Chemical/Light‐Powered Hybrid Micromotors with “On‐the‐Fly” Optical Brakes

Hybrid micromotors capable of both chemically powered propulsion and fuel‐free light‐driven actuation and offering built‐in optical brakes for chemical propulsion are described. The new hybrid micromotors are designed by combining photocatalytic TiO₂ and catalytic Pt surfaces into a Janus microparticle. The chemical reactions on the different surfaces of the Janus particle hybrid micromotor can be tailored by using chemical or light stimuli that generate counteracting propulsion forces on the catalytic Pt and photocatalytic TiO₂ sides. Such modulation of the surface chemistry on a single micromotor leads to switchable propulsion modes and reversal of the direction of motion that reflect the tuning of the local ion concentration and hence the dominant propulsion force. An intermediate Au layer (under the Pt surface) plays an important role in determining the propulsion mechanism and operation of the hybrid motor. The built‐in optical braking system allows “on‐the‐fly” control of the chemical propulsion through a photocatalytic reaction on the TiO₂ side to counterbalance the chemical propulsion force generated on the Pt side. The adaptive dual operation of these chemical/light hybrid micromotors, associated with such control of the surface chemistry, holds considerable promise for designing smart nanomachines that autonomously reconfigure their propulsion mode for various on‐demand operations.     

Core@Satellite Janus Nanomotors with pH‐Responsive Multi‐phoretic Propulsion

We report core@satellite Janus mesoporous silica‐Pt@Au (JMPA) nanomotors with pH‐responsive multi‐phoretic propulsion. The JMPA nanomotors first undergo self‐diffusiophoretic propulsion in 3.0 % H₂O₂ due to the isolation of the Au nanoparticles (AuNPs) from the PtNPs layer. Then the weak acidity of H₂O₂ can trigger the disassembly and reassembly of the AuNPs, resulting in the Janus distribution of large AuNPs aggregates. Such reconstruction of JMPA leads to the contact between PtNPs and AuNPs aggregates, thus changing the propulsion mechanism to self‐electrophoresis. The asymmetric and aggregated AuNPs also enable the generation of a thermal gradient under laser irradiation, which propels the JMPA nanomotors by self‐thermophoresis. Such multi‐phoretic propulsion offers considerable promise for developing advanced nanomachines with a stimuli‐responsive switch of propulsion modes in biomedical applications.     

Continuously Variable Regulation of the Speed of Bubble‐Propelled Janus Microcapsule Motors Based on Salt‐Responsive Polyelectrolyte Brushes

The engineering of self‐propelled micro‐/nanomotors (MNMs) with continuously variable speeds, akin to macroscopic automobiles equipped with a continuously variable transmission, is still a huge challenge. Herein, after grafting with salt‐responsive poly[2‐(methacryloyloxy)ethyltrimethylammonium chloride] (PMETAC) brushes, bubble‐propelled Janus microcapsule motors with polyelectrolyte multilayers exhibited adjustable speeds when the type and concentration of the counterion was changed. Reversible switching between low‐ and high‐speed states was achieved by modulating the PMETAC brushes between hydrophobic and hydrophilic configurations by ion exchange with ClO₄^? and polyphosphate anions. This continuously variable regulation enabled control of the speed in an accurate and predictable manner and an autonomous response to the local chemical environment. This study suggests that the integration of polymer brushes with precisely adjustable responsiveness offers a promising route for motion control of smart MNMs that act like their counterparts in living systems.     

Silica‐Encapsulated Pt‐Sn Intermetallic Nanoparticles: A Robust Catalytic Platform for Parahydrogen‐Induced Polarization of Gases and Liquids

Recently, a facile method for the synthesis of size‐monodisperse Pt, Pt₃Sn, and PtSn intermetallic nanoparticles (iNPs) that are confined within a thermally robust mesoporous silica (mSiO₂) shell was introduced. These nanomaterials offer improved selectivity, activity, and stability for large‐scale catalytic applications. Here we present the first study of parahydrogen‐induced polarization NMR on these Pt‐Sn catalysts. A 3000‐fold increase in the pairwise selectivity, relative to the monometallic Pt, was observed using the PtSn@mSiO₂ catalyst. The results are explained by the elimination of the three‐fold Pt sites on the Pt(111) surface. Furthermore, Pt‐Sn iNPs are shown to be a robust catalytic platform for parahydrogen‐induced polarization for in vivo magnetic resonance imaging.     

Biomass‐derived Nitrogen and Phosphorus Co‐doped Hierarchical Micro/mesoporous Carbon Materials for High‐performance Non‐enzymatic H2O2 Sensing

Nitrogen and phosphorus co‐doped hierarchical micro/mesoporous carbon (N,P‐MMC) was prepared by simple thermal treatment of freeze‐dried okra in the absence of any other additives. The 0.96 wt % of N and 1.47 wt % of P were simultaneously introduced into the graphitic framework of N,P‐MMC, which also possesses hierarchical porous structure with mesopores centered at 3.6 nm and micropores centered at 0.79 nm. Most importantly, N,P‐MMC carbon exhibits excellent catalytic activity for electrocatalytic reduction of H₂O₂, resulting in a new strategy to construct non‐enzymatic H₂O₂ sensor. The N,P‐MMC‐based H₂O₂ sensor displays two linear detection range about 0.1 mM–10 mM (R²=0.9993) and 20 mM–200 mM (R²=0.9989), respectively. The detection limit is estimated to be 6.8 μM at a signal‐to‐noise ratio of 3. These findings provide insights into synthesizing functional heteroatoms doped porous carbon materials for biosensing applications.     

Optically Active Helical Poly[(S)‐3‐vinyl‐2,2′‐dihydroxy‐1,1′‐binaphthyl]: New Ligand for Asymmetric Addition of Diethylzinc to Aryl Aldehyde

Poly[(S)‐3‐vinyl‐2,2′‐dihydroxy‐1,1′‐binaphthyl] (L*) was obtained by taking off the protecting groups of poly[(S)‐3‐vinyl‐2,2′‐bis(methoxymethoxy)‐1,1′‐binaphthyl] (poly‐ 1 ). L* was proved to keep a stable helical conformation in solution. The application of helical L* in the asymmetric addition of diethylzinc to aldehydes has been studied. The catalytic system employing 10 mol% of L* and 150 mol% of Ti(OⁱPr)₄ was found to promote the addition of diethylzinc to a wide range of aromatic aldehydes, giving up to 99% enantiomeric excess (ee) and up to 93% yield of the corresponding secondary alcohol at 0°C. The chiral polymer can be easily recovered and reused without loss of catalytic activity as well as enantioselectivity.     

Pt Nanoparticles Supported on Nitrogen‐Doped‐Carbon‐Decorated CeO2 for Base‐Free Aerobic Oxidation of 5‐Hydroxymethylfurfural

Currently, the base‐free aerobic oxidation of biomass‐derived 5‐hydroxymethylfurfural (HMF) to produce 2,5‐furandicarboxylic acid (FDCA) is attracting intense interest due to its prospects for the green, sustainable, and promising production of biomass‐based aromatic polymers. Herein, we have developed a new Pt catalyst supported on nitrogen‐doped‐carbon‐decorated CeO₂ (NC‐CeO₂) for the aerobic oxidation of HMF in water without the addition of any homogeneous base. It was demonstrated that the small‐sized Pt particles could be well dispersed on the surface of the hybrid NC‐CeO₂ support, and the activity of the supported Pt catalyst depended strongly on the surface structure and properties of the catalysts. The as‐fabricated Pt/NC‐CeO₂ catalyst, with abundant surface defects, enhanced basicity, and favorable electron‐deficient metallic Pt species, enabled an almost 100 % yield of FDCA in water with molecular oxygen (0.4 MPa) at 110 °C for 8 h without the addition of any homogeneous base, which is indicative of exceptional catalytic performance. Furthermore, this Pt/NC‐CeO₂ catalyst also showed good stability and reusability owing to strong metal–support interactions. An understanding of the role of surface structural defects and basicity of the hybrid NC‐CeO₂ support provides a basis for the rational design of high‐performance and stable supported metal catalysts with practical applications in various transformations of biomass‐derived compounds.     

Helicenes as All‐in‐One Organic Materials for Application in OLEDs: Synthesis and Diverse Applications of Carbo‐ and Aza[5]helical Diamines

A set of eight helical diamines were designed and synthesized to demonstrate their relevance as all‐in‐one materials for multifarious applications in organic light‐emitting diodes (OLEDs), that is, as hole‐transporting materials (HTMs), EMs, bifunctional hole transporting + emissive materials, and host materials. Azahelical diamines function very well as HTMs. Indeed, with high T_g values (127–214 °C), they are superior alternatives to popular N,N′‐di(1‐naphthyl)‐N,N′‐diphenyl‐(1,1′‐biphenyl)‐4,4′‐diamine (NPB). All the helical diamines exhibit emissive properties when employed in nondoped as well as doped devices, the performance characteristics being superior in the latter. One of the carbohelical diamines (CHTPA) serves the dual function of hole transport as well as emission in simple double‐layer devices; the efficiencies observed were better by quite some margin than those of other emissive helicenes reported. The twisting endows helical diamines with significantly high triplet energies such that they also function as host materials for red and green phosphors, that is, [Ir(btp)₂acac] (btp=2‐(2′‐benzothienyl)pyridine; acac=acetylacetonate) and [Ir(ppy)₃] (ppy=2‐phenylpyridine), respectively. The results of device fabrications demonstrate how helicity/ helical scaffold may be diligently exploited to create molecular systems for maneuvering diverse applications in OLEDs.     

Stimuli‐Responsive Microjets with Reconfigurable Shape

Flexible thermoresponsive polymeric microjets are formed by the self‐folding of polymeric layers containing a thin Pt film used as catalyst for self‐propulsion in solutions containing hydrogen peroxide. The flexible microjets can reversibly fold and unfold in an accurate manner by applying changes in temperature to the solution in which they are immersed. This effect allows microjets to rapidly start and stop multiple times by controlling the radius of curvature of the microjet. This work opens many possibilities in the field of artificial nanodevices, for fundamental studies on self‐propulsion at the microscale, and also for biorelated applications.     

Relationship between Pt particle size and catalyst activity for catalytic oxidation of ultrahigh‐concentration formaldehyde

The effects of particle size and kinetics of Pt/activated carbon (AC) catalysts on catalytic oxidation of formaldehyde (HCHO) were investigated. AC, f‐SiO₂ and MCM‐41 were used as supports to prepare low‐Pt‐content catalysts using H₂ reduction. Pt/AC catalyst shows the highest activity with the largest Pt particle size. By contrast, 0.1 wt% Pt/AC reduced using KBH₄ has much higher activity than that reduced using H₂, which can oxidize HCHO completely over 6000 ppm at 60°C in a fixed bed reactor. Transmission electron microscopy and X‐ray photoelectron spectroscopy results indicate that Pt/AC‐KBH₄ has larger Pt particles and lower valence state than Pt/AC‐H₂, which may be attributed to the ligand effect between Pt⁴⁺ and the AC support. The result of O₂ temperature‐programmed oxidation suggests that highly dispersed Pt⁴⁺ ions have stronger interaction with AC support and thus are harder to be reduced by H₂. Furthermore, Pt/AC is structure‐sensitive and larger‐sized Pt particles result in a high conversion of HCHO. Investigation of kinetics indicated that it is a zero‐order reaction for such a high HCHO concentration condition for Pt/AC‐KBH₄.     

Preparation of Single‐Handed Helical Carbon/Silica and Carbonaceous Nanotubes by Using 4,4′‐Biphenylene‐Bridged Polybissilsesquioxane

Single‐handed, helical, 4,4′‐biphenylene‐bridged polybissilsesquioxane nanotubes were prepared by using the self‐assemblies of a pair of chiral low‐molecular‐weight gelators as templates. Single‐handed, helical, carbon/silica nanotubes were obtained after carbonization of the self‐assemblies, and single‐handed helical carbonaceous nanotubes were then obtained by removal of silica with aqueous HF. Samples were characterized by using field‐emission SEM, TEM, X‐ray diffraction, thermogravimetric analysis, Raman spectroscopy, and circular dichroism. The polysilsesquioxane and carbonaceous structures exhibited optical activity. The walls of the carbon/silica and carbonaceous nanotubes were predominantly amorphous carbon. The surface area of the left‐handed, helical, carbonaceous nanotubes was 1439 m² g^?1, and such materials have potential applications as catalyst supports, chirality sensors, supercapacitor electrodes, and adsorbents.     

Pyrolytic Carbon‐coated Cu‐Fe Alloy Nanoparticles with High Catalytic Performance for Oxygen Electroreduction

Well‐dispersed carbon‐coated or nitrogen‐doped carbon‐coated copper‐iron alloy nanoparticles (FeCu@C or FeCu@C?N) in carbon‐based supports are obtained using a bimetallic metal‐organic framework (Cu/Fe‐MOF‐74) or a mixture of Cu/Fe‐MOF‐74 and melamine as sacrificial templates and an active‐component precursor by using a pyrolysis method. The investigation results attest formation of Cu?Fe alloy nanoparticles. The obtained FeCu@C catalyst exhibits a catalytic activity with a half‐wave potential of 0.83 V for oxygen reduction reaction (ORR) in alkaline medium, comparable to that on commercial Pt/C catalyst (0.84 V). The catalytic activity of FeCu@C?N for ORR (E_half‐wave=0.87 V) outshines all reported analogues. The excellent performance of FeCu@C?N should be attributed to a change in the energy of the d‐band center of Cu resulting from the formation of the copper–iron alloy, the interaction between alloy nanoparticles and supports and N‐doping in the carbon matrix. Moreover, FeCu@C and FeCu@C?N show better electrochemical stability and methanol tolerance than commercial Pt/C and are expected to be widely used in practical applications.     

Multi‐Light‐Responsive Quantum Dot Sensitized Hybrid Micromotors with Dual‐Mode Propulsion

CdS quantum dots/C₆₀ tubular micromotors with chemical/multi‐light‐controlled propulsion and “on‐the‐fly” acceleration capabilities are described. In situ growth of CdS quantum dots on the outer fullerene layer imparts this layer with light‐responsive properties in connection to inner Pt, Pd or MnO₂ layers. This is the first time that visible light is used to drive bubble‐propelled tubular micromotors. The micromotors exhibit a broad absorption range from 320 to 670 nm and can be wirelessly controlled by modulating light intensity and peroxide concentration. The built‐in accelerating optical system allows for the control of the velocity over the entire UV/Vis light spectra by modulating the catalyst surface chemistry. The light‐responsive properties have been also exploited to accelerate the chemical dealloying and propulsion of micromotors containing a Cu/Pd layer. Such dual operated hybrid micromotors hold considerable promise for designing smart micromachines for on‐demand operations, motion‐based sensing, and enhanced cargo transportation.     

Scalable Low‐Cost SnS2 Nanosheets as Counter Electrode Building Blocks for Dye‐Sensitized Solar Cells

A new type of semitransparent SnS₂ nanosheet (NS) films were synthesized using a simple and environmentally friendly solution‐processed approach, which were subsequently used as a counter electrode (CE) alternative to the noble metal Pt for triiodide reduction in dye‐sensitized solar cells (DSSCs). The resultant SnS₂‐based CE with a thickness of about 300 nm exhibited excellent electrochemical catalytic activity for catalyzing the reduction of triiodide and demonstrated comparable power conversion efficiency of 7.64 % with that of expensive Pt‐based CE in DSSCs (7.71 %). When functionalized with a small amount of carbon nanoparticles, the SnS₂ NS‐based CE showed even better performance of 8.06 % than Pt under the same conditions. Considering the facile fabrication method, optical transparency, low cost, and remarkable catalytic property, this study on SnS₂ NSs may shed light on the large‐scale production of electrocatalytic electrode materials for low‐cost photovoltaic devices.     

CeO2‐Based Pd(Pt) Nanoparticles Grafted onto Fe3O4/Graphene: A General Self‐Assembly Approach To Fabricate Highly Efficient Catalysts with Magnetic Recyclable Capability

New Pd(Pt) catalysts have been fabricated by assembling multicomponents of Fe₃O₄ and CeO₂/Pd(Pt) on the surface of reduced graphene oxide (RGO) nanosheets in layers. The as‐obtained Pd(Pt) catalysts exhibit extremely high catalytic activity in the selective hydrogenation reaction of nitrobenzene. Owing to the presence of Fe₃O₄, the catalysts can be easily recycled from the catalytic system through magnetic separation. Their high activity, stability, and magnetic recyclability make the as‐obtained hybrids very promising as catalysts in catalytic applications. Compared to other traditional multishell magnetic catalysts that were prepared by means of layer‐by‐layer technology, our process is much more facile and more easily controlled.     

Noncontinuous Super‐Diffusive Dynamics of a Light‐Activated Nanobottle Motor

We report a carbonaceous nanobottle (CNB) motor for near infrared (NIR) light‐driven jet propulsion. The bottle structure of the CNB motor is fabricated by soft‐template‐based polymerization. Upon illumination with NIR light, the photothermal effect of the CNB motor carbon shell causes a rapid increase in the temperature of the water inside the nanobottle and thus the ejection of the heated fluid from the open neck, which propels the CNB motor. The occurrence of an explosion, the on/off motion, and the swing behavior of the CNB motor can be modulated by adjusting the NIR light source. Moreover, we simulated the physical field distribution (temperature, fluid velocity, and pressure) of the CNB motor to demonstrate the mechanism of NIR light‐driven jet propulsion. This NIR light‐powered CNB motor exhibits fuel‐free propulsion and control of the swimming velocity by external light and has great potential for future biomedical applications.     

One‐Pot Synthesis of Pt–Co Alloy Nanowire Assemblies with Tunable Composition and Enhanced Electrocatalytic Properties

Three‐dimensional (3D) Pt‐based alloy nanostructures composed of one‐dimensional (1D) nanowires/nanorods have recently attracted significant interest as electrocatalysts. In this work, we report an effective solvothermal method for the direct preparation of 3D Pt–Co nanowire assemblies (NWAs) with tunable composition. The composition‐ and structure‐dependent electrocatalytic performance is thoroughly investigated. Because of the bimetallic synergetic effect and unique structural advantage, the as‐prepared 3D Pt₃Co NWA outperforms commercial Pt/carbon and Pt black catalysts and even 3D Pt NWA. The electrochemical results demonstrate that the 3D Pt₃Co NWA is indeed a promising electrocatalyst with enhanced catalytic activity and improved durability for practical electrocatalytic applications.     

A Solid‐State Fluorescent Host System with a 21‐Helical Column Consisting of Chiral (1R,2S)‐2‐Amino‐1,2‐diphenylethanol and Fluorescent 1‐Pyrenecarboxylic Acid

A solid‐state fluorescent host system was created by self‐assembly of a 2₁‐helical columnar organic fluorophore composed of (1R,2S)‐2‐amino‐1,2‐diphenylethanol and fluorescent 1‐pyrenecarboxylic acid. This host system has a characteristic 2₁‐helical columnar hydrogen‐ and ionic‐bonded network. Channel‐like cavities are formed by self‐assembly of this column, and various guest molecules can be included by tuning the packing of this column. Moreover, the solid‐state fluorescence of this host system can change according to the included guest molecules. This occurs because of the change in the relative arrangement of the pyrene rings as they adjust to the tuning of the packing of the shared 2₁‐helical column, according to the size of the included guest molecules. Therefore, this host system can recognize slight differences in molecular size and shape.     

Dual‐Template Pore Engineering of Whey Powder‐Derived Carbon as an Efficient Oxygen Reduction Reaction Electrocatalyst for Primary Zinc‐Air Battery

Cost‐effective and high‐performance electrocatalysts for oxygen reduction reactions (ORR) are needed for many energy storage and conversion devices. Here, we demonstrate that whey powder, a major by‐product in the dairy industry, can be used as a sustainable precursor to produce heteroatom doped carbon electrocatalysts for ORR. Rich N and S compounds in whey powders can generate abundant catalytic active sites. However, these sites are not easily accessible by reactants of ORR. A dual‐template method was used to create a hierarchically and interconnected porous structure with micropores created by ZnCl₂ and large mesopores generated by fumed SiO₂ particles. At the optimum mass ratio of whey power: ZnCl₂ : SiO₂ at 1 : 3 : 0.8, the resulting carbon material has a large specific surface area close to 2000 m² g^?1, containing 4.6 at.% of N with 39.7% as pyridinic N. This carbon material shows superior electrocatalytic activity for ORR, with an electron transfer number of 3.88 and a large kinetic limiting current density of 45.40 mA cm^?2. They were employed as ORR catalysts to assemble primary zinc‐air batteries, which deliver a power density of 84.1 mW cm^?2 and a specific capacity of 779.5 mAh g^?1, outperforming batteries constructed using a commercial Pt/C catalyst. Our findings open new opportunities to use an abundant biomaterial, whey powder, to create high‐value‐added carbon electrocatalysts for emerging energy applications.     

2,5‐Bis[4‐methyl‐3‐(pyridin‐3‐yl)phenyl]‐1,3,4‐oxadiazole and its one‐dimensional polymeric complex with ZnCl2

2,5‐Bis[4‐methyl‐3‐(pyridin‐3‐yl)phenyl]‐1,3,4‐oxadiazole (L), C₂₆H₂₀N₄O, forms one‐dimensional chains via two types of intermolecular π–π interactions. In catena‐poly[[dichloridozinc(II)]‐μ‐2,5‐bis[4‐methyl‐3‐(pyridin‐3‐yl)phenyl]‐1,3,4‐oxadiazole], [ZnCl₂(C₂₆H₂₀N₄O)]_n, synthesized by the combination of L with ZnCl₂, the Zn^II centres are coordinated by two Cl atoms and two N atoms from two L ligands. [ZnCl₂L]_n forms one‐dimensional P (plus) and M (minus) helical chains, where the L ligand has different directions of twist. The helical chains stack together via interchain π–π and C—H...π interactions.