Chitosan-iron nanowires in porous anodic alumina (PAA) have been successfully prepared under ambient conditions as an adsorbent. The adsorbent was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy and N2-BET surface area. The results showed that PAA can disperse and protect Fe0 nanorods from oxidation. The adsorption characteristics of trace Cr(VI) onto adsorbent have been examined at different initial Cr(VI) concentrations with pH 5. Batch adsorption studies show that the removal percentage of adsorbent for the removal of trace Cr(VI) is strongly dependent on the initial Cr(VI) concentrations. Langmuir and Freundlich isotherm models were used to analyze the experiment data. The adsorption of trace Cr(VI) by adsorbent is well modeled by the Langmuir isotherm and the maximum adsorption capacity of Cr(VI) is calculated as 123.95 mg/g which is very closed to the experiment results. Intraparticle diffusion study shows that the intraparticle diffusion of adsorbent is not the sole rate-controlling step. The negative value of Gibbs free energy change, ΔGo, indicated that the process of Cr(VI) onto adsorbent was spontaneous. This work has demonstrated that chitosan-iron nanowires in porous anodic alumina as an adsorbent has promising potential for heavy metal removal at trace level.
Dopamine (DA) plays an important role in health and peripheral nervous systems. Colorimetric detection of DA has the advantage of color change and simplicity in operation and instrumentation. Herein, we report a highly sensitive and selective colorimetric detection of DA by using two specific ligands modified Ag nanoparticles, where the DA molecules can make dual recognition with high specificity. The colloidal suspension of modified Ag nanoparticles was agglomerated after interacting with DA, while the color of Ag nanoparticles suspension changed from yellow to brown, arising from the interparticle plasmon coupling during the aggregation of Ag nanoparticles. The modified Ag nanoparticles suspension and agglomeration were confirmed by transmission electron microscope images. The optical properties behind the color change were thoroughly investigated by using UV-Vis and Raman techniques. The changes in pH, zeta potential, particle size and surface charge density by adding DA were also determined by using dynamic light scattering measurements. The detection limits of modified Ag probes for DA was calculated to be 6.13×10-6 mol L-1 (S/N=2.04) and the correlation co-efficient was determined to be 0.9878. Because of the simplicity in operation and instrumentation of the colorimetric method, this work may afford a feasible, fast approach for detecting and monitoring the DA levels in physiological and pathological systems.
We report a facile method to synthesize dispersed Fe3O4@C nanoparticles (NPs). Fe3O4 NPs were firstly prepared via the high temperature diol thermal decomposition method. Fe3O4@C NPs were fabricated using glucose as a carbon source by hydrothermal process. The obtained products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and Raman spectra. The results indicate that the original shapes and magnetic property of Fe3O4 NPs can be well preserved. The magnetic particles are well dispersed in the carbon matrix. This strategy would provide an efficient approach for existing applications in Li-ion batteries and drug delivery. Meanwhile, it offers the raw materials to assemble future functional nanometer and micrometer superstructures.
Desorption energies of dichloromethane (CH2Cl2) and water (H2O) in a metal-organic framework, MIL-53(Al), were investigated by the combination of experimental (differential scanning calorimeter, DSC) and computational (ab-initio calculations) methods. The differences of desorption energy and natural log of the frequency factor of CH2Cl2 and H2O in MIL-53(Al) were analyzed by a thermo active process using DSC measurements. The interaction energy of guest molecules with MIL-53(Al), which corresponds to the desorption in the thermal active process, was explored using ab-initio calculation. As a result of the difference in the interaction energies of H2O and CH2Cl2 in MIL-53(Al), the site near the μ2-OH groups has two potential wells. Both experimentally and computationally, MIL-53 presents the preferential adsorption of CH2Cl2 than H2O.
An improved Hummers method was developed for the simple and efficient production of high-quality graphene oxide (GO), and the composite of GO and nickel foam (NF) (GO/NF) was fabricated by ultrasonication-vacuum-assisted deposition of an aqueous solution of GO on NF. After chemical or thermal reduction, the composite of reduced GO and nickel foam (rGO/NF) was obtained. The electrochemical capacitance performance of rGO/NF was investigated using cyclic voltammetry and galvanostatic charge/discharge measurements. The chemically reduced rGO/NF composite (C-rGO/NF) exhibited high specific capacitance of 379 F/g at 1.0 A/g and 266.5 F/g at 10 A/g. We also prepared thermally reduced graphene oxide at 473 K in order to illuminate the difference in effect between the chemical and low-temperature thermal reduction methods on electrochemical properties. The cycling performance of thermally reduced rGO/NF composite (T-rGO/NF) and C-rGO/NF had ~91% and ~95% capacitance retention after 2000 cycles in a 6 mol/L KOH electrolyte, respectively. Electrochemical experiments indicated that the obtained rGO/NF has very good capacitive performance and could be used as a potential application of electrochemical capacitors. Our work revealed high electrochemical capacitor performance of rGO/NF composite and provided a facile method of rGO/NF preparation.
The graphene oxides (GOs) have attracted multidisciplinary study because of their special physicochemical properties. The high surface area and large amounts of oxygen-containing functional groups make GOs suitable materials for the efficient elimination of heavy metal ions from aqueous solutions. Herein the sorption of Ni(Ⅱ) on GOs was studied using batch experiments, and the results showed that the sorption of Ni(Ⅱ) is strongly dependent on pH and ionic strength at pH<8, and independent of ionic strength at pH>8. The sorption of Ni(Ⅱ) is mainly dominated by outer-sphere surface complexation and ion exchange at low pH, and by inner-sphere surface complexation at high pH. The interaction of Ni(Ⅱ) with GOs was also investigated by theoretical density functional theory (DFT) calculations, and the results show that the sorption of Ni(Ⅱ) on GOs is mainly attributed to the -COH and -COC groups and the DFT calculations show that Ni(Ⅱ) forms stable GO_Ni_triplet structure with the binding energy of -39.44 kcal/mol, which is in good agreement with the batch sorption experimental results. The results are important for the application of GOs as adsorbents in the efficient removal of Ni(Ⅱ) from wastewater in environmental pollution cleanup.
The reliable information about interface energetics of organic materials, especially the energy level alignment at organic heterostructures is of pronounced importance for unraveling the photon harvesting and charge separation process in organic photovoltaic (OPV) cells. This article provides an overview of interface energetics at typical planar and mixed donor-acceptor heterostructures, perovskite/organic hybrid interfaces, and their contact interfaces with charge collection layers. The substrate effect on energy level offsets at organic heterostructures and the processes that control and limit the OPV operation are presented. Recent efforts on interface engineering with electrical doping are also discussed.
A series of isomorphic lanthanide coordination polymers [Ln(Ⅲ)(MBP)2(NO3)2(Br)·2C3H6O] [Ln=Eu, Tb, Er, Yb, and Gd; MBP=N,N'-methylene-bis(pyridin-4-one)] featuring polycatenated sql cationic network and incorporated bromide counter ion were prepared. Their visible and near-infrared (NIR) luminescence properties were characterized by steady-state excitation and emission spectra, as well as luminescence lifetimes and quantum yields. The D2d dodecahedron coordination geometry causes visible light excitations and strongly monochromatic emissions. The external heavy-atom environment induces remarkable enhancement on the NIR emissions. The sensitization processes are revealed by analyzing the electronic properties of MBP ligand.
Relativistic quantum chemistry investigations are carried out to tackle the puzzling oxidation state problem in a series of MO3- trioxide anions of all d-and f-block elements with five valence electrons. We have shown here that while the oxidation states of V, Nb, Ta, Db, Pa are, as usual, all +V with divalent oxygen O(-Ⅱ) in MO3- anions, the lanthanide elements Pr and Gd cannot adopt such high +V oxidation state in similar trioxide anions. Instead, lanthanide element Gd retains its usual +Ⅲ oxidation state, while Pr retains a +IV oxidation state, thus forcing oxygen into a non-innocent ligand with an uncommon monovalent radical (O·) of oxidation state -Ⅰ. A unique Pr·-·(O)3 biradical with highly delocalized unpairing electron density on Pr(IV) and three O atoms is found to be responsible for stabilizing the monovalent-oxygen species in PrO3- ion, while GdO3- ion is in fact an OGd+(O22-) complex with Gd(Ⅲ). These results show that a naïve assignment of oxidation state of a chemical element without electronic structure analysis can lead to erroneous conclusions.
A facile one-pot synthetic strategy is developed to prepare high-quality Pt supercubes. The as-synthesized Pt supercubes are composed of the uniform Pt nanocubes arranged in a primitive cubic structure. The shape and size of the Pt superparticles are readily tuned by varying the structures of pyridyl-containing ligands used in the synthesis. The co-presence of CO and nitrogen-containing ligands is critical to the formation of Pt supercubes. While CO molecules play an important role in the synthesis of Pt nanocube, introducing nitrogen-containing ligands is essential to the successful assembly of those nanocubes into Pt supercubes. Our systematic studies reveal that the electrostatic attraction between positively charged ligands and negatively charged Pt nanocubes is the main driving force for the assembly of Pt nanocubes into supercubes. More importantly, the ligands within the Pt supercubes are readily removed at relatively low temperature to yield surface-clean supercubes which are expected to exhibit unique size-selective catalysis.
In this paper, we report a technique for the surface modification of poly-(p-phenylene terephthamide) (PPTA) powder coated with polydopamine (PDOPA). We used air oxidation to self-polymerize dopamine (DOPA) to ensure that the PPTA powder was coated. Our results indicate that the modified surface of PPTA powder enhances compatibility with the polymer matrix without damaging its structure. Additionally, it is possible to control the coating thickness of PDOPA by regulating the reaction time. The modified PPTA powder improved the comprehensive property of ethylene-propylene-diene-terpolymer grafted maleic anhydride (EPDM-g-MAH), and it proved that this method can enhance the strength and electric insulativity of EPDM-g-MAH.
Polymer solar cells (PSCs) were fabricated by combining a diketopyrrolopyrrole-based terpolymer (PTBT-HTID-DPP) as the electron donor, and [6,6]-phenyl C61 butyric acid methyl ester (PC61BM) as the electron acceptor, and the power conversion efficiency (PCE) of 4.31% has been achieved under AM 1.5 G (100 mW cm-2) illumination condition via optimizing the polymer/PC61BM ratio, the variety of solvent and the spin-coating speed. The impact of the spin-coating speed on the photovoltaic performance of the PSCs has been investigated by revealing the effects of the spin-coating speed on the morphology and the absorption spectra of the polymer/PC61BM blend films. When the thickness of the blend films are adjusted by spin-coating a fixed concentration with different spin-coating speeds, the blend film prepared at a lower spin-coating speed shows a stronger absorption per unit thickness, and the correspond device shows higher IPCE value in the longer-wavelength region. Under the conditions of similar thickness, the blend film prepared at a lower spin-coating speed forms a more uniform microphase separation and smaller domain size which leads to a higher absorption intensity per unit thickness of the blend film in long wavenumber band, a larger short-circuit current density (Jsc) and a higher power conversion efficiency (PCE) of the PSC device. Noteworthily, it was found that spin-coating speed is not only a way to control the thickness of active layer but also an influencing factor on morphology and photovoltaic performance for the diketopyrrolopyrrole-based terpolymer.
Glycidyl azide polymer (GAP) with the advantages of non-volatility and excellent thermal stability is a candidate as a replacement for nitroglycerine (NG) in a double base propellant. The GAP-NC double base propellants were formulated with GAP and nitrocellulose (NC) fibers. Tensile test and SEM characterization indicated that GAP-NC propellants had a homogeneous structure. Thermogravimetric analysis of GAP-NC propellants revealed that the onset decomposition temperature reached a high level ranging from 192.9 to 194.6℃, which indicated that the substitution of NG with GAP contributed to the safe storage and process operations for double base propellant. The result analysis of decomposition products of GAP-NC propellants showed that the main gas decomposition products of the propellants were NO, NO2, CO, CO2, NH3, CH4, HCN, N2, CH2O and C2H4O. The thermal decomposition process of the specimens was proposed.
Different from the conventional synthesis methods and substrates, we designed a brand new method for synthesizing amides with platinum nanowires as catalysts and tert-butylhydroperoxide (TBHP) as the oxidant. Influence of factors, such as the catalyst, solvents, and the reaction temperature, were studied to determine the optimal reaction conditions. In addition, we explored the substrate generality and observed excellent yields.
Palladium nanoparticles immobilized on a cross-linked imidazolium-containing polymer were evaluated as a catalyst for Suzuki carbon-carbon cross-coupling reactions using water as the solvent. The nanocatalysts show good catalytic activities for aryl iodides and aryl bromides and moderate activity with aryl chloride substrates. Coupling of sterically hindered substrates could also be achieved in reasonable yields. The heterogeneous catalyst is stable, can be stored without precautions to exclude air or moisture, and can be easily recycled and reused.
The fluorescent carbon dots were successfully synthesized by simply heating the mixture of lactose and NaOH solution. The as-synthesized carbon dots had been systematically characterized by fluorescence, Fourier transform infrared (FTIR), high resolution transmission electron microscopy (HR-TEM) and 13C NMR. Since the fluorescence of the carbon dots was efficiently quenched by folic acid, the carbon dots were employed as selective fluorescence probes for detecting folic acid, depending on the formation of hydrogen bond among the functional group of folic acid (-OH, -COOH and -NH2) and -OH and -COOH of the carbon dots. Moreover, the decrease of fluorescence intensity was capable of detecting folic acid in a linear range of 6×10-5-8×10-8 mol/L with a detection limit of 1.2×10-9 mol/L at a signal-to-noise ratio of 3, suggesting a promising assay for folic acid. Significantly, the practicability of this fluorescence probe to assay folic acid in human urine samples was further evaluated.
Herein, a multiwalled carbon nanotubes (MWNT)-based colorimetric probe was designed to discover and monitor the level of apolipoprotein-L1 (ApoL1) in lumbar disc herniation (LDH) patients. ApoL1 could be easily found in human serum of the LDH group, but not obviously expressed in the normal control group (Ctrl), spine spondylolisthesis (SSP) group, spinal fracture (SFR) group, and spine scoliosis (SSC) group. Furthermore, the as-prepared MWNT-based probe was also used to track the recovery of LDH patients who have successful surgery operation. The P value of early diagnosis and recovery monitoring was <0.001 and >0.05 for the proposed method and a conventional enzyme-linked immunosorbent assay (ELISA), respectively, suggesting this detection strategy had significant differences compared with the traditional ELISA. All experimental results showed that ApoL1 might be a potential biomarker for early diagnosis of LDH. This proposed detection strategy has a potential application in discovering new biomarkers of diseases.
This work presented the results of tungstic precipitation from Na2WO4-Na2SO4-H2O system at 293.15 K, with which the Pitzer parameters of βNa2WO4(0) and βNa2WO4(1) were determined from Pitzer equation by regression. Thus the mean ionic activity coefficients of sodium tungstate were calculated. The obtained βNa2WO4(0) and βNa2WO4(1) were substituted as fixed values in extraction modeling from Na2WO4-H2SO4-H2O system by primary amine (N1923) in toluene as diluent. Meanwhile the activity coefficient expressions in organic phase were varied based on Pitzer theory that the interaction term for the solvent should not be included. The Pitzer parameters for organic phase were re-regressed in order to make the model more accurate. The average absolute relative deviation (AARD) for calculated and experimental molality of WO42- in aqueous phase was 5.24%. The results showed that the model can not only correlate but also predict the liquid-liquid equilibrium (LLE) data.