Optical Sensors for the Detection of Trace Chloroform

Development and mechanism of a fluorescent probe for a Mn(ii) ionic complex capable of recognizing chloroform vapor molecules

The monoclinic [PPh3(Me)]2[MnBr4] complex readily develops ion-dipole interactions with chloroform vapor molecules, causing reversible structural transitions and fluorescence changes.

A simple equipment and colorimetric method for determination of chloroform in water

Chlorination is a common and successful method for disinfection of water all around the world, especially in developing countries. However, this process can produce trihalomethanes (THMs) byproducts which are carcinogen. The major THM occurring in this process is chloroform. The purpose of this study was to design a simple equipment for colorimetric determination of chloroform in various water samples. The method is based on the colorimetric reaction of chloroform with resorcinol in strong basic medium on a filter paper. Response surface methodology (RSM) was employed to optimize the determination condition. The reagents were immobilized on filter paper and the color change was followed to quantify chloroform without using any analytical instrument. Detection limit and linear range of the proposed method were 0.007 mg/L and 0.011-1.192 mg/L, respectively for analysis of samples with volume of 2.0 L. The method was successfully applied to determine chloroform in different water samples and compared with GC-MS as a standard method. Employing the designed device, purge, trap and analysis steps were performed in a single run which can reduce the uncertainties originated by excessive steps of the analysis.

Reversible Ultralong Organic Phosphorescence for Visual and Selective Chloroform Detection

Volatile organic compounds (VOCs) are widespread in our daily life and greatly harmful to human health, as well as to the environment. To date, it remains a formidable challenge to develop a highly sensitive visual system for selective detection of VOCs. Herein, we report on a metal-free organic molecule of 2,4-di(10 H-phenothiazin-10-yl)-1,3,5-triazine (TDP) with ultralong organic phosphorescence (UOP) feature as a visible chemical probe for chloroform detection. In the pristine solid state, this phosphor shows a green UOP with a lifetime of 56 ms after the removal of excitation light source; however, the UOP greatly diminishes when fumed with chloroform, which is ascribed to the variation in both radiative and nonradiative transitions in crystal with embedded chloroform. Remarkably, TDP materials demonstrate great potential as a visual chemical probe for chloroform, showing high sensitivity, excellent selectivity, and good repeatability. The limitation for chloroform detection is as low as 5 ppm. Combining experimental data and theoretical calculations, it is reasoned that the space confinement via intermolecular interactions between chloroform and TDP molecules play a vital role for high selectivity of chloroform detection. These results pave the way toward expanding the scope of organic luminogens with UOP as well as their applications.

Improved ATR-FTIR detection of hydrocarbons in water with semi-crystalline polyolefin coatings on ATR elements

In situ detection of hydrocarbons in water using ATR-FTIR with LLDPE film.

Chemiresistive/SERS dual sensor based on densely packed gold nanoparticles

Chemiresistors are a class of sensitive electrical devices capable of detecting (bio)chemicals by simply monitoring electrical resistance. Sensing based on surface enhanced Raman scattering (SERS) represents a radically different approach, in which molecules are optically detected according to their vibrational spectroscopic fingerprint. Despite different concepts are involved, one can find in the literature examples from both categories reporting sensors made of gold nanoparticles. The same building blocks appear because both sensor classes share a common principle: nanometric interparticle gaps are needed, for electron tunneling in chemiresistors, and for enhancing electromagnetic fields by plasmon coupling in SERS-based sensors. By exploiting such nano-gaps in self-assembled films of gold nanoparticles, we demonstrate the proof of concept of a dual electrical/optical sensor, with both chemiresistive and SERS capabilities. The proposed device is realized by self-assembling 15 nm gold nanoparticles into few micrometers-wide strips across commercially available interdigitated electrodes. The dual-mode operation of the device is demonstrated by the detection of a biologically relevant model analyte, 4-mercaptophenyl boronic acid.