Determination of formaldehyde based on the enhancement of the chemiluminescence produced by CdTe quantum dots and hydrogen peroxide

Refractive index and formaldehyde sensing with silver nanocubes

We report the synthesis of Ag nanocubes by using a sodium sulfide assisted solvothermal method. Small edge-length nanocubes (32 and 44 nm) were obtained at 145 and 155 °C reaction temperature in the synthesis process. The refractive index sensitivity of synthesized nanocubes was investigated with an aqueous solution of glucose. The refractive index sensitivity of 161 nm per RIU was found in the colloidal dispersion of nanocubes. On the LSPR chip made by immobilization of nanocubes on the (3-aminopropyl)trimethoxysilane modified glass coverslip, the obtained sensitivity was 116 nm per RIU. Detection of formaldehyde in water and milk samples was also performed with nanocubes of edge-length of 44 nm. Formaldehyde detection was performed by utilizing the interaction of the aryl amine of 4-aminothiophenol immobilized on the nanocubes and electrophilic carbon atom of the formaldehyde. In water and in diluted milk, the formaldehyde sensitivity of 0.62 and 0.29 nm μM⁻¹ was obtained, respectively.

A detailed description of refractive index and formaldehyde sensing with Ag nanocubes.

Rapid detection of trace formaldehyde in food based on surface-enhanced Raman scattering coupled with assembled purge trap

It has been remained a challenge to detect trace formaldehyde in complex samples, such as rice flour and duck blood products. In this study, a purge-trap device was designed and used for volatile target detection, which avoided interference adsorptions on enhanced particle surfaces during subsequent surface-enhanced Raman spectroscopy (SERS) analysis. The device produced a low detection limit for formaldehyde of 1 × 10^-4 μg/mL in the concentration ranges of 4 × 10^-3-4 μg/mL and 1 × 10^-4-3 × 10^-3 μg/mL. In the process of the detection of duck blood and rice flour, partial least squares regression (PLSR) was adopted for sample analysis. The formaldehyde concentration was calculated and compared to the actual value from the above model with R² of 0.97, which indicated high accuracy and stability. These results suggested that the proposed method was reliable and suitable for rapid analysis of trace formaldehyde in real products.

SERS-based chip for discrimination of formaldehyde and acetaldehyde in aqueous solution using silver reduction

A method is described for surface-enhanced Raman scattering (SERS) discrimination of formaldehyde (FA) and acetaldehyde (AA) in aqueous sample solutions. It is based on the use of a paper strip containing 4-aminothiophenol (Atp)-modified reduced graphene oxide (rGO)/[Ag(NH₃)₂]⁺ (rGO/[Ag(NH₃)₂]⁺/Atp). The addition of FA or AA induces the conversion of [Ag(NH₃)₂]⁺ complex to silver nanoparticles (AgNPs) because of aldehyde-induced silver reduction reaction. The AgNPs possess strong SERS activity. The average interparticle gaps between the AgNPs can be fine-tuned by controlling the experimental conditions, this leading to the formation of optimized SERS hot spots. It is also found that the changes in the spectral shapes and the relative intensity ratio of the bands at 1143 and 1072 cm^-1 result from the difference in the pH value of the surrounding solution. This effect enables the selective discrimination of FA and AA. The paper strip can be used as a SERS dipstick and swab for on-site determination of FA or AA in wine and human urine via the differences in the intensity of the SERS peaks. The assay works over a wide range of concentrations (0.45 ng·L^-1 to 480 μg·L^-1) for FA and AA, and the respective detection limits are 0.15 and 1.3 ng·L^-1. Graphical abstract Schematic presentation of the preparation procedure of 4-aminothiophenol (Atp)-modified reduced graphene oxide (rGO)/[Ag(NH₃)₂]⁺ hybrid paper and its surface-enhanced Raman scattering discrimination of formaldehyde and acetaldehyde based on silver reduction.

A highly selective chemiluminescent probe for the detection of chromium(VI)

In present work, rhodamine B hydrazide and rhodamine 6G hydrazide were synthesized and the chemiluminescence performance has been investigated. Based on the chemiluminescence of rhodamine 6G hydrazide‑chromium(VI), a selective and sensitive method for the direct detection of chromium(VI) was developed. The chemiluminescence intensity was linearly related to the concentration of chromium(VI) in the range of 2.60×10^-8-8.00×10^-6mol/L with a correlation coefficient of r=0.998 and a detection limit of 1.4×10^-8mol/L (S/N=3). The results indicated rhodamine 6G hydrazide was an excellent chemiluminescent probe for chromium(VI) without reduction of chromium(VI) to chromium(III). A possible mechanism of CL emission was also suggested.

Flow analysis with chemiluminescence detection: Recent advances and applications

This article highlights the most important developments in flow analysis with chemiluminescence (CL) detection, describing different flow systems that are compatible with CL detection, detector designs, commonly applied CL reactions and approaches to sample treatment. Recent applications of flow analysis with CL detection (focusing on outputs published since 2010) are also presented. Applications are classified by sample matrix, covering foods and beverages, environmental matrices, pharmaceuticals and biological fluids. Comprehensive tables are provided for each area, listing the specific sample matrix, CL reaction used, linear range, limit of detection and sample treatment for each analyte. Finally, recent and emerging trends in the field are also discussed.

A simple and sensitive flow injection method based on the catalytic activity of CdS quantum dots in an acidic permanganate chemiluminescence system for determination of formaldehyde in water and wastewater

The intensity of emitted light from KMnO₄–HCHO–CdS QDs system is linearly proportional to HCHO concentration.

Size-dependent active effect of cadmium telluride quantum dots on luminol-potassium periodate chemiluminescence system for levodopa detection

It was found that cadmium telluride (CdTe) quantum dots (QDs) with different sizes can have a great sensitizing effect on chemiluminescence (CL) emission from luminol-potassium periodate (KIO4) system. Levodopa, a widely prescribed drug in the treatment of Parkinson's disease, could inhibit luminol-KIO4-CdTe QDs CL reaction in alkaline solution. The inhibited CL intensity was proportional to the concentration of levodopa in the range from 8.0 nM to 10.0 μM. The detection limit was 3.8 nM. This method has been successfully applied to determine levodopa in pharmaceutical preparation and human urine and plasma samples with recoveries of 94.1-105.4%. This was the first work for inhibition effect determination of levodopa using a QD-based CL method.

Design of an ultra-sensitive gold nanorod colorimetric sensor and its application based on formaldehyde reducing Ag+

HCHO could reduce Ag⁺ to Ag on the surface of AuNRs to form Au core–Ag shell nanorods (Au@Ag↓NRs) in AuNRs–Ag⁺–HCHO system, which caused LPAB of AuNRs to redshift. Thus, a responsive AuNRs colorimetric sensor for the detection HCHO has been developed.