Dynamic reaction regulated surface-enhanced Raman scattering for detection of trace formaldehyde

Responsive photonic hydrogel for colorimetric detection of formaldehyde

Formaldehyde (FA) can damage DNA, cause liver and kidney dysfunction, and ultimately lead to malignant tumors. Therefore, it is essential to develop a method that can conveniently detect FA with high detection sensitivity. Here, a responsive photonic hydrogel was prepared by embedding three-dimensional photonic crystal (PC) into amino-functionalized hydrogel to construct a colorimetric sensing film for FA. The amino groups on the polymer chains of the photonic hydrogel reacts with FA to increase the crosslinking density of the hydrogel, resulting in its volume shrinkage and a decrease in microsphere spacing of the PC. That causes the reflectance spectra blue-shift of more than 160 nm and color change from red to cyan for the optimized photonic hydrogel, achieving the sensitive, selective and colorimetric detection of FA. The constructed photonic hydrogel shows good accuracy and reliability for practical determination of FA in air and aquatic products, providing a new strategy for designing other target analytes responsive photonic hydrogels.

Selective determination of formaldehyde by high-performance liquid chromatography with porous graphitic carbon column using N,N'-bis(9-anthrylmethyl)propane-1,3-diamine as derivatizing reagent

Aromatic compounds containing two secondary amino groups were designed and prepared as new derivatizing reagents for aldehydes. One of them, N,N'-bis(9-anthrylmethyl)propane-1,3-diamine (APD), could achieve selective determination of formaldehyde (FA) on a porous graphitic carbon (PGC) column using xylenes, chlorobenzene, and 1-chloronaphthalene as mobile phases by high-performance liquid chromatography (HPLC). The APD-FA derivative was eluted from the PGC column, while the other APD-aldehyde derivatives remained on the column during the HPLC measurements. This specific elution was not observed using mobile phases such as acetonitrile, 1,4-dioxane, tetrahydrofuran, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, chloroform, benzene, toluene, benzyl alcohol, 2-ethyl-1-hexanol, and pyridine. The APD-FA derivative had a six-membered ring of two tertiary amines identified using ¹H NMR spectroscopy. When the π-π interaction of the solvent molecule of the mobile phase with PGC overcame that between the APD-FA derivative and PGC, the APD-FA derivative could be eluted from the column. The best resolution between the peak of the APD-FA derivative and that of free APD was observed when using o-xylene. The optimum derivatization and the HPLC conditions for selective HPLC determination of FA were to conduct the derivatization of FA by heating in an aqueous phase with APD in o-xylene at 100 °C. In this method, FA could be derivatized with APD at a mildly neutral pH of 6.7, unlike the low pH required for the derivatization of aldehydes with 2,4-dinitrophenylhydrazine (DNPH), which is commonly used for the derivatization of aldehydes. The detection and quantification limits of FA were 0.8 and 3.5 ng mL^-1 in this HPLC method with fluorescent detection, respectively. This selective HPLC method could be applied to the determination of FA in various water samples. It was found that only APD among the derivatizing reagents containing two secondary diamines was useful for the selective determination of FA.

Sensitive detection of trace 4-methylimidazole utilizing a derivatization reaction-based ratiometric surface-enhanced Raman scattering platform

Herein, a facile and fast surface-enhanced Raman scattering (SERS) method with ratiometric strategy was developed for detection of 4-methylimidazole (4-MI). Via a chemical derivatization reaction with 3-amino-5-mercapto-1,2,4-triazole (AMTA) diazonium salts, 4-MI could be converted to SERS-sensitive species. The SERS intensity ratio between the peaks at 1243 cm^-1 and 1110 cm^-1 (I₁₂₄₃/I₁₁₁₀) was used for the quantification of 4-MI. In addition, the method sensitivity was further improved by the aggregation of beta-cyclodextrin-modified Ag nanoparticles (beta-CD-AgNPs). Under the optimal conditions, the limit of detection (LOD) and the limit of quantification (LOQ) for 4-MI were 1.7 nM (S/N = 3) and 5.7 nM (S/N = 10), respectively. The relative standard deviation (RSD) for 0.5 μM 4-MI was 8.2% (n = 20). This method was successfully used for the determination of 4-MI in cola samples with recoveries ranging from 92% to 106%. The present method is convenient, sensitive, selective, reliable and may have a promising application in determination of the compounds with an imidazole ring containing active hydrogen atoms.

Fluorescence Sensing of Formaldehyde and Acetaldehyde Based on Responsive Inverse Opal Photonic Crystals: A Multiple-Application Detection Platform

Formaldehyde (FA) and acetaldehyde (AcH) used as common chemicals in many fields are carcinogenic. The presently reported detection methods usually need expensive instruments, professional technicians, and time-consuming processes, and the detection sensitivity still needs further improvement. Herein, we report a highly effective fluorescence (FL) sensing film for FA and AcH based on naphthalimide derivative-infiltrated responsive SiO₂ inverse opal photonic crystals (PCs), establishing a practically multiple-application detection platform for FA and AcH in air, aquatic products, and living cells. Nucleophilic addition products between the amine group of the naphthalimide derivative and aldehydes emit strong FL at ∼550 nm, realizing selective FL detection for FA and AcH. The emitted FL can be enhanced remarkably because of the slow photon effect of PCs, in which the FL wavelength is located at the stopband edge of PCs. A highly sensitive detection for FA and AcH with limits of detection of 10.6 and 7.3 nM, respectively, is achieved, increasing 3 orders of magnitude compared with that in the solution system. Additionally, the interconnected three-dimensional microporous inverse opal structure endows the sensor with a rapid response within 1 min. Furthermore, the as-prepared PC sensor can be reused by simple washing in an acidic aqueous solution. The sensing system can be used as a FL multi-detection platform for FA and AcH in air, aqueous solution, and living cells. This FL sensing approach based on small organic molecule-functionalized PCs is universally available to develop various sensors for target analytes by designing new functional organic compounds.