# Influence of Tripolyphosphate on Electronic Conductivity and Photothermal Relaxation Dynamics in Ti3C2T x MXene

## TL;DR

This paper explores how tripolyphosphate affects the conductivity and heat response of Ti3C2Tx MXene films, showing it can control thermal relaxation without harming conductivity.

## Contribution

The study is the first to investigate how polyphosphate edge-capping affects the electronic and photothermal properties of MXene films.

## Key findings

- TPP addition does not significantly alter charge transport or carrier localization in Ti3C2Tx MXene films.
- Higher TPP concentrations slow thermal relaxation, suggesting hindered phonon transport and heat dissipation.
- Photothermal heating causes transient conductivity suppression followed by slow recovery over picoseconds.

## Abstract

Ti3C2T
x
MXene,
the most extensively studied member of the MXene family, combines
metallic conductivity, strong light absorption, and exceptional photothermal
efficiency, enabling applications ranging from optoelectronics to
thermal management and biomedical systems. However, its practical
use has been challenged by limited environmental stability. While
polyphosphate edge-capping has previously been shown to effectively
suppress oxidation and degradation in aqueous suspensions, its influence
on the intrinsic electronic properties and photothermal behavior of
MXene films has remained unexplored. Here, we investigate the impact
of sodium tripolyphosphate (TPP) introduced during aqueous processing
on the electrical transport and photothermal dynamics of Ti3C2T
x
films. Using terahertz
time-domain spectroscopy (THz-TDS) and four-point probe measurements,
we find that TPP addition does not significantly alter charge transport
or carrier localization, indicating that the electronic structure
of the films is preserved. Optical pump–THz probe spectroscopy
reveals that, upon photoexcitation, all samples exhibit the characteristic
transient suppression of conductivity associated with photothermal
heating, followed by a slow recovery over hundreds of picoseconds.
At higher TPP concentrations, the thermal relaxation is noticeably
slower, suggesting that TPP residues at flake edges and interflake
interfaces hinder phonon transport and heat dissipation. These findings
demonstrate that addition of polyphosphate, while maintaining the
excellent conductivity of Ti3C2T
x
, can be used to control photothermal relaxation
behavior and the thermal response of MXene-based functional materials.