One pressing concern today is to construct sensors that can withstand various disturbances for highly selective and sensitive detecting trace analytes in complicated samples. Molecularly imprinted ...polymers (MIPs) with tailor-made binding sites are preferred to be recognition elements in sensors for effective targets detection, and fluorescence measurement assists in highly sensitive detection and user-friendly control. Accordingly, molecular imprinting-based fluorescence sensors (MI-FL sensors) have attracted great research interest in many fields such as chemical and biological analysis. Herein, we comprehensively review the recent advances in MI-FL sensors construction and applications, giving insights on sensing principles and signal transduction mechanisms, focusing on general construction strategies for intrinsically fluorescent or nonfluorescent analytes and improvement strategies in sensing performance, particularly in sensitivity. Construction strategies are well overviewed, mainly including the traditional indirect methods of competitive binding against pre-bound fluorescent indicators, employment of fluorescent functional monomers and embedding of fluorescence substances, and novel rational designs of hierarchical architecture (core-shell/hollow and mesoporous structures), post-imprinting modification, and ratiometric fluorescence detection. Furthermore, MI-FL sensor based microdevices are discussed, involving micromotors, test strips and microfluidics, which are more portable for rapid point-of-care detection and in-field diagnosing. Finally, the current challenges and future perspectives of MI-FL sensors are proposed.
•Molecular imprinting based fluorescence sensors (MI-FL sensors) are reviewed.•Sensing principle and signal transduction mechanisms are introduced.•General and novel construction strategies for MI-FL sensors are summarized.•MI-FL sensor based microdevices are overviewed.•The present challenges and perspectives of MI-FL sensors are proposed.
A non-equiatomic Ni3.5Co3Cr1.5 medium-entropy alloy (AT0) with a single-phase face-centered cubic structure (FCC) directly obtained by arc-melting shows the low yield strength of 147 MPa, ultimate ...tensile strength of 447 MPa and large total elongation to fracture of 78.8%. By doping Al and Ti, the as-cast (Ni3.5Co3Cr1.5)90Al5Ti5 high-entropy alloy (AT5) exhibits enhanced strength-ductility synergy. Compared to AT0 alloy, the yield strength of AT5 alloy increases more than fivefold to 792 MPa, ultimate tensile strength doubles to 1004 MPa, and still remaining a high elongation of 38.2%. The apparent increase in strength can be attributed to uniformly distributed, high-content, conherent (Ni,Co)3(Al,Ti)-type nanoprecipitates formed in FCC matrix. The formation of various dislocation substructures and crossed stacking faults (SFs) with Lomer-Cottrell locks during tensile deformation is responsible for strain hardening of AT5 alloy.
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A novel adsorbent of N-doped carbonized microspheres were developed from chitin (N-doped CM-chitin) for adsorption of Congo red (CR). The N-doped CM-chitin showed spherical shape and consisted of ...carbon nanofibers with 3D hierarchical architecture. There were many micro/nano-pores existing in N-doped CM-chitin with high surface area (455.703 m
g
). The N element was uniformly distributed on the carbon nanofibers and formed with oxidize-N graphitic-N, pyrrolic-N, and pyridinic-N. The N-doped CM-chitin showed excellent adsorption capability for CR and the maximum adsorption amount was approximate 954.47 mg g
. The π-π/n-π interaction, hydrogen-bond interactions, and pore filling adsorption might be the adsorption mechanisms. The adsorption of N-doped CM-chitin was considered as a spontaneous endothermic adsorption process, and which well conformed to the pseudo-second-order kinetic and Langmuir isotherm model. The N-doped CM-chitin exhibited an effective adsorption performance for dynamic CR water with good reusability. Therefore, this work provides new insights into the fabrication of a novel N-doped adsorbent from low-cost and waste biomasses.
In this work, resveratrol (Res) was incorporated into chitosan microspheres for controlled release and stabilisation. The microspheres were prepared by emulsion chemical cross-linking method, and ...vanillin was used as the novel cross-linker. The microspheres showed a smooth surface with irregular small particles and internal voids with a size distribution between 53 and 311
μm. Interpenetrating network cross-linking mechanisms might account for the Schiff base reaction between chitosan and vanillin. The encapsulation efficiency of Res within microspheres was up to 93.68%. Res contained within microspheres was protected from light and heat compared with the free Res. In addition, release behaviours were governed by two distinct stages and dependent on pH of release media. Diffusion, swelling and erosion mechanisms might coexist for the full controlled release and Higuchi was the most suitable model for the whole release procedure. Thus, controlled release and stabilization of Res were achieved through incorporation of Res into cross-linked chitosan microspheres by vanillin.
Thermosensitive molecularly imprinted polymers (T-MIPs) on porous carriers were prepared via the synergy of dual functional monomers of 4-vinylpyridine (VP) and N-isopropylacrylamide (NIPAM), for ...selective recognition and controlled adsorption and release of bisphenol A (BPA) by the temperature regulation. The porous polymer supporter was synthesized by multistep swelling of polystyrene and then both the NIPAM with temperature responsiveness and the basic monomers of VP were grafted on them in a simple way. The resultant T-MIPs showed high binding capacity, fast kinetics, and the adsorption processes were found to follow Langmuir–Freundlich isotherm and pseudo-second-order kinetic models. The adsorption capacity increased slightly along with the rise of temperature (such as 20°C) under lower critical solution temperature (LCST, 33°C) and decreased fast above LCST (such as 50°C). Subsequently, the T-MIPs were employed as novel adsorbents for selective solid-phase extraction (SPE) of BPA from seawater and yogurt samples. Satisfying recoveries in the range of 94.83–98.47% were obtained with the precision of 3.21% at ambient temperature (20°C). Through 6 adsorption–desorption cycles, the reusable T-MIPs exhibited a good recoverability with the relative standard error within 9.8%. The smart T-MIPs provided great potentials for selective identification, adsorption/release and removal of BPA by simple stimuli responsive regulation.
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•Two functional monomers were employed for the thermosensitive porous MIPs (T-MIPs).•The T-MIPs demonstrated high adsorption, fast kinetics, excellent selectivity and reusability.•The T-MIPs were thermo-dependent, presenting the highest imprinting performances at 20°C.•The applicability was favorable in seawater and food sample analysis.
The pectin (CEP) was used as matrix material to prepare Ag@AgCl/ZnO nanocomposites with a green method for photocatalytic antibacterial activity in visible-light. Briefly, Ag@AgCl plasmonic hybrids ...were prepared in the CEP macromolecule matrix with size control, which was attributed to the stability of carboxyl and hydroxyl groups on the CEP. Subsequently, an effective and green two-steps approach was explored for the fabrication of CEP-Ag@AgCl/ZnO nanocomposites with resource saving and environment friendly. Interestingly, more Ag+ was converted into metallic Ag in the CEP-Ag@AgCl/ZnO than that in the CEP-Ag@AgCl. This phenomenon was attributed that the reducibility of free hemiacetal hydroxyl groups on CEP was realized with the help of NaOH in the preparation of CEP-ZnO. In addition, the CEP chains were not obviously destroyed except for the change in the crystallinity after the preparation of the CEP-Ag@AgCl/ZnO nanocomposites, indicating that the method was non-destructive. Moreover, the pH triggered release of Zn2+ and low release of Ag+ in CEP-Ag@AgCl/ZnO nanocomposites with excellent photocatalytic antibacterial activity were confirmed in this work. The proposed green process provides a new idea for the large-scale production of antibacterial pectin-based nanocomposites in industry with a low-cost.
•Application of pectin from Akebia trifoliata var. australis waste was broadened.•CEP-Ag@AgCl plasmonic hybrids were prepared with non-destructive of CEP.•A green two-steps process was proposed to prepare the CEP-Ag@AgCl/ZnO.•CEP-Ag@AgCl/ZnO exhibit pH triggered release of Zn2+ with low Ag+ loss.•CEP-Ag@AgCl/ZnO exhibit photocatalytic antibacterial activity in visible-light.
The Haiyang-2D (HY2D) satellite is the fourth ocean dynamics environment monitoring satellite launched by China. The satellite operates on a re-entry frozen orbit, which necessitates orbital ...maneuvers to maintain its designated path once the satellite’s sub-satellite point deviates beyond a certain threshold. However, the execution of orbit maneuvers presents a significant challenge to the field of Precise Orbit Determination (POD). The thesis selects the on-board GPS data of HY2D satellite in December 2023 and five maneuvering days of that year. Employing a multifaceted approach that includes the assessment of observational data quality, orbit overlap, external orbit validation, and SLR (Satellite Laser Ranging) verification, the research delves into precise orbit determination during both maneuver and non-maneuver periods. The results indicate that: (1) The average number of satellites tracked by the receiver is 6.4; (2) During the non-maneuver periods, the average RMS (Root Mean Square) value of the radial difference in the 6-h overlapping arc segment is 0.66 cm, and the three-dimensional position difference is about 1.16 cm; (3) When compared with the precision science orbits (PSO) provided by CNES (Centre National d’Études Spatiales), the average values of the RMS values of the differences in the radial (R), transverse (T), and normal (N) directions during the non-maneuver and maneuver periods are respectively 1.32 cm, 2.31 cm, 1.92 cm and 3.04 cm, 8.78 cm, 2.72 cm. (4) The SLR verification of the orbit revealed a residual RMS of 2.24 cm. This suggests that by incorporating the modeling of maneuver forces during the maneuver periods, the impact of orbital maneuvers on orbit determination can be mitigated.
A new single-hole hollow molecularly imprinted polymer (SHH-MIP) was prepared by multistep seed swelling polymerization using Sudan I as template molecule and successfully applied to selective ...solid-phase extraction (SPE) of Sudan dyes in chilli sauce samples. The polymers possessed high specific surface area obtained by nitrogen adsorption and good thermal stability without decomposition lower than 380 °C by thermogravimetry analysis. Much higher binding capacity was exhibited than with irregular solid MIP prepared by bulk polymerization, because most of the binding sites were located in the surface of the polymers, facilitating template removal and mass transfer. Accordingly, the SHH-MIP was employed as SPE adsorbent for chilli sauce analysis and offered high recoveries for Sudan I in the range of 87.5-103.4% with the precision of 1.94-5.33% at three spiked levels. The SHH-MIP with high selectivity and high stability was demonstrated to be potentially applicable for high selective preconcentration and determination of trace Sudan dyes in complicated samples.
A surface-enhanced Raman scattering (SERS) strategy based on 4-mercaptopyridine (MPY)-modified gold nanoparticles (AuNPs) was developed for the rapid and sensitive detection of melamine in milk ...powder. The SERS measurement of melamine strongly relied on the “hotspot” effect, in which AuNPs immediately aggregated upon the addition of melamine, leading to significantly enhanced Raman intensity of the reporter molecule MPY and a color change for the solution from red to blue-gray. The limit of detection based on a signal to noise of 3 (S/N = 3) was found to be as low as 0.1 ppb of melamine, with an excellent linearity of 0.5–100 ppb, demonstrating a higher sensitivity and a wider quantitation range than direct SERS sensing methods based on enhanced substrate. An impressive specificity for melamine detection over various common metal ions and excipients in dairy products, even at concentrations of 100-fold higher than melamine, was achieved. Good recoveries of 88.5% and 111.7% were obtained from milk samples spiked to 20 and 100 ppb levels, respectively. The proposed method is potentially applicable for the rapid in situ determination of melamine in complex matrices.
Figure
An indirect SERS strategy based on 4-mercaptopyridine (MPY) modified gold nanoparticles (AuNPs) for rapid and sensitive detection of melamine
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