Preparation of Paper-Based Fluorescent Sensors and Their Application for the Detection of Cu2+ in Water

Excessive copper (Cu2+) causes adverse effects on human health and the ecological environment. Traditional methods for detecting Cu2+ have drawbacks such as high detection costs, complex operating conditions, and being time consuming. Therefore, there is an urgent need to develop simple detection methods to better meet specific health and environment quality needs. In this work, a paper-based fluorescence sensor was prepared (herein referred to as the as-prepared method) by immersing filter paper in aqueous polyethyleneimine (PEI) solution, and its potential use in Cu2+ detection was investigated. The results showed that the as-prepared paper samples, with fluorescence properties obtained by aggregation-induced luminescence of PEI, have selective recognition of Cu2+ based on the internal filtration effect, and the lowest detection limit is 0.03 μM. In addition, the relative error of this method is in the range of 1.80~2.23%, which is relatively comparable to the national standard method (0.63~630 μM), demonstrating high accuracy. Therefore, paper-based sensors with a simple preparation method have potential applications in the detection of Cu2+ in water.

Verbascoside extracted from Clerodendrum inerme: A natural monomer for the fabrication of a sensitive electrochemical Cu(II) sensor

Verbascoside is isolated from the whole plants of the Verbenaceae family and demonstrates significant levels of bioactivity. In this work, we report on the isolation of verbascoside, a phenolic glycoside, from the stems of Clerodendrum inerme collected in Vietnam and verify its structure by comparing its spectroscopic data with those reported in the literature. Verbascoside is then applied as a monomer for the electrochemical deposition of a layer of polyverbascoside onto glassy carbon electrodes toward Cu2+ sensing. Electrochemical results demonstrate that the polyverbascoside-modified glassy carbon electrode is highly selective for Cu2+ ions compared to other evaluated ions including Ni2+ and Co2+. The developed sensor can detect Cu2+ in a concentration range from 0 to 175 μM with a sensitivity of 0.372 µA µM−1 and a limit of detection of 50 nM Cu2+ ions.

High-Performance Flexible Electrochemical Heavy Metal Sensor Based on Layer-by-Layer Assembly of Ti3C2Tx/MWNTs Nanocomposites for Noninvasive Detection of Copper and Zinc Ions in Human Biofluids

A flexible electrochemical heavy metal sensor based on a gold (Au) electrode modified with layer-by-layer (LBL) assembly of titanium carbide (Ti₃C₂T_x) and multiwalled carbon nanotubes (MWNTs) nanocomposites was successfully fabricated for the detection of copper (Cu) and zinc (Zn) ions. An LBL drop-coating process was adopted to modify the surface of Au electrodes with Ti₃C₂T_x/MWNTs treated via ultrasonication to fabricate this novel nanocomposite electrode. In addition, an in situ simultaneous deposition of "green metal" antimony (Sb) and target analytes was performed to improve the detection performance further. The electrochemical measurement was realized using square wave anodic stripping voltammetry (SWASV). Moreover, the fabricated sensor exhibited excellent detection performance under the optimal experimental conditions. The detection limits for Cu and Zn are as low as 0.1 and 1.5 ppb, respectively. Furthermore, Cu and Zn ions were successfully detected in biofluids, that is, urine and sweat, in a wide range of concentration (urine Cu: 10-500 ppb; urine Zn: 200-600 ppb; sweat Cu: 300-1500 ppb; and sweat Zn: 500-1500 ppb). The fabricated flexible sensor also possesses other advantages of ultra-repeatability and excellent stability. Thus, these advantages provide a great possibility for the noninvasive smart monitoring of heavy metals in the future.

Sterically stabilized fluorescent silver nanoconjugates for optical discrimination of Cu(ii) in real samples and in vitro bioimaging of the Cu(ii) scavenging process in human lymphocytes by atomic force microscopy

The nanosensor (Cf-AgNPs) with low cytotoxicity, hemocompatibility and good selectivity for detection of Cu(ii) in real samples.

Development of an electrochemical metal-ion biosensor using self-assembled peptide nanofibrils

This article describes the combination of self-assembled peptide nanofibrils with metal electrodes for the development of an electrochemical metal-ion biosensor. The biological nanofibrils were immobilized on gold electrodes and used as biorecognition elements for the complexation with copper ions. These nanofibrils were obtained under aqueous conditions, at room temperature and outside the clean room. The functionalized gold electrode was evaluated by cyclic voltammetry, impedance spectroscopy, energy dispersive X-ray and atomic force microscopy. The obtained results displayed a layer of nanofibrils able to complex with copper ions in solution. The response of the obtained biosensor was linear up to 50 μM copper and presented a sensitivity of 0.68 μA cm⁻² μM⁻¹. Moreover, the fabricated sensor could be regenerated to a copper-free state allowing its reutilization.