Charge Density Matching Research Articles

Coupling charge pump and BUCK circuits to efficiently enhance the output performance of triboelectric nanogenerator

Triboelectric nanogenerator (TENG) faces significant challenges in practical applications because of its low output charge density and high matching impedance, and the development of its energy management circuits is hindered by high initial device requirements, large circuit size and poor portability. In this work, we propose a simple, efficient and versatile energy management strategy that two-stage amplification of TENG output performance by coupling a charge pump circuit with a BUCK circuit. By implementing the energy management strategy, the charge output per cycle of an ordinary TENG can be increased by more than 40 times, resulting in a power density of 25.2 mWm−2 and a total energy transfer efficiency of exceeding 88% in constant mode. At a working frequency of 1 Hz, the TENG can charge a 1000 μF capacitor to 5.04 V in 240 s and store the energy of more than 12.72 mJ, of which represents an 848-fold increase in stored energy compared to using TENG directly. Remarkably, this TENG device exhibits exceptional an average power of 100.7 μW/Hz, setting a new record for devices with smaller TENG size (< 50 cm2) or limited PM circuit size (< 10 cm2). Moreover, an ordinary TENG can continuously power a wireless sensor by integrating the portable power management circuit, facilitating real-time wireless data transmission. This study is of great significance for the practical application of the TENG power supply in the sensor network of the Internet of Things and for expanding the application range of the TENG.

Facile Synthesis of Fluorine-Doped Hollow Mesoporous Carbon Nanospheres for Supercapacitor Application

Hollow mesoporous carbon nanospheres doped with fluorine (FHMC) were synthesized for high-performance supercapacitor applications. Monodisperse nanospheres with a copolymeric core-silica shell were produced by charge density matching. The copolymeric chains in the core phase were crosslinked through a Friedel-Crafts reaction, followed by carbonization at 800 °C under a N2 atmosphere to obtain the core-shell (CSC) nanospheres with a carbon core and silica/carbon composite shell. The silica phase of these core-shell nanospheres was etched selectively during the thermal decomposition of Teflon to synthesize the FHMC nanospheres. During the etching process of silica in the shell phase, the surfaces of the nanospheres were doped with fluorine. The BET surface area was increased significantly from 788 m2/g and 1.31 cm3/g for the CSC nanospheres to 1021 m2/g and 2.55 cm3/g for the FHMC nanospheres. The specific capacitance of the FHMC nanospheres prepared was approximately 174 F/g at a current density of 0.5 A/g. The capacity retention after 10000 charge/discharge cycles at a current density of 1 A/g was approximately 93.6%.

High Efficiency Multi-Level Flexible Triboelectric Nanogenerator for Wearable Electronics

With the rapid development of wearable electronics and sensor networks, batteries cannot meet the sustainable energy requirement due to their limited lifetime, size and degradation. With miniaturization leading to high-power and robustness, triboelectric nanogenerators(TENGs) have been conceived as a promising technology by harvesting mechanical energy to power small electronics and wearables. The main issues associated with TENGs are their very low output power leading to lower output charge density and high impedance matching. In this work, a state of the art multilayer flexible structure is devised which not only increases the charge density but also provides a high average power output. Thin-film organic flexible materials are deposited to acquire charges from the triboelectrification process, allowing the acceptance of more charges from an electrode and thereby increasing the power output. Material work function provide better understanding towards charge transfer process. A proof of concept device is conceptualized for use in a highly efficient self-powered sensor network system, converting ambient mechanical energy to electricity with a 1.2kV peak amplitude and a very high device performance. This device structure makes the TENGs attractive to charging applications for wearables and large-scale harvesting without massive volume. By this technique, we have overcome numerous friction-based operation challenges including lack of uniform contact, material loss through wear, high sensitivity to humidity, and output power storage. By considering these merits of simple fabrication, outstanding performance, robust characteristic and low-cost technology, we believe that multi level flexible TENGs can open great opportunities not only for powering small electronics but can contribute to large-scale energy harvesting through engineering design being complementary to existing energy sources.

Templated vanadium tellurites: Identifying the effects of low density attractions on inorganic layer topology

Exploration of the NH4VO3/Na2TeO3/2,4,6-triaminopyrimidine/H2O system yielded the formation of two new phases, [C4H8N5][VO3] and [C4H8N5]2[V2Te2O10]. Phase selection in this system is largely dictated by the tellurium concentration during reaction. Differences in the [V2Te2O10]n2n− layer topologies in [C4H8N5]2[V2Te2O10] and two related phases, [C6H16N2][V2Te2O10] and [C5H14N2][V2Te2O10] were probed using noncovalent interaction energy ratios. These ratios allow for one to directly visualize and quantify differences in intermolecular interaction strengths between compounds. The presence or absence of π - π stacking interactions between organic ammonium cations in [C4H8N5]2[V2Te2O10] and two related phases, [C6H16N2][V2Te2O10] and [C5H14N2][V2Te2O10] is the source of layer connectivity differences. These π - π interactions between 2,4,6-triaminopyrimidinium cations in [C4H8N5]2[V2Te2O10] dictate their orientations between [V2Te2O10]n2n− layers, and direct the locations of hydrogen-bonding interactions. Effects associated with reactant concentrations, charge density matching and intermolecular interactions were probed using composition space analyses, Iterative Hirshfeld partial atomic charge, molecular surface area calculations and noncovalent interaction index calculations, respectively.

Structural unit charge density and molecular cation templating effects on orientational geometric isomerism and interlayer spacing in 2-D uranyl sulfates

The new uranyl aqua sulfate compound [({CH3}3N2C3H3{CH2COOH})(H3O)] [(UO2)2(SO4)3(H2O)]·1.5H2O was synthesized and the crystal structure determined. The two-dimensional uranyl-aqua sulfate compound exhibits a previously reported anionic structural unit topology, but features an interstitial complex incorporating hydronium in the form of a disorder Zundel cation and the cation moiety from the ionic liquid 1-carboxymethyl 3-methylimidazolium bistriflimide [HBetMIm][Tf2N], which forms hydrogen bonding dimer pairs. An analysis of similar uranyl sulfate complexes from the literature is conducted to explore the relative importance and role of structure directing factors in alkylammonium charge-balanced two-dimensional uranyl sulfates. A correlation is observed between structural unit charge density and interlayer spacing, with a concomitant direction of structural and orientational geometric isomerism of the anionic structural unit. We discuss the role of synthetic conditions and molecular cation properties in directing structural unit formation through charge density matching and hydrogen bonding.

Oil-in-water synthesis of hollow-shell mesoporous peapod-like silicates: Electron microscopy insights

Hollow mesoporous silica nanoparticles (HMSN) receive a remarkable attention for their many advantages in several applications. Hollow-shell mesoporous peapod-like silicates were synthesized based on the recently introduced drug structure-directing agent (DSDA) concept. The anionic DSDA was formed by the amidation of L-tryptophan with palmitoyl chloride. 3-Aminopropyltrimethoxysilane (APS) was employed as co-structure directing agent (CSDA). The interactions among DSDA, CSDA and silica source promoted the formation of the oil-in-water emulsions. We hypothesized that the emulsions aggregated in micelles that merged into sheet-like structures that curved, bent and closed to form spherical hollow structures. Finally, the hollow structures fused between them to form the final hollow-shell peapod-like silicates with 0.6–2.5 μm in length. Interestingly, the formation of inner lamellar-like mesoporous pillars separated by large mesovoids with sizes around 50 nm was promoted. The role of the APS is determinant in the synthesis of the hollow morphologies, since its absence disrupts the formation of HMSNs. The changes in the organic component packing and the charge density matching between the silica framework, continuously transforming, and the surfactant headgroups are postulated as the driving forces in determining the particles morphology. Moreover, based on an original TEM sample preparation, perpendicular views over the long axis, and mainly over the short axis were acquired, proving the symmetry of revolution of these materials along their axis. Perpendicular slices of the nanoparticles demonstrated the internal hollows and the inner crossing walls with lamellar-like mesoporosity. These materials are expected to have potential applications in fields including, batteries, adsorption, and mainly in biomedicine processes.

Probing structural adaptability in templated vanadium selenites

The structural adaptability of [V3O5(SeO3)3]n2n− layers in organically templated vanadium selenites was determined using a three step approach involving (i) an 84 reaction study with 14 distinct organic amines and 6 different reaction conditions, (ii) decision tree construction using both dependent and independent variables, and (iii) the derivation of chemical hypotheses. Formation of [V3O5(SeO3)3]n2n− layers requires that three criteria be met. First, compound stabilization through hydrogen-bonding with specific nucleophilic oxide ions is needed, requiring the presence of a primary ammonium site on the respective organic amine. Second, layer formation is facilitated through the use of compact ammonium cations that are able to achieve charge density matching with the anionic layers. Third, competition between organic ammonium cations and NH4+, which affects product formation, can be controlled through reagent choice and initial reactant concentrations. This approach to elucidate structural adaptability is generalizable and can be applied to a range of chemical systems.

Effect of Charge Density Matching on the Temperature Response of PNIPAAM Block Copolymer–Gold Nanoparticles

Upon conjugation of thermoresponsive polymers to nanomaterials such as gold nanoparticles (Aunps), whether and to what extent the properties of the polymer-coated Aunps differ from that of the free...

Generally applicable procedure for in situ formation of fluorescent protein-gold nanoconstructs

Small noble metal nanoclusters can be formed in situ by direct reduction and stabilization of a metal precursor by biomolecules such as proteins. Considering the diversity in amino acid composition of proteins, and hence their reductive ability, a general method for synthesis of gold nanoclusters using proteins is presented here. A range of proteins (bovine serum albumin, fibrinogen, α-lactalbumin, lysozyme, cytochrome c, myoglobin, β-lactoglobulin and α-chymotrypsin) have been studied, based on size, isoelectric point, flexibility and 3-dimensional structure. Results show protein-gold nanoconstructs with complex protein-specific photophysical properties. The effect on the 3-dimensional conformation of the proteins upon formation of gold nanoclusters and/or nanoparticles within the protein structure is also shown to be highly protein-dependent. A general mechanism for the formation of protein-gold nanoconstructs is proposed, based on charge density matching, yielding a high local concentration of the metal precursor on the protein structure which in turn can nucleate, grow and be stabilized by amino acid residues in the protein.

A template self-assembly strategy to synthesize free-standing TiO 2–MO (M = Mg, Co, Ni, Cu or Zn) colloidal films

A series of binary free-standing colloidal films, TiO 2–MO (M = Mg, Co, Ni, Cu and Zn) have been synthesized via a self-assembly technology, utilizing sodium dodecyl sulfonate (SDS) as template and the mixture of titanium butoxide and MCl 2 as precursor. X-ray diffraction (XRD) and transmission electron microscope (TEM) have been employed to characterize TiO 2–MO samples. Results show that TiO 2–MO films are mainly composed by well-ordered nanostructures (e.g. mesoporous particles and lamellar pieces) and more importantly, the increased Ti(OC 4H 9) 4 precursor have significant effect on modifying the as-synthesized nanostructures. A structural model based on SDS micellar template, the complex metallic oxide precursor and charge-density matching between the template and precursor has been proposed. Remarkably, this template self-assembly method has a potential to design a variety of functional multicomponent materials with high-ordered nanostructures, such as high gas sensing SnO 2–ZnO films.

Beyond Charge Density Matching: The Role of C–H···O Interactions in the Formation of Templated Vanadium Tellurites

Differences in the [V2Te2O10]n2n– layer topologies in [C6H16N2][V2Te2O10] and [C5H14N2][V2Te2O10] are the result of deviations in the C–H···O hydrogen-bonding networks. Stronger influences, such as reagent concentrations and charge density matching, were minimized through the use of both nearly identical reaction gels and 2,5-dimethylpiperazine and 2-methylpiperaine, which have very similar charge densities. Reactant concentration and charge density matching effects were quantified using composition space analyses, molecular and geometric decomposition surface areas, and Iterative Hirshfeld partial atomic charges.

Effect of glucose on self-assembly of free-standing air–water interfacial lamellar ZrO 2 films

A series of free-standing air–water interfacial ZrO 2 films have been self-assembled, using sodium dodecyl sulfonate (SDS) as template, glucose (Glu) as cosurfactant and zirconium(IV) butoxide as precursor. The formed nanostructures of ZrO 2 films have been carefully characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). Results show that the as-prepared ZrO 2 films display significant structural changes by adjusting the mass ratios of Glu to SDS. An architectural model based on SDS packing and charge-density matching has been proposed to illustrate the effect of Glu on various self-assembled nanostructures of ZrO 2 films.

ChemInform Abstract: The Role of Stereoactive Lone Pairs in Templated Vanadium Tellurite Charge Density Matching.

AbstractThe crystal structure of the new compound (II) is determined by single crystal XRD (triclinic, space group P$\bar 1$, Z = 1).

The Role of Stereoactive Lone Pairs in Templated Vanadium Tellurite Charge Density Matching

The role of charge density matching was investigated in the formation of templated vanadium tellurites under mild hydrothermal conditions. Reactions were conducted using a fixed NaVTeO(5):amine ratio in an ethanol/water solution to isolate the effects of amine structure. The use of 1,4-diaminobutane, 1,3-diaminopropane, and piperazine resulted in three distinct vanadium tellurite connectivities, [V(2)Te(2)O(10)](n)(2n-) chains, [V(2)TeO(8)](n)(2n-) layers, and [V(2)Te(2)O(10)](n)(2n-) layers, respectively. Charge density matching with the protonated amines is the primary influence over the structure of each vanadium tellurite anion, as quantified by molecular surface area and geometric decomposition methods. Electron localization functions were calculated using the Stuttgart tight-binding linear muffin-tin orbital, atomic sphere approximation code, to visualize the location and relative size, shape, and orientation of the stereoactive lone pair in the tellurite groups. [C(4)H(14)N(2)][V(2)Te(2)O(10)]: a = 5.649(5) A, b = 6.348(5) A, c = 9.661(5) A, alpha = 84.860(5) degrees , beta = 85.380(5) degrees , gamma = 81.285(5) degrees , triclinic, P1 (No. 2), Z = 1.

Uranyl selenates with organic templates: Principles of structure and characteristics of self-organization

Basic structural principles of uranyl selenates with organic templates are outlined as follows. In compounds with short chain amine molecules (C:N < 8) the primary role plays the correspondence between topology of inorganic complex (isomerism) and structure and shape of a template. In the structures with long chain molecules (C:N ≤ 8), the molecules are associated to form 2- or 1-dimensional supramolecular templates that are connected with inorganic structure according to the charge density matching principle. Compounds with electro neutral molecules (crown ethers) have composite structure, where bonding between organic and inorganic parts is achieved through hydrogen bonding via intermediate oxonium clusters.

Simple synthesis and characterization of nanoporous materials from talc

AbstractSynthetic siliceous mesoporous materials are of great value in many different applications, including nanotechnology, biotechnology, information technology, and medical fields, but historically the resource materials used in their synthesis have been expensive. Recent efforts have focused on indirect synthesis methods which utilize less expensive silicate minerals as a resource material. The purpose of the present study was to investigate talc, a natural silicate mineral, as one such resource. It was used as raw material to prepare two advanced materials: porous silica (PS) and ordered mesoporous silica (MCM-41). The PS, with a specific surface area of 260 m2/g and bimodal pore-size distribution of 1.2 nm and 3.7 nm, was prepared by grinding and subsequent acid leaching. The MCM-41, with a large surface area of 974 m2/g and a narrow pore-size distribution of 2.8 nm, was obtained using a surfactant, cetyltrimethylammonium bromide (CTAB), by hydrothermal treatment using the as-prepared PS as a source of Si. The two resultant materials were characterized by small angle X-ray diffraction (SAXRD) and wide-angle X-ray diffraction (WAXRD), high-resolution transmission electron microscopy (HRTEM), solid-state magic-angle-spinning nuclear magnetic resonance (MAS NMR), Fourier transform infrared spectroscopy (FTIR), and N2 adsorption-desorption measurements. Based on these measurements, possible processes of transformation of PS from talc, upon acid treatment, and the formation of MCM-41 were investigated systemically. Acid leaching induced the transformation of a rigid layered structure to a nearly amorphous one, with micropores formed by a residual layered structure and mesopores formed from a condensed framework. The MCM-41 was a mixture of silanol groups (Si(SiO)3(OH)) and a condensed Q4 framework structure (Si(SiO)4), with a small amount of remaining Q3 layered structure (Si(SiO)3OMg). The increased Q4/Q3 value confirmed greater polymerization of MCM-41 than of PS. At the low CTAB concentration used (2 wt.%), the highly charged silicate species controlled the surfactant geometry. Charge-density matching, together with the degree of polymerization of the silicates, determined the resultant mesophase.

Charge density matching in templated molybdates

The role of charge density matching in the formation of templated molybdates under mild hydrothermal conditions was investigated through the use of a series of structurally related amines: piperazine, 1,4-dimethylpiperazine, 2,5-dimethylpiperazine and 2,6-dimethylpiperazine. A series of reactions was conducted in which the relative mole fractions of each component were fixed at 2.5 MoO 3:1 amine:330 H 2O:2 H 2SO 4 in order to isolate the effects of the amine, the only variation between reactions was the structure of the amine. Four distinct polyoxomolybdates anions were observed, ranging from zero-dimensional β-[Mo 8O 26] 4− molecular anions to [Mo 3O 10] n 2 n− and [Mo 8O 26] n 4 n− chains and [Mo 5O 16] n 2 n− layers. The primary influence over the structure of the molybdate anion is charge density matching with the protonated amine, which was quantified through surface area approximations based upon both calculated molecular surfaces and polyhedral representations of each anion. Secondary influences include amine symmetry and hydrogen-bonding preferences. The synthesis and characterization of two new compounds are reported. Crystal data: [C 6H 16N 2][Mo 3O 10]·H 2O ( 1), triclinic, P-1 (no. 2), a=8.0973(7) Å, b=8.8819(9) Å, c=11.5969(11) Å, α=71.362(9)°, β=82.586(8)°, γ=74.213(8)°, Z=2, R/ R w=0.0262/0.0564, and [C 6H 16N 2] 2[Mo 8O 26] ( 2), monoclinic, P2 1/ n (no. 14), a=7.9987(11) Å, b=12.5324(19) Å, c=16.003(3) Å, β=97.393(14)°, Z=2, R/ R w=0.0189/0.0454.

Facile synthesis of hollow anatase titania prepared by charged polymeric nanosphere template

Two main synthetic routes have been employed to produce inorganic-coated polymer nanoparticles. The first approach is to precipitate to form a thin inorganic shell of hydrolyzed metal oxide precursors onto the polymeric template. The second approach is a layer-by-layer(LBL) deposition technique to form alternate layers of oppositely charged inorganic and organic species on the core materials. Various inorganic materials, including silica, titania, zirconia, clay and iron oxide, are used as a coating material. Among them, titania has attracted a great deal of recent attention, due to their application in catalysis, photovoltaics and photoelectronics. Titaniacoated particles are particularly useful as catalysts, white pigments and electrophoretic particles. These inorganic-coated polymer nanoparticles have been also used to prepare inorganic hollow nanoparticles, which are prepared by removal of the polymer core either by etching in solution or by calcination at high temperature. Hollow titania spheres have been prepared by the LBL manipulation of preformed inorganic nanoparticles onto polymeric colloidal. Recently, templated syntheses of hollow titania spheres was reported based on sulfonated polystyrene particles, which were prepared by seed emulsion polymerization, followed by treatment in concentrated sulfuric acid. We also reported the preparation of hollow titania nanospheres, based on the cationically-charged copolymer core, comprised of styrene, butyl acrylate and cationic [2-(methacryloxy) ethyl]trimethyl ammonium chloride (MOTAC), was prepared by soap-free emulsion polymerization. Cationically-charged polystyrene nanospheres were prepared by using an ionogenic initiator of 2,2’-azo bis(2methylpropionamidine)dihydrochloride (AIBA). The formation of the organic-inorganic hybrids was achieved by adsorption of titania through the hydrolysis of titania precursor. In the present study, to achieve the rapid and sufficient adsorption of inorganic precursor species onto the surfaces of polymer nanospheres, we synthesize positively-charged, monodisperse polymeric cores which are easily associated with negatively-charged inorganic titania precursors by charge density matching. To enhance the charge density of the polymer nanospheres, the polymer cores were prepared by surfactant-free emulsion copolymerization of methyl methacrylate (MMA), ethylene glycol dimethacrylate (EGDMA) and methacryloxyethyltrimethyl ammonium chloride (MOTAC) in the presence of azo bis(isobutylamidine) hydrochloride (AIBA) as an initiator. Unlike our previous study, the component monomers used in the present work are all acrylic, relatively-large amount of the cationic MOTAC monomer can be incorporated within the polymer backbone, which results in the increase in the charge density onto the surface of the polymer core in an attempt to achieve the sufficient adsorption of negatively-charged titania and obtain hollow titania nanospheres with adequate shell thickness.

Syntheses, structures, characterizations and charge-density matching of novel amino-templated uranyl selenates

Five hybrid organic–inorganic uranyl selenates have been synthesized, characterized and their structures have been determined. The structure of (C 2H 8N) 2[(UO 2) 2(SeO 4) 3(H 2O)] (EthylAUSe) is monoclinic, P2 1, a=8.290(1), b=12.349(2), c=11.038(2) Å, β=104.439(4)°, V=1094.3(3) Å 3, Z=2, R 1=0.0425. The structure of (C 7H 10N) 2[(UO 2)(SeO 4) 2(H 2O)]H 2O (BenzylAUSe) is orthorhombic, Pna2 1, a=24.221(2), b=11.917(1), c=7.4528(7) Å, V=2151.1(3) Å 3, Z=4, R 1=0.0307. The structure of (C 2H 10N 2)[(UO 2)(SeO 4) 2(H 2O)](H 2O) 2 (EDAUSe) is monoclinic, P2 1/ c, a=11.677(2), b=7.908(1), c=15.698(2) Å, β=98.813(3)°, V=1432.4(3) Å 3, Z=4, R 1=0.0371. The structure of (C 6H 22N 4)[(UO 2)(SeO 4) 2(H 2O)](H 2O) (TETAUSe) is monoclinic, P2 1/ n, a=13.002(2), b=7.962(1), c=14.754(2) Å, β=114.077(2)°, V=1394.5(3) Å 3, Z=4, R 1=0.0323. The structure of (C 6H 21N 4)[(UO 2)(SeO 4) 2(HSeO 4)] (TAEAUSe) is monoclinic, P2 1/ m, a=9.2218(6), b=12.2768(9), c=9.4464(7) Å, β=116.1650(10)°, V=959.88(12) Å 3, Z=2, R 1=0.0322. The inorganic structural units in these compounds are composed of uranyl pentagonal bipyramids and selenate tetrahedra. In each case, tetrahedra link bipyramids through vertex-sharing, resulting in chain or sheet topologies. The charge-density matching principle is discussed relative to the orientations of the organic molecules between the inorganic structural units.

Fabrication of porous/hollow tin (IV) oxide skeletons from polypeptide mediated self-assembly

We demonstrate the aqueous self-assembly of ligand-assisted SnO2 sol precursors onto preformed poly-l-lysine templates through interfacial electrostatic forces (COO−/NH3+). On the removal of organics, two unique coral-like and sea worm-like textures consisting of hierarchical pores (macropores and mesopores) and nanocrystalline SnO2 frameworks are synthesized, mainly depending on the chelator/Sn molar ratio. Structural formation is discussed based on acid-base interaction and interfacial charge density matching. For the first time, metal oxide structures mediated by polypeptides are reported. More importantly, the method described here might open a generally attractive route for synthesizing complex nanostructures of other oxides (e.g., ZnO, TiO2, and ZrO2).