Copper Nanoclusters Anchored on Crumpled N-Doped MXene for Ultra-Sensitive Electrochemical Sensing

Abstract

Simultaneous detection of dopamine (DA) and uric acid (UA) is essential for diagnosing neurological and metabolic diseases but hindered by overlapping electrochemical signals. We present an ultrasensitive electrochemical sensor using copper nanoclusters anchored on nitrogen-doped crumpled Ti₃C₂T_x MXene (Cu-N/Ti₃C₂T_x). The engineered 3D crumpled architecture prevents MXene restacking, exposes active sites, and enhances ion transport, while Cu nanoclusters boost electrocatalytic activity via accelerated electron transfer. Structural analyses confirm uniform Cu dispersion (3.0 wt%), Ti-N bonding, and strain-induced wrinkles, synergistically improving conductivity. The sensor achieves exceptional sensitivity (1958.3 and 1152.7 μA·mM^-1·cm^-2 for DA/UA), ultralow detection limits (0.058 and 0.099 μM for DA/UA), rapid response (<1.5 s), and interference resistance (e.g., ascorbic acid). Differential pulse voltammetry enables independent linear detection ranges (DA: 2-60 μM; UA: 5-100 μM) in biofluids, with 94.4% stability retention over 7 days. The designed sensor exhibits excellent capabilities for DA and UA detection. This work provides a novel design strategy for developing high-performance electrochemical sensors.

Keywords: Cu nanoclusters; MXene; crumpled structure; dopamine; uric acid.

Figure 1

Schematic synthesis process and microstructure characterizations of Cu-N/Ti₃C₂T_x. (a) Schematic synthesis of Cu-N/Ti₃C₂T_x. (b) SEM image. (c) Atomic-resolution HAADF-STEM image (the red circles mark the Cu nanoclusters). (d) HAADF-STEM image and (e) EDS mapping images (Ti, purple; Cu, green; C, red; N, blue) of Cu-N/Ti₃C₂T_x.

Figure 2

XPS analysis results of Cu-N/Ti₃C₂T_x, N/Ti₃C₂T_x, and Cu-Ti₃C₂T_x. (a) XPS survey spectra of Cu-N/Ti₃C₂T_x, N/Ti₃C₂T_x, and Cu/Ti₃C₂T_x. (b) N 1s high-resolution XPS spectra. (c) C 1s high-resolution XPS spectra. (d) Ti 2p high-resolution XPS spectra. (e) Cu 2p high-resolution XPS spectra.

Figure 3

Electrochemical responses. CV curves of Cu-N/Ti₃C₂T_x, N/Ti₃C₂T_x, and Cu-Ti₃C₂T_x in 0.1 M KCl with (a) 5 mM [Fe(CN)₆]^3−/4−, and in PBS (pH = 7.4, 0.1 M) with (b) 0.5 mM DA, (c) 0.5 mM UA. (d) The Nyquist plots of EIS at Cu-N/Ti₃C₂T_x, N/Ti₃C₂T_x, and Cu-Ti₃C₂T_x in 0.1 M KCl with 5 mM [Fe(CN)₆]^3−/4− electrolyte.

Figure 4

Electrochemical sensing performance. (a) DPV curves for Cu-N/Ti₃C₂T_x at different concentrations of DA. (b) The linear relationship between the peak current responses and the DA concentration. (c) DPV curves for Cu-N/Ti₃C₂T_x at different concentrations of UA. (d) The linear relationship between the peak current responses and the UA concentration.

Figure 5

Response time, selectivity, repeatability, and stability of electrochemical sensing. Instantaneous response time of Cu-N/Ti₃C₂T_x to (a) DA and (b) UA. (c) DPV responses of Cu-N/Ti₃C₂T_x for DA, UA, and other interferences. (d) Influence of multiple interfering substances on the effects of simultaneous detection of 50 μM DA and UA. (e) Stability of Cu-N/Ti₃C₂T_x after 10 and 20 cycles of scanning in 0.1 mM DA and UA. (f) The oxidation peak current on the same Cu-N/Ti₃C₂T_x at 15 days of storage at room temperature.