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- 2019
- Dye-sensitized solar cell
- Hierarchical structure
- Light scattering
- TiO2 photoanode
- Nanomaterials and Technology
- National Sun Yat-sen University
- Wenzao Ursuline University of Languages
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A Nanostructured Gold/Graphene Microfluidic Device for Direct and Plasmonic-Assisted Impedimetric Detection of Bacteria
摘要： Hierarchical 3D gold nano-micro islands (NMIs) are favourably structured for direct and probe-free capture of bacteria in optical and electrochemical sensors. Moreover, their unique plasmonic properties make them a suitable candidate for plasmonic-assisted electrochemical sensors, yet the charge transfer needs to be improved. In the present study, we propose a novel plasmonic-assisted electrochemical impedimetric detection platform based on hybrid structures of 3D gold NMIs and graphene (Gr) nanosheets for probe-free capture and label-free detection of bacteria. The inclusion of Gr nanosheets significantly improves the charge transfer, addressing the central issue of using 3D gold NMIs. Notably, the 3D gold NMIs/Gr detection platform successfully distinguishes between various types of bacteria including Escherichia coli (E. coli) K12, Pseudomonas putida (P. putida) and Staphylococcus epidermidis (S. epidermidis) when electrochemical impedance spectroscopy is applied under visible light. We show that distinguishable and label-free impedimetric detection is due to dissimilar electron charge transfer caused by various sizes, morphologies, and compositions of the cells. In addition, the finite-difference time-domain (FDTD) simulation of the electric field indicates the intensity of charge distribution at the edge of the NMI structures. Furthermore, the wettability studies demonstrated that contact angle is a characteristic feature of each type of captured bacteria on the 3D gold NMIs, which strongly depends on the shape, morphology, and size of the cells. Ultimately, exposing the platform to various dilutions of the three bacteria strains, revealed the ability to detect dilutions as low as ~20 CFU/mL in a wide linear range of detection of 2(cid:3)101-105, 2(cid:3)101-104 and 1(cid:3)102-1(cid:3)105 CFU/mL for E. coli, P. putida, and S. epidermidis, respectively. The proposed hybrid structure of 3D gold NMIs and Gr combined by novel plasmonic and conventional impedance spectroscopy techniques open interesting avenues in ultrasensitive label-free detection of bacteria with low cost and high stability.
关键词： Label-free bacteria detection,Hierarchical gold nano-micro islands,Surface properties,Impedance spectroscopy,plasmonic-assisted electrochemical detection platform
更新于2025-09-23 15:19:57
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Laser Direct Structuring of Bioinspired Spine with Backward Microbarbs and Hierarchical Microchannels for Ultrafast Water Transport and Efficient Fog Harvesting
摘要： Achieving effective dropwise capture and ultrafast water transport is essential for fog harvesting. In nature, Cactus uses the conical spine with micro-barbs to effectively capture fog while Sarracenia utilizes the trichome with hierarchical microchannels to quickly transport water. Herein, we combined their advantages to present a novel configuration, spine with barbs and hierarchical channels (SBHC), for simultaneous ultrafast water transport and high-efficient fog harvesting. This bio-inspired SBHC exhibited the fastest water transport ability and the highest fog harvesting efficiency in comparison with spine with hierarchical channels (SHC), spine with barbs and grooves (SBG) and spine with barbs (SB). Based on the fundamental SBHC unit, we further designed and fabricated a 2D spider-web alike fog collector and a 3D cactus alike fog collector using direct laser structuring and Origami techniques. The 2D spider-web and 3D cactus alike fog collectors showed high-efficient fog collection capacity. We envision that this fundamental understanding and rational design strategy can be applied in fog harvesting, heat transfer, liquid manipulation, and microfluidics.
关键词： Direct laser structuring,Water transport,Spine and micro-barbs,Fog harvesting,Hierarchical microchannels
更新于2025-09-23 15:19:57
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[IEEE 2019 6th International Conference on Advanced Control Circuits and Systems (ACCS) & 2019 5th International Conference on New Paradigms in Electronics & information Technology (PEIT) - Hurgada, Egypt (2019.11.17-2019.11.20)] 2019 6th International Conference on Advanced Control Circuits and Systems (ACCS) & 2019 5th International Conference on New Paradigms in Electronics & information Technology (PEIT) - Co-Planar Waveguide Resonator to Mediate Coupling between Superconducting Quantum Bits
摘要： Cloud data owners prefer to outsource documents in an encrypted form for the purpose of privacy preserving. Therefore it is essential to develop efficient and reliable ciphertext search techniques. One challenge is that the relationship between documents will be normally concealed in the process of encryption, which will lead to significant search accuracy performance degradation. Also the volume of data in data centers has experienced a dramatic growth. This will make it even more challenging to design ciphertext search schemes that can provide efficient and reliable online information retrieval on large volume of encrypted data. In this paper, a hierarchical clustering method is proposed to support more search semantics and also to meet the demand for fast ciphertext search within a big data environment. The proposed hierarchical approach clusters the documents based on the minimum relevance threshold, and then partitions the resulting clusters into sub-clusters until the constraint on the maximum size of cluster is reached. In the search phase, this approach can reach a linear computational complexity against an exponential size increase of document collection. In order to verify the authenticity of search results, a structure called minimum hash sub-tree is designed in this paper. Experiments have been conducted using the collection set built from the IEEE Xplore. The results show that with a sharp increase of documents in the dataset the search time of the proposed method increases linearly whereas the search time of the traditional method increases exponentially. Furthermore, the proposed method has an advantage over the traditional method in the rank privacy and relevance of retrieved documents.
关键词： security,multi-keyword search,Cloud computing,ranked search,hierarchical clustering,ciphertext search
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE International Conference on Real-time Computing and Robotics (RCAR) - Irkutsk, Russia (2019.8.4-2019.8.9)] 2019 IEEE International Conference on Real-time Computing and Robotics (RCAR) - A Hierarchical Searching Approach for Laser SLAM Re-localization on Mobile Robot Platform
摘要： Simultaneous localization and mapping (SLAM) is an important issue for mobile robot system. Re-localization, as a part of close loop checking of SLAM, focuses on localize the position of a robot agent when it is restarted. Traditional localization methods couldn’t reach both a high accuracy and a little time cost. In this paper, we proposed a newly hierarchical searching approach for laser SLAM re-localization. We do hierarchically searching to match an input laser frame with the whole 2-D map, instead of comparing it with each frame in the map. By using such approach, we could accelerate re-localization speed, so the performance of SLAM is improved. Our SLAM system is well organized on a mobile robot platform. After ?eld test, our approach reaches a average precision (AP) of 90.6% on a 20m× 20m map area, and the time cost is averagely 30ms. The result shows our hierarchical searching approach is effective for re-localization problems on laser SLAM.
关键词： SLAM,laser SLAM,hierarchical searching,mobile robot,re-localization
更新于2025-09-23 15:19:57
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Bio-template assisted hierarchical ZnO superstructures coupled with graphene quantum dots for enhanced water oxidation kinetics
摘要： Due to anisotropic growth behavior and tunable electrical properties, ZnO nanostructures having dimensions such as 0-D, 1-D, 2-D and 3-D are actively studied for their optoelectronic properties. However, ZnO based photoanodes suffer from unfavorable recombination of electron hole pair, which hinders its use in photoelectrochemical (PEC) water oxidation. Herein, we demonstrate a strategy to enhance the PEC performance using bio-template assisted in-situ grown hierarchical ZnO superstructures directly over fluorine-doped tin oxide (FTO) modified by graphene quantum dots (GQDs). GQDs decorated hierarchical ZnO superstructures displayed a significant increment of ~77% in photocurrent density value compared to pristine ZnO with an impressive carrier density of 3.19 × 1020 cm?3, which is ~1.8 orders of magnitude higher than that of pristine ZnO. It is observed that GQDs acts as an efficient hole extractor, which improves the carrier separation on ZnO surface and reduces the hole trapping probability.
关键词： Hole extracting agent,Polygalacturonic acid,Hierarchical ZnO superstructures,Photoelectrochemical water oxidation,Graphene quantum dots
更新于2025-09-23 15:19:57
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Hierarchical Core-Shell Structure of 2D VS2@VC@N-Doped Carbon Sheets Decorated by Ultrafine Pd Nanoparticles: Assembled in 3D Rosette-like Array on Carbon Fiber Microelectrode for Electrochemical Sensing
摘要： The development of two-dimension (2D) nanohybrid materials with heterogeneous component in nanoscale and three-dimension (3D) well-ordered assembly in microscale has been regarded as an effective way to improve their overall performances by synergistic coupling of the optimized structure and composition. In this work, we reported the design and synthesis of a new type of hierarchically core-shell structure of 2D VS2@VC@N-doped carbon (NC) sheets decorated by ultrafine Pd nanoparticles (PdNPs), which were vertically grown on carbon fiber (CF) and assembled into a unique 3D rosette-like array. The resultant VS2@VC@NC-PdNPs modified CF microelectrode integrated the structural and electrochemical properties of the heterogeneous hybridization of core-shell VS2@VC@NC-PdNPs sheets with unique rosette-like array structure, and gave rise to a significant improvement in terms of electron transfer ability, electrocatalytic activity, stability and biocompatibility. Under the optimized conditions, the VS2@VC@NC-PdNPs modified CF microelectrode demonstrated excellent electrochemical sensing performance towards biomarker hydrogen peroxide (H2O2) including high sensitivity of 152.7 μA cm-2 mM-1, low detection limit of 50 nM (a signal-to-noise ratio of 3:1), as well as good reproducibility and anti-interference ability, which could be used for real-time in situ electrochemical detection of H2O2 in live cancer cells and cancer tissue. The remarkable performances of the proposed nanohybrid microelectrode will have a profound impact on the design of diverse 2D layered materials as promising candidate for electrochemical biosensing applications.
关键词： electrochemical sensing,hierarchical core-shell structure,three-dimension rosette-like sheets array,Two-dimension layered nanomaterials,cancer biomarker detection
更新于2025-09-23 15:19:57
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-matrix based master equation for Coulomb drag in double quantum dots
摘要： Recently, novel Coulomb drag mechanisms in capacitively coupled double quantum dots were uncovered by the T -matrix based master equation (TME). The TME is so far the primary approach to studying Coulomb drag in the weak-coupling regime; however, its accuracy and reliability remain unexplored. Here, we evaluate the performance of the TME for Coulomb drag via a comparison with numerically exact results obtained by the hierarchical equation-of-motion approach. We ?nd that the TME can capture qualitative current evolutions versus dot levels, temperature, and effective coupling strengths but only partially succeeds at the quantitative level. Speci?cally, the TME gives highly inaccurate drag currents when large charge ?uctuations on dots exist and the fourth-order tunneling processes make a leading-order contribution. This failure of the TME is attributed to the combined effect of the unique drag mechanisms and its overlook of the fourth-order single-electron tunnelings. We identify the reliable regions to facilitate further quantitative studies on Coulomb drag by the TME.
关键词： weak-coupling regime,Coulomb drag,double quantum dots,T-matrix based master equation,hierarchical equation-of-motion approach
更新于2025-09-23 15:19:57
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Self-Aligned Hierarchical ZnO Nanorod/NiO Nanosheet Arrays for High Photon Extraction Efficiency of GaN-Based Photonic Emitter
摘要： Advancements in nanotechnology have facilitated the increased use of ZnO nanostructures. In particular, hierarchical and core–shell nanostructures, providing a graded refractive index change, have recently been applied to enhance the photon extraction e?ciency of photonic emitters. In this study, we demonstrate self-aligned hierarchical ZnO nanorod (ZNR)/NiO nanosheet arrays on a conventional photonic emitter (C-emitter) with a wavelength of 430 nm. These hierarchical nanostructures were synthesized through a two-step hydrothermal process at low temperature, and their optical output power was approximately 17% higher than that of ZNR arrays on a C-emitter and two times higher than that of a C-emitter. These results are due to the graded index change in refractive index from the GaN layer inside the device toward the outside as well as decreases in the total internal re?ection and Fresnel re?ection of the photonic emitter.
关键词： ZnO nanorod/NiO nanosheet,photon extraction e?ciency,photonic emitter,self-align,hierarchical nanostructures
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Technoeconomic Analysis of Photovoltaics Module Manufacturing with Thin Silicon Wafers
摘要： Under the case of exponentially growth of wireless services and the scarcity of spectrum resources, cognitive radio (CR) has been proposed to access licensed channels opportunistically, and thus improve spectrum utilization. In CR devices, accurate spectrum sensing is the prerequisite for opportunistic access. The current cooperative spectrum sensing still cannot effectively exploit the temporal correlations among sensing data, especially the correlations between the current sensing data and the historical data. This paper uses sticky hierarchical Dirichlet process-hidden Markov model to exploit the historical sensing data of multiple users, and classi?es the historical sensing data into groups according to their latent spectrum states. The proposed spectrum sensing algorithm can fuse the historical sensing data into prior knowledge, which can be used to improve the accuracy in spectrum decision. Furthermore, a rejection process is proposed to ?lter out some sensing data with high uncertainty in classi?cation, which guarantees the effectiveness of historical sensing data. The simulation results show that the proposed algorithm performs the best, compared with other three typical cooperative spectrum sensing algorithms, in terms of detection probability and false alarm probability. Speci?cally, when the false alarm probability is 0.2, the proposed algorithm has more than 10% and 60% detection probability improvement under channel signal-to-noise ratio as 0 and ?5 dB, respectively.
关键词： hidden Markov model,Cognitive radio,hierarchical Dirichlet process,historical sensing data mining,spectrum sensing
更新于2025-09-23 15:19:57
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Hierarchically decomposed finite element method for a triply coupled piezoelectric, structure, and fluid fields of a thin piezoelectric bimorph in fluid
摘要： This paper proposes a numerical method for analyzing a thin piezoelectric bimorph in fluid. A hierarchically decomposed finite element method (FEM) is proposed for modeling the triply coupled piezoelectric-structure–fluid interaction. The electromechanical coupling (piezoelectric-structure interaction) behavior in a thin piezoelectric bimorph is described by the classical constitutive equation, the incompressible fluid flows by the Navier–Stokes equation and the structure by the Cauchy equation of motion. The piezoelectric-structure–fluid interaction system is decomposed into subsystems of fluid–structure interaction (FSI) and piezoelectric field, then the piezoelectric field and the FSI are coupled using the block Gauss–Seidel method, the fluid–structure interaction is split into the fluid–structure velocity field and the pressure field using an algebraic splitting and the fluid–structure velocity field is partitioned into fluid velocity field and structure velocity field. Using the proposed method, the resonance characteristics of a piezoelectric bimorph cantilever made of PVDF and PZT-5H material in fluid are investigated for actuation and sensor configurations.
关键词： Thin piezoelectric bimorph,Hierarchical decomposition,Finite element method (FEM),Fluid–structure interaction (FSI),Piezoelectricity,Piezoelectric-structure interaction
更新于2025-09-23 15:19:57