Ruifen Hu

A Dibutyl Phthalate Sensor Based on a Nanofiber Polyaniline Coated Quartz Crystal Monitor

Dibutyl phthalate (DBP) is a commonly used plasticizer and additive to adhesives, printing inks and nail polishes. Because it has been found to be a powerful reproductive and developmental toxicant, a sensor to monitor DBP in some working spaces and the environment is required. In this work polyaniline nanofibers were deposited on the electrode of a quartz crystal oscillator to form a Quartz Crystal Microbalance gas sensor. The coated quartz crystal and a non-coated quartz crystal were mounted in a sealed chamber, and their frequency difference was monitored. When DBP vapor was injected into the chamber, gas adsorption decreased the frequency of the coated quartz crystal oscillator and thereby caused an increase in the frequency difference between the two crystals. The change of the frequency difference was recorded as the sensor response. The sensor was extremely sensitive to DBP and could be easily recovered by N2 purging. A low measurement limit of 20 ppb was achieved. The morphologies of the polyaniline films prepared by different approaches have been studied by SEM and BET. How the nanofiber-structure can improve the sensitivity and stability is discussed, while its selectivity and long-term stability were investigated.

Development of a high-sensitivity plasticizer sensor based on a quartz crystal microbalance modified with a nanostructured nickel hydroxide film

Nanostructured nickel hydroxide (nano-Ni(OH)2) was synthesized at a low temperature without annealing. Accordingly, a plasticizer sensor based on a quartz crystal microbalance (QCM) modified with the nano-Ni(OH)2 sensing film was fabricated to detect dibutyl phthalate (DBP) and its relative film thickness was optimized. The sensor worked at room temperature and exhibited a high sensitivity of 4.91 Hz ppb−1 to DBP in a low concentration range of 5–20 ppb, and an ultra-low detection limit of 5 ppb was achieved. In addition, the sensor maintained good repeatability as well as stability shown by the experimental data. The responses to five possible interferences and four other plasticizers were also measured, which indicated the excellent selectivity of the sensor and its potential use in monitoring plasticizers in a gaseous state.

Nonenzymatic all-solid-state coated wire electrode for acetylcholine determination in vitro

A nonenzymatic all-solid-state coated wire acetylcholine electrode was investigated. Poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT/PSS) as conducting polymer was coated on one end of a gold wire (0.5mm in diameter). The acetylcholine selective membrane containing heptakis(2,3,6-tri-Ο-methyl)-β-cyclodextrin as an ionophore covered the conducting polymer layer. The electrode could work stably in a pH range of 6.5-8.5 and a temperature range of 15-40°C. It covered an acetylcholine concentration range of 10(-5)-10(-1)M with a slope of 54.04±1.70mV/decade, while detection limit was 5.69±1.06µM. The selectivity, dynamic response, reproducibility and stability were evaluated. The electrode could work properly in the rat brain homogenate to detect different concentrations of acetylcholine.

A Noncontact Dibutyl Phthalate Sensor Based on a Wireless-Electrodeless QCM-D Modified with Nano-Structured Nickel Hydroxide

Dibutyl phthalate (DBP) is a widely used plasticizer which has been found to be a reproductive and developmental toxicant and ubiquitously existing in the air. A highly sensitive method for DBP monitoring in the environment is urgently needed. A DBP sensor based on a homemade wireless-electrodeless quartz crystal microbalance with dissipation (QCM-D) coated with nano-structured nickel hydroxide is presented. With the noncontact configuration, the sensing system could work at a higher resonance frequency (the 3rd overtone) and the response of the system was even more stable compared with a conventional quartz crystal microbalance (QCM). The sensor achieved a sensitivity of 7.3 Hz/ppb to DBP in a concentration range of 0.4–40 ppb and an ultra-low detection limit of 0.4 ppb of DBP has also been achieved.

Improved analysis of inorganic coal properties based on near-infrared reflectance spectroscopy

Near-infrared reflectance spectroscopy (NIRS) is a fast and convenient analytical tool, and it has become the preferred choice for online coal property analysis in recent years. Organic molecules have much stronger absorption ability than inorganic molecules. Therefore, better analysis accuracy can be achieved for organic properties of coal such as volatile matter and fixed carbon than that for inorganic properties such as ash and sulfur. This paper used a much better algorithm (least squares support vector machine) than a previous study and proposes a new method to improve the analysis accuracy of inorganic properties by utilizing the analysis results of volatile matter and fixed carbon to enhance the regression models for ash and sulfur. Four types of coal (i.e. fat, coking, lean and meager lean) were considered in our experiments. Individual models for each type of coal have been established and predicted values of volatile matter and fixed carbon based on NIRS were added with the relevant PCA components during the modeling. The experimental results have shown that our proposed method which utilizes information of the organic properties could improve the analysis results of the inorganic properties by around 35% using NIRS.

Study on the EEG Rhythm in Meditation

Meditation affects the brain rhythm significantly. Compared with non-meditators, the power of delta band was lower while high frequency band was higher for a meditator. Alpha band over the scalp was much more active in normal state for meditator with decreased dominant alpha frequency. Obvious transient process between normal eyes-closed rest and meditation was observed after EEG analysis. The active time and the power of beta and gamma band increased significantly in meditation. The inter-hemispheric and intra-hemispheric coherence beta and low gamma bands for meditative state were higher than normal state.