# 2,2′-Biquinoline Modified Expanded Graphite Electrode for the Detection of Cuprous Ions in Electrolytic Copper Foil Electrolyte

## TL;DR

A new sensor detects cuprous ions in copper foil electrolyte with high accuracy and selectivity, improving copper foil quality.

## Contribution

A novel electrochemical sensor using BIQ-modified expanded graphite enables selective and sensitive detection of Cu+ in complex electrolytes.

## Key findings

- The sensor achieves a Cu+ recovery rate of 101.00–105.00% even with 10,000-fold excess Cu2+.
- The detection limit is 8 μg/L with a linear response (R² = 0.9989).
- The sensor has an RSD of less than 2%, indicating high precision.

## Abstract

What are the main findings?
A 2,2′-biquinoline (BIQ)-modified expanded graphite (EG) electrode electrochemical sensor was fabricated for the selective determination of Cu+ in copper sulfate electrolyte, and differential pulse voltammetry (DPV) was adopted for the electrochemical detection of Cu+ with high sensitivity, excellent selectivity, a low detection limit and a rapid response.BIQ’s specific coordination with Cu+ enables the modified sensor to realize rapid and effective quantification of Cu+; the BIQ-modified EG electrode exhibits outstanding selectivity for Cu+, with a Cu+ recovery rate of 101.00–105.00% even in the presence of 10,000-fold excess Cu2+ and a relative standard deviation (RSD) of less than 2%.

A 2,2′-biquinoline (BIQ)-modified expanded graphite (EG) electrode electrochemical sensor was fabricated for the selective determination of Cu+ in copper sulfate electrolyte, and differential pulse voltammetry (DPV) was adopted for the electrochemical detection of Cu+ with high sensitivity, excellent selectivity, a low detection limit and a rapid response.

BIQ’s specific coordination with Cu+ enables the modified sensor to realize rapid and effective quantification of Cu+; the BIQ-modified EG electrode exhibits outstanding selectivity for Cu+, with a Cu+ recovery rate of 101.00–105.00% even in the presence of 10,000-fold excess Cu2+ and a relative standard deviation (RSD) of less than 2%.

What are the implications of the main findings?
The developed BIQ-modified EG electrode sensor provides a novel, accurate and efficient analytical method for the selective detection of trace Cu+ in the complex electrolytic copper foil electrolyte system with high-concentration Cu2+ interference.Precise and reliable quantification of Cu+ in copper sulfate electrolyte via this sensor can support the rational regulation of Cu+ content in the electrolyte, thereby facilitating the optimization of the microstructure and performance of electrolytic copper foil.

The developed BIQ-modified EG electrode sensor provides a novel, accurate and efficient analytical method for the selective detection of trace Cu+ in the complex electrolytic copper foil electrolyte system with high-concentration Cu2+ interference.

Precise and reliable quantification of Cu+ in copper sulfate electrolyte via this sensor can support the rational regulation of Cu+ content in the electrolyte, thereby facilitating the optimization of the microstructure and performance of electrolytic copper foil.

The coexistence of Cu in copper sulfate electrolyte significantly affects the microstructure and performance of the copper foil. So far, there has been little quantitative analysis of Cu+ in the electrolyte during the copper foil production process. This paper fabricated a 2,2′-Biquinoline (BIQ) modified expanded graphite (EG) electrode electrochemical sensor for the selective determination of Cu+. EG, with its large specific surface area and excellent adsorption and electrochemical properties, significantly enhances analytical sensitivity. Additionally, BIQ’s specific coordination with Cu+ improves the sensor’s rapid and effective quantification of Cu+ in the electrolytic copper foil electrolyte. The linear equation of this sensor is I = 0.03769 + 0.29997 × c (R2 = 0.9989), with a detection limit of 8 μg/L (S/N = 3). The BIQ-modified EG electrode has good selectivity for Cu+, with a recovery rate for cuprous ions of 101.00% to 105.00% under the coexistence of 10,000 times Cu2+, and an RSD of less than 2%. This sensor’s efficient, sensitive, and selective detection of Cu+ can be an effective method to improve the quality of electrolytic copper foil products.