Hui Fang

California University of Pennsylvania

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Hai‐Lung Dai

Temple University

Zahra Fakhraai

University of Pennsylvania

Danielle L. Kuhn

United States Army Combat Capabilities Development Command

Michael J. Wilhelm

Temple University

Brendan G. DeLacy

U.S. Army Combat Capabilities Development Command Chemical Biological Center

Anupma Thakur

Purdue University West Lafayette

Babak Anasori

Purdue University West Lafayette

Zachary Zander

U.S. Army Combat Capabilities Development Command Chemical Biological Center

Jianqiang Ma

Temple University

Wei Gan

Harbin Institute of Technology

Cooperative Institutions

Chinese Academy of Sciences

Dalian University of Technology

Zhejiang University

University of Pennsylvania

University of Chinese Academy of Sciences

Dalian University

South China University of Technology

Central South University

Purdue University West Lafayette

Indiana University – Purdue University Indianapolis

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Signatures of Band-like Optical and Charge Transport in Ti3C2Tx MXene Flakes

Hui Fang Zhenyao Fang Anupma Thakur Babak Anasori Andrew M. Rappe

MXenes are promising materials for various electronic and optoelectronic applications. However, the understanding of MXene optical properties and charge transport mechanisms remains rather incomplete. Here, we demonstrate that the photon absorption in the near-IR region (≈1.5 eV) in titanium carbide Ti3C2Tx MXenes is due to the inter-band transition of the oxygen terminations, rather than a localized surface plasmon resonance. This peak shifts to higher energy as the film thickness is increased and the trapped water is removed. We provide a unifying picture of charge transport in monoflake and multiflake MXenes. We show that in both monoflake and out-of-plane direction of multiflake Ti3C2Tx MXenes, charge transport is predominantly band-like. In multiflake MXenes, however, in-plane charge transport is governed by thermally activated interflake hopping, which is facilitated by the presence of trapped water. We also demonstrate that surface plasmon propagation on MXene surfaces can strongly depend on the termination state and is hindered by strong loss in experimentally prepared mixed terminated MXenes. Our results reconcile previous debates and shed light on both optical properties and charge transport mechanisms in Ti3C2Tx MXenes, opening avenues for further exploration in electronic and optoelectronic applications.

MXenes

10.26434/chemrxiv-2024-rpf17

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Polymer-Based Device Fabrication and Applications Using Direct Laser Writing Technology

Polymers (2019)

Zhenlin Wu Ya-Nan Qi Xiaojie Yin Xin Yang Chang‐Ming Chen

Polymer materials exhibit unique properties in the fabrication of optical waveguide devices, electromagnetic devices, and bio-devices. Direct laser writing (DLW) technology is widely used for micro-structure fabrication due to its high processing precision, low cost, and no need for mask exposure. This paper reviews the latest research progresses of polymer-based micro/nano-devices fabricated using the DLW technique as well as their applications. In order to realize various device structures and functions, different manufacture parameters of DLW systems are adopted, which are also investigated in this work. The flexible use of the DLW process in various polymer-based microstructures, including optical, electronic, magnetic, and biomedical devices are reviewed together with their applications. In addition, polymer materials which are developed with unique properties for the use of DLW technology are also discussed.

10.3390/polym11030553

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Citations (48)

Excited State Dynamics and Transport of Self-Trapped Excitons in Bi-Doped Cs₂Na_0.4Ag_0.6In_(1–y)Bi_yCl₆ Double Perovskites

The Journal of Physical Chemistry Letters (2024)

Hui Fang Yanfeng Yin Zeng Chen Wenjuan Zhu Yang Yang

Lead-free double perovskites (DPs) have become notable in white light emission applications due to the self-trapped exciton (STE) formation in the excited state. However, the mechanism understanding of the excited state dynamics and transport of STE remains ambiguous. Here, we demonstrate a new STE (Bi-STE) forming in tiny Bi-doped Cs

10.1021/acs.jpclett.4c01232

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Rhodamine B doped PMMA—A potential material in laser cooling of solid

Gongneng cailiao yu qijian xuebao (2004)

Hui Fang

Through the comparative study on the solid solutions of the Rhodmine B in PMMA, theyare found to be effective to produce fluorescence. Spectrum analysis by fluorescence spectrophotometerreveals that the materials appear to produce anti-stokes fluorescence peak with excitation sources atwavelengths longer than those corresponding to the peak of the luminescent bend. This means fluores-cence photons have redundant energy than pumping photons. That is to say that the Rhodamine B-doped PMMAs are potential material for laser cooling. One of the materials we proposed is solid solu-tion of Rhodamine B in PMMA. It is excited at 630nm and produced fluorescence peak about 595nm, and has energy difference of 0.11eV.

Rhodamine

Rhodamine B

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Ag nanoplatelets as efficient photosensitizers for TiO2 nanorods

The Journal of Chemical Physics (2021)

Hui Fang Michael J. Wilhelm Jianqiang Ma Yi Rao Danielle L. Kuhn

The lifetime for injecting hot electrons generated in Ag nanoplatelets to nearby TiO2 nanorods was measured with ultrafast transient IR absorption to be 13.1 ± 1.5 fs, which is comparable to values previously reported for much smaller spherical Ag nanoparticles. Although it was shown that the injection rate decreases as the particle size increases, this observation can be explained by the facts that (1) the platelet has a much larger surface to bulk ratio and (2) the platelet affords a much larger surface area for direct contact with the semiconductor. These two factors facilitate strong Ag-TiO2 coupling (as indicated by the observed broadened surface plasmon resonance band of Ag) and can explain why Ag nanoplatelets have been found to be more efficient than much smaller Ag nanoparticles as photosensitizers for photocatalytic functions. The fast injection rate, together with a stronger optical absorption in comparison with Au and dye molecules, make Ag nanoplatelets a preferred photosensitizer for wide bandgap semiconductors.

Nanorod

10.1063/5.0074322

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Evidence of the adsorption of hydroxide ion at hexadecane/water interface from second harmonic generation study

RSC Advances (2015)

Hui Fang Wei Wu Yajun Sang Shunli Chen Xuefeng Zhu

The effect of hydroxide ion, impurities and oleic acid on molecular structure at hexadecane/water interface was studied with second harmonic generation.

Hexadecane

Harmonic

Interface (matter)

10.1039/c4ra15401k

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Citations (60)

THERMAL STABILITY OF NANOSTRUCTURED γ-Fe_2O_3 MAGNETIC POWDER

Cailiao yanjiu xuebao (1997)

Xisheng Ye Jian Sha Hui Fang Jiao Zheng kuan Peng Zifei Zhang Lide

Thermal Stability

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Step‐by‐Step Guide for Synthesis and Delamination of Ti₃C₂T_x MXene (Small Methods 8/2023)

Small Methods (2023)

Anupma Thakur Nithin Chandran Karis Davidson Annabelle Bedford Hui Fang

Inside Back Cover In article number 2300030, Anasori and co-workers present a detailed guide for the optimized synthesis of titanium carbide (Ti3C2Tx) MXene and investigate the effects of selective etching and delamination conditions. The resulting Ti3C2Tx MXene film exhibits high electrical conductivity (≈21,000 S/cm) and a synthesis yield of 38 %. This study also provides a detailed step-by-step recipe for high-quality Ti3C2Tx MXene synthesis.

Titanium carbide

Delamination

10.1002/smtd.202370045

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Why Ti3C2Tx MXenes Are Conductive but Not Plasmonic in the Optical Domain

Hui Fang Zhenyao Fang Anupma Thakur Vahid Rad Nithin Chandran

MXenes have shown great potential in electronic and optoelectronic applications. However, optical properties of these highly conductive two-dimentional materials are not fully understood. The near-infrared (IR) optical peak (∼1.5 eV) in Ti3C2Tx with mixed terminations (T: O, OH, F, Cl) has sparked debates, attributing the peak to a localized surface plasmon resonance (LSPR) or an inter-band transition (IBT). Here, density functional theory calculations conclusively assign the peak to an IBT that exists only in Ti3C2O2. Both experiments and calculations corroborate that this peak is absent in Ti3C2Cl2. Moreover, calculations predict SPR in the mid-IR (∼0.5 eV, outside optical domain) for Ti3C2O2, but not for Ti3C2Cl2. Our results reconcile conflicting interpretations of the debate, allowing for optimized use of Ti3C2Tx MXenes, by leveraging their IBT optical signature, which is size-independent and distinct from the size-dependent plasmonic effect.

MXenes

Optical phenomena

10.26434/chemrxiv-2024-rpf17-v2

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Diazonium-Functionalized Silicon Hybrid Photoelectrodes: Film Thickness and Composition Effects on Photoelectrochemical Behavior

Langmuir (2024)

Taylor S. Teitsworth Hui Fang Alexis K. Harvey Andre D. Orr Carrie L. Donley

Aryl diazonium electrografting is a powerful method for imparting molecular functionality onto various substrates by forming a stable carbon-surface covalent bond. While the high reactivity of the aryl radical intermediate makes this method fast and reliable, it can also lead to the formation of an insulating and disordered multilayer film. These thick films affect electrochemical performance, especially for semiconductor substrates used in photoelectrochemical applications. We studied the effects of film thickness and composition by electrografting in situ-generated aminobenzene diazonium salts onto both n-type and p-type silicon electrodes at fixed potentials. Next, we attached ferrocene to the amine-terminated films and probed their (photo)electrochemical behavior. Cyclic voltammetry measurements showed decreased electrochemical reversibility with increasing diazonium film thickness; this reversibility was restored when ferrocene was incorporated throughout the film with a layer-by-layer deposition process. Finally, we compared the behavior of dark p-type electrodes to n-type photoelectrodes and observed differences in the electrochemical reversibility that we attribute to the change in potential drop across the two interfaces.

Surface Modification

Reactivity

Diazonium Compounds

10.1021/acs.langmuir.4c01787

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