Electrochemiluminescence Sensors based on Lanthanide Nanomaterials as Modifiers

Facile electrochemiluminescence sensing platform based on Gd2O3:Eu3+ nanocrystals for organophosphorus pesticides detection in vegetable samples

In this work, europium ion-doped gadolinium trioxide nanocrystals (Gd2O3:Eu3+ NCs) were successfully synthesized and applied to construct an electrochemiluminescence (ECL) sensor. Compared with pure Gd2O3, the doping of Eu3+ ions caused enhanced ECL intensity and more stable signals. Based on the excellent ECL performance of Gd2O3:Eu3+ NCs, we constructed a new ECL sensing platform for the detection of organophosphorus pesticides (OPs). The ECL sensor showed a good linear relationship in the concentration range of 1 nM to 1 pM, with a limit of detection of 0.12 pM (S/N = 3) for dichlorvos (DDVP). In addition, the constructed ECL sensor was applied for the detection of DDVP in vegetable samples, and good recoveries were obtained. The results indicated that the ECL sensor exhibited fantastic performance properties and had good application prospects in OPs detection.

Conductivity and aging behavior of Sr(Ti0.6Fe0.4)1-x O3-δ mixed conductor materials

Perovskite materials play a significant role in oxygen sensors due to their fascinating electrical and ionic conductivities. The sol-gel technique was employed to prepare various compositions of B-site-deficient Fe-doped SrTiO3 (iron-doped strontium titanate) or Sr(Ti0.6Fe0.4)1-x O3-δ , where x = 0.01, 0.02, and 0.03. The XRD results revealed that the principle crystalline phase of the samples was the cubic perovskite structure. The B-site deficiency improved the ionic and total conductivities of Sr(Ti0.6Fe0.4)1-x O3-δ . A small polaron conduction behavior occurred in the total electrical conductivity. The XPS results showed that the oxygen vacancy value decreased with the rise in the amount of B-site deficiencies. A lower B-site deficiency amount could produce more oxygen vacancies in the lattice but resulted in the ordering of vacancies and then lower ionic conductivity. The aging behavior was caused by the ordering of oxygen vacancies and resulted in a degeneration of electrical features under a long service time. Conversely, augmentation of the B-site deficiency amount inhibited the tendency for the ordering of oxygen vacancies and then promoted the electrical performance under a long usage time. The conduction mechanism of oxygen ions through oxygen vacancies was thoroughly investigated and discussed. The current study presents a feasible approach to ameliorate the physical features of conductors through doping the B-site of the perovskite layer with Fe, which would be a fruitful approach for numerous applications, including oxygen sensors and fuel cells anodes.

Experimental and Theoretical Studies on Optical Properties of Tetra(Imidazole) of Palladium (II) Phthalocyanine

In this work, the optical properties of tetra(imidazole) of palladium phthalocyanine (PdPc(Im)₄) in solution form and thin films on glass and fluorine-doped tin oxide (FTO) substrates were investigated via the thermal evaporation technique. The optical band gap was evaluated by ultraviolet–visible spectroscopy (UV-Vis). The energy band gap values were determined based on the Tauc graph. In addition, time-dependent density functional theory (TD-DFT) was used to simulate the UV-Vis absorption spectrum of the (PdPc(Im)₄) molecule in the Dimethyl Sulfoxide (DMSO) solution phase. A good correlation was found between the DFT results and the experimental optical results. The band gap values between the experimental and DFT-simulated values are presented. The energy band gap of (PdPc(Im)₄) obtained from the DFT calculations showed that it can be efficiently regulated. Frontier molecular orbitals and molecular electrostatic potentials were also proposed in this work. The surface study of the layers deposited on FTO was considered by atomic force microscopy (AFM) and scanning electron microscopy (SEM), and the results demonstrated good homogeneity covering the entire surface. The SEM image showed a homogeneous distribution of the grains with some spherical or rod-shaped structures and no agglomeration structures. This work rendered a strategy for regulating the energy band gap and compared the experimental observations obtained with theoretical studies, which provides a fundamental insight into the optical band for optoelectronic and thin-film solar cells.

Critical review and recent advances of 2D materials-Based gas sensors for food spoilage detection

Many people around the world are concerned about meat safety and quality, which has resulted in the ongoing advancement of packaged food technology. Since the emergence of graphene in 2004, the number of studies on layered two-dimensional materials (2DMs) for applications ranging from food packaging to meat quality monitoring has been expanding quickly. Recently, scientists have been working hard to develop a novel class of 2DMs that keep the good things about graphene but don't have zero bandgaps at room temperature. Much work has been done on layered transition metal dichalcogenides (TMDCs) like different metal sulfides and selenides for meat spoilage gas sensors. This review looks at (i) the main indicators of meat spoilage and (ii) the detection methods that can be used to find out if meat has been spoiled, such as chemiresistive, electrochemical, and optical methods. (iii) the role of 2DMs in meat spoilage detection and (iv) the emergence of advanced methods for selective classification of target analytes in meat/food spoilage detection in recent years. Thus, this review demonstrates the potential scope of 2DMs for developing intelligent sensor systems for food and meat spoilage detection with high viability, simplicity, cost-effectiveness, and other multipurpose tools.

Development of a Portable and Modular Gas Generator: Application to Formaldehyde Analysis

This work aims at developing and validating under laboratory-controlled conditions a gas mixture generation device designed for easy on-site or laboratory calibration of analytical instruments dedicated to air monitoring, such as analysers or sensors. This portable device, which has been validated for formaldehyde, is compact and is based on the diffusion of liquid formaldehyde through a short microporous interface with an air stream to reach non-Henry equilibrium gas–liquid dynamics. The geometry of the temperature-controlled assembly has been optimised to allow easy change of the aqueous solution, keeping the microporous tube straight. The formaldehyde generator has been coupled to an on-line formaldehyde analyser to monitor the gas concentration generated as a function of the liquid formaldehyde concentration, the temperature, the air gas flow rate, and the microporous tube length. Our experimental results show that the generated gaseous formaldehyde concentration increase linearly between 10 and 1740 µg m−3 with that of the aqueous solution ranging between 0 and 200 mg L−1 for all the gas flow rates studied, namely 25, 50 and 100 mL min−1. The generated gas phase concentration also increases with increasing temperature according to Henry’s law and with increasing the gas–liquid contact time either by reducing the gas flow rate from 100 to 25 mL min−1 or increasing the microporous tube length from 3.5 to 14 cm. Finally, the performances of this modular formaldehyde generator are compared and discussed with those reported in the scientific literature or commercialised by manufacturers. The technique developed here is the only one allowing to operate with a low flow rate such as 25 to 100 mL min−1 while generating a wide range of concentrations (10–1000 µg m−3) with very good accuracy.