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The controlled synthesis of titanium-oxo clusters (TOCs) completely stabilized by organic dye ligands with high stability and superior light absorption remains a significant challenge. In this study, we report the syntheses of three atomically precise catechol (Cat)-functionalized TOCs, [Ti2(Cat)2(OEgO)2(OEgOH)2] (Ti2), [Ti8O5(Cat)9(iPrO)4(iPrOH)2] (Ti8), and [Ti16O8(OH)8(Cat)20]·H2O·PhMe (Ti16), using a solvent-induced strategy (HOEgOH = ethylene glycol; iPrOH = isopropanol; PhMe = toluene). Interestingly, the TiO core of Ti16 is almost entirely enveloped by catechol ligands, making it the first all-catechol-protected high-nuclearity TOC. In contrast, Ti2 and Ti8 have four weakly coordinated ethylene glycol ligands and six weakly coordinated iPrOH ligands, respectively, in addition to the catechol ligands. Ti16 is visually evident in its distinctively black appearance, which belongs to black TOCs (B-TOCs) and exhibits an ultralow optical band gap. Furthermore, Ti16 displays exceptional stability in various media/environments, including exposure to air, solvents, and both acidic and alkaline aqueous solutions due to its comprehensive protection by catechol ligands and rich intra-cluster supramolecular interactions. Ti16 has superior photoelectric response qualities and photothermal conversion capabilities compared to Ti2 and Ti8 due to its ultralow optical band gap and remarkable stability. This discovery not only represents a huge step forward in the creation of all-catecholate-protected B-TOCs with ultralow optical band gaps and outstanding stability, but it also gives key valuable mechanistic insights into their photothermal/electric applications.
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The effective control of light plays an important role in optoelectronic devices. However, the effect of anti-reflection thin film (ARTF) in inverted perovskite solar cells (PSCs) (p-i-n) has so far remained elusive. Herein, MgF2 ARTF with different thicknesses (approximately 100, 330, and 560 nm) were deposited on the glass side of FTO conductive glass substrates by vacuum thermal evaporation. The results of reflectance and transmittance spectroscopy show that approximately 330 nm MgF2 ARTF can reduce reflectivity and increase transmittance on FTO conductive glass substrates. The results of SEM, XRD, and AFM show that the surface of amorphous MgF2 ARTF possesses a lot of nanoscale pits. The effect of the MgF2 ARTF on the performance of inverted perovskite solar cells (PSCs) (p-i-n) was investigated. The power conversion efficiencies (PCE) of inverted PSCs without and with MgF2 ARTF are 18.20 and 21.28%, respectively. The significant improvement in PCE of the devices with MgF2 ARTF is caused by the improvement in short-circuit current density. The stability results of the devices show that the PCE remains above 70% of the initial PCE after 300 h illumination.
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Vanadium oxides are excellent cathode materials with large storage capacities for aqueous zinc-ion batteries, but their further development has been hampered by their low electronic conductivity and slow Zn2+ diffusion. Here, an electrochemically induced phase transformation strategy is proposed to mitigate and overcome these barriers. In situ X-ray diffraction analysis confirms the complete transformation of tunnel-like structural V6O13 into layered V5O12·6H2O during the initial electrochemical charging process. Theoretical calculations reveal that the phase transformation is crucial to reducing the Zn2+ migration energy barrier and facilitating fast charge storage kinetics. The calculated band structures indicate that the bandgap of V5O12·6H2O (0.0006 eV) is lower than that of V6O13 (0.5010 eV), which enhanced the excitation of charge carriers to the conduction band, favoring electron transfer in redox reactions. As a result, the transformed V5O12·6H2O delivers a high capacity of 609 mA h g-1 at 0.1 A g-1, superior rate performance (300 mA h g-1 at 20 A g-1), fast-charging capability (<7 min charging for 465 mA h g-1), and excellent cycling stability with a reversible capacity of 346 mA h g-1 at 5 A g-1 after 5000 cycles.
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Vanadium-based compounds are identified as promising cathode materials for aqueous zinc ion batteries due to their high specific capacity. However, the low intrinsic conductivity and sluggish Zn2+ diffusion kinetics seriously impede their further practical application. Here, oxygen vacancies on NH4 V4 O10 is reported as a high-performing cathode material for aqueous zinc ion batteries via a facile hydrothermal strategy. The introduction of oxygen vacancy accelerates the ion and charge transfer kinetics, reduces the diffusion barrier of zinc ions, and establishes a stable crystal structure during zinc ion (de-intercalation). As a result, the oxygen vacancy enriched NH4 V4 O10 exhibits a high specific capacity of ≈499 mA h g-1 at 0.2 A g-1 , an excellent rate capability of 296 mA h g-1 at 10 A g-1 and the specific capacity cycling stability with 95.1% retention at 5 A g-1 for 4000 cycles, superior to the NVO sample (186.4 mAh g-1 at 5 A g-1 , 66% capacity retention).
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Synthesizing SnO2 composite nanostructures via a facile one-step method has been proven to be a great challenge. By adjusting operating variables, such as the reaction solution's pH and solvent type, several SnO2 nanostructures, in particular, a function-matching SnO2 hybrid structure composed of irregular zero-dimensional nanoparticles (NPs) and two-dimensional nanosheets (NSs), could be created. The as-prepared SnO2 composites were then characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscope (SEM), and diffuse reflectance spectroscopy (DRS) to determine their physical properties. Dye-sensitized solar cells (DSCs) constructed with the resultant multifunctional SnO2 NPs/NSs composite exhibited the highest overall power conversion efficiency (PCE) of 5.16% among all products with a corresponding short-circuit current density of 18.6 mA/cm2 and an open-circuit voltage of 0.626 V. The improved performance can be attributed to the combined effects of each component in the composite, i.e., the intentionally introduced nanosheets provide desired electron transport and enhanced light scattering capability, while the nanoparticles retain their large surface area for efficient dye absorption.
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A simple and efficient coagulation method was used for the rapid preparation of nitrogen-doped copper-cobalt oxide (N-Cu0.92Co2·08O4) supported on cerium dioxide (CeO2), that is, N-Cu0.92Co2·08O4@CeO2. A low concentration of N-Cu0.92Co2·08O4@CeO2 (0.15 g L-1) was shown to rapidly activate permonosulfate (PMS) (0.15 g L-1) to achieve 100% degradation of ranitidine within 10 min. A 100% degradation of ranitidine enabled by the catalyst was achieved over a wide range of pH (5.5-9.0), which could be completed within 8 min in the presence of anionic H2PO4-. Moreover, the N-Cu0.92Co2·08O4@CeO2 catalyst enabled more than 90% degradation of various typical antibiotics within 30 min, including tetracycline, sulfaixoxazole, and chloramphenicol, with degradation rates of 100%, 93.51%, and 90.01%, respectively. Even after four catalytic cycles, N-Cu0.92Co2·08O4@CeO2 could be regenerated to achieve 100% degradation of ranitidine. Electrochemical analysis demonstrated that the combination of N-Cu0.92Co2·08O4@CeO2 and PMS immediately produced a strong current density, thereby rapidly producing reactive oxygen species (ROS) with high performance for the degradation of the target pollutant. Combined ion quenching and electron paramagnetic resonance analyses indicated that the main ROS was the non-free radical 1O2. Finally, a plausible ranitidine degradation pathway was deduced based on liquid chromatography-mass spectrometry (LC-MS) analysis, wherein the toxic substance N-nitrosodimethylamine was not produced during the degradation process. In short, this study provides a new perspective for preparing ternary metal catalysts for advanced oxidation processes with practical application significance.
Asunto(s)
Cerio , Nanopartículas , Especies Reactivas de Oxígeno , Ranitidina , Nitrógeno , Nanopartículas/química , Cerio/química , Peróxidos/químicaRESUMEN
This study presents a unique and straightforward room temperature-based wet-chemical technique for the self-seeding preparation of three-dimensional (3D) hierarchically branched rutile TiO2, abbreviated HTs, employing titanate nanotubes as the precursor. In the course of the synthesis, spindle-like rutile TiO2 and the intermediate anatase phase were first obtained through a dissolution/precipitation/recrystallization process, with the former serving as the substrates and the latter as the nucleation precursor to growing the branches, which finally gave birth to the production of 3D HTs nanostructures. When the specifically created hierarchical TiO2 was used as the photoanode in dye-sensitized solar cells (DSCs), a significantly improved power conversion efficiency (PCE) of 8.32% was achieved, outperforming a typical TiO2 (P25) nanoparticle-based reference cell (η = 5.97%) under the same film thickness. The effective combination of robust light scattering, substantial dye loading, and fast electron transport for the HTs nanostructures is responsible for the remarkable performance.
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The structural and electronic transport properties of tetragonal CH3NH3SnBr3 single crystals (T-MASnBr3 SCs) are rarely reported. In this study, we synthesized T-MASnBr3 single crystals by volatilizing DMF solvent at room temperature. The crystal system and space group of the T-MASnBr3 SC are tetragonal and P4/mmm, respectively. In addition, the nitrogen atom in the methylamine group exhibits position disorder. The band gap of the T-MASnBr3 SC was determined to be 2.07 eV using the Tauc plot. Six fluorescence peaks and a lifetime up to 10 microseconds were observed in the steady-state fluorescence spectra and time-resolved fluorescence spectra of the T-MASnBr3 SC, respectively. The carrier mobility (electron) of T-MASnBr3 was 321 cm2 V-1 s-1. The curve of ln(square resistance) against T-1 was a straight line. The value of the activation energy (Ea) was 5421 J mol-1. The stability of the T-MASnBr3 SC was good before 473 K. The results indicate that T-MASnBr3 SCs have promising applications in the field of temperature sensors.
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The structure, mobility and memristor properties of tetragonal CH3NH3PbBr3 single crystals (T-MAPbBr3 SC) are rarely reported. In this study, we synthesized T-MAPbBr3 SC with the P4/mmm (123) space group by the growing, dropping and growing (GDG) crystal seed method. A CH3NH3+ cation is a disordered state in T-MAPbBr3 SC. The mobility values of T-MAPbBr3 SC under light and dark conditions are 464.28 and -1685.3 cm2 V-1 s-1, respectively. The carrier types under light and dark conditions are holes and electrons, respectively. The memristor based on T-MAPbBr3 SC has a wide and low operating voltage window (0-0.9 V). The high and low resistances of the memristor based on T-MAPbBr3 SC achieve values of 41 and 0.35 GΩ, respectively. The values of high and low resistances are relatively stable for 100 cycles. Thus, the memristor device based on T-MAPbBr3 SC has good applications in the field of memristors.
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In this work, a thrombin photoelectrochemical aptasensor was reported based on a photoanode of perylene-3,4,9,10-tetracarboxylic acid (PTCA), Au nanoparticle co-functionalized ZnO nanorods (ZnO NRs) and the "signal-off" amplification effect of Ag@Ag2S. The photocurrent response of the ZnO NRs was improved greatly due to the excellent visible-light photoelectric performance of PTCA and the surface plasmon resonance (SPR) effect of Au nanoparticles. Due to the specific recognition between thrombin and aptamers, the non-conductive complex with a steric hindrance structure blocked the diffusion path of the electron donating ascorbic acid (AA) and then the "signal-off" Ag@Ag2S quencher was captured. The quencher blocked the irradiation light toward the ZnO NRs/PTCA/Au electrode and competitively consumed the electron donor AA that could have been involved in the oxidation reaction with photogenerated holes of PTCA, resulting in the further decrease of the photocurrent. Based on the evident photocurrent response of the photoanode and the superior quenching strategies, the detection limit of thrombin is as low as 33 fM with a wide linear detection range from 0.0001 nM to 50 nM. The prepared biosensor also exhibited good specificity, reproducibility and stability, suggesting potential application in thrombin specific detection.
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Técnicas Biosensibles , Nanopartículas del Metal , Perileno , Óxido de Zinc , Técnicas Electroquímicas , Oro , Límite de Detección , Reproducibilidad de los Resultados , Plata , TrombinaRESUMEN
Exploring excellent peroxidase mimics with enhanced peroxidase-like activity is important to the construction of a fast, low-cost, and convenient colorimetric sensing platform for heavy ions. In this work, 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (H2TCPP) was first used to modify ZnS/CoS and make it show better peroxidase-like activity. The metal-cation vacancies generated by Hg2+ contacting H2TCPP/ZnS/CoS further stimulate the catalytic activity. It is reported that the addition of Hg2+ usually causes a decrease of the peroxidase-like activity of metal sulfides. Oppositely, in our work, Hg2+ can trigger the colorimetric signal amplification because of lots of metal-cation vacancies generated on the surface of the nanocomposites (bimetallic sulfides). The peroxidase-like activity of ZnS/CoS was evaluated by virtue of the chromogenic substrate 3,3,5,5-tetramethylbenzidine (TMB) from colorless to blue in 3 min. The enhanced catalytic activity of H2TCPP/ZnS/CoS was attributed to lots of active sites from the metal-cation defects on the surface of H2TCPP/ZnS/CoS as well as the synergistic effect of porphyrin molecules and ZnS/CoS. The adsorption behavior of H2O2 on the H2TCPP/ZnS/CoS surface with defects was studied by density functional theory calculation. Thus, a colorimetric sensing platform based on Hg2+ trigger signal amplification has been successfully constructed, which can be used to sensitively and selectively determine Hg2+ in environmental samples.
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Cobalto/química , Mercurio/química , Peroxidasas/metabolismo , Porfirinas/química , Sulfuros/química , Compuestos de Zinc/química , Técnicas Biosensibles , Contaminantes Ambientales , Límite de Detección , Sustancias Macromoleculares , Imitación Molecular , Oxidación-Reducción , Peroxidasas/químicaRESUMEN
Pt deposited on CdS nanorods (Pt/CdS) have been prepared via the UV light photoreduction method. The Pt/CdS nanocomposites possess highly significant peroxidase-like activity with the assistance of the colorless substrate 3,3,5,5-tetramethylbenzidine (TMB). In the presence of peroxidase mimic Pt/CdS, TMB is quickly oxidized into a typical blue product (oxTMB, which has an obvious absorption at 652 nm) by H2O2 only in 3 min, which is easily detected visually. The catalytic activity of Pt/CdS originates from the accelerated electron transfer between the reactants. Combining the peroxidase-like activity of Pt/CdS with the blue change of TMB, a fast colorimetric sensing platform for detection of H2O2 has been constructed with a linear range 0.10-1.00 mM and a detection limit of 45.5 µM. The platform developed is further used to detect hydroquinone (HQ) in the range1.0-10 µM with a lower detection limit of 0.165 µM. The colorimetric platform has a potential to detect HQ residue in real water samples with recoveries ranging from 83.56 to 91.76%. Graphical abstract.
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Peroxidasa , Platino (Metal) , Colorimetría , Peróxido de Hidrógeno , HidroquinonasRESUMEN
In this study, a simple method was adopted for the synthesis of MnO@C nanocomposites by combining in-situ reduction and carbonization of the Mn3O4 precursor. The carbon content, which was controlled by altering the annealing time in the C2H2/Ar atmosphere, was proved to have great influences on the electrochemical performances of the samples. The relationships between the carbon contents and electrochemical performances of the samples were systematically investigated using the cyclic voltammetry (CV) as well as the electrochemical impedance spectroscopy (EIS) method. The results clearly indicated that the carbon content could influence the electrochemical performances of the samples by altering the Li+ diffusion rate, electrical conductivity, polarization, and the electrochemical mechanism. When being used as the anode materials in lithium-ion batteries, the capacity retention rate of the resulting MnO@C after 300 cycles could reach 94% (593 mAh g-1, the specific energy of 182 mWh g-1) under a current density of 1.0 A g-1 (1.32 C charge/discharge rate). Meanwhile, this method could be easily scaled up, making the rational design and large-scale application of MnO@C possible.
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N,N-dicarboxymethyl Perylene-diimide (PDI) modified CeCoO3 nanocomposites were prepared by a two-step method. After modification with PDI molecules, the obtained PDI-CeCoO3 nanocomposites were demonstrated to possess the heightened peroxidase-like activity, compared with that of pure CeCoO3 nanoparticles. In the presence of H2O2, the heightened peroxidase-like behaviors of PDI-CeCoO3 were evaluated by the oxidation of the colorless substrate 3,3,5,5-tetramethylbenzidine (TMB) into blue oxTMB, which was detected visually only in 4 min. Importantly, a systematic study of catalytic activity of PDI-CeCoO3 by different means, including fluorescent probe, electrochemical data, diffuse reflection spectra together with free radical scavenger is executed, verifying that the catalytic activity were from O2- and electron holes (h+). And, the transfer of photogenerated carriers in the PDI-CeCoO3 was the Z-scheme heterojuntion mechanism. Furthermore, the peroxidase-like activity of PDI-CeCoO3 was significantly inhibited by Glutathione (GSH), resulting in fading of blue oxTMB. Based on this, a colorimetric assay for GSH biosensing has been developed. And, the liner range for GSH detection is from 1 to 10 µM with a detection limit of 0.658 µM. The recovery of GSH with different concentrations from 90.0% to 105.9% and the relative standard deviation (RSD) from 1.9% to 5.1%. This colorimetric sensor can be used to detect GSH in real samples.
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The aqueous zinc ion battery has emerged as a promising alternative technology for large-scale energy storage due to its low cost, natural abundance, and high safety features. However, the sluggish kinetics stemming from the strong electrostatic interaction of divalent zinc ions in the host crystal structure is one of challenges for highly efficient energy storage. Oxygen vacancies (VOâ¢â¢), in the present work, lead to a larger tunnel structure along the b axis, which improves the reactive kinetics and enhances Zn-ion storage capability in VO2 (B) cathode. DFT calculations further support that VOâ¢â¢ in VO2 (B) result in a narrower bandgap and lower Zn ion diffusion energy barrier compared to those of pristine VO2 (B). VOâ¢â¢-rich VO2 (B) achieves a specific capacity of 375 mAh g-1 at a current density of 100 mA g-1 and long-term cyclic stability with retained specific capacity of 175 mAh g-1 at 5 A g-1 over 2000 cycles (85% capacity retention), higher than that of VO2 (B) nanobelts (280 mAh g-1 at 100 mA g-1 and 120 mAh g-1 at 5 A g-1, 65% capacity retention).
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The performance of lead halogen perovskite is often closely related to its crystal structure. However, the chemical and optoelectronic properties of tetragonal phase single crystal MAPbCl3 (SC T-MAPbCl3) are rarely reported. In this study, we synthesized SC T-MAPbCl3 with the P4/mcc (124) space group by a modified inverse temperature crystallization (M-ITC) method. The twist angle of the Cl anion on the equatorial plane of the PbCl64- octahedron around the c-axis is 8.4°. The resistance (62 MΩ) of SC T-MAPbCl3 obviously decreased to 3 MΩ under 395 and 404 nm ultraviolet light. The photodetector based on SC T-MAPbCl3 under 3 V bias voltage exhibits high sensitivity (2.60 µA cm-2 under 1 W m-2 light intensity). The high selectivity of the device is in the ultraviolet region, rather than the visible region.
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Photodetectors play a key role in the military, aerospace, communications, bio-imaging, etc. In this study, we fabricate photodetector devices based on (CH3NH3)2FeCuI4Cl2 (MA2FeCuI4Cl2) and (CH3NH3)2InCuI6 (MA2InCuI6) for the first time. We find that the device based on MA2InCuI6 is highly selective for ultraviolet light (880 nA mW-1) and shows high anti-interference for visible-light (20-50 nA mW-1). The electrochemical impedance results indicate that the value (480 ± 10 Ω) of the resistance based on the MA2InCuI6 photodetector device is much smaller than that (1 ± 0.001 MΩ) based on the MA2FeCuI4Cl2 photodetector device, which in turn proves the difference in photoelectric response.
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Formamidinium lead iodide-based (FAPbI3 ) perovskite is widely used in the field of photovoltaics, owing to its suitable bandgap (ca.â 1.45â eV) and better thermal stability. FAPbI3 has two polymorphs (black α-FAPbI3 and yellow δ-FAPbI3 ) at ambient temperature. The yellow δ-FAPbI3 , which has no photoactivity, has a chain-like structure that likely hinders electron transport and reduces photovoltaic performance. However, pure-phase black α-FAPbI3 without any yellow phase is difficult to obtain and the underlying mechanism of the phase transition is rarely investigated. In this study, a facile bi-additive method (BA method) has been developed to completely eliminate the yellow δ-FAPbI3 phase by inducing a phase transition from δ-FAPbI3 to α-FAPbI3 . HI and Pb(SCN)2 were employed as dual additives. Based on the investigation of the annealing time and temperature, we determined that the BA method can induce the phase transition and enhance the stability of α-FAPbI3 . Owing to the enhanced crystallization as well as uniform morphology of the BA film, the perovskite solar cells (PSCs) exhibited an increased power conversion efficiency (PCE). Furthermore, the optimal devices displayed excellent stability and maintained over 80 % of initial PCE after aging for 400â h in air. This work provides a new insight into the fabrication of high-quality pure α-FAPbI3 perovskite films and makes high efficiency photovoltaic devices a reality.
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The development of low-cost noble metal-free and high-active electrocatalysts for methanol electrooxidation is highly worthwhile but remains a challenge. In this paper, 5, 10, 15, 20-tetrakis(4-carboxylphenyl)porphyrin (H2TCPP) modified nickel-cobalt layer double hydroxides nanosheets (NiCo-LDH) were prepared by one-pot hydrothermal method and characterized by the powder X-ray diffraction (XRD), the scanning electron microscopy (SEM) and X-ray photoelectron spectra (XPS), etc. H2TCPP/NiCo-LDH was demonstrated as superior a photoelectrocatalyst towards methanol oxidation in the alkaline media. Due to the introduction of H2TCPP photosensitizer, H2TCPP/NiCo-LDH exhibits the outstanding photoeletrocatalytic activity toward methanol oxidation under the visible-light irradiation. The great enhancement in the photoelectrocatalytic activity are attributed to high exposed surface active sites, efficient widen adsorption wavelength of H2TCPP in visible region, as well as efficient electron transfer between the electrode surface and the active sites. The H2TCPP/NiCo-LDH nanosheets show mass activity of 246.6 mA mg-1 and specific activity of 34.9 mA cm-2 for methanol oxidation under visible-light, which are 2.32 times higher than that of NiCo-LDH at the same conditions. The developing catalytic activity of H2TCPP/NiCo-LDH for methanol oxidation are attributed to the synergistic effect of H2TCPP and NiCo-LDH. This study may offer new ideas for developing highly effective noble metal-free catalysts for the application in methanol oxidation.
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Signal amplification is crucial in electrochemical biosensor to obtain low detection limits. In this work, a highly sensitive sandwich-type thrombin aptasensor is constructed, based on dual signal amplification of uniform silver nanowires (AgNWs) and hollow Au-CeO2 nanocomposites. AgNWs are decorated on the ITO surface to immobilize amino functionalized thrombin capture apemeter 1 (Apt1). And Au nanoparticles (AuNPs) grown directly on the surface of hollow CeO2 microstructure are used to immobilize sulfydryl functionalized thrombin reporter apemeter 2 (Apt2). Thus, sandwich-type apatasensor has been successfully designed, due to the specific recognition between thrombin and the two kinds of aptamers. One of the signal amplifications is from the good conductivity of uniform AgNWs. Moreover, uniform AgNWs together with hollow Au-CeO2 exhibit the good catalytic performance for the reduction of H2O2, further resulting in significant electrochemical signal amplification. Because the electrochemical signal amplification is closely related to the thrombin concentration, differential pulse voltammetry is used to specifically detect thrombin. Under the optimized conditions, the proposed method has a good linear response ranged from 0.5 pM to 30â¯nM with a low detection limit of 0.25 pM (S/Nâ¯=â¯3) for thrombin. The proposed thrombin aptasensor displays good selectivity, reproducibility and stability, providing a good platform for the ultrasensitive detection of thrombin.