Polymer microcantilever biochemical sensors with integrated polymer composites for electrical detection

Micro fabricated sensors based on nanomechanical motion with piezoresistive electrical readout have become a promising biochemical sensing tool. The conventional microcantilever materials are mostly silicon-based. The sensitivity of the sensor depends on Young's modulus of the structural material, thickness of the cantilever as well as on the gauge factor of the piezoresistor. UV patternable polymers such as SU-8 have a very low Young's modulus compared to the silicon-based materials. Polymer cantilevers with a piezoresistive material having a large gauge factor and a lower Young's modulus are therefore highly suited for sensing applications. In this work, a spin coatable and photopatternable mixture of carbon black (CB) and SU-8, with proper dispersion characteristics, has been demonstrated as a piezoresistive thin film for polymer microcantilevers. Results on percolation experiments of SU-8/CB composite and fabrication of piezoresistive SU-8 microcantilevers using this composite are presented. With our controlled dispersion experiments, we could get a uniform piezoresistive thin film of thickness less than 1.2 μm and resistivity of 2.7 Ω cm using 10 wt% of CB in SU-8. The overall thickness of the SU-8/composite/SU-8 is approximately 3 μm. We further present results on the electromechanical characterization and biofunctionalization of the cantilever structures for biochemical sensing applications. These cantilevers show a deflection sensitivity of 0.55 ppm/nm. Since the surface stress sensitivity is 4.1 × 10⁻³ [N/m]⁻¹, these cantilevers can well be used for detection of protein markers for pathological applications.     

In-situ growth of PbI2 on ligand-free FAPbBr3 nanocrystals to significantly ameliorate the stability of CO2 photoreduction

Excellent optical properties involving strong visible light response and superior carrier transport endow metal halide perovskites （MHP） with a fascinating prospect in the field of photocatalysis.Nevertheless,the poor stability of MHP nanocrystals （NCs） in water-contained system,especially without the protection of long alkyl chain ligands,severely restricts their photocatalytic performance.In this context,we report an effortless strategy for the generation of ligand-free MHP NCs based photocata...     

Soft,Oxidative Stripping of Alkyl Thiolate Ligands from Hydroxyapatite‐Supported Gold Nanoclusters for Oxidation Reactions

A strategy for the mild deprotection of alkyl‐thiolated (6‐mercaptohexanoic acid, MHA, and 3‐mercaptopropanoic acid, MPA) gold nanoclusters (Au NCs) supported on hydroxyapatite (HAP) has been developed by employing a peroxide (tert‐butyl hydroperoxide, TBHP, or hydrogen peroxide, H₂O₂) as an oxidant. The thiol ligands on the supported Au NCs were removed after oxidation, and the size and integrity of the supported clusters were well‐preserved. The bare gold clusters on HAP after removal of the ligands were catalytically effective for the epoxidation of styrene and the aerobic oxidation of benzyl alcohol. These two reactions were also investigated on calcined Au NCs that were supported on HAP for comparison, and the resulting Au NCs that were prepared by using this new strategy showed superior catalytic activity.     

Size‐Tunable Highly Luminescent SiO2 Particles Impregnated with Number‐Adjusted CdTe Nanocrystals

Highly luminescent SiO₂ particles impregnated with CdTe nanocrystals (NCs) are prepared by a sol–gel procedure. Partial ligand exchange from thioglycolic acid to 3‐mercaptopropyltrimethoxysilane (MPS) on the NCs enables retention of the initial photoluminescence (PL) efficiency of the NCs in water, while the simultaneous addition of a poor solvent (ethanol) results in regulated assembly of the NCs through condensation of hydrolyzed MPS. The SiO₂ particles thus prepared have, for example, a diameter of 16 nm and contain three NCs each. The PL efficiency of these particles is 40 %, while the initial efficiency is 46 % in a colloidal solution. The redshift and narrowed spectral width in PL observed after impregnation indicate that the concentration of NCs in these nearly reaches the ultimate value (on the order of 10²¹ particles per liter). The porosity of these particles is investigated by means of N₂ adsorption–desorption isotherms. Due to the SiO₂ shell, these particles have higher stability in phosphate‐buffered saline buffer solution than the initial NCs. Their potential use for labeling in bio‐applications is investigated by conjugating biotinylated immunoglobulin G to them by using streptavidin maleimide as linker. Successful conjugation is confirmed by electrophoresis in agarose gel. This preparation method is an important step towards fabricating intensely emitting biocompatible SiO₂ particles impregnated with semiconductor NCs.     

A Facile Chemical Synthesis of Cu2O Nanocubes Covered with Co3O4 Nanohexagons for the Sensitive Detection of Glucose

Copper (I) oxide nanocubes (Cu₂O NCs) covered with cobalt oxide nanohexagons (Co₃O₄ NHs) were prepared through simple chemical method. Here, ascorbic acid is used as reducing and capping agent for the synthesis of nanocubes and nanohexagons. Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Energy‐dispersive X‐ray spectroscopy (EDX) and X‐ray diffraction spectroscopy (XRD) were employed to confirm the prepared nanocomposite. Cu₂O NCs?Co₃O₄ NHs nanocomposite is drop cast on the glassy carbon electrode (GCE) for the fabrication of glucose sensor. The fabricated Cu₂O NCs?Co₃O₄ NHs/GCE exhibited a better electrocatalytic activity towards the determination of glucose than that of individually fabricated Cu₂O NCs and Co₃O₄ NHs modified GCE. Our finding exhibited a wide linear range from 1 μM to 5330 μM with LOD of 0.63 towards glucose. In addition, the sensor attained appreciable stability, repeatability and reproducibility. Practicality of the sensor was demonstrated in human serum samples. The main advantages of the fabricated sensor are simple, biocompatible, cost effective, fast response and highly stable electrode surface.     

Glycine-Functionalized CsPbBr3 Nanocrystals for Efficient Visible-Light Photocatalysis of CO2 Reduction

Capping ligands are indispensable for the preparation of metal-halide-perovskite (MHP) nanocrystals (NCs) with good stability; however, the long alkyl-chain capping ligands in conventional MHP NCs will be unfavorable for CO₂ adsorption and hinder the efficient carrier separation on the surface of MHP NCs, leading to inferior catalytic activity in artificial photosynthesis. Herein, CsPbBr₃ nanocrystals with short-chain glycine as ligand are constructed through a facile ligand-exchange strategy. Owing to the reduced hindrance of glycine and the presence of the amine group in glycine, the photogenerated carrier separation and CO₂ uptake capacity are noticeably improved without compromising the stability of the MHP NCs. The CsPbBr₃ nanocrystals with glycine ligands exhibit a significantly increased yield of 27.7 μmol g⁻¹ h⁻¹ for photocatalytic CO₂-to-CO conversion without any organic sacrificial reagents, which is over five times higher than that of control CsPbBr₃ NCs with conventional long alkyl-chain capping ligands.     

Enhanced Anticancer Cells Effects of Optimized Suspension Stable As2O3‐Loaded Poly(lactic‐co‐glycolic acid) Nanocapsules

This study is to prepare a nanosuspension based on poly(lactic‐co‐glycolic acid) (PLGA) for delivery, controlled release and enhanced anti‐solid tumor effects of As₂O₃. As₂O₃‐loaded PLGA nanocapsules (As₂O₃‐PLGA NCs) were prepared by double emulsion‐solvent evaporation method and were optimized by univariate analysis in combination with orthogonal experimental according to several factors. The optimized As₂O₃‐PLGA NCs presented suitable physical stability, favorable size of (200.2±10.6) nm (PDI=0.117±0.008), spherical shape, and high encapsulation efficiency (92.48%±2.14%). The in vitro suspension stability of the NCs was excellent. The release of As₂O₃ from the NCs showed pH responsive release characteristics. The NCs can be efficiently taken up by SMMC‐7721 cell and showed excellent antitumor efficacy against SMMC‐7721 cell line. Then, As₂O₃‐PLGA NCs could be considered as a promising formulation for the pH dependent release of As₂O₃ in cancer cells and enhance the anti‐solid tumor effects of As₂O₃.     

Up/downconversion luminescence rare-earth ion-doped Y2O3 1D nanocrystals

Multicolor luminescent rare-earth ion-doped Y2O3 nanocrystals(NCs) were prepared by a solvethermal method.The as-synthesized NCs yielded nanosheets,nanowires(NWs) and nanorods(NRs) with the increase of alkali(NaOH) in oleic acid system.Moreover,Y2O3 nanowires with controllable size have also been obtained.After sintering,the PL intensity of Y2O3:Ln 3+ nanocrystals increased with the changed morphology of the precursor,that is,Y(OH) 3 nanocrystals.Both downconversion(red emission for Y2O3:Eu 3+ and green emission for Y2O3:Tb 3+) and upconversion(red emission for Y2O3:Yb/Er 3+) luminescence of the as-prepared nanocrystals have been demonstrated in this work.We also found that the PL intensity of Y2O3:Ln 3+ NCs dispersed in polar solvent was stronger than that in nonpolar solvent.Their up/downconversion fluorescence and controllable morphology might promise further fundamental research and biochemistry such as nanoscale optoelectronics,nanolasers,and ultrasensitive multicolor biolables.     

Atomically Precise Copper Nanoclusters for Highly Efficient Electroreduction of CO2 towards Hydrocarbons via Breaking the Coordination Symmetry of Cu Site

We propose an effective highest occupied d-orbital modulation strategy engendered by breaking the coordination symmetry of sites in the atomically precise Cu nanocluster (NC) to switch the product of CO₂ electroreduction from HCOOH/CO to higher-valued hydrocarbons. An atomically well-defined Cu₆ NC with symmetry-broken Cu−S₂N₁ active sites (named Cu₆(MBD)₆, MBD=2-mercaptobenzimidazole) was designed and synthesized by a judicious choice of ligand containing both S and N coordination atoms. Different from the previously reported high HCOOH selectivity of Cu NCs with Cu−S₃ sites, the Cu₆(MBD)₆ with Cu−S₂N₁ coordination structure shows a high Faradaic efficiency toward hydrocarbons of 65.5 % at −1.4 V versus the reversible hydrogen electrode (including 42.5 % CH₄ and 23 % C₂H₄), with the hydrocarbons partial current density of −183.4 mA cm⁻². Theoretical calculations reveal that the symmetry-broken Cu−S₂N₁ sites can rearrange the Cu 3d orbitals with as the highest occupied d-orbital, thus favoring the generation of key intermediate *COOH instead of *OCHO to favor *CO formation, followed by hydrogenation and/or C−C coupling to produce hydrocarbons. This is the first attempt to regulate the coordination mode of Cu atom in Cu NCs for hydrocarbons generation, and provides new inspiration for designing atomically precise NCs for efficient CO₂RR towards highly-valued products.     

Completely Green Synthesis of Colloid Adams’ Catalyst α‐PtO2 Nanocrystals and Derivative Pt Nanocrystals with High Activity and Stability for Oxygen Reduction

We report a first solution strategy for controlled synthesis of Adams’ catalyst (i.e., α‐PtO₂) by a facile and totally green approach using H₂PtCl₆ and water as reactants. The prepared α‐PtO₂ nanocrystals (NCs) are ultrasmall in size and have very “clean” surfaces, which can be reduced to Pt NCs easily in ethanol under ambient conditions. Such Adams’ catalysts have been applied as electrocatalysts beyond the field of heterogeneous catalysis. Noticeably, the water‐only synthesized α‐PtO₂ NCs and their derivative Pt NCs all exhibit much higher oxygen reduction reaction (ORR) activities and stabilities than that of the state‐of‐art Pt/C electrocatalysts. This study provides an example on the organics‐free synthesis of α‐PtO₂ and Pt NCs as promising cathode catalysts for fuel cell applications and, particularly, this simple, straightforward method may open a new way for the synthesis of other “clean” functional nanomaterials.     

Probing defect-originated properties,actinide-lanthanide doping,and gamma irradiation effect in Lu2Hf2O7 pyrochlore nanocrystals for phosphor and nuclear applications

Multifunctional materials are in high demand these days by virtue of their efficacy to perform more than one role and are expected to ease the high global materials crunch. This work is directed towards probing defect emission in undoped and doping of uranium (U), plutonium (Pu), curium (Cm), cerium (Ce), and samarium (Sm) Lu₂Hf₂O₇ (LuHO) pyrochlore nanocrystals (NCs) for photoluminescence and radioactive waste immobilization. Density of state calculations shows abundant defects in the undoped LuHO NCs. Multiple visible luminescence spanning violet to red in the undoped LuHO pyrochlore NCs upon ultraviolet irradiation was ascribed to the presence of neutral and ionized oxygen vacancies. The doped LuHO NCs show typical blue (Ce³⁺), orange-red (Sm³⁺), and green (U⁶⁺) emissions endowed by 4f→5d, 4f→4f, and charge transfer transitions, respectively. Moreover, uranium is stabilized as UO₆^6? ion (octahedral uranate) in the LuHO pyrochlore lattice. Luminescence lifetime spectroscopy and density functional theory (DFT) calculated defect formation energies suggest that Ce, Sm, Cm, and Pu ared stabilized at Lu³⁺ site whereas U is stabilized at Hf⁴⁺ site in the LuHO NCs. The LuHO pyrochlore NCs also demonstrate high radiation stability on gamma exposure retaining the crystallinity and undergoing structural phase transition from defect fluorite to ideal pyrochlore structure. Considering the significant health hazard posed by radioactive elements present in the spent fuel, these LuHO NCs possess high potential to immobilize U, Pu, Cm, Ce, and Sm. This work poses high significance for immobilizing radioactive nuclear waste and designing tunable luminescent solid-state NCs.     

Electrogenerated chemiluminescence and electrochemical bi-functional sensors for H2O2 based on CdS nanocrystals/hemoglobin multilayers

A novel bi-functional sensor, based on CdS nanocrystals (NCs) and hemoglobin (Hb) multilayer films, designated as {Hb/CdS}_n, modified glassy carbon electrode (GCE) by layer-by-layer (LbL) assembly, has been presented. The electrogenerated chemiluminescence (ECL) and electrochemical properties of {Hb/CdS}_n have been investigated in detail. Hb in the multilayer films can enhance the stability of electrogenerated species of CdS NCs, and CdS NCs can also promote the direct electron transfer between Hb and GCE. As a consequence experimentally, the multilayer films modified GCE is suitable to be used as a bi-functional sensor, ECL sensor and electrochemical sensor, to determine H₂O₂ in obviously different concentration. In high concentration of H₂O₂, this sensor as an ECL sensor shows a linear response from 15 μM up to 18 mM. In the lower concentration of H₂O₂, it as an amperometric one shows two linear ranges of amperometric responses to the concentration of H₂O₂ ranging from 6.0 to 31.0 μM and from 6.0 μM down to 40 nM with a detection limit of 20 nM, based on the high stability of ECL by {Hb/CdS}_n and the excellent electrocatalytical ability of Hb to H₂O₂. Thus, {CdS/Hb}_n modified electrodes would have a great merit to expand the application of biosensors to life science and environmental science.     

Synthesis of nanocrystalline CdS from cadmium(II) complex of S-benzyl dithiocarbazate as a precursor

The single X-ray crystal structure of the cadmium(II)–S-benzyl dithiocarbazate (SBDTC) complex, [Cd(SBDTC)Cl₂]₂, is reported. The compound has been found to be an effective single-source precursor for the preparation of CdS nanocrystals (NCs) via solvothermal method. CdS NCs including spheres and rods were prepared at a relatively low temperature by thermolysis of the precursor using chelating solvent like ethylene glycol (EG), ethylenediamine (EN), hydrazine hydrate (HH) or in a mixture of EG and EN. The influence of solvent, temperature and reaction time was investigated on the size and morphology of the NCs. Use of EG afforded spherical CdS NCs while EN uniquely yielded rod-shaped NCs, and mixture of spheres and rods are obtained from the mixture of EN and EG with a ratio 0.2 (v/v: EN/EG). UV–visible spectroscopy established pronounced quantum confinement with enhanced band gap and XRD analyses revealed hexagonal crystal phase for so obtained CdS NCs. The NCs were also characterized by transmission electron microscopy (TEM), photoluminescence spectroscopy (PL), energy-dispersive X-ray spectroscopy (EDS) and FTIR. The possible formation mechanism for the anisotropic growth of NCs was also discussed.     

The influence of hematite nano-crystals on the thermal stability of polystyrene

A synthetic procedure based on thermal hydrolysis of iron(III) chloride solutions for the preparation of hematite (α-Fe₂O₃) sol consisting of nano-crystals (NCs) is described. The α-Fe₂O₃ NCs were characterized by transmission electron microscopy and X-ray diffraction measurements. Incorporation of α-Fe₂O₃ NCs into polystyrene (PS) was based on the transfer of α-Fe₂O₃ NCs from the aqueous phase to the organic solvent. A significant shift in the glass transition temperature of PS by 17 °C towards higher temperatures was observed after incorporation of α-Fe₂O₃ NCs. Also, the thermal stability of PS was improved by about 100 °C in the presence of 3.6 wt% of α-Fe₂O₃ NCs.     

Synthesis,characterization, and KOH activation of nanoporous carbon for increasing CO2 adsorption capacity

Ordered nanoporous carbons (ONCs) were prepared using a soft-templating method. To improve the CO₂ adsorption efficiency, ONCs were chemically activated to obtain high specific surface area and micro-/mesopore volume with different KOH amounts (i.e., 0, 1, 2, 3, and 4) as an activating agent. The prepared nanoporous carbons (NCs) materials were analyzed by low-angle X-ray diffraction for confirmation of synthesized ONCs structures. The structural properties of the NCs materials were analyzed by high-angle X-ray diffraction. The textural properties of the NCs materials were examined using the N₂/77 K adsorption isotherms according to the Brunauer–Emmett–Teller equation. The CO₂ adsorption capacity was measured by CO₂ isothermal adsorption at 298 K/1 bar. From the results, the NCs activated with KOH showed that the increasing specific surface areas and total pore volumes resulted in the enhancement of CO₂ adsorption capacity.     

Improved Transversal Relaxivity for Highly Crystalline Nanoparticles of Pure γ‐Fe2O3 Phase

Pure and highly crystalline γ‐Fe₂O₃ nanocrystals (NCs) are obtained when hydrolysis and oxidation of a Fe^II organometallic precursor are performed in successive steps. Their synthesis in pure alkylamine leads to NCs of about 6 nm. In aqueous solutions of poly(vinyl)pyrrolidone, such pristine NCs form aggregates of about 150 nm that exhibit a high transversal relaxivity (r₂=466 mM ^?1 s^?1) about four times higher than that of a commercial Feridex magnetic resonance imaging (MRI) contrast agent. Consequently, they provide a significant decrease in the NMR signal at very short echo time (8 ms), which is of paramount importance in clinical practice because of the reduced duration of MRI measurements.     

Comparative Structural,Optical, and Photoluminescence Studies of YF3:Pr,YF3:Pr@LaF3, and YF3:Pr@LaF3@SiO2 Core–Shell Nanocrystals

Praseodymium (Pr³⁺)‐doped YF₃ (core) and LaF₃ ‐covered YF₃ :Pr (core–shell) nanocrystals (NCs ) were prepared successfully by an ecofriendly, polyol‐based, co‐precipitation process, which were then coated with a silica shell by using a sol–gel‐based Stober method. X‐ray diffraction (XRD), transmission electron microscopy (TEM ), thermal analysis, Fourier transform infrared (FTIR) , UV /vis, energy bandgap, and photoluminescence studies were used to analyze the crystal structure, morphology, and optical properties of the nanomaterial. XRD and TEM results show that the grain size increases after sequential growth of crystalline LaF₃ and the silica shell. The silica surface modification enhances the solubility and colloidal stability of the core–shell‐SiO₂ NCs . The results indicate that the surface coating affects the optical properties because of the alteration in crystalline size of the materials. The emission intensity of silica‐modified NCs was significantly enhanced compared to that of core and core–shell NCs . These results are attributed to the formation of chemical bonds between core–shell and noncrystalline SiO₂ shell via La–O–Si bridges, which activate the “dormant” Pr³⁺ ions on the surfaces of the nanoparticles. The luminescence efficiency of the as‐prepared core, core–shell, and core–shell‐SiO₂ NCs are comparatively analyzed, and the observed differences are justified on the basis of the surface modification surrounding the luminescent seed core NCs .     

Ultra‐Small Plutonium Oxide Nanocrystals: An Innovative Material in Plutonium Science

Apart from its technological importance, plutonium (Pu) is also one of the most intriguing elements because of its non‐conventional physical properties and fascinating chemistry. Those fundamental aspects are particularly interesting when dealing with the challenging study of plutonium‐based nanomaterials. Here we show that ultra‐small (3.2±0.9 nm) and highly crystalline plutonium oxide (PuO₂) nanocrystals (NCs) can be synthesized by the thermal decomposition of plutonyl nitrate ([PuO₂(NO₃)₂] ? 3 H₂O) in a highly coordinating organic medium. This is the first example reporting on the preparation of significant quantities (several tens of milligrams) of PuO₂ NCs, in a controllable and reproducible manner. The structure and magnetic properties of PuO₂ NCs have been characterized by a wide variety of techniques (powder X‐ray diffraction (PXRD), X‐ray absorption fine structure (XAFS), X‐ray absorption near edge structure (XANES), TEM, IR, Raman, UV/Vis spectroscopies, and superconducting quantum interference device (SQUID) magnetometry). The current PuO₂ NCs constitute an innovative material for the study of challenging problems as diverse as the transport behavior of plutonium in the environment or size and shape effects on the physics of transuranium elements.     

Fabrication of Heterostructured Fe2TiO5–TiO2 Nanocages with Enhanced Photoelectrochemical Performance for Solar Energy Conversion

Photocatalysts with well‐designed compositions and structures are desirable for achieving highly efficient solar‐to‐chemical energy conversion. Heterostructured semiconductor photocatalysts with advanced hollow structures possess beneficial features for promoting the activity towards photocatalytic reactions. Here we develop a facile synthetic strategy for the fabrication of Fe₂TiO₅–TiO₂ nanocages (NCs) as anode materials in photoelectrochemical (PEC) water splitting cells. A hydrothermal reaction is performed to transform MIL‐125(Ti) nanodisks (NDs) to Ti–Fe–O NCs, which are further converted to Fe₂TiO₅–TiO₂ NCs through a post annealing process. Owing to the compositional and structural advantages, the heterostructured Fe₂TiO₅–TiO₂ NCs show enhanced performance for PEC water oxidation compared with TiO₂ NDs, Fe₂TiO₅ nanoparticles (NPs) and Fe₂TiO₅–TiO₂ NPs.     

普鲁士蓝/CdS纳米复合物电致化学发光及其H2O2传感应用

通过一定体积比的CdS和普鲁士蓝(PB)胶体纳米溶液的简单混合,制备了PB/CdS纳米复合物。在共反应剂存在条件下,PB纳米粒子含量较低时,在ITO电极上CdS纳晶的电致化学发光(ECL)强度可以增强3倍左右。PB纳米粒子含量较高时,CdS纳晶的ECL强度则显著降低。详细讨论了PB纳米粒子对CdS纳晶ECL影响的机理。PB纳米粒子对CdS纳晶的ECL增强可用于H2O2传感。该传感器对H2O2响应的线性范围为3.3×10-8～6.5×10-3 mol.L-1(R=0.999 2),检测限为12 nmol.L-1(S/N=3),传感器具有良好的稳定性和重现性。