Fabrication of liquid crystal based sensor for detection of hydrazine vapours (original) (raw)
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Fast and ratiometric “naked eye” detection of hydrazine for both solid and vapour phase sensing
New J. Chem., 2015
A new ''naked-eye'' ratiometric colorimetric and fluorescence chemodosimeter (PBF) was constructed to enable trace vapor detection of hydrazine. This probe utilizes an irreversible and fast hydrazine -promoted cleavage of ester linkage in PBF. This probe was shown to be highly selective 10 for hydrazine, and showed real time response as well as a positive linear relationship to hydrazine concentration. The probe also shows an excellent performance in the ''dip stick'' method.
Rebirth of Liquid Crystals for Sensoric Applications: Environmental and Gas Sensors
Advances in Condensed Matter Physics, 2015
Films and droplets of liquid crystals may soon become an essential part of sensitive environmental sensors and detectors of volatile organic compounds (VOCs) in the air. In this paper a short overview of recent progress in the area of sensors based on liquid crystals is presented, along with the studies of low molar mass liquid crystals as gas sensors. The detection of VOCs in the air may rely on each of the following effects sequentially observed one after the other: (i) slight changes in orientation and order parameter of liquid crystal, (ii) formation of bubbles on the top of the liquid crystalline droplet, and (iii) complete isotropisation of the liquid crystal. These three stages can be easily monitored by a photo camera and/or optical microscopy. Detection limits corresponding to the first stage are typically lower by a factor of at least 3–6 than detection limits corresponding to isotropisation. The qualitative model taking into account the reorientation of liquid crystals is...
European Journal of Chemistry
Hydrazine and its derivatives, as harmful substances, seriously risk the health of humans and the environment. On the basis of the admirable luminescent properties and low biological harmfulness of the biphenyl moiety, a biphenyl moiety can be combined with a naphthalene ring via the chalcone scaffold easily traced by a nucleophilic group. Therefore, biphenyl chalcones (BPCs) decorated with various naphthalene systems as fluorescent sensors for hydrazine are synthesised by Claisen-Schmidt condensation. The present work describes the comparative studies of two different protocols for the synthesis of three different BPCs. The structures of all novel BPCs were investigated by FT-IR, NMR, and HRMS spectroscopy. These BPCs show a red shift with a fluorescent peak and an enhancement in intensity with increasing solvent polarity from hexane to methanol. Methanol shows strong fluorescence emission; therefore, methanol is used as the solvent in hydrazine sensing experiments. The BPCs displa...
Spectral, electrochemical and thermal characteristics of glass forming hydrazine derivatives
Optical Materials, 2014
The azines being condensation products of benzophenone hydrazone with triphenylamine substituted with different numbers of aldehyde groups and also with terephthaldicarboxaldehyde were prepared. Their spectral, thermal and electronic properties that is, orbital energies and resulting energy gap calculated theoretically by density functional theory (DFT) and estimated by electrochemical measurements were explored. The prepared hydrazine derivatives exhibited glass-forming properties with glass-transition temperatures in the range of 10-98°C and high thermal stability with decomposition temperatures placed between 231 and 337°C. The photoluminescence (PL) studies showed that all investigated compounds both in solid state as blends with PMMA and in NMP solution emitted blue light, however, with different intensity. Relative PL intensity of azines was investigated in NMP in relation to rhodamine-B used as a standard. Moreover, the stability of azines during doping with acid and ferric chloride was spectroscopically demonstrated via repeated doping/dedoping in solution and in film. All compounds are electrochemically active. Depend on chemical structure of azines they undergo reversible or irreversible electrochemical oxidation and reduction processes. The LUMO levels were found in the range from À2.66 to À3.0 eV. They exhibited energy band gap (E g ) estimated electrochemically from 2.57 to 3.22 eV.
DESALINATION AND WATER TREATMENT
Mn-ZnS QDs synthesized by hydrothermal method and modified by L-cysteine for better stability emit phosphorescence at 590 nm. The characterization of L-cysteine-capped Mn-Doped ZnS quantum dots were studied by transmission electron microscopy (TEM), phosphorescence, fluorimetry and UV-Vis absorption spectroscopy. To fabricate a new electrochemical sensor, L-cysteine-capped Mn-Doped ZnS quantum dots and multiwall carbon nanotube (MWCNT) were placed on the surface of glassy carbon electrode (ZnS/MnQDs-MWCNTs/GCE). Then, it was applied for the determination and detection of environmental pollutant hydrazine in water samples. The electrooxidation behaviors and the effective stepwise assembly procedure of the modified electrode were confirmed by electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Based on the findings, ZnS/Mn QDs-MWCNT composite can be considered a suitable candidate for hydrazine electrooxidation. The linear rang, detection of limit (DL), limit of quantification (LOQ) and sensitivity were 90-1,200 nanomolar, 28 nM, 95 nM and 0.001 µA nM-1 , respectively. The repeatability in the presence of hydrazine (100 µM) was studied and the variation coefficient (R.S.D) was 2% for five consecutive tests. The proposed sensor shows many advantages such as very low detection of limit, high sensitivity, stability and it can be used for detection of hydrazine in real samples.
Seeing the Unseen: The Role of Liquid Crystals in Gas‐Sensing Technologies
Advanced Optical Materials
based technology has permeated almost every section of society, from large industrial units to individual homes and offices. In particular, LC phases are widely used in display systems, for example, in liquid crystal displays (LCDs). [2] Liquid crystals, further detailed in Section 2, combine order and fluidity, that is they flow like conventional liquids but also they exhibit significant orientational order and in some cases positional order. These features are considered fundamental requirements for self-organization and formation of hierarchical structures. Additionally, they respond rather easily to external stimuli, such as electrical and magnetic fields, mechanical shear, pressure, surface effects, light, temperature, and chemical analytes with a change in their configuration that can be traced using a variety of characterization techniques. Due to this responsive and dynamic nature, the exploitation of LCs covers a wide range of discipline fields and applications in line with the current technological and societal needs, such as flat panel displays, [3] adaptive lenses and filters, [4,5] energy, [6-8] photonics, [9,10] biomedicine, [11,12] and design and architecture. [13,14] An emerging field of research is the development of LCassisted sensing technologies, since LC-sensing materials can be tailored to respond to targeted biological and chemical species. [15-21] Regarding biosensors, the concept involves either the imaging of targeted species displayed at solid surfaces, or sensing at LC/aqueous interfaces (LC thin films or droplets). So far, LC-based biosensors have been reported to detect a wide range of biomolecules such as glucose, [22] cholesterol, [23] lipids, [24] antimicrobial peptides, [25] proteins, [26,27] antigens, [28] pathogen DNA, [29] viruses, [30] bacteria, [31] or mammalian cells. [32,33] Nonetheless, the exploitation of LCs in biosensing devices has already been reviewed by other authors [16,19] and is outside the scope of this work. The prime topic of this review is the development and application of LC-based soft systems in gas sensing, a field that has been gaining interest within the scientific community. Gas sensors represent an increasing market worth valued at USD 2.05 billion in 2018 (expecting to register a Compound Annual Growth Rate of 7.8% from 2019 to 2025 [34]) and play a significant role in several fields such as industrial production (e.g., methane detection in mines [35]); automotive industry Fast, real-time detection of gases and volatile organic compounds (VOCs) is an emerging research field relevant to most aspects of modern society, from households to health facilities, industrial units, and military environments. Sensor features such as high sensitivity, selectivity, fast response, and low energy consumption are essential. Liquid crystal (LC)-based sensors fulfill these requirements due to their chemical diversity, inherent self-assembly potential, and reversible molecular order, resulting in tunable stimuliresponsive soft materials. Sensing platforms utilizing thermotropic uniaxial systems-nematic and smectic-that exploit not only interfacial phenomena, but also changes in the LC bulk, are demonstrated. Special focus is given to the different interaction mechanisms and tuned selectivity toward gas and VOC analytes. Furthermore, the different experimental methods used to transduce the presence of chemical analytes into macroscopic signals are discussed and detailed examples are provided. Future perspectives and trends in the field, in particular the opportunities for LC-based advanced materials in artificial olfaction, are also discussed.
Sensors and Actuators B-chemical, 2008
A novel 1,3-bis(p-hydrazonobenzoicacid)indane (HBI) molecule was synthesised for the study of monolayer properties at the air-water interface, the fabrication of a Langmuir-Blodgett film, and the investigation of organic vapor sensing properties. Langmuir properties of HBI were studied by taking an isotherm graph. Two different surface pressures were selected for the fabrication of multilayer LB films that were deposited onto glass and quartz crystal substrates.
Development of water-based polyaniline sensor for hydrazine detection
Sensors and Actuators A: Physical, 2021
In this study, water-soluble polyaniline-methylcellulose complex (PAni-MC) was applied as an environmental friendly chemical sensor for hydrazine detection. PAni was rendered water-soluble through chemical modification with MC. Fourier transform infrared (FTIR) and Ultraviolet-visible (UV-vis) spectroscopies confirmed the chemical structures of PAni-MC to be the conducting emeraldine salt form with electrical conductivity values of 0.068 S cm −1 for pristine PAni and 0.132 S cm −1 for PAni-MC respectively. In the hydrazine detection procedure, PAni-MC solution was added into samples containing various concentrations of hydrazine (10−100 ppm) and the sensor responses were recorded using a conductivity meter. Several parameters have been studied, including (i) different volume ratio of PAni to hydrazine, (ii) different mass ratio of aniline (Ani) monomer to MC, and (iii) detection at low concentration range of hydrazine (1−10 ppm). From the results obtained, PAni-MC (volume ratio 2:5 of PAni-MC: hydrazine) with the mass ratio 0.2:1 of Ani: MC has achieved the best sensitivity of 0.0143 ppm −1 , hence it was selected to further study its sensor performance. Calibration has shown a good sensitivity of 0.0132 ppm-1 and a good linear correlation (R 2 = 0.9953), the limit of detection (LOD) of 0.55 ppm, and the limit of quantitation (LOQ) of 1.82 ppm respectively. The sensor performance was supported by UV-vis and FTIR analyses. Significant decrease in the UV-vis absorbance was observed at bipolaron (∼821 nm) and polaron (∼450 nm) bands, meanwhile the intensity of quinoid/benzenoid (I Q /I B) ratio in the FTIR spectra has shown a decrease from 1.03 to 0.97. In real sample analysis, PAni-MC eventually indicated the best recovery range of 96-136 % and a good relative standard deviation (RSD) of 2.69-5.84 %.