High Sensitivity and Wide Linear Range Flexible Piezoresistive Pressure Sensor with Microspheres as Spacers for Pronunciation Recognition.

Flexible piezoresistive pressure sensors have received great popularity in flexible electronics due to their simple structure and promising applications in health monitoring and artificial intelligence. However, the contradiction between sensitivity and detection range limits the application of the sensors in the medium-pressure regime. Here, a flexible piezoresistive pressure sensor is fabricated by combining a hierarchical spinous microstructure sensitive layer and a periodic microsphere array spacer. The sensor achieves high sensitivity (39.1 kPa-1) and outstanding linearity (0.99, R2 coefficient) in a medium-pressure regime, as well as a wide range of detection (100 Pa-160.0 kPa), high detection precision (<0.63‰ full scale), and excellent durability (>5000 cycles). The mechanism of the microsphere array spacer in improving sensitivity and detection range was revealed through finite element analysis. Furthermore, the sensors have been utilized to detect muscle and joint movements, spatial pressure distributions, and throat movements during pronouncing words. By means of a full-connect artificial neural network for machine learning, the sensor's output of different pronounced words can be precisely distinguished and classified with an overall accuracy of 96.0%. Overall, the high-performance flexible pressure sensor based on a microsphere array spacer has great potential in health monitoring, human-machine interface, and artificial intelligence of medium-pressure regime.

Ultra-sensitive, Multi-directional Flexible Strain Sensors Based on an MXene Film with Periodic Wrinkles.

The fast-growing motion capturing/monitoring technique has raised a great demand for flexible strain sensors. For capturing complex motions (e.g., facial motion), both the strain amplitude and direction should be accurately detected. Although some reported sensors based on anisotropic conductive networks are proved to show accurate localization of strain directions, it is still a great challenge to achieve both high sensitivity and a high sensing range in these designs. Here, a self-assembled Ti3C2Tx MXene film with parallel and periodic wrinkles is fabricated on a stretchable poly(dimethylsiloxane) substrate for constructing multi-directional strain sensors. During stretching, relative slip and crack will occur between the stacked MXene nanosheets, which contribute to high structural sensitivity in the MXene film. Meanwhile, the wrinkled structure contributes to high stretchability. As a result, the sensor based on the film with one-dimensional periodic wrinkles shows a large sensing range (>50%) and a gauge factor of 45. Furthermore, the sensor can accurately detect both the strain amplitude and direction by using the MXene film with two-dimensional wrinkles. It shows distinguishable electrical responses when detecting different-amplitude human/robot motions such as joint bending and walking. Additionally, the directions in complex human motions (e.g., facial motion) can also be well-tracked. This work provides an effective strategy to detect multi-directional motions.

Albumin-Templated Bi2Se3-MnO2 Nanocomposites with Promoted Catalase-Like Activity for Enhanced Radiotherapy of Cancer.

Novel and effective radiosensitizers that can enhance radiosensitivity of tumor tissues and increase the local radiation dose are highly desirable. In this work, templated by bovine serum albumin (BSA), Bi2Se3-MnO2 nanocomposites (Bi2Se3-MnO2@BSA) were fabricated via biomineralization, while Bi2Se3 nanodots act as radiosensitizers to increase the local radiation dosage because of their strong X-ray attenuation ability, and MnO2 with catalase-like activity can increase the oxygen concentration in tumors by triggering the decomposition of tumor endogenous H2O2 so as to improve the hypoxia-associated radioresistance of tumors. Owing to the interaction of the two components in the interface, Bi2Se3-MnO2@BSA showed promoted catalytic activity compared to MnO2@BSA, favoring tumor radiotherapy (RT) sensitization. BSA templating enabled the nanocomposites with high colloidal stability and biocompatibility as well as satisfactory tumor targeting both in vitro and in vivo; thus, an enhanced RT efficacy was obtained. Moreover, the proposed Bi2Se3-MnO2@BSA exhibited excellent performances in computerized tomography and magnetic resonance imaging. Thus, this work provides a tumor microenvironment-responsive multifunctional theranostic nanoagent with an improved performance for imaging-guided tumor RT sensitization.

Single-molecule optical mapping of the distribution of DNA phosphorothioate epigenetics.

DNA phosphorothioate (PT) modifications, with the nonbridging phosphate oxygen replaced by sulfur, governed by DndABCDE or SspABCD, are widely distributed in prokaryotes and have a highly unusual feature of occupying only a small portion of available consensus sequences in a genome. Despite the presence of plentiful non-PT-protected consensuses, DNA PT modification is still employed as a recognition tag by the restriction cognate, for example, DndFGH or SspE, to discriminate and destroy PT-lacking foreign DNA. This raises a fundamental question about how PT modifications are distributed along DNA molecules to keep the restriction components in check. Here, we present two single-molecule strategies that take advantage of the nucleophilicity of PT in combination with fluorescent markers for optical mapping of both single- and double-stranded PT modifications across individual DNA molecules. Surprisingly, PT profiles vary markedly from molecule to molecule, with different PT locations and spacing distances between PT pairs, even in the presence of DndFGH or SspE. The results revealed unprecedented PT modification features previously obscured by ensemble averaging, providing novel insights into the riddles regarding unusual target selection by PT modification and restriction components.

Magnetic Nanoparticles with Surface Nanopockets for Highly Selective Antibody Isolation.

Monoclonal antibodies (mAbs) are key components of revolutionary disease immunotherapies and are also essential for medical diagnostics and imaging. The impact of cost is illustrated by a price >$200,000 per year per patient for mAb-based cancer therapy. Purification represents a major issue in the final cost of these immunotherapy drugs. Protein A (PrA) resins are widely used to purify antibodies, but resin cost, separation efficiency, reuse, and stability are major issues. This paper explores a synthesis strategy for low-cost, reusable, stable PrA-like nanopockets on core-shell silica-coated magnetic nanoparticles (NPs) for IgG antibody isolation. Mouse IgG2a, a strong PrA binder, was used as a template protein, first attaching it stem-down onto the NP surface. The stem-down orientation of IgG2a on the NP surface before polymerization is critical for designing the films to bind IgGs. Following this, 1-tetraethoxysilane and four organosilane monomers with functional groups capable of mimicking binding interactions of proteins with IgG antibody stems were reacted to form a thin polymer coating on the NPs. After blocking nonspecific binding sites, removal of the mouse IgG2a provided nanopockets on the core-shell NPs that showed binding characteristics for antibodies remarkably similar to PrA. Both smooth and rough core-shell NPs were used, with the latter providing much larger binding capacities for IgGs, with an excellent selectivity slightly better than that of commercial PrA magnetic beads. This paper is the first report of IgG-binding NPs that mimic PrA selectivity. These nanopocket NPs can be used for at least 15 regeneration cycles, and cost/use was 57-fold less than a high-quality commercial PrA resin.

Effects of Zr substitution on soot combustion over cubic fluorite-structured nanoceria: Soot-ceria contact and interfacial oxygen evolution.

Ceria is widely used as a catalyst for soot combustion, but effects of Zr substitution on the reaction mechanism is ambiguous. The present work elucidates effects of Zr substitution on soot combustion over cubic fluorite-structured nanoceria. The nanostructured CeO2, Ce0.92Zr0.08O2, and Ce0.84Zr0.16O2 composed of 5-6 nm crystallites display Tm-CO2 (the temperature at maximum CO2 yield) at 383, 355, and 375°C under 10 vol.% O2/N2, respectively. The size of agglomerate decreases from 165.5 to 51.9-57.3 nm, which is beneficial for the soot-ceria contact. Moreover, Zr increases the amount of surface oxygen vacancies, generating more active oxygen (O2- and O-) for soot oxidation. Thus, the activities of Ce0.92Zr0.08O2 and Ce0.84Zr0.16O2 in soot combustion are better than that of CeO2. Although oxygen vacancies promote the migration of lattice O2-, the enriched surface Zr also inhibits the mobility of lattice O2-. Therefore, the Tm-CO2 of Ce0.84Zr0.16O2 is higher than that of Ce0.92Zr0.08O2. Based on reaction kinetic study, soot in direct contact with ceria preferentially decomposes with low activation energy, while the oxidation of isolated soot occurs through diffusion with high activation energy. The obtained findings provide new understanding on the soot combustion over nanoceria.

Engineered Cell-Derived Microparticles Bi2Se3/DOX@MPs for Imaging Guided Synergistic Photothermal/Low-Dose Chemotherapy of Cancer.

Cell-derived microparticles, which are recognized as nanosized phospholipid bilayer membrane vesicles, have exhibited great potential to serve as drug delivery systems in cancer therapy. However, for the purpose of comprehensive therapy, microparticles decorated with multiple therapeutic components are needed, but effective engineering strategies are limited and still remain enormous challenges. Herein, Bi2Se3 nanodots and doxorubicin hydrochloride (DOX) co-embedded tumor cell-derived microparticles (Bi2Se3/DOX@MPs) are successfully constructed through ultraviolet light irradiation-induced budding of parent cells which are preloaded with Bi2Se3 nanodots and DOX via electroporation. The multifunctional microparticles are obtained with high controllability and drug-loading capacity without unfavorable membrane surface destruction, maintaining their excellent intrinsic biological behaviors. Through membrane fusion cellular internalization, Bi2Se3/DOX@MPs show enhanced cellular internalization and deepened tumor penetration, resulting in extreme cell damage in vitro without considering endosomal escape. Because of their distinguished photothermal performance and tumor homing target capability, Bi2Se3/DOX@MPs exhibit admirable dual-modal imaging capacity and outstanding tumor suppression effect. Under 808 nm laser irradiation, intravenous injection of Bi2Se3/DOX@MPs into H22 tumor-bearing mice results in remarkably synergistic antitumor efficacy by combining photothermal therapy with low-dose chemotherapy in vivo. Furthermore, the negligible hemolytic activity, considerable metabolizability, and low systemic toxicity of Bi2Se3/DOX@MPs imply their distinguished biocompatibility and great potential for tumor theranostics.

Mesoporous Molybdenum-Tungsten Mixed Metal Oxide: A Solid Acid Catalyst for Green, Highly Efficient sp3-sp2 C-C Coupling Reactions.

A mesoporous molybdenum tungsten mixed metal oxide with high surface area (173 m2/g) was synthesized by using metal dissolution coupled with a surfactant assisted reverse micelle formation synthesis method. Comprehensive characterization of the mixed oxide was performed by using PXRD, Raman, BET, SEM, EDX, TEM, and XPS. Thus, the formation of α-Mo0.5W0.5O3 with a homogeneous distribution of Mo and W throughout the material was seen. Furthermore, multiple oxidation states of molybdenum (Mo6+ and Mo5+) and a single oxidation state of tungsten (W6+) were observed. The weak/moderate acidic sites present in the mixed metal oxide resulted in excellent catalytic properties toward the sp3-sp2 carbon-carbon coupling reactions. The coupling of benzyl alcohol and toluene was completed within 15 min at 110 °C with 99% yield.

A novel, mesoporous molybdenum doped titanium dioxide/reduced graphene oxide composite as a green, highly efficient solid acid catalyst for acetalization.

A novel, mesoporous composite of Mo doped TiO2/reduced graphene oxide is synthesized to be used as a highly efficient heterogeneous acid catalyst. The composite has a high surface area (263 m2 g-1) and a monomodal pore size distribution with an average pore diameter of 3.4 nm. A comprehensive characterization of the synthesized material was done using PXRD, Raman, BET, SEM, EDX, TEM, TGA, and XPS. The composite exhibited excellent catalytic activity (1.6 h-1 TOF, >99% GC yield, and >99% selectivity) towards acetalization of cyclohexanone at room tempertaure within 30 minutes. The catalyst was reusable up to 4 reaction cycles without any significant loss in the activity and the acidic site calculations showed that the reaction is mostly driven by the weak acidic sites on the composite.

Highly active oxygen evolution integrated with efficient CO2 to CO electroreduction.

Electrochemical reduction of CO2 to useful chemicals has been actively pursued for closing the carbon cycle and preventing further deterioration of the environment/climate. Since CO2 reduction reaction (CO2RR) at a cathode is always paired with the oxygen evolution reaction (OER) at an anode, the overall efficiency of electrical energy to chemical fuel conversion must consider the large energy barrier and sluggish kinetics of OER, especially in widely used electrolytes, such as the pH-neutral CO2-saturated 0.5 M KHCO3 OER in such electrolytes mostly relies on noble metal (Ir- and Ru-based) electrocatalysts in the anode. Here, we discover that by anodizing a metallic Ni-Fe composite foam under a harsh condition (in a low-concentration 0.1 M KHCO3 solution at 85 °C under a high-current ∼250 mA/cm2), OER on the NiFe foam is accompanied by anodic etching, and the surface layer evolves into a nickel-iron hydroxide carbonate (NiFe-HC) material composed of porous, poorly crystalline flakes of flower-like NiFe layer-double hydroxide (LDH) intercalated with carbonate anions. The resulting NiFe-HC electrode in CO2-saturated 0.5 M KHCO3 exhibited OER activity superior to IrO2, with an overpotential of 450 and 590 mV to reach 10 and 250 mA/cm2, respectively, and high stability for >120 h without decay. We paired NiFe-HC with a CO2RR catalyst of cobalt phthalocyanine/carbon nanotube (CoPc/CNT) in a CO2 electrolyzer, achieving selective cathodic conversion of CO2 to CO with >97% Faradaic efficiency and simultaneous anodic water oxidation to O2 The device showed a low cell voltage of 2.13 V and high electricity-to-chemical fuel efficiency of 59% at a current density of 10 mA/cm2.

Constructing Bifunctional 3D Holey and Ultrathin CoP Nanosheets for Efficient Overall Water Splitting.

Pursuing cost-effective water-splitting catalysts is still a significant scientific challenge to produce renewable fuels and chemicals from various renewable feedstocks. The construction of controllable binder-free nanostructures with self-standing holey and ultrathin nanosheets is one of the promising approaches. Herein, by employing a combination of the potentiodynamic mode of electrodeposition and low-temperature phosphidation, three-dimensional (3D) holey CoP ultrathin nanosheets are fabricated on a carbon cloth (PD-CoP UNSs/CC) as bifunctional catalysts. Electrochemical tests show that the PD-CoP UNSs/CC exhibits outstanding hydrogen evolution reaction performance at all pH values with overpotentials of 47, 90, and 51 mV to approach 10 mA cm-2 in acidic, neutral, and alkaline media, respectively. Meanwhile, only a low overpotential of 268 mV is required to drive 20 mA cm-2 for the oxygen evolution reaction in alkaline media. Cyclic voltammetry and impedance studies suggest the enhanced performance is mainly attributed to the unique 3D holey ultrathin nanosheets, which could increase the electrochemically active area, facilitate the release of gas bubbles from electrode surfaces, and improve effective electrolyte diffusion. This work suggests an efficient path to design and fabricate non-noble bifunctional electrocatalysts for water splitting at a large scale.

Surface redox characters and synergetic catalytic properties of macroporous ceria-zirconia solid solutions.

Macroporous CeO2-ZrO2 (CZ) solid solutions with gradually changing ceria content were prepared through the EISA method. Pore sizes of the samples are about 100 nm-1 µm and pore walls are 100 nm-1.5 µm. The surface and near surface reduction bands of Ce4+ below 600 °C were maximized for the Ce0.5Zr0.5O2 sample (C5) according to the quantitative de-convolution to the acquired TPR curves. The area percentage of the O2-2p6 → Ce3+3d94f2 electronic transition band on XPS spectra, which related to the concentration of the Ce3+, was found to be a function of the ceria content. The oxygen storage capacity showed a positive relationship with the chemical compositions. Redox reactions below 600 °C play a key role in determining the reduction performances of ceria based TWCs. Three-way catalytic performances of the Pd + Rh + Pt /C5 sample showed an ignition temperature for CO and NOx at about 240 °C, and finished before 300 °C. The ignition of C3H8 started at 270 °C while finished at differed samples. The maximum catalytic efficiencies of CO, NOx, and C3H8 on C5 sample were revealed to 100%, 98%, and 97%, respectively. The performances showed that porous CZ solid solutions are suitable for high performance catalytic applications.

Niobium-substituted octahedral molecular sieve (OMS-2) materials in selective oxidation of methanol to dimethoxymethane.

Octahedral molecular sieve (OMS-2) refers to a one-dimensional 2 × 2 framework of octahedral manganese oxo units based on the cryptomelane-type framework. Herein, we describe a niobium (Nb) substituted mixed metal oxide of Nb and Mn where the cryptomelane-type framework is retained. These materials are hydrothermally synthesized from the reaction of potassium permanganate, manganese sulfate, and homogeneous niobium(v) precursors. Niobium incorporation up to 31 mol% can be achieved without destroying the one dimensional 2 × 2 framework. The yields of the materials vary between 70 and 90%. These materials are analyzed by powder XRD, BET isotherm, TEM, SEM, XRF, and XPS studies. The synthesized materials show promising activity in selective oxidation of methanol to dimethoxymethane (DMM) at 200 °C. Normalized activity correlations followed the trend 21% Nb-OMS-2 > 15% Nb-OMS-2 > 31% Nb-OMS-2 > 68% Nb-OMS-2 > K-OMS-2. A fluctuation in methanol conversion was observed around 125-150 °C in most samples, suggesting this to be a catalytically important temperature regime when forming active sites for DMM production.

Hierarchical Mesoporous NiO/MnO2@PANI Core-Shell Microspheres, Highly Efficient and Stable Bifunctional Electrocatalysts for Oxygen Evolution and Reduction Reactions.

We report on the new facile synthesis of mesoporous NiO/MnO2 in one step by modifying inverse micelle templated UCT (University of Connecticut) methods. The catalyst shows excellent electrocatalytic activity and stability for both the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) in alkaline media after further coating with polyaniline (PANI). For electrochemical performance, the optimized catalyst exhibits a potential gap, ΔE, of 0.75 V to achieve a current of 10 mA cm-2 for the OER and -3 mA cm-2 for the ORR in 0.1 M KOH solution. Extensive characterization methods were applied to investigate the structure-property of the catalyst for correlations with activity (e.g., XRD, BET, SEM, HRTEM, FIB-TEM, XPS, TGA, and Raman). The high electrocatalytic activity of the catalyst closely relates to the good electrical conductivity of PANI, accessible mesoporous structure, high surface area, as well as the synergistic effect of the specific core-shell structure. This work opens a new avenue for the rational design of core-shell structure catalysts for energy conversion and storage applications.

Mesoporous Iron Sulfide for Highly Efficient Electrocatalytic Hydrogen Evolution.

We report a facile synthetic protocol to prepare mesoporous FeS2 without the aid of hard template as an electrocatalyst for the hydrogen evolution reaction (HER). The mesoporous FeS2 materials with high surface area were successfully prepared by a sol-gel method following a sulfurization treatment in an H2S atmosphere. A remarkable HER catalytic performance was achieved with a low overpotential of 96 mV at a current density of 10 mA·cm-2 and a Tafel slope of 78 mV per decade under alkaline conditions (pH 13). The theoretical calculations indicate that the excellent catalytic activity of mesoporous FeS2 is attributed to the exposed (210) facets. The mesoporous FeS2 material might be a promising alternative to the Pt-based electrocatalysts for water splitting.

Albumin removal from human serum using surface nanopockets on silica-coated magnetic nanoparticles.

Selective removal of albumin from human serum is an essential step prior to proteomic analyses, especially when using mass spectrometry. Here we report stable synthetic nanopockets on magnetic nanoparticle surfaces that bind to human serum albumin (HSA) with high affinity and specificity. The nanopockets are created by templating HSA on 200 nm silica-coated paramagnetic nanoparticles using polymer layers made using 4 organo-silane monomers. These monomers have amino acid-like side chains providing hydrophobic, hydrophilic and H-bonding interactions that closely mimic features of binding sites on antibodies. The binding capacity of the material was 21 mg HSA g-1, and consistently removed ∼88% albumin from human serum in multiple repeated use.

An ultrasonic atomization assisted synthesis of self-assembled manganese oxide octahedral molecular sieve nanostructures and their application in catalysis and water treatment.

Manganese oxides of octahedral molecular sieve (OMS-2) type have important applications in oxidation catalysis, adsorption, and as battery materials. The synthesis methods employed determine their morphology and textural properties which markedly affect their catalytic activity. In this work, a room temperature ultrasonic atomization assisted synthesis of OMS-2 type materials is demonstrated. This synthesis differs from previously reported methods in that it is a simple, no-heat application that leads to a striking morphological characteristic of uniformly sized OMS-2 fibers and their self-assembly into dense as well as hollow spheres. Control of various parameters in the ultrasonic atomization assisted synthesis led to OMS-2 with high surface areas (between 136-160 m2 g-1) and mesoporosity. Catalytically these materials have higher activities in the oxidation of hydroxymethylfurfural (HMF), a bio-based chemical, (65% conversion of HMF vs. 14% with conventional OMS-2 catalyst) and a higher adsorption of lead from aqueous solutions (70% vs. 12% in conventional OMS-2 materials).

Highly Conductive In-SnO2/RGO Nano-Heterostructures with Improved Lithium-Ion Battery Performance.

The increasing demand of emerging technologies for high energy density electrochemical storage has led many researchers to look for alternative anode materials to graphite. The most promising conversion and alloying materials do not yet possess acceptable cycle life or rate capability. In this work, we use tin oxide, SnO2, as a representative anode material to explore the influence of graphene incorporation and In-doping to increase the electronic conductivity and concomitantly improve capacity retention and cycle life. It was found that the incorporation of In into SnO2 reduces the charge transfer resistance during cycling, prolonging life. It is also hypothesized that the increased conductivity allows the tin oxide conversion and alloying reactions to both be reversible, leading to very high capacity near 1200 mAh/g. Finally, the electrodes show excellent rate capability with a capacity of over 200 mAh/g at 10C.

The viability of photocatalysis for air purification.

Photocatalytic oxidation (PCO) air purification technology is reviewed based on the decades of research conducted by the United Technologies Research Center (UTRC) and their external colleagues. UTRC conducted basic research on the reaction rates of various volatile organic compounds (VOCs). The knowledge gained allowed validation of 1D and 3D prototype reactor models that guided further purifier development. Colleagues worldwide validated purifier prototypes in simulated realistic indoor environments. Prototype products were deployed in office environments both in the United States and France. As a result of these validation studies, it was discovered that both catalyst lifetime and byproduct formation are barriers to implementing this technology. Research is ongoing at the University of Connecticut that is applicable to extending catalyst lifetime, increasing catalyst efficiency and extending activation wavelength from the ultraviolet to the visible wavelengths. It is critical that catalyst lifetime is extended to realize cost effective implementation of PCO air purification.

Infrared and infrared emission spectroscopic study of typical Chinese kaolinite and halloysite.

The structure and thermal stability between typical Chinese kaolinite and halloysite were analysed by X-ray diffraction (XRD), infrared spectroscopy, infrared emission spectroscopy (IES) and Raman spectroscopy. Infrared emission spectroscopy over the temperature range of 300-700°C has been used to characterise the thermal decomposition of both kaolinite and halloysite. Halloysite is characterised by two bands in the water bending region at 1629 and 1648 cm(-1), attributed to structural water and coordinated water in the interlayer. Well defined hydroxyl stretching bands at around 3695, 3679, 3652 and 3625 cm(-1) are observed for both kaolinite and halloysite. The 550°C infrared emission spectrum of halloysite is similar to that of kaolinite in 650-1350 cm(-1) spectral region. The infrared emission spectra of halloysite were found to be considerably different to that of kaolinite at lower temperatures. These differences are attributed to the fundamental difference in the structure of the two minerals.