Electrochemically synthesized polymers in molecular imprinting for chemical sensing

This critical review describes a class of polymers prepared by electrochemical polymerization that employs the concept of molecular imprinting for chemical sensing. The principal focus is on both conducting and nonconducting polymers prepared by electropolymerization of electroactive functional monomers, such as pristine and derivatized pyrrole, aminophenylboronic acid, thiophene, porphyrin, aniline, phenylenediamine, phenol, and thiophenol. A critical evaluation of the literature on electrosynthesized molecularly imprinted polymers (MIPs) applied as recognition elements of chemical sensors is presented. The aim of this review is to highlight recent achievements in analytical applications of these MIPs, including present strategies of determination of different analytes as well as identification and solutions for problems encountered

Resonance Frequency Readout Circuit for a 900 MHz SAW Device

A monolithic resonance frequency readout circuit with high resolution and short measurement time is presented for a 900 MHz RF surface acoustic wave (SAW) sensor. The readout circuit is composed of a fractional-N phase-locked loop (PLL) as the stimulus source to the SAW device and a phase-based resonance frequency detecting circuit using successive approximation (SAR). A new resonance frequency searching strategy has been proposed based on the fact that the SAW device phase-frequency response crosses zero monotonically around the resonance frequency. A dedicated instant phase difference detecting circuit is adopted to facilitate the fast SAR operation for resonance frequency searching. The readout circuit has been implemented in 180 nm CMOS technology with a core area of 3.24 mm2. In the experiment, it works with a 900 MHz SAW resonator with a quality factor of Q = 130. Experimental results show that the readout circuit consumes 7 mW power from 1.6 V supply. The frequency resolution is 733 Hz, and the relative accuracy is 0.82 ppm, and it takes 0.48 ms to complete one measurement. Compared to the previous results in the literature, this work has achieved the shortest measurement time with a trade-off between measurement accuracy and measurement time

Novel sulfhydryl functionalized covalent organic frameworks for ultra-trace Hg2+ removal from aqueous solution

Two kinds of novel sulfhydryl functionalized covalent organic frameworks were fabricated as adsorbents for the removal of ultra-trace concentrations of Hg(2+)from water. The two kinds of sulfhydryl functionalized covalent organic frameworks were obtained via a thiol-ene click reaction between the thiol groups of trithiocyanuric acid (TTC) or bismuththiol (BMT) and vinyl groups on the surface of covalent organic frameworks. The material structure was characterized by XRD, SEM, EDS, FT-IR, BET, and TG analysis. Due to their rich sulfur content, both adsorbents (COF-SH-1 and COF-SH-2) exhibited a high level of selective Hg2+ removal from aqueous solution with maximum adsorption capacities of 763.4 mg g(-1) and 526.3 mg g(1,) respectively. Furthermore, in the presence of ultra-low concentrations of Hg2+ both materials exhibited excellent performance, achieving rapid Hg2+ removal at concentrations from 10 mu g L-1 to less than 0.02 ng L-1. Analysis of the adsorption mechanism indicates that the sulfur containing chelating groups exhibit a strong binding capacity for Hg2 +. Results show that the structure determines the performance, with the amount of adsorption sites being related to the adsorption capacity. Therefore, as sulfhydryl functionalized covalent organic frameworks contain an abundance of adsorption sites, these materials can effectively achieve the removal of ultra-low trace Hg2+ concentrations and have promising future application potential for the environmental detection of heavy metals. (C) 2021 Published by Elsevier Ltd on behalf of Chinese Society for Metals

A 164-μW 915-MHz sub-sampling phase-tracking zero-IF receiver with 5-Mb/s data rate for short-range applications

This article presents a 915-MHz ultra-low-power (ULP) sub-sampling phase-tracking receiver (SSPT-RX). It is targeted for the power-constrained devices that need short range but medium high-speed data receiving, such as the multi-channel neural stimulator with arbitrary waveform generation. The zero-intermediate frequency (zero-IF) phase-tracking receiver (PT-RX) topology is adopted to simplify the sub-sampling RX architecture with direct demodulation of frequency-shift keying (FSK) signal while improving the image frequency issue. The frequency of local oscillator (LO) is reduced by ten times with the proposed architecture, which leads to greatly reduced power consumption. Fabricated in 65-nm CMOS process, the RX chip occupies an active area of 0.58 mm2. The RX consumes one of the lowest power consumptions of 164 μW from 0.5-/1-V supplies. It achieves an energy efficiency of 32.8 pJ/bit at a data rate of 5 Mb/s, which is improved by ∼5.6× compared to the stateof- the-art RXs. The measured sensitivity of 915-MHz FSK signal receiving is -69.5 dBm with an LO frequency of 91.5 MHz, which is 1/10 of the carrier frequency. The achieved RX sensitivity figure-of-merit (FoM) is 174.3 dB.Agency for Science, Technology and Research (A*STAR)This work was supported in part by “Nanosystems at the Edge” through the Singapore A∗STAR SERC AME Program under Grant A18A4b0055, in part by the Minister of Science and Technology, China, through the National Science and Technology Major Project under Grant 2018AAA0103100, in part by the National Natural Science Foundation of China under Contract 61661166010, and the in part by the Shenzhen Science and Technology Program under Grant JCYJ20180306170435280