In this research fluorescent optochemical pH probes for the detection of ischaemia have been investigated. Myocardial ischaemia is the most prominent risk during heart surgery. During open heart surgery the heart is temporarily arrested and, since there no blood flowing, oxygen supply and removal of waste products is stopped and heart cells can be damaged. In this paper we propose a novel method to monitor the condition of the heart by placing optochemical pH sensors on several strategic places around the heart during surgery. Low cost opto-chemical pH sensors, using a HPTS (8-hydroxy-1,3,6-pyrene trisulfonic acid trisodium salt) fluorescent dye encapsulated in a thin bio-compatible hydrogel layer, were investigated for this application. Our research started with an extensive optical characterization of several types of hydrogel layers at different pH levels. Secondly a reflection probe prototype using several of these layers was designed, built and tested. Dual wavelength excitation and ratiometric detection of the fluorescent signals was used to detect the pH level. Typical output signals of 35% to 53% per pH in the range from 6.5-8.0 pH have been measured and a response time of typically 400 seconds was obtained for the prototypes. Finally based on our measurements on the HPTS layers and the reflection probe we propose an improved type of pH probe for the detection of ischaemia during open heart surgery.

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Thanks to the low cost and earth's abundant potassium resources, potassium ion batteries (PIBs) have attracted much interest as alternative energy storage devices. However, there is still a great challenge to develop suitable anode materials for PIBs with high specific capacity, fast charge/discharge and stable ion storage. Nowadays, conductive metal-organic frameworks (c-MOFs) with excellent physicochemical properties are employed for different electrochemical applications, but the study of their potassium storage performance remains unknown, and the detailed potassium storage mechanism needs to be explored. Herein, nanostructured Co₃(HHTP)₂ c-MOF (Co-CAT MOF, HHTP: 2,3,6,7,10,11-hexahydroxytriphenylene) is synthesized by a liquid-phase method and evaluated as the anode for PIBs. The active sites and open pathways in the conductive Co-CAT MOF promote ion diffusion and electron transfer, exhibiting high reversible specific capacity (332 mA h g⁻¹ at 0.1 A g⁻¹), excellent long-cycle stability (230 mA h g⁻¹ at the current density of 1.0 A g⁻¹ after 700 cycles) and outstanding rate performance (165 mA h g⁻¹ at 4.0 A g⁻¹), which is superior to the typical PIB anodes. Combined with different ex situ characterization techniques, the potassium storage mechanism based on 8-electron transfer is revealed. Furthermore, Co-CAT MOF exhibits excellent Li-ion storage performance. In the half-cell, the Co-CAT MOF electrode displays a high reversible capacity of 800 mA h g⁻¹ at 200 mA g⁻¹. In addition, the Co-CAT//LiCoO₂ full cell cycles for 100 cycles at 200 mA h g⁻¹. It is believed that Co-CAT MOF is a promising electrode material for potassium/lithium storage, and the proposed ion storage mechanism can be used to discover other MOF-based electrodes for energy storage.

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The addition of nitrogen doped mesoporous carbon spheres (NMCSs) to Portland cement-based materials was studied as an approach to produce materials of desired properties. Lower electrical resistivity and higher compressive strength were recorded in the presence of NMCSs, while the addition of a dispersion agent (Pluronic F127), caused an increase in electrical resistivity and strength reduction. This performance was related to the variation in zeta potential and hydrodynamic radius of NMCSs in alkaline medium. The zeta-potential of NMCSs was defined by the non-ionic surfactant F127. This led to a “poisoning” of the active NMCSs surface, consequently hindering the interaction of NMCSs with the cement-based material. Therefore, F127 is a non-suitable dispersing agent. In contrast, the presence of NMCSs alone enhances the desired cement-based materials properties, where reduced electrical resistivity and increased compressive strength were achieved, while cement hydration and pore network development were maintained close to NMCSs-free specimens.@en