The effect of gold nanostructure morphology on label-free electrochemical immunosensor design

In this research, various electrodeposition techniques were used to form gold nanostructures (AuNSs) on the surface of graphite rod electrode (GE). Three distinct AuNS morphologies on GE have been achieved based on the composition of electrodeposition solution. The use of H2SO4 as a supporting electrolyte resulted in the formation of smaller but more numerous AuNSI with a modified electrode's electroactive surface area (EASA) of 0.213 cm2. Exchanging the supporting electrolyte to KNO3 and increasing HAuCl4 concentration facilitated the formation of bigger AuNSII particles with electrode EASA of 0.116 cm2. Finally, a partial coverage of GE by branched gold nanostructures (AuNSIII) was achieved with an estimated EASA of 0.110 cm2, when the HAuCl4 and KNO3 concentrations were increased further. Estimated values of heterogeneous electron transfer rate constant did not depend on AuNS morphology. Electrode modified with AuNSI exhibited the highest bovine serum albumin (BSA) immobilization efficiency and the highest relative response for the detection of specific polyclonal antibodies against BSA (p-anti-BSA) compared to other modified electrodes. The limit of p-anti-BSA detection in PBS buffer was calculated as 0.63 nM, while in blood serum it was 0.71 nM. Linear ranges were from 1 to 7 nM and from 1 to 5 nM, respectively.

Removal of chloride ions from a copper leaching solution, using electrodialysis, to improve the uranium extraction through ion-exchange

This study shows the technical feasibility to recover uranium from copper Pregnant Leaching Solutions (PLS) using ion-exchange, after a removal of chloride ions using the electrodialysis (ED) technique. The original copper PLS solutions came from the National Copper Corporation (CODELCO), from their hydrometallurgical operations, which contained high concentrations of chloride ions. These solutions contained average concentrations of 22 g/L chloride ions, pH 1.5 - 1.8 and 20 mg/L uranium. The high chloride contents made the uranium recovery technically unfeasible, because of the high volumes of chemical reagents needed to operate. To eliminate the chloride ions selectively, a modified electrodialysis (ED) process was developed. The ED process was made of a three-compartment cell. This system removed selectively the chloride ions, and replaced them with sulphuric ions, without modifying the composition of the copper PLS solution, to allow a continuous operation of the copper production plant. The ED process decreased the chloride content from 22 g/L to 6 g/L. Finally, static and dynamic load tests were performed for both the original PLS and the treated PLS, using 3 different anion-exchange resins: Dowex-1, Lewatit A365 and Lewatit MP62-WS. The loading capacity of the ion-exchange resins was increased 4 times approximately.

Th4+ tuned aggregation-induced emission: A novel strategy for sequential ultrasensitive detection and separation of Th4+ and Hg2

A novel strategy, Th⁴⁺ tuned aggregation-induced emission, for sequential ultrasensitive detection and separation of Th⁴⁺ and Hg²⁺ was developed successfully. For demonstration this strategy, we designed and synthesized two tripodal gelators TH (tri-(isoniazid-4-yl)-functionalized trimesic acylhydrazine) and TA (tri-(pyridine-4-yl)-functionalized trimesic amide). The TH and TA could assemble into a stable supramolecular polymer hydrogel THTA-G in DMSO/H₂O (3.3:6.7, v/v) binary-solution. The THTA-G does not show aggregation-induced emission (AIE) effect. However, after addition of Th⁴⁺ into the THTA-G, the obtained metallogel THTA-GTh shows strong green AIE effect, which indicated that Th⁴⁺ could tune the gel generation of AIE effect. Interestingly, the THTA-G could ultrasensitive fluorescently detect Th⁴⁺, and the corresponding metallogel THTA-GTh could ultrasensitively detect Hg²⁺. The detection limits of THTA-G and THTA-GTh for Th⁴⁺ and Hg²⁺ are 8.61 × 10^-11 mol/L and 1.08 × 10^-11 mol/L, respectively. Additionally, the xerogels of THTA-G and THTA-GTh could separate Th⁴⁺ and Hg²⁺ from aqueous solution with excellent ingestion capacity, and the THTA-G could be used as a writable smart light-emitting material.

Highly selective Fe3+ and F-/H2PO4- sensor based on a water-soluble cationic pillar[5]arene with aggregation-induced emission characteristic

A water-soluble cationic pillar[5]arene (CWP5) without lager conjugated construction was first reported as a novel pillar[5]arene-based aggregation-induced emission luminogen (AIEgen), which showed a remarkable aggregation-induced emission (AIE) with the concentration increasing. The AIE effect of CWP5 has affected by different solvent, it had the lowest critical aggregation concentration (CAC) value and highest fluoresence emission intensity in DMSO solution. Simultaneously, CWP5 can serve as a chemosensor for the successively fluorescent detection of Fe³⁺ and F^-/H₂PO₄^- with high sensitivity and selectivity. A rewritable portable test kit made from CWP5 provides a possibility to on-site detection and manufacture of encryption and decryption materials.

Preparation of platinum-based 'cauliflower microarrays' for enhanced ammonia gas sensing

In amperometric gas sensors, the flux of gas to electrode surfaces determines the analytical response and detection limit. For trace concentration detection, the resulting low current prevents the miniaturisation of such sensors. Therefore, in this study, we have developed repeating arrays of nanostructures which maximise flux towards their surface. Unique platinum 3D cauliflower-shaped deposits with individual floret-shaped segments have been produced in a single step electrodeposition process. The confined walls of recessed microelectrode arrays (10 μm in diameter, 90 electrodes) are utilized to produce these structures with a high surface area. Distinct segments are observed, with the gaps corresponding to electrodes adjacent in the microarray; thus the majority of the deposits face the primary diffusion zones. The sizes and shapes of the deposits are characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM) and the largest structures are found to be 22 ± 1 μm in width and 7.9 ± 0.2 μm in height over the microhole. These modified electrodes are employed to detect ammonia using the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C₂mim][NTf₂], as an electrolyte. Current responses on the cauliflower arrays were seven times higher for linear sweep voltammetry and ca. 12 times higher for chronoamperometry, relative to the bare microrrays, and limits of detection were less than 1 part per million of ammonia (gas phase concentration). This work highlights the use of modified microarrays with highly accessible 3D structures for enhanced electroanalytical detection of analyte species at ultra low concentrations.

A novel organic electrochromic device with hybrid capacitor architecture towards multicolour representation

A multicolour novel electrochromic device containing both anodic and cathodic EC materials was fabricated with the simple hybrid capacitor architecture.