Surface engineering of ultrathin MXene nanosheets vial-ascorbic acid treatment under ambient conditions makes them more appealing for practical applications.
MXenes have attracted
great attention as promising substrates for
surface-enhanced Raman scattering (SERS) applications. However, the
underlying SERS mechanism has not been a focus of any investigation.
Herein, we report the first systematic experimental study on the SERS
activity of titanium carbide (Ti3C2TX) nanosheets with thicknesses ranging from 5 to 120 nm, using methylene
blue (MB) as a probe molecule. The experimental and mathematical modeling
results show that the Raman enhancement factor (EF) increases monotonically
with the increasing thickness of Ti3C2TX nanosheets; however, it falls drastically around a sheet
thickness of 0.8 and 1.0 μm under 532 and 633 nm laser excitations,
respectively. The Raman EF reaches a maximum value around a thickness
of 2.0 μm, suggesting that a maximum EF can be achieved with
a 2.0 μm-thick Ti3C2TX film
substrate. The thickness dependence of the Raman enhancement can be
accounted for by the adsorption and intercalation of MB molecules
into the interlayer spacing of Ti3C2TX. Furthermore, by combining experimental observations and numerical
calculation, we confirm that the charge-transfer mechanism is dominantly
responsible for Raman enhancement on Ti3C2TX. Additionally, we report an observation of resonance coupling
of charge transfer and molecular transition as a contributing factor
to the higher EF obtained with a 633 nm laser excitation. Taken together,
these findings have significant implications for cost and performance
optimization in designing MXene-based SERS substrates for next-generation
chemical and biological sensing platforms.
Electrospun polyacrylonitrle (PAN) nanofibers integrated with different loadings of the photosensitizer rose bengal (RB) were synthesized for photodynamic inactivation of bacteria. Our results suggest that the ionic strength in the...
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