A one-dimensional organic-inorganic hybrid based on the bimolecular {[Cu(en)2]2[Cu2Si2W22O78]} polyoxometalate

A one-dimensional coordination polymer [Cu(en)₂]₂[Cu(en)₂(H₂O)]₂{[Cu(en)₂]₂[Cu₂Si₂W₂₂O₇₈]}·4.5H₂O (en=ethylenediamine), which represents the first example of one-dimensional organic-inorganic hybrid based on the bimolecular Keggin polyoxometalates {[Cu(en)₂]₂[Cu₂Si₂W₂₂O₇₈]}⁸⁻ has been hydrothermally synthesized and characterized by elemental analyses, IR, TG and single crystal X-ray diffraction. Crystal data: C₂₄H₈₅Cu₈N₂₄O_84.5Si₂W₂₂, monoclinic, P2₁/c, a=18.8126(3), b=23.0896(4), c=26.0711(4) Å, β=96.3790(10)°, V=11254.5(3) Å³, T=293(2) K; Z=4, μ=23.983 mm⁻¹, R₁=0.0628, wR₂=0.1210 [I>2σ], R₁=0.0854, wR₂=0.1285 (all data ).     

Visual detection of cancer cells by colorimetric aptasensor based on aggregation of gold nanoparticles induced by DNA hybridization

A simple but highly sensitive colorimetric method was developed to detect cancer cells based on aptamer–cell interaction. Cancer cells were able to capture nucleolin aptamers (AS 1411) through affinity interaction between AS 1411 and nucleolin receptors that are over expressed in cancer cells, The specific binding of AS 1411 to the target cells triggered the removal of aptamers from the solution. Therefore no aptamer remained in the solution to hybridize with complementary ssDNA-AuNP probes as a result the solution color is red. In the absence of target cells or the presence of normal cells, ssDNA-AuNP probes and aptamers were coexisted in solution and the aptamers assembled DNA-AuNPs, produced a purple solution. UV–vis spectrometry demonstrated that this hybridization-based method exhibited selective colorimetric responses to the presence or absence of target cells, which is detectable with naked eye. The linear response for MCF-7 cells in a concentration range from 10 to 10⁵ cells was obtained with a detection limit of 10 cells. The proposed method could be extended to detect other cells and showed potential applications in cancer cell detection and early cancer diagnosis.     

Fabrication of self-assembled ultrathin photochromic films containing mixed-addenda polyoxometalates H5[PMo10V2O40] and 1,10-decanediamine

A layered phosphovanadomolybdate/1,10-decanediamine (1,10-DAD) self-assembled ultrathin film was fabricated by means of alternating adsorption of mixed-addenda polyoxometalates (POMs) (phosphovanadomolybdate, H₅[PMo₁₀V₂O₄₀]) and 1,10-DAD, and its photochromic properties were investigated. It is found that the self-assembled multilayer (SAM) film shows high-photochromic response, excellent photochromic stability and reversibility. The photochromic behavior of the SAM is closely related to the reduction potentials of addenda atoms in mixed-addenda POMs. In the case of photo-reduced mixed-addenda POMs, the electron is localized on the more reducible atom, and the addenda atoms with higher reduction potentials show prior photochromism compared with those with lower reduction potentials. The coloration speed is improved after introduction of V into molybdenum POM. The well-ordered lamellar structure of the film was well maintained during the coloration.     

Preparation and characterization of the nanoporous ultrathin multilayer films based on molybdenum polyoxometalate (Mo38)n

Ultrathin multilayer films of the wheel-shaped molybdenum polyoxometalate cluster (Mo₃₈)_n and poly(allylamine hydrochloride)(PAH) have been prepared by the layer-by-layer (LbL) self-assembly method. The ((Mo₃₈)_n/PAH)_m multilayer films have been characterized by X-ray photoelectron spectra (XPS) and atomic force microscopy (AFM). UV-VIS measurements reveal regular film growth with each (Mo₃₈)_n adsorption. The electrochemistry behavior of the film at room temperature was investigated.     

Raman spectra of hybrid materials based on carbon nanotubes and Cs3PMo12O40

A route for the synthesis of hybrid materials using multiwalled carbon nanotubes (MWCNTS) and Cs₃PMo₁₂O₄₀ was confirmed. The Cs₃PMo₁₂O₄₀ salt was synthesized from H₃PMo₁₂O₄₀·14H₂O and CsCl. All compounds were characterized by Raman spectroscopy. The synthesis method can produce a chemically stable Cs₃PMo₁₂O₄₀ molecule and pure and oxidized MWCNTS. Raman spectroscopy showed that the chemical interaction between MWCNTS and Cs₃PMo₁₂O₄₀ was essentially of electrostatic nature. Raman spectra obtained with different wavelengths showed thermal decomposition of H₃PMo₁₂O₄₀·14H₂O (raw materials) from laser heating process. On the contrary, the synthesized compound (i.e. Cs₃PMo₁₂O₄₀) was stable under the experimental conditions.     

[C6(MIm)2]2W10O32. 2H2O: A novel and powerful catalyst for the synthesis of 4-arylidene-2-phenyl-5(4)-oxazolones under ultrasonic condition

Di[1,6-bis(3-methylimidazolium-1-yl)hexane] decatungstate dihydrate ([C₆(MIm)₂]₂W₁₀O₃₂. 2H₂O) as a new family of polyoxometalate-based dicationic ionic liquids (POM-DIL) is synthesized and employed as a novel and powerful heterogeneous catalyst in the synthesis of 4-arylidene-2-phenyl-5(4)-oxazolones (azlactones) under ultrasound-assisted solvent-free condition. On the basis of the results, the products were obtained in excellent yields under mild condition. Utilization of easy work-up and purification make it very interesting from an economic perspective. Moreover, a recycling study confirmed that the catalyst can be reused multiple times without significant loss of its activity.     

Facile synthesis of enzyme functional metal-organic framework for colorimetric detecting H2O2 and ascorbic acid

In this work,a metal-organic frameworks material MIL-88 was prepared easily using solvent-thermal method,and was first found to have catalytic activities similar to those of biological enzymes such as catalase and peroxidase.The material was characterized by XRD,SEM,TEM,EDX,FT-IR techniques and an N_2 adsorption method.It exhibited peroxidase-like activity through catalytic oxidation of the peroxidase substrate 3,3',5,5'-tetramethylbenzidine(TMB) in the presence of H_2O_2,producing a blue-colored solution.Under optimal conditions,the absorbance at 652 nm is linearly correlated with the concentration of H_2O_2 from 2.0×10~(-6) mol/L to 2.03×10~(-5) mol/L(R~2=0.981) with a detection limit of 5.62×10~(-7) mol/L(S/N=3).More importantly,a sensitive and selective method for ascorbic acid detection was developed using this material as a catalyst.The analytical method for ascorbic acid detection was observed to have a linear range from 2.57×10~(-6) mol/L to 1.01×10~(-5) mol/L(R~2=0.989) with a detection limit of 1.03×10~(-6) mol/L(S/N=3).This work suggests MOFs have advantages of preparing biomimetic catalysts and extends applications of the functional MOFs in the field of biosensor.     

A colorimetric chemosensor based on new water-soluble PODIPY dye for Hg2+ detection

The phosphorus-containing PODIPY 1 as a chemosensor can detect Hg~(2+) by a color change from pink to violet red without the use of any instrumentation. PODIPY 1 was selective to Hg~(2+)with a remarkable absorption change, and addition of other relevant metal ions caused almost no absorption change. The new PODIPY dye 1 was sensitive to various concentrations of Hg~(2+). The energy gap between the HOMO and LUMO of the metal complex 1–Hg~(2+)is smaller than that of chemosensor 1, which is in good agreement with the red shift in the absorption observed upon treatment of 1 with Hg~(2+). The 1-based test strips were easily fabricated and low-cost, useful in practical and efficient Hg~(2+)test kits.     

A novel 1D organic-inorganic hybrid based on alternating heteropolyanions [GeMo12O40] and isopolyanions [Mo6O22]

A novel one-dimensional (1D) coordination polymer [{Cu(2,2′-bpy)}₆(Mo₆O₂₂)][GeMo₁₂O₄₀]·H₂O (2,2′-bpy=2,2′-bipyridine), which represents the first example of 1D organic-inorganic hybrid based on a Keggin-type heteropolyanion [GeMo₁₂O₄₀]⁴⁻ and an unprecedented isopolyanion [Mo₆O₂₂]⁸⁻, has been hydrothermally synthesized and characterized by single crystal X-ray diffraction. Crystal data: C₆₀H₅₀Cu₆GeMo₁₈N₁₂O₆₃, monoclinic, P2₁/c, a=13.9344(3), b=20.0329(3), c=17.2151(3) Å; β=94.0220(10)°, V=4793.70(15) Å³, T=293(2) K; Z=2.     

Synthesis, characterization and study of the chromogenic properties of the hybrid polyoxometalates [PW11O39(SiR)2O] (R = Et, (CH2)nCHCH2 (n = 0, 1, 4), CH2CH2SiEt3, CH2CH2SiMe2Ph)

Reaction of Cl₃SiR or (EtO)₃SiR with [PW₁₁O₃₉]⁷⁻ affords the disubstituted hybrid anions [PW₁₁O₃₉(SiR)₂O]³⁻. These species have been characterized by IR spectroscopy in the solid state and by multinuclear NMR (¹H, ²⁹Si, ³¹P and ¹⁸³W) and cyclic voltammetry in solution. The hydrosilylation of [PW₁₁O₃₉(Si-CHCH₂)₂O]³⁻ has been achieved with Et₃SiH and PhSiMe₂H. These are the first examples of hydrosilylation on a hybrid tungstophosphate core. The chromogenic behaviour of hybrid species has been demonstrated in solution.     

A new colorimetric platform for ultrasensitive detection of protein and cancer cells based on the assembly of nucleic acids and proteins

An amplified colorimetric method has been developed for the detection of protein and cancer cells based on the assembly of nucleic acids and proteins for the first time. In this process, the assembly of nucleic acids was triggered by a biotinylated DNA strand after a sandwich immunoreaction. The biotinylated DNA strand and sandwich immunocomplex were connected by streptavidin. Then, the assembly of biotinylated bovine serum albumin (Biotin-BSA) and streptavidin-horseradish peroxidase (SA-HRP) occurred at a node of the assembled products of nucleic acids through the biotin-streptavidin reaction. Under the catalysis of horseradish peroxidase, 3,3′,5,5′-tetramethylbenzidine (TMB) was oxidized by H₂O₂ and the oxidized product was analyzed by its UV–vis absorbance signal and sensitive colorimetric detection. This colorimetric sensor could not only achieve the quantitative determination of protein by UV–vis absorbance but could also be applied for semiquantitative determination by digital visualization. Using alpha-fetoprotein (AFP) as the model target, this proposed colorimetric method showed a wide linear range from 5 pg/mL to 1 ng/mL with a detection limit of 1.95 pg/mL by the instrument, and even 5 pg/mL target protein could be distinguished simply by the naked eye. This approach was then expanded to detect cancer cells based on the recognition of folic acid receptors that were over-expressed on the cancer cells by folic acid-tethered DNA. More importantly, this strategy can be further used as a universal colorimetric method for the determination of viruses or other proteins by changing the corresponding antibodies.     

Intrinsic peroxidase-like catalytic activity of nitrogen-doped graphene quantum dots and their application in the colorimetric detection of H2O2 and glucose

In this paper, the highly intrinsic peroxidase-like catalytic activity of nitrogen-doped graphene quantum dots (N-GQDs) is revealed. This activity was greatly dependent on pH, temperature and H₂O₂ concentration. The experimental results showed that the stable N-GQDs could be used for the detection of H₂O₂ and glucose over a wide range of pH and temperature, offering a simple, highly selective and sensitive approach for their colorimetric sensing. The linearity between the analyte concentration and absorption ranged from 20 to 1170 μM for H₂O₂ and 25 to 375 μM for glucose with a detection limit of 5.3 μM for H₂O₂ and 16 μM for glucose. This assay was also successfully applied to the detection of glucose concentrations in diluted serum and fruit juice samples.     

A colorimetric assay of DNA methyltransferase activity based on the keypad lock of duplex DNA modified meso-SiO2@Fe3O4

Abnormal level of DNA methyltransferase (MTase) – mediated DNA methylation is closely related with cancer and bacterial diseases. Herein, a novel strategy based on the keypad lock of duplex DNA modified meso-SiO₂@Fe₃O₄ was developed for colorimetric assay of Dam MTase activity. When the Dam MTase was introduced, the duplex DNA can be methylated at a palindrome sequence of 5′-GATC-3′ and cleaved by the methylation-sensitive restriction endonuclease Dpn I. Due to the instability of the newly formed DNA fragment, the hybrid will separated into a single-stranded DNA. Then the keypad lock will open, and the catalytic reaction of TMB and H₂O₂ can be initiated through the pores of meso-SiO₂@Fe₃O₄, and a high color signal can be clearly observed by the naked eye. Contrarily, without Dam MTase, the catalytic reaction will not be initiated, and result no color signal. The proposed method exhibited a wide dynamic range with a low detection limit of 0.73 U/mL. Additionally, this way can be performed in human serum with satisfying recovery. And the inhibition of Dam MTase can also be well demonstrated by using paclitaxel as a model. Therefore, the designed way not only provides a platform for monitoring Dam MTase activity, but also useful for further application in disease diagnosis and drug discovery.     

Polyelectrolyte-based electrochemiluminescence enhancement for Ru(bpy)3 loaded by SiO2 nanoparticle carrier and its high sensitive immunoassay

In this paper the strong electrochemiluminescence (ECL) nanoparticles have been prepared based on the anionic polyelectrolyte sodium polyacrylate (PAA)-ECL enhancement for Ru(bpy)₃²⁺, which were loaded by the carrier of SiO₂ nanoparticle. There were two kinds of Ru(bpy)₃²⁺ for the as-prepared nanoparticles, the doped one and the exchanged one. The former was loaded inside the ECL nanoparticles by doping, in a form of ion-pair macromolecules PAA–Ru(bpy)₃²⁺. The corresponding ECL was enhanced about 2 times owing to the doping increase of Ru(bpy)₃²⁺. The latter was loaded on the PAA-doped Nafion membrane by ion exchange. The corresponding ECL was enhanced about 3 times owing to the ion-exchanging increase of Ru(bpy)₃²⁺. At the same time, ECL intensity of the doped-inside Ru(bpy)₃²⁺ was further enhanced 13 times because polyelectrolyte PAA in the doped membrane could obviously enhance electron transfer between the doped Ru(bpy)₃²⁺ and the working electrode. Furthermore, based on hydrophobic regions of the doped membrane antibody labeling could be easily realized by the as-prepared nanoparticles and then a high sensitive ECL immunoassay for HBsAg was developed. The linear range was between 1.0 and 100 pg mL⁻¹ (R² = 0.9912). The detection limit could be as low as 0.11 pg mL⁻¹ (signal-to-noise ratio = 3).     

A colorimetric and ratiometric fluorescent chemosensor based on furan-pyrene for selective and sensitive sensing Al3+

A new pyrene derivative BF bearing a furan group was synthesized via a one-step reaction as a colorimetric and ratiometric chemosensor for Al³⁺in ethanol-H₂O (9:1,v/v,pH 7.2,HEPES buffer) solution.This chemosensor could selectively recognize Al³⁺ in the presence of other competing ions.Low limit of detection (LOD) and high association constant revealed its superior sensitivity and binding affinity toward Al³⁺.Besides,the probe BF performed perfectly in a reversibility test using EDTA.The mechanism of the interaction has been confirmed by ¹H NMR titration.Importantly,chemosensor BF has also been utilized to detect Al³⁺ on test paper strips,which showed its potential for practical applications.     

TiO2/Au纳米棒阵列的制备及其光催化性能

采用电沉积和旋转涂膜相结合的方法成功制备了高度有序的TiO2/Au纳米棒阵列催化剂.扫描电镜和透射电镜结果表明,TiO2薄膜均匀地包覆在Au纳米棒的表面,形成核壳型的一维阵列结构.X射线衍射分析表明所获得TiO2为(101)晶面优先生长的锐钛矿晶相.紫外-可见漫反射光谱显示,由于Au和TiO2间肖特基结的存在造成吸收红...     

TiO2 nanorods branched on fast-synthesized large clearance TiO2 nanotube arrays for dye-sensitized solar cells

A large clearance TiO₂ nanotube arrays (LTAs) has been synthesized by a not more than 12 h anodization duration and based on this a branched TiO₂ nanotube arrays (BLTs) has been achieved through TiO₂ nanorods branch-like grown on the LTAs. Some key factors and probable mechanisms of the fabrication processes on two novel nanoarchitectures are discussed. Exhilaratingly, it is found that the obtained LTAs has demonstrated large pore diameter and void spaces (pore diameter ∼350 nm; void spaces ∼160 nm; and tube length ∼3.5 μm), and the synthesized hierarchical BLTs, compared with conventional TiO₂ nanotube arrays, has shown a much stronger dye absorption performance and an approximately double of the solar cell efficiency (in our case from 1.62% to 3.18% under simulated AM 1.5 conditions).     

Amperometric biosensor based on reductive H2O2 detection using pentacyanoferrate-bound polymer for creatinine determination

Pentacyanoferrate-bound poly(1-vinylimidazole) (PVI[Fe(CN)₅]) was selected as a mediator for amperometric creatinine determination based on the reductive H₂O₂ detection. Creatinine amidohydrolase (CNH), creatine amidohydrolase (CRH), sarcosine oxidase (SOD), peroxidase (POD), and PVI[Fe(CN)₅] were crosslinked with poly(ethylene glycol) diglycidyl ether (PEGDGE) on a glassy carbon (GC) electrode for a creatinine biosensor fabrication. Reduction current was monitored at −0.1 V in the presence of creatinine and O₂. It is revealed that PVI[Fe(CN)₅] is suitable as a mediator for a bioelectrocatalytic reaction of POD, since PVI[Fe(CN)₅] neither reacts with reactants nor works as an electron acceptor of SOD. The amounts of PVI[Fe(CN)₅], PEGDGE, and enzymes were optimized toward creatinine detection. Nafion as a protecting film successfully prevented the enzyme layer from interferences. The detection limit and linear range in creatinine determination were 12 μM and 12–500 μM (R² = 0.993), respectively, and the sensitivity was 11 mA cm⁻² M⁻¹, which is applicable for urine creatinine tests. The results of the creatinine determination for four urine samples measured with this proposed method were compared with Jaffe method, and a good correlation was obtained between the results.     

Hydrothermal synthesis, crystal structure, and magnetic property of a three-dimensional inorganic-organic hybrid material: Mn(H2O)[HO3PCH2NH(CH2CO2)2]

A novel three-dimensional inorganic-organic hybrid compound, Mn(H₂O)[HO₃PCH₂NH(CH₂CO₂)₂] from a hydrothermal reaction of Mn (II) ion with N-(phosphonomethyl)iminodiacetic acid (H₄PMIDA) was reported. The compound crystallizes in the monoclinic P2₁/n with cell dimensions of a=5.215(5) Å, b=14.111(15) Å, c=12.727(12) Å, β=93.646(16)°, V=934.6(16) Å³ and Z=4. In this structure each Mn atom is six-coordinated with the carboxylic groups and phosphonic groups to form layers along the bc plane. These layers are further connected with the organic moieties of H₂PMIDA, resulting in a complicated three-dimensional network structure. Thermogravimetric analysis, IR spectrum and magnetic susceptibility of this compound are given.     

添加Al2O3对Ni0.5Zn0.5Fe2O4纳米纤维结构和磁性能的影响

采用静电纺丝技术制备了添加0～20wt%Al2O3的Ni0.5Zn0.5Fe2O4纳米纤维。通过XRD、FESEM、TEM和VSM对样品的物相结构、形貌和磁性能进行了表征。结果表明,所合成的复合纳米纤维的直径都分布在40～150 nm之间,添加到纤维中的Al2O3主要以非晶态形式分布于铁氧体晶粒边界;随着Al2O3添加量的增加,可观察到γ-Fe2O3相逐渐析出,Ni-Zn铁氧体的晶格常数单调减小,说明有一些Al2O3进入到尖晶石晶格中取代了B位的Fe3+离子,Ni-Zn铁氧体的平均晶粒尺寸先增大后减小,在Al2O3添加量为8wt%时达到最大值39.2 nm;比饱和磁化强度和矫顽力随Al2O3添加量的增加呈现出相同的变化规律,先减小后增大,当Al2O3添加量超过5wt%时又开始变小。