes is limited by the sheet restacking, hindering their further development. Herein, Ti3C2Tx MXene/graphene/carbon nanotubes (MXene/graphene/CNTs) flexible film was successfully fabricated by vacuum assisted filtration. Intercalation and confinement of graphene and carbon nanotubes between the Ti3C2Tx MXene nanosheets could increase the spacing and specific surface area, alleviate the stacking of MXene nanosheets, thus enhancing the electrochemical properties. The prepared MXene/graphene/CNTs film possesses increased specific surface area, average pore size, pore volume (112.259 m2g−1, 9.982 nm, 0.276 cm3g−1), compared to MXene (93.088 m2g−1, 3.786 nm, 0.088 cm3g−1). Consequently, MXene/graphene/CNTs delivers high area specific capacitance of 1862.5 mF cm−2 at 1 mA cm−2 and excellent rate capability (1525 mF cm−2, 81.88 % at 20 mA cm−2). Flexible asymmetric supercapacitor constructed with MXene/graphene/CNTs film and active carbon as positive and negative electrodes, and PVA/H2SO4 gel as solid electrolyte, achieves an energy density of 133.75 μWh cm−2 at the power density of 750 μW cm−2. In addition, there is still 94.9 % of the initial performance after cycling 8000 charge/discharge cycles at 10 mA cm−2, corresponding to a single-turn decay rate down to 0.00019 %. Besides, this flexible supercapacitor manifests outstanding electrochemical stability at different bending times. These advantages make the flexible supercapacitor device very promising for wearable electronics applications.

Halloysite-derived hierarchical cobalt silicate hydroxide hollow nanorods assembled by nanosheets for highly efficient electrocatalytic oxygen evolution reaction

The oxygen evolution reaction (OER) is regarded as the bottleneck of electrolytic water splitting. Thus, developing robust earth-abundant electrocatalysts for efficient OER has received a great deal of attention and it is an ongoing scientific challenge. Herein, hierarchical hollow nanorods assembled with ultrathin mesoporous cobalt silicate hydroxide nanosheets (denoted as CoSi) were successfully fabricated, using the silica nanotube derived from halloysite as a sacrificial template, via a simple hydrothermal method. The resulting cobalt silicate hydroxide nanosheets stack with thicknesses ∼10 nm, as confirmed by transmission electron microscopy. The elaborated nanoarchitecture possesses a high specific surface area (SSA) allowing good exposure to the cobalt active centers exhibiting superior catalytic activity vs analogs synthesized using sodium silicate. Among all as-prepared CoSi samples, those synthesized at 150 °C (CoSi-150) exhibited the minimum overpotential of ∼347 mV at a current density of 10 mA cm–2. In addition, CoSi-150 also exhibited superior performance against typical cobalt-based catalysts, and its surface hydroxyl groups were beneficial for the enhancement of OER performance. Furthermore, the CoSi-150 showed excellent durability and stability after the 105 s chronopotentiometry test in 1 M KOH. This design concept provides a new strategy for the low-cost preparation of high-quality cobalt water splitting electrocatalysts.

FeF3·0.33H2O nanoparticles decorated Ti3C2 MXene as high-performance bifunctional sulfur host for lithium‑sulfur batteries

Lithium‑sulfur batteries are deemed as a potential next-generation energy storage system, but their development is hindered by the shuttle effect of lithium polysulfides. Design and synthesis of multifunctional sulfur host materials are expected to adsorb lithium polysulfides and catalyze their conversion during the lithiation process, thereby suppressing the shuttle effect. In this work, FeF3·0.33H2O nanoparticles is in situ grown on the surface of Ti3C2 nanosheets (FeF3@Ti3C2) and used as the bifunctional sulfur host for lithium‑sulfur batteries. Ti3C2 nanosheets not only provide two-dimensional (2D) conductive substrate for sulfur, but also strongly adsorb lithium polysulfides and suppress the shuttle effect. Meanwhile, FeF3 nanoparticles can accelerate the conversion reaction of lithium polysulfides, which also contributes to inhibiting the shuttle of lithium polysulfides. In addition, decorating Ti3C2 nanosheets with FeF3 nanoparticles can prevent the stacking of Ti3C2 nanosheets and enhance the interaction between Ti3C2 and lithium polysulfides. Therefore, sulfur-loaded FeF3@Ti3C2 (FeF3@Ti3C2@S) displays excellent electrochemical performance, such as a high reversible capacity of 687 mAh g−1 at 2C after 1000 cycles, and the capacity decay rate is only 0.023 %. This work paves a simple way for improving the performance of Ti3C2 as the sulfur host and expanding its application in lithium‑sulfur batteries.

Polyphenol assisted assembly of prussian blue analogs nanocrystals decorated 3D GO functional microspheres for polymer fiber bifunctional membrane with high oil-water emulsion permeability and powerful photocatalytic self-cleaning ability

Due to the intricate components of wastewater and physical stacking of graphene oxide (GO), the current GO membranes exhibit the fatal defects of low porosity and poor anti-fouling ability. Herein, a three dimensional (3D) FeCo-PBA@GO functional microsphere was constructed via anchoring GO nanosheets onto hard template of 3D polymethyl methacrylate (PMMA) microsphere driven by hydrogen bond and van der Waals force. On this basis, the Prussian blue analogs nanocrystals (FeCo-PBA) grew in situ on such functional microsphere and further assembled onto porous polyacrylonitrile (PAN) fiber mat through the tannic acid assisted spraying technique, resulting in highly permeable and photocatalytic self-cleaning FeCo-PBA@GO/PAN fibrous composite membrane. Interestingly, the unique 3D nanostructure of FeCo-PBA@GO microsphere arranging on membrane surface effectively prevented the dense physical stacking of GO nanosheets and increased the oil repellence property, thereby regulating the water channel and breaking through permeability limitation of membrane. As a result, the composite membrane exhibited superior separation fluxes (˃3029 L m−2 h−1) for different oil/water (O/W) emulsions, with rejection rate above 99.0 %. Owing to rich active sites and enhanced electron/mass transport property of FeCo-PBA functional layer, the composite membrane could effectively degrade various dyes by peroxymonosulfate (PMS) activation, with the degradation efficiency of 93.1–96.9 % within 40 min and demonstrated favorable antifouling and photocatalytic self-cleaning ability after cycling separation of O/W emulsion. In addition, the generated multiple reactive oxygen species and photocatalytic mechanism were proposed. This work provides a versatile pathway to prepare multifunctional GO advanced membranes for large-scale treatment of complex emulsified oily wastewater.

P-doped MoS2 nanosheets embedded in 3D porous carbon for electrocatalytic hydrogen evolution reaction

Due to its inherent electrochemical catalytic activity, molybdenum sulfide (MoS2) is a potential electrocatalyst for hydrogen evolution reaction (HER). However, the limited exposure of its active sites resulting from the easy stacking of nanosheets and inert basal plane hampered its optimal catalytic activity. Herein, we developed a novel facile hydrothermal method to prepare phosphorus-doped MoS2 nanosheets anchored on agar-derived 3D nitrogen-doped porous carbon (P-MoS2/NC). The synthesized P-MoS2/NC electrocatalyst possesses high HER catalytic activity with a low overpotential of 167 mV at 10 mA cm−2 and a small Tafel slope of 45 mV dec−1. The excellent performance is attributed to the unique 3D network carbon structure, which avoids the stacking of the MoS2 sheets resulting in more exposed active sites. Additionally, the P atom introduced on the surface of MoS2 sheets successfully activated the in-plane inertness. This work provides an efficient strategy for designing and preparing high-quality catalysts with enhanced electrocatalytic HER activity.

An Ultra‐Smooth rGO Nano‐Thin Film from a Homogeneous Thin Liquid Film Confined by a Conical Fiber Array: Toward the Highly Sensitive Pressure Sensor

AbstractReduced graphene oxide (rGO) thin films have demonstrated various advantages in flexible electronics. So far, solution processes are widely used for making rGO thin films for their mild operation conditions and low cost. However, wrinkles are frequently formed due to the capillary contraction during drying, which severely deteriorates the conductivity and the transparency of rGO thin films. Here, an ultra‐smooth rGO nano‐thin film, featuring wrinkle‐free and a rather low surface roughness of 1.38 nm is developed, which is attributable to a steady and homogeneous thin liquid film confined by a conical fiber array. The thin liquid film facilitates both in‐plane stacking of nanosheets and reducing the buried solvent under nanosheets. Notably, with the capillary flow replenishing the tri‐phase contact line evaporation, a semi‐dry film near the tri‐phase contact line is produced, that enables the force equilibrium of multi‐directional capillary forces on dispersed nanosheets for depositing a wrinkle‐free nanofilm. The as‐prepared rGO nanofilm gives a low sheet resistance of 8.3 kΩ sq−1 and a high transmittance of 91.9%, showing better performances than other reported rGO nanofilms. On this basis, it is demonstrated that a high‐sensitive pressure sensor with a detection limit as low as 0.02 Pa, highlighting the solution‐processed innovative ultra‐smooth 2D nanomaterial thin films, and devices.

Construction of PEO@g-C3N4 supported ionic liquid membrane with interactive network structure for enhanced carbon capture efficiency

Polyethylene oxide (PEO) shows a high CO2-philic due to its dipolar-quadrupolar interaction with CO2 molecules. As a result, it is an excellent candidate for gas separation applications, yet it faces problems such as crystallization and low permeance. Herein, we show a versatile strategy to enhance gas permeation fluxes, which is mainly achieved by hindering the crystallization of PEO and the stacking of nanosheets. Specifically, graphite-like phase carbon nitride (g-C3N4) nanosheets are introduced and interaction networks (PGCN) are constructed by taking full advantage of the dipole-level quadrupole moment interactions between the ether-oxygen groups contained in PEO and CO2. In order to compensate the membrane surface defects for enhancing gas selectivity, we used the suspension coating method to create a PEO@g-C3N4 supported ionic liquid membrane (PGCN/ILX SILM) by coating IL on the surface of membrane. The results show that, when the IL concentration is 30 wt%, the PGCN/IL30 % membrane separates CO2/N2 with a CO2 permeance of 1396 GPU and an optimal selectivity of 58. While overcoming the “Trade-off” effect, it has demonstrated good thermal stability and long-term stable operation for 72 h. The development of this work will generate solutions for overcoming PEO crystallization and achieving efficient CO2 capture.

Fabrication of multi-sensory Ti3C2Tx MXene/Nylon 6 composite fibers via interfacial deposition method

Here, we present a composite material in the form of Ti3C2Tx MXene/nylon 6 (MPA6) core-shell fibers. These fibers were synthesized through a process involving the systematic stacking of Ti3C2Tx MXene nanosheets to form a continuous film via interfacial self-assembly, followed by coating onto the surface of nylon 6 fibers. Notably, despite a minimal MXene coating of just 1.53 wt%, the MPA6 fibers exhibit remarkable electrical conductivity, reaching 11.39 ± 2.51 S/cm. The interwoven conductive network within the fabric's fibers contributes to its exceptional properties, including rapid response time (with a response time of 63 ms during pressing behavior), fatigue resistance (maintaining a stable response over 300 cycles), and consistent reproducibility of response during repeated cycles. With its increased sensitivity to various human activities, this composite fiber is well-suited for use as a wearable personal activity monitor. Additionally, its exceptional sensitivity to gravitational objects makes it a valuable tool for gravity detection, capable of detecting changes as small as 1 g.

Mixed-matrix membranes based on semi-oxidation MXene modified g-C3N4 nanosheet for enhanced CO2 separation

While mixed matrix membranes (MMMs) containing two-dimensional (2D) layered materials (such as, GO, g-C3N4 and MXene, etc.) have revealed potential application prospects for gas separation applications, it still faces a serious challenge to enhance the performance of CO2 separation. Owing to the structural defects of g-C3N4 nanosheets produced during the exfoliation process, which has greatly reduced the gas selectivity. Herein, we describe the construction of g-C3N4-MXene/Pebax MMM composed by MXene modified the structural defects in g-C3N4 nanosheets to surmount the low gas selectivity of g-C3N4 membrane. However, the stacking of nanosheets on each other hinder the gas transport channels. The TiO2 nanoparticles derived in-situ from MXene semi-oxidation can support an intermediate layer between g-C3N4 nanosheet and MXene nanosheet to expand the gas transport channels. Eventually, a novel g-C3N4-TiO2@MXene/Pebax MMM was obtained that exhibited maximum CO2 permeability of 1673.69 Barrer in separation of CO2/CH4, CO2/N2 selectivity of 45.13, and CO2/CH4 selectivity of 47.76, exceeding the bond 2008 limit on Robeson. What's more, the MMM within 100 h (1 bar and 298 K) are measured to have outstanding separation performance. Overall, this concept offers a novel strategy to enhance CO2 separation by MXene modified defects in g-C3N4 nanosheets.

Two-Dimensional Nanosheet Stacking Structure Films for Li/Na/K-Ion Batteries and Supercapacitors

Two-Dimensional Nanosheet Stacking Structure Films for Li/Na/K-Ion Batteries and Supercapacitors

Supergravity-Steered Generic Manufacturing of Nanosheets-Embedded Nanocomposite Hydrogel with Highly Oriented, Heterogeneous Architecture.

Designing nanocomposite hydrogels with oriented nanosheets has emerged as a promising toolkit to achieve preferential performances that go beyond their disordered counterparts. Although current fabrication strategies via electric/magnetic force fields have made remarkable achievements, they necessitate special properties of nanosheets and suffer from an inferior orientation degree of nanosheets. Herein, a facile and universal approach is discovered to elaborate MXene-based nanocomposite hydrogels with highly oriented, heterogeneous architecture by virtue of supergravity to replace conventional force fields. The key to such architecture is to leverage bidirectional, force-tunable attributes of supergravity containing coupled orthogonal shear and centrifugal force field for steering high-efficient movement, pre-orientation, and stacking of MXene nanosheets in the bottom. Such a synergetic effect allows for yielding heterogeneous nanocomposite hydrogels with a high-orientation MXene-rich layer (orientation degree, f = 0.83) and a polymer-rich layer. The authors demonstrate that MXene-based nanocomposite hydrogels leverage their high-orientation, heterogeneous architecture to deliver an extraordinary electromagnetic interference shielding effectiveness of 55.2dB at 12.4GHz yet using a super-low MXene of 0.3 wt%, surpassing most hydrogels-based electromagnetic shielding materials. This versatile supergravity-steered strategy can be further extended to arbitrary nanosheets including MoS2, GO, and C3N4, offering a paradigm in the development of oriented nanocomposites.

Crystallization-Induced Flower-like Superstructures via Peptoid Helix Assembly.

We report a unique method to construct hierarchical superstructures based on molecular programming of peptidomimetics. Chiral steric hindrance in the polymer backbone stabilizes peptoid helices that crystallize into nanosheets during solvent evaporation. The stacking of nanosheets results in flower-like superstructures. The helical peptoid, nucleated from chiral monomers, is characterized as locally stiffer and more extended than the unstructured peptoid. Molecular dynamics (MD) simulations further suggest a constraint on the dihedral angles and a preference toward the trans configuration, resulting in an extended chain structure. The nanosheet assemblies at various length scales indicate an extent of intermolecular ordering amplified by chiral steric hindrance. Such molecular programming and processing protocols will benefit the future design and controlled assembly of hierarchical peptidomimetics.

One-step synthesis of a diverting erythrocyte-like heterojunction and the augmented activity of wastewater treatment: Morphology modulation, theoretical calculations and mechanism explanation

As a green and sustainable technology, semiconductor photocatalysis mediated by heterojunction has shown great potential in the removal of organic pollutants from water environment. Yet, the nugatory recombination of photogenerated carriers induced by strong Coulombic forces lead to inferior photoactivity of semiconductor photocatalysts. In this paper, the erythrocyte-like composite (BiBrW) was designed to drive Z-type separation of photogenerated carriers through heterojunction interface by tight coupling between BiOBr and Bi2WO6. Combined with the results of characterizations, CTAB used in the synthesis process not only provides a bromine source but also serves as a surfactant to modulate the morphology of Bi2WO6 from petal-like to erythrocyte-like morphology. In contrast with the BiOBr/Bi2WO6 material fabricated via the in-situ growth method, the BiBrW composite displayed a uniform erythrocyte-like morphology with fewer grain boundaries by lamellar stacking of nanosheets. The combined effect of the construction of heterojunction and lessened grain boundaries endowed the BiBrW composite with augmented physicochemical properties, thereby enhancing its photocatalytic removal performance for various contaminants. Based on theoretical calculations, HPLC-MS tests and toxicity analysis, the reaction sites, degradation pathway and toxic evolution of ciprofloxacin (CIP) during the process of photodegradation were thoroughly elucidated, respectively. Moreover, the BiBrW catalyst still exhibits significant degradation performance for CIP under the excitation of natural sunlight. For different water qualities and distinct target pollutants (2-sec-butyl-4,6-dinitrophenol (DNBP), tetracycline (TC) and bisphenol A (BPA)), the catalyst maintains excellent photocatalytic removal capabilities, reflecting the superior universality of BiBrW catalyst. This research proposed novel mentality for preparation of heterojunction photocatalysts with less grain boundaries to assist in restoration of water environment.

Strong green up-conversion luminescence and optical thermometry of Ho3+/Yb3+ Co-doped AlN submicron towers

Rare-earth (RE) doped aluminum nitride (AlN) holds great promise for integrated optoelectronic devices. Here, the Ho and Yb co-doped AlN (AlN:Ho3+/Yb3+) submicron towers were prepared by a direct nitridation route. XRD, Raman, XPS and EDS studies showed successful doping of Ho and Yb ions into AlN. SEM images show that the submicron towers have an interesting layered structure by layer-by-layer stacking of hexagonal AlN nanosheets. Under excitation at 980 nm, AlN:Ho3+/Yb3+ submicron towers exhibit up-conversion (UC) luminescence at 540, 550, 659, and 762 nm, which are due to Ho3+/Yb3+ system from 5F4, 5S2→5I8, 5F5→5I8, and 5F4, 5S2→5I7 respectively. Based on the intensity ratio and decay lifetime of UC luminescence, the optical temperature sensing characteristics are investigated from 298 K to 548 K. The maximum relative sensitivities associated with the intensity ratio of I540, 550 and I659 and decay lifetime of 659 nm are as high as 2.73% K−1 and 0.43% K−1, respectively. This work broadens the optoelectronic properties of RE doped AlN.