Defect engineering of 2D materials offers enormous opportunities to tune material properties. This presentation will show two types of substitutional defects in 2D materials, self-limited along the out-of-plane and in-plane directions, respectively. The first type is atomic substitution: a nitrogen atom substituting a chalcogen atom in 2D transition metal dichalcogenides (TMDs), which yields new distinct photoluminescence features well separated from the free excitons of 2D TMDs. The second type is layer substitution: an entire layer of chalcogen atoms in 2D TMD substituted by another type of chalcogen atoms, namely, Janus TMDs. Due to the intrinsic vertical dipole, Janus TMDs form unconventional interaction with adjacent materials including other 2D material layers. These unconventional interactions were probed by optical signature changes such as ultra-low frequency Raman modes and photoluminescence yield change. Engineering such substitutional defects in 2D materials promises potential for optoelectronic devices and quantum information platforms.
Bioimaging techniques with molecular specific information will provide important insights into diagnosis, treatment, and understanding of disease pathology. To obtain molecular information, it is important to have high multiplexity and high specificity hyperspectral imaging, together with analysis techniques to interpret spectral signatures. This talk introduces pioneering discoveries and novel approaches to achieve these goals. I will introduce a new bioimaging mechanism, Raman imaging enhanced through 2D materials, an enhancement effect of molecular Raman fingerprints on the atomically-flat 2D material surfaces. It offers a new paradigm of biochemical sensing with high specificity, high multiplexity, and low noise. The selection rule for the 2D material substrates has been revealed, which is critical for device design. Hyperspectral imaging examples for brain tissues with Alzheimer’s disease will be discussed, where interpretable machine learning was further applied for new knowledge discovery. The works presented offer important guidelines to design high-performance biosensing and imaging devices, and are significant in fundamental material science and quantum science.
Substitutional defects in 2D materials present unique opportunities for optoelectronic and quantum information platforms. This paper will introduce two types of substitutional defects. The first type is atomic substitution: a nitrogen atom substituting a chalcogen atom in 2D transition metal dichalcogenides (TMDs), which yields new photoluminescence features [1]. The second type is layer substitution: an entire layer of chalcogen atoms in 2D TMD substituted by another type of chalcogen atoms, namely, Janus TMDs. Janus TMDs form unconventional interaction with adjacent materials [2,3].
[1] ACS Nano, 16(5), 7428 (2022).
[2] JACS, 142(41), 17499 (2020).
[3] ACS Nano, 15(9), 14394 (2021).
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