| 1. |
- Cao, Yuehan, et al.
(author)
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Modulating electron density of vacancy site by single Au atom for effective CO2 photoreduction
- 2021
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
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Journal article (peer-reviewed)abstract
- The surface electron density significantly affects the photocatalytic efficiency, especially the photocatalytic CO2 reduction reaction, which involves multi-electron participation in the conversion process. Herein, we propose a conceptually different mechanism for surface electron density modulation based on the model of Au anchored CdS. We firstly manipulate the direction of electron transfer by regulating the vacancy types of CdS. When electrons accumulate on vacancies instead of single Au atoms, the adsorption types of CO2 change from physical adsorption to chemical adsorption. More importantly, the surface electron density is manipulated by controlling the size of Au nanostructures. When Au nanoclusters downsize to single Au atoms, the strong hybridization of Au 5d and S 2p orbits accelerates the photo-electrons transfer onto the surface, resulting in more electrons available for CO2 reduction. As a result, the product generation rate of AuSA/Cd1−xS manifests a remarkable at least 113-fold enhancement compared with pristine Cd1−xS.
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| 2. |
- Yin, Dong-min, et al.
(author)
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Upgrading the anaerobic membrane bioreactor treatment of chicken manure by introducing in-situ ammonia stripping and hyper-thermophilic pretreatment
- 2020
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In: Bioresource Technology. - : Elsevier Ltd. - 0960-8524 .- 1873-2976. ; 310
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Journal article (peer-reviewed)abstract
- The slow hydrolysis rate and ammonia inhibition effects significantly limit the performance of anaerobic digestion (AD) of nitrogen rich wastes. An innovative two-stage AD was therefore investigated for chicken manure by combining hyper-thermophilic (70 °C) pretreatment and a anaerobic membrane bioreactor (AnMBR). An in-situ stripping unit was assembled into the AnMBR to remove the ammonium-N, thus alleviating the inhibition effects. Through the 120-day experiment, the hydraulic retention time was optimized at 15 days for AnMBR with a constant retention 4 days for pretreatment. The hydrolysis efficiency and methane yield reached 72.4% and 352 mL-CH4/g-VSin respectively. About 3000 mg/L ammonium-N was removed through stripping, attributing to methane yield increased by 139 mL-CH4/g-VSin and volatile fatty acids decreased by 2683 mg/L compared to the control. No significant fouling was observed for the membrane. Conclusively, the combined two-stage AD process may offer an alternative approach for the treatment of nitrogen rich organic waste.
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| 3. |
- Alvarez, Sol Gutierrez, et al.
(author)
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Charge Carrier Diffusion Dynamics in Multisized Quaternary Alkylammonium-Capped CsPbBr3 Perovskite Nanocrystal Solids
- 2021
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In: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 13:37, s. 44742-44750
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Journal article (peer-reviewed)abstract
- CsPbBr3 quantum dots (QDs) are promising candidates for optoelectronic devices. The substitution of oleic acid ( OA) and oleylamine ( OLA) capping agents with a quaternary alkylammonium such as di-dodecyl dimethyl ammonium bromide (DDAB) has shown an increase in external quantum efficiency (EQE) from 0.19% (OA/OLA) to 13.4% (DDAB) in LED devices. The device performance significantly depends on both the diffusion length and the mobility of photoexcited charge carriers in QD solids. Therefore, we investigated the charge carrier transport dynamics in DDAB-capped CsPbBr3 QD solids by constructing a bi-sized QD mixture film. Charge carrier diffusion can be monitored by quantitatively varying the ratio between two sizes of QDs, which varies the mean free path of the carriers in each QD cluster. Excited-state dynamics of the QD solids obtained from ultrafast transient absorption spectroscopy reveals that the photogenerated electrons and holes are difficult to diffuse among small-sized QDs (4 nm) due to the strong quantum confinement. On the other hand, both photoinduced electrons and holes in large-sized QDs (10 nm) would diffuse toward the interface with the small-sized QDs, followed by a recombination process. Combining the carrier diffusion study with a Monte Carlo simulation on the QD assembly in the mixture films, we can calculate the diffusion lengths of charge carriers to be similar to 239 +/- 16 nm in 10 nm CsPbBr3 QDs and the mobility values of electrons and holes to be 2.1 (+/- 0.1) and 0.69 (+/- 0.03) cm(2)/V s, respectively. Both parameters indicate an efficient charge carrier transport in DDAB-capped QD films, which rationalized the perfect performance of their LED device application.
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| 4. |
- Guo, Ruiqi, et al.
(author)
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Exploiting Flexible Memristors Based on Solution-Processed Colloidal CuInSe2 Nanocrystals
- 2020
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In: Advanced Electronic Materials. - : Wiley. - 2199-160X. ; 6:5
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Journal article (peer-reviewed)abstract
- Compared to analogous bulk materials, colloidal nanocrystals have presented a powerful platform for building up electronic devices on the nano/micrometer scale and flexible portable electronic apparatus with the benefits of solution-based processing approach at room temperature. Herein, memristors based on CuInSe2 (CISe) colloidal nanocrystals prepared using a solution-based process at room temperature are constructed. The memristors exhibit obvious bipolar resistive switching performance with a high–low resistance ratio larger than 5.7 and a steady retention time over 104 s. This is attributed to the copper ion redox reaction and the migration of these ions under an applied electric field. When the SET voltage is reached, the ions are separated from one of the electrodes, and the memristor changes from a low-resistance state (LRS) to a high-resistance state (HRS). Conversely, when the voltage reaches the RESET voltage, the memristor switches from a HRS to a LRS. In addition, the flexible memristor can be fabricated by spincoating nanocrystal solution onto polyethylene terephthalate (PET) at room temperature, showing excellent reproducibility of the performance including 100 times of continuous operation, 104 s of reproducible reading, 600 times of antifatigue testing, and thermal stability up to 95 °C. The flexible devices demonstrate promising applications for portable electronic devices.
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| 5. |
- Guo, Ruiqi, et al.
(author)
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Manganese doped eco-friendly CuInSe2 colloidal quantum dots for boosting near-infrared photodetection performance
- 2021
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In: Chemical Engineering Journal. - : Elsevier BV. - 1385-8947. ; 403
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Journal article (peer-reviewed)abstract
- CuInSe2 (CISe) colloidal quantum dots (QDs) display promising applications in photodetection especially within near-infrared (NIR) regions due to their high extinction coefficient and environmental-friendly. However, the high trap density and poor crystal quality introduced by the ternary structure result in low photodetection of CISe QDs devices. Herein, we dope transition metal manganese ions (Mn2+) into CISe QDs to tackle the above problems. Structural characterization results demonstrate the crystal quality of CISe QDs is improved by doping Mn2+ during the synthesis of QDs. The transient absorption (TA) spectroscopic study together with the space-charge-limited current (SCLC) measurements show the charge carrier lifetime of Mn-CISe QDs is much longer than that of the CISe QDs, due to the Mn2+ doping state serve as hole capturer forming a charge-compensated pair with the Cu2+ defect that makes the long-lived Cu2+ radiative recombination dominate. Furthermore, Mn2+ doping concurrently modifies the conduction band minimum and valence band maximum level of the QDs verified by the ultraviolet photoelectron spectroscopy (UPS), which determines the driving force for charge carrier transfer to acceptors. The optimal Mn2+ doping level (0.01 Mn:Cu feed ratio) balanced the above two factors in the QDs. The detector based on such Mn-CISe QDs exhibits responsivity of 30 mA/W and specific detectivity of 4.2 × 1012 Jones at near-infrared wavelength, the response speed of 0.76 µs, and suppressed dark current density of 1.6 × 10−10 A cm−2.
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| 6. |
- Guo, Sisi, et al.
(author)
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Thermoelectric Characteristics of Self-Supporting WSe2-Nanosheet/PEDOT-Nanowire Composite Films
- 2023
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In: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 15:29, s. 35430-35438
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Journal article (peer-reviewed)abstract
- Conducting polymer poly(3,4-ethylenedioxythiophene) nanowires(PEDOTNWs) were synthesized by a modified self-assembled micellar soft-templatemethod, followed by fabrication by vacuum filtration of self-supportingexfoliated WSe2-nanosheet (NS)/PEDOT-NW composite films.The results showed that as the mass fractions of WSe2 NSsincreased from 0 to 20 wt % in the composite films, the electricalconductivity of the samples decreased from & SIM;1700 to & SIM;400S cm(-1), and the Seebeck coefficient increased from12.3 to 23.1 & mu;V K-1 at 300 K. A room-temperaturepower factor of 44.5 & mu;W m(-1) K-2 was achieved at 300 K for the sample containing 5 wt % WSe2 NSs, and a power factor of 67.3 & mu;W m(-1) K-2 was obtained at 380 K. The composite film containing5 wt % WSe2 NSs was mechanically flexible, as shown byits resistance change ratio of 7.1% after bending for 500 cycles ata bending radius of 4 mm. A flexible thermoelectric (TE) power generatorcontaining four TE legs could generate an output power of 52.1 nWat a temperature difference of 28.5 K, corresponding to a power densityof & SIM;0.33 W/m(2). This work demonstrates that the fabricationof inorganic nanosheet/organic nanowire TE composites is an approachto improve the TE properties of conducting polymers.
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| 7. |
- Hattori, Yocefu, et al.
(author)
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Phonon-Assisted Hot Carrier Generation in Plasmonic Semiconductor Systems
- 2021
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In: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 21:2, s. 1083-1089
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Journal article (peer-reviewed)abstract
- Plasmonic materials have optical cross sections that exceed by 10-fold their geometric sizes, making them uniquely suitable to convert light into electrical charges. Harvesting plasmon-generated hot carriers is of interest for the broad fields of photovoltaics and photocatalysis; however, their direct utilization is limited by their ultrafast thermalization in metals. To prolong the lifetime of hot carriers, one can place acceptor materials, such as semiconductors, in direct contact with the plasmonic system. Herein, we report the effect of operating temperature on hot electron generation and transfer to a suitable semiconductor. We found that an increase in the operation temperature improves hot electron harvesting in a plasmonic semiconductor hybrid system, contrasting what is observed on photodriven processes in nonplasmonic systems. The effect appears to be related to an enhancement in hot carrier generation due to phonon coupling. This discovery provides a new strategy for optimization of photodriven energy production and chemical synthesis.
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| 8. |
- Hattori, Yocefu, et al.
(author)
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Role of the Metal Oxide Electron Acceptor on Gold-Plasmon Hot-Carrier Dynamics and Its Implication to Photocatalysis and Photovoltaics
- 2021
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In: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 4:2, s. 2052-2060
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Journal article (peer-reviewed)abstract
- The recent discovery that metal nanoparticles can generate hot carriers upon light excitation is seen as a breakthrough in the fields of plasmonics and photonics. However, the high expectations for a plasmonic revolution in applications have been dampened by the ultrafast energy dissipation of surface plasmon polariton modes. While research aimed at suppressing loss mechanisms is still pursued, another research direction has emerged where charges are harnessed before they relax. Despite the effort, efficiencies of devices based on hot carriers harnessed from plasmonics are typically very low (a few percent), which is somehow paradoxical since efficiencies for electron injection efficiency have been reported to be in the range from 25% to 40% and hole injection up to 85%. This indicates that the low device performance relates to the undesirable charge back-transfer process, which happens in the picosecond time scale. In this context, we performed a comparative ultrafast spectroscopy investigation with gold nanoparticles in direct contact with different metal oxides, namely, TiO2, ZnO, SnO2, and Al:ZnO. Electron dynamics revealed the decisive role of metal/semiconductor interfaces and semiconductor electronic structure in electron injection efficiency and recombination, with significant implications to the fields of photocatalysis and photovoltaics.
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| 9. |
- Honarfar, Alireza, et al.
(author)
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Ultrafast Spectroelectrochemistry Reveals Photoinduced Carrier Dynamics in Positively Charged CdSe Nanocrystals
- 2021
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In: Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 125:26, s. 14332-14337
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Journal article (peer-reviewed)abstract
- Extra charges in semiconductor nanocrystals are of paramount importance for their electrically driven optoelectronic and photovoltaic applications. Optical excitations of such charged nanocrystals lead to rapid recombinationviaan Auger process, which can deteriorate the performance of the corresponding devices. While numerous articles report trion Auger processes in negatively charged nanocrystals, optical studies of well-controlled positive charging of nanocrystals and detailed studies of positive trions remain rare. In this work, we used electrochemistry to achieve positive charging of CdSe nanocrystals, so-called quantum dots (QDs), in a controlled way. Femtosecond transient absorption spectroscopy was applied forin situinvestigation of the charge carrier dynamics after optical excitation of the electrochemically charged QD assembly on TiO2. We observe that without bias (i.e., neutral QDs), sub-picosecond hot carrier cooling is followed by multiple phases of the dynamics corresponding to electron injection and transfer to the TiO2. Positive charging first leads to activation of the hole traps close to the valence band maximum, which opens a rapid recombination channel of the optical excitation. A further increase in the positive bias interrupts the electron injection to TiO2, and if nanocrystals are positively charged, it leads to Auger relaxation in a few hundred picosecond timescale. This study represents a step toward the understanding of the effect of positive charging on the performance of semiconductor nanocrystals under conditions which closely mimic their potential applications.
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| 10. |
- Huang, He, et al.
(author)
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Material informatics for uranium-bearing equiatomic disordered solid solution alloys
- 2021
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In: Materials Today Communications. - : Elsevier BV. - 2352-4928. ; 29
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Journal article (peer-reviewed)abstract
- Near-equiatomic, multi-component alloys with disordered solid solution phase (DSSP) are associated with outstanding performance in phase stability, mechanical properties and irradiation resistance, and may provide a feasible solution for developing novel uranium-based alloys with better fuel capacity. In this work, we build a machine learning (ML) model of disordered solid solution alloys (DSSAs) based on about 6000 known multicomponent alloys and several materials descriptors to efficiently predict the DSSAs formation ability. To fully optimize the ML model, we develop a multi-algorithm cross-verification approach in combination with the SHapley Additive exPlanations value (SHAP value). We find that the Delta S-C, Lambda, Phi(s), gamma and 1/Omega, corresponding to the former two Hume - Rothery (H - R) rules, are the most important materials descriptors affecting DSSAs formation ability. When the ML model is applied to the 375 uranium-bearing DSSAs, 190 of them are predicted to be the DSSAs never known before. 20 of these alloys were randomly synthesized and characterized. Our predictions are in-line with experiments with 3 inconsistent cases, suggesting that our strategy offers a fast and accurate way to predict novel multi-component alloys with high DSSAs formation ability. These findings shed considerable light on the mapping between the material descriptors and DSSAs formation ability.
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