Recent Submissions

  • Plasmon-Enhanced Solar-Driven Hydrogen Evolution Using Titanium Nitride Metasurface Broadband Absorbers

    Yu, Meng-Ju; Chang, Chih-Li; Lan, Hao-Yu; Chiao, Zong-Yi; Chen, Yu-Chia; Howard Lee, Ho Wai; Chang, Yia-Chung; Chang, Shu-Wei; Tanaka, Takuo; Tung, Vincent; Chou, Ho-Hsiu; Lu, Yu-Jung (ACS Photonics, American Chemical Society (ACS), 2021-10-14) [Article]
    Broadband perfect absorbers in the visible region have attracted considerable attention in many fields, especially in solar thermophotovoltaic and energy harvesting systems. However, developing light absorbers with high absorptivity, thermal stability, and a broad bandwidth remains a great challenge. Here, we theoretically and experimentally demonstrate that a titanium nitride metasurface absorber exhibits broadband absorption with an average absorption of more than 92% over a wavelength range of 400 to 750 nm. The increase in absorption is attributed to the localized surface plasmon resonance (LSPR). We demonstrate the plasmon-enhanced visible-light-driven hydrogen production from water using a polymer photocatalyst integrated with a TiN metasurface absorber. A 300% increase in the hydrogen evolution rate was observed due to the LSPR that enhances the rates of light absorption, carrier separation, and hot-carrier transfer in polymer photocatalyst. These results enable a new approach to prepare high-efficiency solar energy harvesting systems.
  • Chemical Design Rules for Non-Fullerene Acceptors in Organic Solar Cells

    Markina, Anastasia; Lin, Kun-Han; Liu, Wenlan; Poelking, Carl; Firdaus, Yuliar; Villalva, Diego Rosas; Khan, Jafar Iqbal; Paleti, Sri Harish Kumar; Harrison, George T.; Gorenflot, Julien; Zhang, Weimin; De Wolf, Stefaan; McCulloch, Iain; Anthopoulos, Thomas D.; Baran, Derya; Laquai, Frédéric; Andrienko, Denis (Advanced Energy Materials, Wiley, 2021-10-08) [Article]
    Efficiencies of organic solar cells have practically doubled since the development of non-fullerene acceptors (NFAs). However, generic chemical design rules for donor-NFA combinations are still needed. Such rules are proposed by analyzing inhomogeneous electrostatic fields at the donor–acceptor interface. It is shown that an acceptor–donor–acceptor molecular architecture, and molecular alignment parallel to the interface, results in energy level bending that destabilizes the charge transfer state, thus promoting its dissociation into free charges. By analyzing a series of PCE10:NFA solar cells, with NFAs including Y6, IEICO, and ITIC, as well as their halogenated derivatives, it is suggested that the molecular quadrupole moment of ≈75 Debye Å balances the losses in the open circuit voltage and gains in charge generation efficiency.
  • Lignin Derived Porous Carbons: Synthesis Methods and Supercapacitor Applications

    Zhang, Wenli; Yin, Jian; Wang, Caiwei; Zhao, Lei; Jian, Wenbin; Lu, Ke; Lin, Haibo; Qiu, Xueqing; Alshareef, Husam N. (Small Methods, Wiley, 2021-10-07) [Article]
    Lignin, one of the renewable constituents in natural plant biomasses, holds great potential as a sustainable source of functional carbon materials. Tremendous research efforts have been made on lignin-derived carbon electrodes for rechargeable batteries. However, lignin is considered as one of the most promising carbon precursors for the development of high-performance, low-cost porous carbon electrode materials for supercapacitor applications. Yet, these efforts have not been reviewed in detail in the current literature. This review, therefore, offers a basis for the utilization of lignin as a pivotal precursor for the synthesis of porous carbons for use in supercapacitor electrode applications. Lignin chemistry, the synthesis process of lignin-derived porous carbons, and future directions for developing better porous carbon electrode materials from lignin are systematically reviewed. Technological hurdles and approaches that should be prioritized in future research are presented.
  • Uphill and downhill charge generation from charge transfer to charge separated states in organic solar cells

    Alam, Shahidul; Nádaždy, Vojtech; Váry, Tomáš; Friebe, Christian; Meitzner, Rico; Ahner, Johannes; Anand, Aman; Karuthedath, Safakath; De Castro, Catherine S. P.; Göhler, Clemens; Dietz, Stefanie; Cann, Jonathan; Kästner, Christian; Konkin, Alexander; Beenken, Wichard; Anton, Arthur Markus; Ulbricht, Christoph; Sperlich, Andreas; Hager, Martin D.; Ritter, Uwe; Kremer, Friedrich; Brüggemann, Oliver; Schubert, Ulrich S.; Egbe, Daniel A. M.; Welch, Gregory C.; Dyakonov, Vladimir; Deibel, Carsten; Laquai, Frédéric; Hoppe, Harald (Journal of Materials Chemistry C, Royal Society of Chemistry (RSC), 2021-10-06) [Article]
    It is common knowledge that molecular energy level offsets of a type II heterojunction formed at the donor–acceptor interface are considered to be the driving force for photoinduced charge transfer in organic solar cells. Usually, these offsets – present between molecular energy levels of the donor and acceptor – are obtained via cyclic voltammetry (CV) measurements of organic semiconductors cast in a film or dissolved in solution. Simply transferring such determined energy levels from solution or film of single materials to blend films may be obviously limited and not be possible in full generality. Herein, we report various cases of material combinations in which novel non-fullerene acceptors did not yield successful charge transfer, although energy levels obtained by CV on constituting single materials indicate a type II heterojunction. Whilst the integer charge transfer (ICT) model provides one explanation for a relative rise of molecular energy levels of acceptors, further details and other cases have not been studied so far in great detail. By applying energy-resolved electrochemical impedance spectroscopy (ER-EIS) on several donor–acceptor combinations, a Fano-like resonance feature associated with a distinctive molecular energy level of the acceptor as well as various relative molecular energy level shifts of different kinds could be observed. By analyzing ER-EIS and absorption spectra, not only the exciton binding energy within single materials could be determined, but also the commonly unknown binding energy of the CT state with regard to the joint density of states (jDOS) of the effective semiconductor. The latter is defined by transitions between the highest occupied molecular orbitals (HOMO) of the donor and the lowest unoccupied molecular orbitals (LUMO) of the acceptor. Using this technique among others, we identified cases in which charge generation may occur either via uphill or by downhill processes between the charge transfer exciton and the electronic gap of the effective semiconductor. Exceptionally high CT-exciton binding energies and thus low charge generation yields were obtained for a case in which the donor and acceptor yielded a too intimate blend morphology, indicating π–π stacking as a potential cause for unfavorable molecular energy level alignment.
  • Emissive Charge-Transfer States at Hybrid Inorganic/Organic Heterojunctions Enable Low Non-Radiative Recombination and High-Performance Photodetectors.

    Eisner, Flurin D.; Foot, Georgie; Yan, Jun; Azzouzi, Mohammed; Georgiadou, Dimitra G; Sit, Wai Yu; Firdaus, Yuliar; Zhang, Guichuan; Lin, Yen-Hung; Yip, Hin-Lap; Anthopoulos, Thomas D.; Nelson, Jenny (Advanced materials (Deerfield Beach, Fla.), Wiley, 2021-10-06) [Article]
    Hybrid devices based on a heterojunction between inorganic and organic semiconductors have offered a means to combine the advantages of both classes of materials in optoelectronic devices, but, in practice, the performance of such devices has often been disappointing. Here, it is demonstrated that charge generation in hybrid inorganic–organic heterojunctions consisting of copper thiocyanate (CuSCN) and a variety of molecular acceptors (ITIC, IT-4F, Y6, PC70BM, C70, C60) proceeds via emissive charge-transfer (CT) states analogous to those found at all-organic heterojunctions. Importantly, contrary to what has been observed at previous organic–inorganic heterojunctions, the dissociation of the CT-exciton and subsequent charge separation is efficient, allowing the fabrication of planar photovoltaic devices with very low non-radiative voltage losses (0.21 ±  0.02 V). It is shown that such low non-radiative recombination enables the fabrication of simple and cost-effective near-IR (NIR) detectors with extremely low dark current (4 pA cm−2) and noise spectral density (3 fA Hz−1/2) at no external bias, leading to specific detectivities at NIR wavelengths of just under 1013 Jones, close to the performance of commercial silicon photodetectors. It is believed that this work demonstrates the possibility for hybrid heterojunctions to exploit the unique properties of both inorganic and organic semiconductors for high-performance opto-electronic devices.
  • Chemical Solution Deposition of Epitaxial Indium- and Aluminum-Doped Ga2O3 Thin Films on Sapphire with Tunable Bandgaps

    Tang, Xiao; Li, Kuang-Hui; Liao, Che-Hao; Taboada Vasquez, Jose Manuel; Wang, Chuanju; Xiao, Na; Li, Xiaohang (Journal of the European Ceramic Society, Elsevier BV, 2021-10-02) [Article]
    Compared to the vacuum-required deposition techniques, the chemical solution deposition (CSD) technique is superior in terms of low cost and ease of cation adjustment and upscaling. In this work, highly epitaxial indium- and aluminum-doped Ga2O3 thin films are deposited using a novel CSD technique. The 2θ, rocking curve, and φ-scan modes of x-ray diffraction (XRD) measurements and high-resolution transmission electron microscopy suggest that these thin films have a pure beta phase with good in- and out-of-plane crystallization qualities. The effect of incorporating indium and aluminum into the crystallization process is studied using high-temperature in situ XRD measurements. The results indicate that indium and aluminum doping can shift the crystallization of the thin films to lower and higher temperatures, respectively. Additionally, ultraviolet-visible spectroscopy measurements indicate that the bandgap of the sintered thin films can be tuned from 4.05 to 5.03 eV using a mixed precursor solution of In:Ga = 3:7 and Al:Ga = 3:7. The photodetectors based on the (InGa)2O3, pure Ga2O3, and (AlGa)2O3 samples exhibit the maximum photocurrents at 280, 255, and 230 nm, respectively. The results suggest that the described CSD technique is promising for producing high-quality bandgap tunable deep-ultraviolet photoelectrical and high-power devices.
  • Advances and Challenges in Tin Halide Perovskite Nanocrystals

    Chen, Jia-Kai; Zhang, Bin-Bin; Liu, Qi; Shirahata, Naoto; Mohammed, Omar F.; Bakr, Osman; Sun, Hong-Tao (ACS Materials Letters, American Chemical Society (ACS), 2021-10-01) [Article]
    A major application limit for lead halide perovskite nanocrystals (NCs) is the presence of the highly toxic lead element, raising critical concerns of environmental pollution and health problems. To address this issue, tin halide perovskite NCs have been pushed to the forefront of perovskite research owing to their eco-friendly merit and tantalizing photophysical properties. In this Review, we critically summarize and assess the latest advances in the synthesis approaches of tin halide perovskite NCs including the hot injection, ligand-assisted reprecipitation, and chemical vapor deposition. More specifically, we detail the state-of-the-art preliminary studies in modulating their photophysical properties and in enhancing the stability with a variety of strategies such as precursor engineering, ligand engineering, and alloyed structure construction. Finally, we highlight the remaining challenges that need to be overcome to attain tin halide perovskite NCs with clear structure–property relationships and comparable physical and chemical properties to their lead-based cousins.
  • Control of spin–charge conversion in van der Waals heterostructures

    Galceran, Regina; Tian, Bo; Li, Junzhu; Bonell, Frédéric; Jamet, Matthieu; Vergnaud, Céline; Marty, Alain; Garcia, Jose H.; Sierra, Juan F.; Costache, Marius V.; Roche, Stephan; Valenzuela, Sergio O.; Manchon, Aurélien; Zhang, Xixiang; Schwingenschlögl, Udo (APL Materials, AIP Publishing, 2021-10-01) [Article]
    The interconversion between spin and charge degrees of freedom offers incredible potential for spintronic devices, opening routes for spin injection, detection, and manipulation alternative to the use of ferromagnets. The understanding and control of such interconversion mechanisms, which rely on spin–orbit coupling, is therefore an exciting prospect. The emergence of van der Waals materials possessing large spin–orbit coupling (such as transition metal dichalcogenides or topological insulators) and/or recently discovered van der Waals layered ferromagnets further extends the possibility of spin-to-charge interconversion to ultrathin spintronic devices. Additionally, they offer abundant room for progress in discovering and analyzing novel spin–charge interconversion phenomena. Modifying the properties of van der Waals materials through proximity effects is an added degree of tunability also under exploration. This Perspective discusses the recent advances toward spin-to-charge interconversion in van der Waals materials. It highlights scientific developments which include techniques for large-scale growth, device physics, and theoretical aspects.
  • Single-Particle Spectroscopy as a Versatile Tool to Explore Lower-Dimensional Structures of Inorganic Perovskites

    Bose, Riya; Zhou, Xiaohe; Guo, Tianle; Yang, Haoze; Yin, Jun; Mishra, Aditya; Slinker, Jason D.; Bakr, Osman; Mohammed, Omar F.; Malko, Anton V. (ACS Energy Letters, American Chemical Society (ACS), 2021-09-27) [Article]
    The remarkable defect-tolerant nature of inorganic cesium halide perovskites, leading to near unity photoluminescence (PL) quantum yield and narrow emission line width across the entire visible spectrum, has provided a tantalizing platform for the development of a plethora of light-emitting applications. Recently, lower-dimensional (2D, 1D, and 0D) perovskites have attracted further attention due to their enhanced thermal, photo, and chemical stability as compared to their three-dimensional (3D) analogues. The combination of external size quantization and internal octahedral organization provides a unique opportunity to study and harness “multi-dimensional” electronic properties engineered on both atomic scale and nanoscale. However, crucial research to understand the elementary charge carrier dynamics in lower-dimensional perovskites lags far behind the enormous effort to incorporate them into optoelectronic devices. In this Perspective, we provide a review of recent developments that focus on studies of the dynamics of excitonic complexes in Cs-based perovskite nanocrystals using single-particle time-resolved PL spectroscopy and photon correlation measurements. Single-photon statistical studies not only offer an unprecedented level of detail to directly assess various recombination pathways, but also provide insights into specifics of the charge carriers' localization. We discuss the underlying physicochemical processes that govern PL emission and draw attention to a number of attributes within this class of the materials, especially lower-dimensional perovskites, that may indicate the common origin of the PL emission as well as provide a route map for the vast unexplored territories where single-particle spectroscopy can be a powerful tool to unravel crucial information.
  • Phosphatidylcholine-mediated regulation of growth kinetics for colloidal synthesis of cesium tin halide nanocrystals

    Wang, Lu-Ming; Chen, Jia-Kai; Zhang, Bin-Bin; Liu, Qi; Zhou, Yang; Shu, Jie; Wang, Zuoshan; Shirahata, Naoto; Song, Bo; Mohammed, Omar F.; Bakr, Osman; Sun, Hong-Tao (Nanoscale, Royal Society of Chemistry (RSC), 2021-09-27) [Article]
    Cesium tin halide (CsSnX3, where X is halogen) perovskite nanocrystals (NCs) are one of the most representative alternatives to their lead-based cousins. However, a fundamental understanding of how to regulate the growth kinetics of colloidal CsSnX3 NCs is still lacking and, specifically, the role of surfactants in affecting their growth kinetics remains incompletely understood. Here we report a general approach for colloidal synthesis of CsSnX3 perovskite NCs through a judicious combination of capping agents. We demonstrate that introducing a small amount of zwitterionic phosphatidylcholine in the reaction is of vital importance for regulating the growth kinetics of CsSnX3 NCs, which otherwise merely leads to the formation of large-sized powders. Based on a range of experimental characterization, we propose that the formation of intermediate complexes between zwitterionic phosphatidylcholine and the precursors and the steric hindrance effect of branched fatty acid side-chains of phosphatidylcholine can regulate the growth kinetics of CsSnX3, which enables us to obtain CsSnX3 NCs with emission quantum yields among the highest values ever reported. Our finding of using zwitterionic capping agents to regulate the growth kinetics may inspire more research on the synthesis of high-quality tin-based perovskite NCs that could speed up their practical applications in optoelectronic devices.
  • Accordion-Like Carbon with High Nitrogen Doping for Fast and Stable K Ion Storage

    Zhang, Wenli; Sun, Minglei; Yin, Jian; Lu, Ke; Schwingenschlögl, Udo; Qiu, Xueqing; Alshareef, Husam N. (Advanced Energy Materials, Wiley, 2021-09-24) [Article]
    Potassium ion battery (PIB) is a potential candidate for future large-scale energy storage. A key challenge is that the (de)potassiation stability of graphitic carbon anodes is hampered by the limited (002) interlayer spacing. Amorphous carbon with a hierarchical structure can buffer the volume change during repeated (de)potassiation and enable stable cycling. Herein, a direct pyrolysis approach is demonstrated to synthesize a highly nitrogen-doped (26.7 at.%) accordion-like carbon anode composed of thin carbon nanosheets and a turbostratic crystalline structure. The hierarchical structure of accordion-like carbon is endowed by a self-assembly process during pyrolysis carbonization. The hierarchical nitrogen-doped accordion structure enables a high reversible capacity of 346 mAh g−1 and superior cycling stability. This work constitutes a general synthesis methodology that can be used to prepare hierarchical carbon anodes for advanced PIBs.
  • Efficient and Spectrally Stable Blue Perovskite Light-Emitting Diodes Employing a Cationic π-Conjugated Polymer

    Yuan, Shuai; Cui, Lin-Song; Dai, Linjie; Liu, Yun; Liu, Qing-Wei; Sun, Yu-Qi; Auras, Florian; Anaya, Miguel; Zheng, Xiaopeng; Ruggeri, Edoardo; Yu, You-Jun; Qu, Yang-Kun; Abdi-Jalebi, Mojtaba; Bakr, Osman; Wang, Zhao-Kui; Stranks, Samuel D.; Greenham, Neil C.; Liao, Liang-Sheng; Friend, Richard H. (Advanced Materials, Wiley, 2021-09-24) [Article]
    Metal halide perovskite semiconductors have demonstrated remarkable potentials in solution-processed blue light-emitting diodes (LEDs). However, the unsatisfied efficiency and spectral stability responsible for trap-mediated non-radiative losses and halide phase segregation remain the primary unsolved challenges for blue perovskite LEDs. In this study, it is reported that a fluorene-based π-conjugated cationic polymer can be blended with the perovskite semiconductor to control film formation and optoelectronic properties. As a result, sky-blue and true-blue perovskite LEDs with Commission Internationale de l'Eclairage coordinates of (0.08, 0.22) and (0.12, 0.13) at the record external quantum efficiencies of 11.2% and 8.0% were achieved. In addition, the mixed halide perovskites with the conjugated cationic polymer exhibit excellent spectral stability under external bias. This result illustrates that π-conjugated cationic polymers have a great potential to realize efficient blue mixed-halide perovskite LEDs with stable electroluminescence.
  • Topological Aspects of Antiferromagnets

    Bonbien, V.; Zhuo, Fengjun; Salimath, Akshaykumar; Ly, Ousmane; About, Adel; Manchon, Aurelien (Journal of Physics D: Applied Physics, IOP Publishing, 2021-09-22) [Article]
    The long fascination antiferromagnetic materials have exerted on the scientific community over about a century has been entirely renewed recently with the discovery of several unexpected phenomena including various classes of anomalous spin and charge Hall effects and unconventional magnonic transport, but also homochiral magnetic entities such as skyrmions. With these breakthroughs, antiferromagnets standout as a rich playground for the investigation of novel topological behaviors, and as promising candidate materials for disruptive low-power microelectronic applications. Remarkably, the newly discovered phenomena are all related to the topology of the magnetic, electronic or magnonic ground state of the antiferromagnets. This review exposes how non-trivial topology emerges at different levels in antiferromagnets and explores the novel mechanisms that have been discovered recently. We also discuss how novel classes of quantum magnets could enrich the currently expanding field of antiferromagnetic spintronics and how spin transport can in turn favor a better understanding of exotic quantum excitations.
  • 3D Printing of Hydrogels for Stretchable Ionotronic Devices

    Ge, Gang; Wang, Qian; Zhang, Yi-Zhou; Alshareef, Husam N.; Dong, Xiaochen (Advanced Functional Materials, Wiley, 2021-09-21) [Article]
    In the booming development of flexible electronics represented by electronic skins, soft robots, and human–machine interfaces, 3D printing of hydrogels, an approach used by the biofabrication community, is drawing attention from researchers working on hydrogel-based stretchable ionotronic devices. Such devices can greatly benefit from the excellent patterning capability of 3D printing in three dimensions, as well as the free design complexity and easy upscale potential. Compared to the advanced stage of 3D bioprinting, 3D printing of hydrogel ionotronic devices is in its infancy due to the difficulty in balancing printability, ionic conductivity, shape fidelity, stretchability, and other functionalities. In this review, a guideline is provided on how to utilize the power of 3D printing in building high-performance hydrogel-based stretchable ionotronic devices mainly from a materials’ point of view, highlighting the systematic approach to balancing the printability, printing quality, and performance of printed devices. Various 3D printing methods for hydrogels are introduced, and then the ink design principles, balancing printing quality, printed functions, such as elastic conductivity, self-healing ability, and device (e.g., flexible sensors, shape-morphing actuators, soft robots, electroluminescent devices, and electrochemical biosensors) performances are discussed. In conclusion, perspectives on the future directions of this exciting field are presented.
  • Revealing the Side-Chain Dependent Ordering Transition of Highly-Crystalline Double-Cable Conjugated Polymers

    Feng, Guitao; Tan, Wenliang; Karuthedath, Safakath; Li, Cheng; Jiao, Xuechen; Liu, Amelia C. Y.; Venugopal, Hariprasad; Tang, Zheng; Ye, Long; Laquai, Frédéric; McNeill, Christopher R.; Li, Weiwei (Angewandte Chemie International Edition, Wiley, 2021-09-21) [Article]
    Highly-crystalline conjugated polymers are important for microstructure analysis and charge transport in organic electronics. In this work, we have developed a series of highly-crystalline double-cable conjugated polymers for application in single-component organic solar cells (SCOSCs). These polymers contain conjugated backbones as electron donor and pendant perylene bisimide units (PBIs) as electron acceptor. PBIs are connected to the backbone via alkyl units varying from hexyl (C6H12) to eicosyl (C20H40) as flexible linkers. The highly-crystalline nature of these materials allows us to systematically study the effect of the length of the alkyl linkers on the nanostructure and photovoltaic performance. In particular, we find that for double-cable polymers with short linkers, the PBIs tend to stack in a head-to-head fashion, resulting in large d-spacing (e.g. 64 Å for the polymer P12 with C12H24 linker) along the lamellar stacking direction. When the length of the linker groups is longer than a certain length, the PBIs instead adopt a more ordered packing likely via H-aggregation, resulting in short d-spacings (e.g. 50 Å for the polymer P16 with C16H32 linker). Evidence for this transition is provided by X-ray diffraction measurements along with cryo-transmission electron microscopy measurements, where different packing motifs of the PBI units are clearly imaged. The different packing facilitated by longer linker groups is associated with improved exciton separation and charge transport, resulting in enhanced efficiencies of SCOSCs based on the polymer P16. The findings in this work demonstrate that double-cable conjugated polymers can be an important family of highly-crystalline conjugated polymers. Furthermore, this work demonstrates how the precise molecular packing of the acceptor units influences the photovoltaic performance of SCOSCs.
  • Bottom-Up Synthesized All-Thermal-Catalyst Aerogels for Heat-Regenerative Air Filtration

    Ji, Xiang; Zhao, Jiayuan; Jung, Sung Mi; Hrdina, Amy I. H.; Wolf, Martin J.; Yang, Xiulin; Vaartstra, Geoffrey; Xie, Helen; Luo, Shao-Xiong Lennon; Lu, Ang-yu; Welsch, Roy E.; Wang, Evelyn N.; Li, Lain-Jong; Kong, Jing (Nano Letters, American Chemical Society (ACS), 2021-09-20) [Article]
    Airborne particular matter (PM) pollution is an increasing global issue and alternative sources of filter fibers are now an area of significant focus. Compared with relatively mature hazardous gas treatments, state of the art high-efficiency PM filters still lack thermal decomposition ability for organic PM pollutants, such as soot from coal-fired power plants and waste-combustion incinerators, resulting in frequent replacement, high cost, and second-hand pollution. In this manuscript, we propose a bottom-up synthesis method to make the first all-thermal-catalyst air filter (ATCAF). Self-assembled from ∼50 nm diameter TiO<sub>2</sub> fibers, ATCAF could not only capture the combustion-generated PM pollutants with >99.999% efficiency but also catalyze the complete decomposition of the as-captured hydrocarbon pollutants at high temperature. It has the potential of in situ eliminating the PM pollutants from burning of hydrocarbon materials leveraging the burning heat.
  • The DNA–carbon nanotube binding mode determines the efficiency of carbon nanotube-mediated DNA delivery to intact plants

    Ali, Zahir; Serag, Maged F.; Demirer, Gozde; Torre, Bruno; Di Fabrizio, Enzo M.; Landry, Markita; Habuchi, Satoshi; Mahfouz, Magdy M. (Cambridge University Press (CUP), 2021-09-20) [Preprint]
    Efficient delivery of DNA, RNA, and genome engineering machinery to plant cells will enable efforts to genetically modify plants for global food security, sustainable energy production, synthetic biology applications, and climate change resilience. For the delivery of functional genetic units into plant cells, charged nanoparticles, particularly carbon nanotubes (CNT), have attracted considerable interest. Although some success has been achieved using CNT-based approaches, the efficiency, batch reproducibility, and the limits of their applicability remain to be assessed. Here, we provide a mechanistic understanding of plasmid DNA-loaded CNTs based transfection of plant cells, and factors affecting the expression of the transformed plasmid. We show that transfection is inherently limited by the presence of the cell wall, Coulomb interactions between DNA and polymer coated CNT, and DNA size, whereas expression of the transformed plasmid is limited by relative gene-to-plasmid size and the intracellular accessibility of DNA. We further show that the formation of partially condensed DNA on the CNT surface is a prerequisite for successful transfection and expression. Furthermore, DNA does not detach completely from the CNT, so the accessibility of the transcription machinery to DNA is the key for transformation efficiency. This irreversible DNA plasmid binding and partial condensation limit the length of DNA that can be expressed, thus negatively affecting efficiency and reproducibility. Understanding the underlying mechanisms and limitations of CNT-mediated delivery of DNA through the plant cell wall is of considerable importance in guiding efforts to design nanomaterials for efficient transformation, trait engineering, and synthetic biology applications.
  • Epitaxial growth of beta-Ga2O3 (-201) thin film on four-fold symmetry CeO2 (001) substrate for heterogeneous integrations

    Tang, Xiao; Li, Kuang-Hui; Liao, Che-Hao; Zheng, Dongxing; Liu, Chen; Lin, Rongyu; Xiao, Na; Krishna, Shibin; Tauboada, Jose; Li, Xiaohang (JOURNAL OF MATERIALS CHEMISTRY C, Royal Society of Chemistry (RSC), 2021-09-20) [Article]
    β-Ga2O3 is a wide bandgap semiconductor material that is promising for many fields such as gas sensors, UV detectors, and high-power electronics. Until now, most epitaxial β-Ga2O3 thin films could only be realized on six-fold symmetric single crystal substrates including sapphire (0001), 3C-SiC (001), and native β-Ga2O3. In this report, we demonstrate the epitaxial growth of β-Ga2O3 (−201) thin films on non-six-fold symmetric substrates, i.e., the CeO2 (001) substrate. Different from the conventional six-fold symmetric sapphire substrates, the four-fold symmetric cubic phase CeO2 (001) induces the formation of two sets of hexagonal-like atom frameworks with a mutual rotation angle of 90° in the β-Ga2O3 (−201) plane. This is due to the small lattice mismatch between the β-Ga2O3 (−201) plane and the CeO2 (001) plane in two directions: CeO2 [100]//β-Ga2O3 [010] and CeO2 [010]//β-Ga2O3 [010]. Besides, the valence band offset (VBO) and the conduction band offset (CBO) at the β-Ga2O3/CeO2 heterojunction are examined using high-resolution X-ray photoelectron spectroscopy (HR-XPS) and are estimated to be 1.63 eV and 0.18 eV, respectively, suggesting a type-II heterostructure. The obtained epitaxial β-Ga2O3 thin films are fabricated into photodetectors (PDs), which show key photoelectrical characteristics that are similar to those of PDs using the conventional sapphire substrate. The results indicate the epitaxial β-Ga2O3 thin films on CeO2 have a high crystallization quality, and thus are capable of producing various essential devices. Moreover, the epitaxy between β-Ga2O3 (−201) and CeO2 (001) demonstrated in this work can pave the way for constructing heterostructures between β-Ga2O3 and other cubic-phase functional materials, such as p-type semiconductors, piezoelectric semiconductors, and superconductors.
  • Halide Perovskite-2D Material Optoelectronic Devices

    Liu, Zhixiong (2021-09-17) [Dissertation]
    Advisor: Alshareef, Husam N.
    Committee members: Schwingenschlögl, Udo; Mohammed, Omar F.; Quevedo-Lopez, Manuel
    Metal-halide perovskites have attracted intense research endeavors because of their excellent optical and electronic properties. Different kinds of electronic and optoelectronic devices have been fabricated using perovskites. A feasible approach to utilize these properties in real device applications with improved performance and new functionalities is by fabricating heterostructures with extraneous materials. We have developed mixed-dimensional heterostructure systems using three-dimensional (3D) metal-halide perovskites and different types of different two-dimensional (2D) materials, including semimetal graphene, semiconducting phosphorus-doped graphitic-C3N4 sheets (PCN-S), and plasmonic Nb2CTx MXenes. First, selective growth of single-crystalline MAPbBr3 platelets on monolayer graphene by chemical vapor deposition (CVD) is achieved to prepare the MAPbBr3/graphene heterostructures. P-type doping from MAPbBr3 is observed in the monolayer graphene with a decreased work function of 272 meV under illumination. The photoresponse of the fabricated phototransistor heterostructure verifies the enhanced p-type character in graphene. Such kind of charge transfer can be used to improve device performance. Then, bulk-heterojunctions made of MAPbI3-xClx and PCN-S are prepared in solution. The matched band diagram and the midgap states in PCN-S present a convenient and efficient approach to reduce the dark current and increase the photocurrent of the as-fabricated photodetectors. As a result, the on/off ratio increases from 103 to 105, and the detectivity is up to 1013 Jones with an order of magnitude enhancement compared to the perovskite-only device. Last, plasmonic Nb2CTx MXenes and MAPbI3 heterostructures are prepared for photodiodes to broaden the detection band to near-infrared (NIR) lights. The use of the perovskite layer expanded the operation of the diode to the visible range while suppressing the dark current of the NIR-absorbing Nb2CTx layer. The fabricated photodiode reveals a detectivity of 0.25 A/W with a linear dynamic range of 96 dB in the visible region. In the NIR region, the device demonstrates an increased on/off ratio from less than 2 to near 103 and much faster response times of less than 30 ms. The improved performance is attributed to the passivation of the MAPbI3/Nb2CTx interface.
  • Two-Dimensional TiO2/TiS2 Hybrid Nanosheet Anodes for High-Rate Sodium-Ion Batteries

    Bayhan, Zahra; Huang, Gang; Yin, Jian; Xu, Xiangming; Lei, Yongjiu; Liu, Zhixiong; Alshareef, Husam N. (ACS Applied Energy Materials, American Chemical Society (ACS), 2021-09-15) [Article]
    The sodium-ion battery (NIB) is promising for next-generation energy storage systems. One promising anode material is titanium dioxide (TiO2). However, the sluggish sodiation/desodiation kinetics of TiO2 hinders its application in NIBs. Herein, we converted TiO2 into a two-dimensional (2D) TiO2/TiS2 hybrid to improve its sodium storage capability. The 2D TiO2/TiS2 hybrid nanosheet electrode provides high kinetics and excellent cycling performance for sodium-ion storage. This work provides a promising strategy to develop 2D hybrid nanomaterials for high-performance sodium storage devices.

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