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Introduction to Smart Polymers
Published in Asit Baran Samui, Smart Polymers, 2022
Density functional theory calculations indicate that, in the closed form, the electric dipole moment of the molecule is 6.4 D, while in the open form, it is more than double, i.e., 13.9 D.4 Substantial variations in the electrostatic environment are caused by such changes in the dipole moment. It is expected that photochromic SP, when employed as one component of the gate dielectric, can alter the dielectric capacitance of the latter during illumination. In effect, the device performance is modulated. The methodology and the resultant performance form the basis for new types of ultrasensitive devices for chemical and environmental sensing in a non-invasive manner. The results are expected to offer new opportunities for fabricating more rational designs of multifunctional molecular sensors and devices.
Single-Molecule Organic Electronics and Optoelectronics
Published in Sam-Shajing Sun, Larry R. Dalton, Introduction to Organic Electronic and Optoelectronic Materials and Devices, 2016
Ling Zang, Xiaomei Yang, Tammene Naddo
As confirmed by the CFET investigation, the electrical conductivity of a molecule can be modulated by changing the local electrostatic field, which in turn can be altered by chemical binding, complexation, protonation, ionization, or other chemical processes. Using such a chemical field effect, people have developed various molecular sensors through monitoring the conductivity change. In most cases, the sensing devices are based on a two-electrode system, as shown in Figures 21.23 and 21.24. Owing to the high sensitivity in conductivity measurement (resolution of femtoampere), CFET-based devices can potentially be developed as a new class of sensors that will operate at the single-molecule level, enabling both high sensitivity and selectivity. Single-molecule probing and recognition offer exceptional application in studying complicated materials and large molecular systems, such as biological molecules, by revealing the heterogeneous distribution of physical parameters behind the samples. In contrast, the conventional ensemble measurement of such heterogeneous samples usually produces average values, leading to underestimation or misunderstanding of the chemical and physical properties. Various single-molecule sensory systems have been developed and explored. However, most systems to date are based on measurement of the optical properties, such as fluorescence [109–115]. Described herein are two recent examples that employ CFET mechanism in single-molecule sensing, one is on metal binding and the other on protonation.
Nanoengineered Material Applications in Electronics, Biology, and Energy Harnessing
Published in Anupama B. Kaul, Microelectronics to Nanoelectronics, 2017
Daniel S. Choi, Zhikan Zhang, Naresh Pachauri
The field of nanobioelectronics includes active field effect transistors, and electrochemical biosensors such as enzyme electrodes and immunosensors. These nanoelectrodes can be plugged into locations such as inside proteins where electrochemistry cannot perform. SWCNTs are one molecular layer thick; every atom is exposed to the adsorption of any molecule. The transfer of electrons is easier and hence the systems have high sensitivity over a broad range of gaseous and liquid analytes. This is the principle of nanoscale molecular sensors used to detect gas molecules with fast response time and high sensitivity at room temperature.
Gold sensing with rhodamine immobilized hydrogel-based colorimetric sensor
Published in Environmental Technology, 2020
Sastiya Kampaengsri, Banchob Wanno, Thawatchai Tuntulani, Buncha Pulpoka, Chatthai Kaewtong
Although heavy metals have many beneficial uses such as in catalysts used in industry, they have also been involved in rampant pollution of the environment [1] resulting in contamination of food and drinking water [2]. The effects of heavy metal pollutants on aquatic ecosystems in urban, agricultural and industrial environments have been considered [3]. Gold, one of the heavy metals, has been widely used in many fields (medicine [4], catalysis [5], and electronics [6]) but gold-containing wastewater produced in processing has resulted in negative impacts on the environment. Therefore, it is essential to find an effective method for the recovery of heavy metals from aqueous solution to support environmental monitoring and protection and also to support full utilization of the gold resource. Conventional methods for the recovery of heavy metals from aqueous solutions included precipitation [7], ions exchange [8], and solvent extraction [9]. However, these methods are not effective (incomplete metal removal) or economical (high cost, high reagent and/or energy requirement). In the past few years, molecular sensors have become powerful tools for sensing of samples because of their simplicity and sensitivity. Nevertheless, these methods have shown several problems such as low mechanical and thermal stability, weak chemical union with the metals, poor removal efficiency, high cost, etc. In contrast with molecular sensors, gel sensors exhibited prominent advantages, such as the ease of fabrication of devices, a wide choice of incorporating specific units into the gel, low cost, and so on [10–12]. Recently, a preparation of a Neutral Red (NR)-ACG optical sensor was reported as a long life pH optical sensor for pH measurements in a range of 2–8.5 and showed more stability than a standalone agarose membrane with the easier handling and storage [7]. Dithizone has also been immobilized on agarose membrane for determination of Hg2+ and Pb2+ and had good selectivity for target ions compared with a large number of alkali, alkaline earth, transition, and heavy metal ions [2]. In our earlier work, we developed a solvatochromic rhodamine-based sensor for Cr3+using commercially available rhodamine simply dissolved in THF to produce rhodamine lactone (RhoL) via the rhodamine lactone–zwitterion equilibrium [13]. In this work, we exposed the simple way for preparation and response features of a new highly sensitive optical sensor by immobilization of rhodamine derivative on agarose hydrogel as a gold probe as shown in Scheme 1.