Porous Carbon Architecture Assembled by Cross-Linked Carbon Leaves with Implanted Atomic Cobalt for High-Performance Li-S Batteries.

The practical application of lithium-sulfur batteries is severely hampered by the poor conductivity, polysulfide shuttle effect and sluggish reaction kinetics of sulfur cathodes. Herein, a hierarchically porous three-dimension (3D) carbon architecture assembled by cross-linked carbon leaves with implanted atomic Co-N4 has been delicately developed as an advanced sulfur host through a SiO2-mediated zeolitic imidazolate framework-L (ZIF-L) strategy. The unique 3D architectures not only provide a highly conductive network for fast electron transfer and buffer the volume change upon lithiation-delithiation process but also endow rich interface with full exposure of Co-N4 active sites to boost the lithium polysulfides adsorption and conversion. Owing to the accelerated kinetics and suppressed shuttle effect, the as-prepared sulfur cathode exhibits a superior electrochemical performance with a high reversible specific capacity of 695 mAh g-1 at 5 C and a low capacity fading rate of 0.053% per cycle over 500 cycles at 1 C. This work may provide a promising solution for the design of an advanced sulfur-based cathode toward high-performance Li-S batteries.

A chemiluminescence aptasensor for thrombin detection based on aptamer-conjugated and hemin/G-quadruplex DNAzyme signal-amplified carbon fiber composite.

In this work, a highly sensitive and selective chemiluminescence (CL) aptasensor was prepared for thrombin (THR) detection based on aptamer-conjugated and hemin/G-quadruplex DNAzyme signal-amplified carbon fiber composite (HG-DNAzyme/T-Apt/SiO2@GO@CF). Initially, SiO2@GO@CF was successfully prepared and characterized by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). Thrombin aptamer (T-Apt) as an identification element and simulated enzyme - hemin/G-quadruplex DNAzyme (HG-DNAzyme) as a signal-amplified material, were applied in the CL aptasensor. Then, the immobilization properties of SiO2@GO@CF and adsorption properties of T-Apt/SiO2@GO@CF were studied. Lastly, HG-DNAzyme/T-Apt/SiO2@GO@CF was applied in construction of the CL aptasensor. When THR existed, HG-DNAzyme was desorbed from the surface of T-Apt/SiO2@GO@CF and catalyzed the CL system of luminol-H2O2. Under optimized CL conditions, THR was measured with the linear concentration range of 1.5 × 10-14 to 2.5 × 10-11 moL/L and the detection limit of 6.3 × 10-15 moL/L (3δ). The proposed CL aptasensor was used to the determination of THR in human serum samples and recoveries ranged from 99.0% to 102.4%. Those satisfactory results illustrated the CL aptasensor could achieve highly sensitive and selective detection of THR and revealed potential application in practical samples.

Highly selective and sensitive chemiluminescence biosensor for adenosine detection based on carbon quantum dots catalyzing luminescence released from aptamers functionalized graphene@magnetic ß-cyclodextrin polymers.

In this work, a highly selective and sensitive chemiluminescence (CL) biosensor was prepared for adenosine (AD) detection based on carbon quantum dots (CQDs) catalyzing the CL system of luminol-H2O2 under alkaline environment and CQDs was released from the surface of AD aptamers functionalized graphene @ magnetic ß-cyclodextrin polymers (GO@Fe3O4@ß-CD@A-Apt). Firstly, GO@Fe3O4@ß-CD and CQDs were prepared and characterized by transmission electron microscopy (TEM), scanning electron microscope (SEM), UV-Vis absorption spectra (UV), fluorescence spectra (FL), fourier transform infrared (FTIR) and X-ray powder diffraction (XRD). For GO@Fe3O4@ß-CD, Fe3O4 was easy to separate, GO had good biocompatibility and large specific surface area, and ß-CD further increased the specific surface area of the adenosine polymers (A-Apt) to provided larger binding sites to A-Apt. Then, A-Apt was modified on the surface of GO@Fe3O4@ß-CD while CQDs was modified by ssDNA (a single stranded DNA partially complementary to A-Apt). The immobilization property (GO@Fe3O4@ß-CD to A-Apt) and the adsorption property (GO@Fe3O4@ß-CD@A-Apt to CQDs-ssDNA) were sequentially researched. The base-supported chain-like polymers - GO@Fe3O4@ß-CD@A-Apt/CQDs-ssDNA was successfully obtained. When AD existed, CQDs-ssDNA was released from the surface of GO@Fe3O4@ß-CD@A-Apt and catalyzed CL. After that, under optimized CL conditions, AD could be measured with the linear concentration range of 5.0 × 10-13-5.0 × 10-9 mol/L and the detection limit of 2.1 × 10-13 mol/L (3δ) while the relative standard deviation (RSD) was 1.4%. Finally, the GO@Fe3O4@ß-CD@A-Apt/CQDs-ssDNA-CL biosensor was used for the determination of AD in urine samples and recoveries ranged from 98.6% to 101.0%. Those satisfactory results illustrated the proposed CL biosensor could achieve highly selective, sensitive and reliable detection of AD and revealed potential application for AD detection in monitoring and diagnosis of human cancers.

Morphology-dependent electrochemical behavior of 18-facet Cu7S4 nanocrystals based electrochemical sensing platform for hydrogen peroxide and prostate specific antigen.

18-facet polyhedron Cu7S4 nanocrystal and CuS sphere were prepared from Cu2O precursor, and CuS flower was synthesized through a simple solvothermal approach. Their electrochemical performances were investigated towards H2O2 and it was interesting to discover that Cu7S4 nanocrystal had the best electrochemical catalysis compared with CuS sphere and CuS flower. It can deduce that the special structure of Cu7S4 nanocrystal endowed it more exposed active points, higher surface area and higher Cu/S ratio. Therefore, Cu7S4 nanocrystal was firstly employed to prepare a nonenzymatic biosensor for H2O2. Satisfactory results were obtained. In addition, a label-free sensing platform for prostate specific antigen (PSA) was constructed based on electrochemical catalysis towards H2O2 of Cu7S4 nanocrystal. The label-free immunosenosr offered accurate PSA in the range of 0.001-15 ng/mL with the detection limit of 0.001 ng/mL. Besides, the immunosensor possessed good sensitivity, selectivity and stability and could detect PSA in real sample. More importantly, this work demonstrated that Cu7S4 nanocrystal hold great promising application in electrochemical sensors.

A turn-on chemiluminescence biosensor for selective and sensitive detection of adenosine based on HKUST-1 and QDs-luminol-aptamer conjugates.

In this work, HKUST-1 and QDs-luminol-aptamer conjugates were prepared. The QDs-luminol-aptamer conjugates can be adsorbed by graphene oxide through π-π conjugation. When the adenosine was added, the QDs-luminol-aptamer conjugates were released from magnetic graphene oxide (MGO), the chemiluminescent switch was turned on. It was reported that HKUST-1 can catalyze the chemiluminescence reaction of luminol-H2O2 system in an alkaline medium, and improve the chemiluminescence resonance energy transfer (CRET) between chemiluminescence and QDs indirectly. Thus, the adenosine can be detected sensitively. Based on this phenomenon, the excellent platform for detection of adenosine was established. Under the optimized conditions, the linear detection range for adenosine was 1.0 × 10-12-2.2 × 10-10 mol/L with a detection limit of 2.1 × 10-13 mol/L. The proposed method was successfully used for adenosine detection in biological samples.

Highly selective adsorption of hydroquinone by hydroxyethyl cellulose functionalized with magnetic/ionic liquid.

Magnetic hydroxyethyl cellulose/ionic liquid (MHEC/IL) materials were fabricated through a facile and fast process and their application as excellent adsorbents for hydroquinone was also demonstrated. The thermal stability, chemical structure and magnetic property of the MHEC/IL were characterized by the Scanning electron microscope (SEM), Transmission Electron Microscope (TEM), Fourier transform infrared spectrometer (FT-IR) and X-ray diffraction (XRD), respectively. The adsorbents were used for the removal of hydroquinone from simulated wastewater with a fast solid-liquid separation in the presence of external magnetic field. The influence of various analytical parameters on the adsorption of hydroquinone such as pH, contact time and initial ion concentration were studied in detail. The results showed that the maximum adsorption capacity was 335.68mgg-1, observed at pH 5 and temperature 30°C. Equilibrium adsorption was achieved within 30min. The kinetic data, obtained at the optimum pH 5, could be fitted with a pseudo-second order equation. Adsorption process could be well described by Freundlich adsorption isotherms. The obtained results indicated that the impregnation of the room temperature IL significantly enhances the removal efficiency of hydroquinone. The MHEC/IL may be suitable materials in phenols pollution cleanup if they are synthesized in largescale and at low price in near future.

A chemiluminescence biosensor for the detection of thrombin based on the aptamer composites.

An efficient, rapid, simple and ultrasensitive chemiluminescence (CL) approach was proposed for thrombin detection based on the aptamer-thrombin recognition. The aptamer composites were synthesized in this work using graphene oxide (GO) as the backing material. The thrombin was adsorbed on the aptamer composites based on the aptamer-thrombin recognition. Thus, thrombin could be quantified by the difference value of the CL intensity between supernate of the sample and the mixture which composed of thrombin and coexisted substances. The CL intensity exhibits a stable response to thrombin over a concentration range from 2.5×10-10 to 1×10-9mol·L-1 with a detection limit as low as 8.3×10-11mol·L-1, the relative standard deviation (RSD) was found to be 4.9% for 11 determinations of 1.25×10-9mol·L-1 thrombin. Finally, the applicability of the method was verified by applying to serum samples. The recoveries were in the range of 90.3-101.0% with RSD of 2.6-3.2%.

An ultrasensitive chemiluminescence aptasensor for thrombin detection based on iron porphyrin catalyzing luminescence desorbed from chitosan modified magnetic oxide graphene composite.

In this work, an ultrasensitive chemiluminescence (CL) aptasensor was prepared for thrombin detection based on iron porphyrin catalyzing luminol - hydrogen peroxide luminescence under alkaline conditions, and iron porphyrin was desorbed from chitosan modified magnetic oxide graphene composite (CS@Fe3O4@GO). Firstly, CS@Fe3O4@GO was prepared. CS@Fe3O4@GO has advantages of the good biocompatibility and positively charged on its surface of CS, the large specific surface area of GO and the easy separation characteristics of Fe3O4. GO, Fe3O4 and CS@Fe3O4@GO were confirmed by transmission electron microscopy (TEM), scanning electron microscope (SEM), fourier transform infrared (FTIR) and X-ray powder diffraction (XRD). Then, thrombin aptamer (T-Apt) and hemin (HM, an iron porphyrin) were sequentially modified on the surface of CS@Fe3O4@GO to form CS@Fe3O4@GO@T-Apt@HM. The immobilization properties of CS@Fe3O4@GO to T-Apt and adsorption properties of CS@Fe3O4@GO@T-Apt to HM were sequentially researched through the curves of kinetics and the curves of thermodynamics. When thrombin existed in solutions, HM was desorbed from the surface of CS@Fe3O4@GO@T-Apt@HM owing to the strong specific recognition ability between thrombin and T-Apt, causing the changes of CL signal. Under optimized CL conditions, thrombin could be measured with the linear concentration range of 5.0×10-15-2.5×10-10mol/L. The detection limit was 1.5×10-15mol/L (3δ) while the relative standard deviation (RSD) was 3.2%. Finally, the CS@Fe3O4@GO@T-Apt@HM-CL aptasensor was used for the determination of thrombin in practical serum samples and recoveries ranged from 95% to 103%. Those satisfactory results revealed potential application of the CS@Fe3O4@GO@T-Apt@HM-CL aptasensor for thrombin detection in monitoring and diagnosis of human blood diseases.

Adsorbent for resorcinol removal based on cellulose functionalized with magnetic poly(dopamine).

A simple chemical bonding method to synthesize magnetic cellulose-poly(dopamine) (Fe3O4@CMC@PDA) was reported. The adsorption behaviors of resorcinol in aqueous solution on Fe3O4@CMC@PDA were systematically investigated. As the results shown that, with the advantage of high surface area, abundant hydroxyl and amino groups of Fe3O4@CMC@PDA, and the magnetic property of Fe3O4, the resorcinol can be easily and rapidly extracted from the water by magnetic attraction under investigation. The adsorption equilibrium of Fe3O4@CMC@PDA for resorcinol corresponded with Freundlich isotherm, and the novel adsorbent exhibited better resorcinol removal efficiency in solutions with low pH. It was found that the resorcinol adsorption performance of Fe3O4@CMC@PDA strongly depends on their surface charge concentration and specific surface area. These results provide evidences for estimating and optimizing the removal of phenols from the wastewater by using of Fe3O4@CMC@PDA composites in the future.

A chemiluminescence biosensor based on the adsorption recognition function between Fe3O4@SiO2@GO polymers and DNA for ultrasensitive detection of DNA.

In this work, a chemiluminescence (CL) biosensor was prepared for ultrasensitive determination of deoxyribonucleic acid (DNA) based on the adsorption recognition function between core-shell Fe3O4@SiO2 - graphene oxide (Fe3O4@SiO2@GO) polymers and DNA. The Fe3O4@SiO2@GO polymers were composed by GO and magnetite nanoparticles. And the core-shell polymers were confirmed by Scanning Electron Microscope (SEM), X-Ray Powder Diffraction (XRD) and Fourier Transform Infrared (FTIR). Then Fe3O4@SiO2@GO was modified by DNA. Based on the principle of complementary base, Fe3O4@SiO2@GO-DNA was introduced to the CL system and the selectivity, sensitivity of DNA detection was significantly improved. The adsorption properties of Fe3O4@SiO2@GO to DNA were researched through the adsorption equilibrium, adsorption kinetic and thermodynamics. Under optimized CL conditions, DNA could be assayed with the linear concentration range of 5.0×10-12-2.5×10-11mol/L. The detection limit was 1.7×10-12mol/L (3δ) and the relative standard deviation (RSD) was 3.1%. The biosensor was finally used for the determination of DNA in laboratory samples and recoveries ranged from 99% to 103%. The satisfactory results revealed the potential application of Fe3O4@SiO2@GO-DNA-CL biosensor in the diagnosis and the treatment of human genetic diseases.

Ultra-sensitive film sensor based on Al2O3-Au nanoparticles supported on PDDA-functionalized graphene for the determination of acetaminophen.

An electrochemical sensor of acetaminophen based on poly(diallyldimethylammonium chloride) (PDDA)-functionalized reduced graphene-loaded Al2O3-Au nanoparticles coated onto glassy carbon electrode (Al2O3-Au/PDDA/reduced graphene oxide (rGO)/glass carbon electrode (GCE)) were prepared by layer self-assembly technique. The as-prepared electrode-modified materials were characterized by scanning electron microscopy, X-ray powder diffraction, and Fourier transform infrared spectroscopy. The electrocatalytic performances of Al2O3-Au/PDDA/rGO-modified glassy carbon electrode toward the acetaminophen were investigated by cyclic voltammetry and differential pulse voltammetry. The modified electrodes of graphene oxide (GO)/GCE, PDDA/rGO/GCE, and Al2O3-Au/PDDA/rGO/GCE were constructed for comparison and learning the catalytic mechanism. The research showed Al2O3-Au/PDDA/rGO/GCE having good electrochemical performance, attributing to the synergetic effect that comes from the special nanocomposite structure and physicochemical properties of Al2O3-Au nanoparticles and graphene. A low detection limit of 6 nM (S/N = 3) and a wide linear detection range from 0.02 to 200 µM (R (2) = 0.9970) was obtained. The preparation of sensor was successfully applied for the detection of acetaminophen in commercial pharmaceutical pills. Graphical abstract Schematic diagram of synthesis of Al2O3-Au/PDDA/rGO/GCE.