Over the past decade, some groups have reported that nanofluids, which are liquids containing sus... more Over the past decade, some groups have reported that nanofluids, which are liquids containing suspensions of nanoparticles, have substantially higher thermal conductivity than that of the base fluids. However, the reported high thermal conductivity sometimes cannot be reproduced. Theoretically, potential mechanisms leading to this enhancement are still under scrutiny. In this thesis, we present experimental studies aiming at understanding heat conduction mechanisms in nanofluids. We use graphite flakes as additives and developed methods to prepare stable graphite suspensions. The thermal conductivity enhancement of our suspensions achieved record high thermal conductivity values in different base fluids including water, engine oil, and ethylene glycol. This thesis investigates the effect of graphite flake preparation methods such as microwave and ultrasonic on the thermal conductivity of the suspensions, and found that graphite flakes of tens of nanometer in thickness but tens of mi...
Experimental search for high-efficiency perovskite solar cells (PSCs) is an extremely challenging... more Experimental search for high-efficiency perovskite solar cells (PSCs) is an extremely challenging task due to the vast search space comprising the materials, device structures, and preparation methods. Herein, by using...
Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, United States... more Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, United States, Institute for Physical Science and Technology, University of Maryland, College Park, MD, United States, Institute for AdvancedMaterials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, China, State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, China, Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, United States, Institute of Inorganic Chemistry, Graz University of Technology, Graz, Austria, Department of Physics, Boston College, Chestnut Hill, MA, United States, APPM-MCA AttoLab, imec, Leuven, Belgium, Yale Cleanroom, Department of Applied Physics, Yale University, New Haven, CT, United States, KLA Corporation, Concorezzo, Italy, Walker Department of Mechanical Engineering, Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, TX, United States
The booming market of portable and wearable electronics has aroused the requests for advanced fle... more The booming market of portable and wearable electronics has aroused the requests for advanced flexible self-powered energy systems featuring both excellent performance and high safety. Herein, we report a safe, flexible, self-powered wristband system by integrating high-performance zinc-ion batteries (ZIBs) with perovskite solar cells (PSCs). ZIBs were first fabricated on the basis of a defective MnO2-x nanosheet-grown carbon cloth (MnO2-x@CC), which was obtained via the simple lithium treatment of the MnO2 nanosheets to slightly expand the interlayer spacing and generate rich oxygen vacancies. When used as a ZIB cathode, the MnO2-x@CC with a ultrahigh mass loading (up to 25.5 mg cm-2) exhibits a much enhanced specific capacity (3.63 mAh cm-2 at current density of 3.93 mA cm-2), rate performance, and long cycle stability (no obvious degradation after 5000 cycles) than those of the MnO2@CC. Importantly, the MnO2-x@CC-based quasi-solid-state ZIB not only achieves excellent flexibility and an ultrahigh energy density of 5.11 mWh cm-2 (59.42 mWh cm-3) but also presents a high safety under a wide temperature range and various severe conditions. More importantly, the flexible ZIBs can be integrated with flexible PSCs to construct a safe, self-powered wristband, which is able to harvest light energy and power a commercial smart bracelet. This work sheds light on the development of high-performance ZIB cathodes and thus offers a good strategy to construct wearable self-powered energy systems for wearable electronics.
Quantum dots generate unique luminescent and chemical properties due to the ultra-small particle ... more Quantum dots generate unique luminescent and chemical properties due to the ultra-small particle sizes. In this contribution, a novel silicon nanoparticles (Si-NPs)-based platform has been established via (3-aminopropyl) trimethoxysilane (APS) and ascorbic acid (AA) as raw materials within only 30 min. A switched off effect has been achieved for the determination of Ni2+ ions and the strategy has been simply realized by recording the luminescence changes in the green band of Si-NPs. This developed approach possesses a variety of merits such as label free, low cost, easy post-treatment and convenient operations. The linear equation range is yielded between 0 and 20 μM with the detection limit of 1.73 μM. The nano-sensor provides a versatile route for the monitoring of mercury ions in practical environments.
A series of novel fluorinated small molecules have been designed and used as interfacial material... more A series of novel fluorinated small molecules have been designed and used as interfacial materials to improve the contact between perovskite and spiro-OMeTAD, with an enhanced PCE enabling by a significant FF, up to ∼80%.
Carbonaceous materials have long been developed to utilize “nano-spaces” and numerous guest speci... more Carbonaceous materials have long been developed to utilize “nano-spaces” and numerous guest species could be encapsulated.
This paper presents a new constitutive model of high particles concentrated magnetorheological fl... more This paper presents a new constitutive model of high particles concentrated magnetorheological fluids (MRFs) that is based on the hexagonal close-packed structure, which can reflect the micro-structures of the particles under the magnetic field. Firstly, the particle dynamic simulations for the forces sustained by carbonyl iron powder (CIP) particles of MRFs are performed in order to investigate the particles chain-forming process at different time nodes. Subsequently, according to the force analyses, a hexagonal close-packed structure, which differs from the existing single-chain structure and body-cantered cubic structure, is adopted to formulate a constitutive model of MRFs with high concentration of the magnetic-responsive particles. Several experiments are performed while considering crucial factors that influence on the chain-forming mechanism and, hence, change the field-dependent shear yield stress in order to validate the proposed model. These factors include the magnetic i...
Metallic networks have been regarded as one of the promising indium tin oxide replacements due to... more Metallic networks have been regarded as one of the promising indium tin oxide replacements due to its optoelectronic advantages and possible low-cost manufacturing cost. The electrothermal and optical properties of transparent conductive films (TCFs) are closely related to the geometry of the metallic networks. Therefore, the in-depth understanding of the geometry effect is quite important for designing a desirable metallic network TCF. In this paper, we conducted an in-depth theoretical study on the geometry effect on the electrothermal and optical properties of the metallic network TCF by using a coupled electrothermal model. We found that the metallic wire segments in different directions have different current densities and power densities, which mainly depends on the directions of the electric field. Besides, the inner corner of the branch junctions of networks has a current density 14.5 times higher than the average. The maximum temperature difference inside the network is up to 19.6 K. Importantly, the mechanisms for network breakdown under excessive operating power are summarized as thermal assisted electronic migration and excessive temperature. Finally, we proposed several optimized network geometries with a reduced sheet resistance (48.4%) and internal temperature difference (60.1%). We believed that the outcomes and analyses of this work help us to design the transparent metallic networks with optimal performance and potentially applicable to the transparent heaters and smart windows.Metallic networks have been regarded as one of the promising indium tin oxide replacements due to its optoelectronic advantages and possible low-cost manufacturing cost. The electrothermal and optical properties of transparent conductive films (TCFs) are closely related to the geometry of the metallic networks. Therefore, the in-depth understanding of the geometry effect is quite important for designing a desirable metallic network TCF. In this paper, we conducted an in-depth theoretical study on the geometry effect on the electrothermal and optical properties of the metallic network TCF by using a coupled electrothermal model. We found that the metallic wire segments in different directions have different current densities and power densities, which mainly depends on the directions of the electric field. Besides, the inner corner of the branch junctions of networks has a current density 14.5 times higher than the average. The maximum temperature difference inside the network is up to 19.6 K. Importantly,...
Over the past decade, some groups have reported that nanofluids, which are liquids containing sus... more Over the past decade, some groups have reported that nanofluids, which are liquids containing suspensions of nanoparticles, have substantially higher thermal conductivity than that of the base fluids. However, the reported high thermal conductivity sometimes cannot be reproduced. Theoretically, potential mechanisms leading to this enhancement are still under scrutiny. In this thesis, we present experimental studies aiming at understanding heat conduction mechanisms in nanofluids. We use graphite flakes as additives and developed methods to prepare stable graphite suspensions. The thermal conductivity enhancement of our suspensions achieved record high thermal conductivity values in different base fluids including water, engine oil, and ethylene glycol. This thesis investigates the effect of graphite flake preparation methods such as microwave and ultrasonic on the thermal conductivity of the suspensions, and found that graphite flakes of tens of nanometer in thickness but tens of mi...
Experimental search for high-efficiency perovskite solar cells (PSCs) is an extremely challenging... more Experimental search for high-efficiency perovskite solar cells (PSCs) is an extremely challenging task due to the vast search space comprising the materials, device structures, and preparation methods. Herein, by using...
Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, United States... more Department of Chemistry and Biochemistry, University of Maryland, College Park, MD, United States, Institute for Physical Science and Technology, University of Maryland, College Park, MD, United States, Institute for AdvancedMaterials, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou, China, State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Opto-Electronics, Collaborative Innovation Center of Extreme Optics, Shanxi University, Taiyuan, China, Department of Chemistry, University of Pittsburgh, Pittsburgh, PA, United States, Institute of Inorganic Chemistry, Graz University of Technology, Graz, Austria, Department of Physics, Boston College, Chestnut Hill, MA, United States, APPM-MCA AttoLab, imec, Leuven, Belgium, Yale Cleanroom, Department of Applied Physics, Yale University, New Haven, CT, United States, KLA Corporation, Concorezzo, Italy, Walker Department of Mechanical Engineering, Materials Science and Engineering Program, Texas Materials Institute, The University of Texas at Austin, Austin, TX, United States
The booming market of portable and wearable electronics has aroused the requests for advanced fle... more The booming market of portable and wearable electronics has aroused the requests for advanced flexible self-powered energy systems featuring both excellent performance and high safety. Herein, we report a safe, flexible, self-powered wristband system by integrating high-performance zinc-ion batteries (ZIBs) with perovskite solar cells (PSCs). ZIBs were first fabricated on the basis of a defective MnO2-x nanosheet-grown carbon cloth (MnO2-x@CC), which was obtained via the simple lithium treatment of the MnO2 nanosheets to slightly expand the interlayer spacing and generate rich oxygen vacancies. When used as a ZIB cathode, the MnO2-x@CC with a ultrahigh mass loading (up to 25.5 mg cm-2) exhibits a much enhanced specific capacity (3.63 mAh cm-2 at current density of 3.93 mA cm-2), rate performance, and long cycle stability (no obvious degradation after 5000 cycles) than those of the MnO2@CC. Importantly, the MnO2-x@CC-based quasi-solid-state ZIB not only achieves excellent flexibility and an ultrahigh energy density of 5.11 mWh cm-2 (59.42 mWh cm-3) but also presents a high safety under a wide temperature range and various severe conditions. More importantly, the flexible ZIBs can be integrated with flexible PSCs to construct a safe, self-powered wristband, which is able to harvest light energy and power a commercial smart bracelet. This work sheds light on the development of high-performance ZIB cathodes and thus offers a good strategy to construct wearable self-powered energy systems for wearable electronics.
Quantum dots generate unique luminescent and chemical properties due to the ultra-small particle ... more Quantum dots generate unique luminescent and chemical properties due to the ultra-small particle sizes. In this contribution, a novel silicon nanoparticles (Si-NPs)-based platform has been established via (3-aminopropyl) trimethoxysilane (APS) and ascorbic acid (AA) as raw materials within only 30 min. A switched off effect has been achieved for the determination of Ni2+ ions and the strategy has been simply realized by recording the luminescence changes in the green band of Si-NPs. This developed approach possesses a variety of merits such as label free, low cost, easy post-treatment and convenient operations. The linear equation range is yielded between 0 and 20 μM with the detection limit of 1.73 μM. The nano-sensor provides a versatile route for the monitoring of mercury ions in practical environments.
A series of novel fluorinated small molecules have been designed and used as interfacial material... more A series of novel fluorinated small molecules have been designed and used as interfacial materials to improve the contact between perovskite and spiro-OMeTAD, with an enhanced PCE enabling by a significant FF, up to ∼80%.
Carbonaceous materials have long been developed to utilize “nano-spaces” and numerous guest speci... more Carbonaceous materials have long been developed to utilize “nano-spaces” and numerous guest species could be encapsulated.
This paper presents a new constitutive model of high particles concentrated magnetorheological fl... more This paper presents a new constitutive model of high particles concentrated magnetorheological fluids (MRFs) that is based on the hexagonal close-packed structure, which can reflect the micro-structures of the particles under the magnetic field. Firstly, the particle dynamic simulations for the forces sustained by carbonyl iron powder (CIP) particles of MRFs are performed in order to investigate the particles chain-forming process at different time nodes. Subsequently, according to the force analyses, a hexagonal close-packed structure, which differs from the existing single-chain structure and body-cantered cubic structure, is adopted to formulate a constitutive model of MRFs with high concentration of the magnetic-responsive particles. Several experiments are performed while considering crucial factors that influence on the chain-forming mechanism and, hence, change the field-dependent shear yield stress in order to validate the proposed model. These factors include the magnetic i...
Metallic networks have been regarded as one of the promising indium tin oxide replacements due to... more Metallic networks have been regarded as one of the promising indium tin oxide replacements due to its optoelectronic advantages and possible low-cost manufacturing cost. The electrothermal and optical properties of transparent conductive films (TCFs) are closely related to the geometry of the metallic networks. Therefore, the in-depth understanding of the geometry effect is quite important for designing a desirable metallic network TCF. In this paper, we conducted an in-depth theoretical study on the geometry effect on the electrothermal and optical properties of the metallic network TCF by using a coupled electrothermal model. We found that the metallic wire segments in different directions have different current densities and power densities, which mainly depends on the directions of the electric field. Besides, the inner corner of the branch junctions of networks has a current density 14.5 times higher than the average. The maximum temperature difference inside the network is up to 19.6 K. Importantly, the mechanisms for network breakdown under excessive operating power are summarized as thermal assisted electronic migration and excessive temperature. Finally, we proposed several optimized network geometries with a reduced sheet resistance (48.4%) and internal temperature difference (60.1%). We believed that the outcomes and analyses of this work help us to design the transparent metallic networks with optimal performance and potentially applicable to the transparent heaters and smart windows.Metallic networks have been regarded as one of the promising indium tin oxide replacements due to its optoelectronic advantages and possible low-cost manufacturing cost. The electrothermal and optical properties of transparent conductive films (TCFs) are closely related to the geometry of the metallic networks. Therefore, the in-depth understanding of the geometry effect is quite important for designing a desirable metallic network TCF. In this paper, we conducted an in-depth theoretical study on the geometry effect on the electrothermal and optical properties of the metallic network TCF by using a coupled electrothermal model. We found that the metallic wire segments in different directions have different current densities and power densities, which mainly depends on the directions of the electric field. Besides, the inner corner of the branch junctions of networks has a current density 14.5 times higher than the average. The maximum temperature difference inside the network is up to 19.6 K. Importantly,...
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Papers by Jinwei Gao