Molecular schizophrenics as sensors and actuators

‘Sensornets’ are large-scale distributed sensing networks comprised of many small sensing devices equipped with memory, processors, and short-range wireless communications capabilities.1 These devices, assembled from building blocks known as ‘Motes’ can gather and share sensor data from multiple locations through in-built wireless communications capabilities. The vision of incorporating chemical and biological sensing dimensions into these platforms is very appealing, and the potential applications in areas critical to society are truly revolutionary.2 For example, the environment; sensors monitoring air and water quality will be able to provide early warning of pollution events arising at industrial plants, landfill sites, reservoirs, and water distribution systems at remote locations. The crucial missing part in this scenario is the gateway through which these worlds will communicate; how can the digital world sense and respond to changes in the real world? Unfortunately, it would appear from the lack of field deployable devices in commercial production that attempts to integrate molecular sensor science into portable devices have failed to bear the fruits promised; this problem is what we call ‘the chemo-/ bio-sensing paradox’.3 In this work, we shall discuss how sensors and sensing systems are likely to develop in the coming years, with a particular focus on the critical importance of new concepts in fundamental materials science to the realisation of these futuristic chemo-/bio-sensing systems. This work focuses on the fundamental challenges, such as the ability to control the characteristics and behaviour of polymers and fluids, and processes occurring at solid-liquid interfaces. We will highlight the key role that stimuli-responsive materials can play in producing new “adaptive” materials capable of exhibiting dramatic changes in properties by external stimuli, such as, photon irradiation.4 In particular, the photochromic processes of spirobenzopyran, figure 1. These materials have the potential to revolutionise the way we design chemical and biological sensing systems

Electrochemical study of 1,3-indandione derivatives of terthiophenes

Properties and behavior of a group of four newly synthesized derivatives of terthiophene and terthienylenvinylene was studied. All four investigated monomers bear a 1,3-indandione substituent at the central thiophene ring and two of them (ThIV, ThIVM) have additional vinyl bonds introduced between the thiophene rings. In addition, ThIM and ThIVM have 5 positions of the two terminal rings blocked with methyl groups. The measurements were done using cyclic voltamperometry (CV) in solutions of 0.1M Bu4NBF4 in CH2Cl2. It was found that ThI and ThIV polymerise easily. CV of ThI reveals a reduction peak resulting probably from the abstraction of a proton. During polymerisation of ThIV a group of peaks is observed indicating its stepwise oxidation process. The polymerisation potential of ThIV was found to be lower than that of ThI which could mean that formation of radical-cation is easier in the former. Stability measurements indicated that polymer films of ThI are electrochemically stable in CH2Cl2 and films of ThIV are not. Efforts to polymerise ThIM and ThIVM failed. Their CVs revealed only peaks coming from oxidation of the monomers, some of which were semi-reversible

A multiswitchable poly(terthiophene) bearing a spiropyran functionality: understanding photo and electrochemical control

An electroactive nitrospiropyran-substituted polyterthiophene, 2-(3,3′′-dimethylindoline-6′-nitrobenzospiropyranyl)ethyl 4,4′′-didecyloxy-2,2′:5′,2′′-terthiophene-3′-acetate, has been synthesized for the first time. The spiropyran, incorporated into the polymer backbone by covalent attachment to the alkoxyterthiophene monomer units, leads to multiple coloured states as a result of both electrochemical isomerization of the spiropyran moiety to merocyanine forms as well as electrochemical oxidation of the polyterthiophene backbone and the merocyanine substituents. While electrochemical polymerization of the terthiophene monomer could occurs without the apparent oxidation of the spiropyran, the subsequent electrochemistry is complex and clearly involves this substituent. In order to understand this complex behaviour, the first detailed electrochemical study of the oxidation of the precursor spiropyran, 1-(2-hydroxyethyl)-3,3-dimethylindoline-6’-nitrobenzospiropyran, was undertaken, showing that, in solution, an irreversible electrochemical oxidation of the spiropyran occurs leading to reversible redox behaviour of at least two merocyanine isomers. With these insights, an extensive electrochemical and spectroelectrochemical study of the nitrospiropyran-substituted polyterthiophene films reveals an initial irreversible electrochemical oxidative ring opening of the spiropyran to oxidized merocyanine. Subsequent reduction and cyclic voltammetry of the resulting nitromerocyanine-substituted polyterthiophene film gives rise to the formation of both merocyanine π-dimers or oligomers and π-radical cation dimers, between polymer chains. Although merocyanine formation is not electrochemically reversible, the spiropyran can be photochemically regenerated, at least in part, through irradiation with visible light. SEM and AFM images support the conclusion that the bulky spiropyran substituent is electrochemically isomerizes to the planar merocyanine moiety affording a smoother polymer film. The conductivity of the freestanding polymer film was found to be 0.4 S cm-1

Towards a flexible Decision Support Tool for MSY-based Marine Protected Area design for skates and rays

Peer-reviewed Paper. This is a pre-copyedited, author-produced version of an article accepted for publication in ICES Journal of Marine Science following peer review. The version of record Dedman, S., Officer, R., Brophy, D., Clarke, M., & Reid, D. G. (2017). Towards a flexible Decision Support Tool for MSY-based Marine Protected Area design for skates and rays. Ices Journal of Marine Science, 74(2), 576–587. https://doi.org/10.1093/icesjms/fsw147 is available online at: https://academic.oup.com/icesjms/article/74/2/576/2669563 & https://doi.org/10.1093/icesjms/fsw147.It is recommended that demersal elasmobranchs be managed using spatial proxies for Maximum Sustainable Yield. Here we combine escapement biomass—the percentage of the stock which must be retained each year to conserve it—with maps of predicted Catch Per Unit Effort (CPUE) of four ray species [cuckoo (Leucoraja naevus), thornback (Raja clavata), blonde (Raja brachyura), and spotted (Raja montagui)], created using Boosted Regression Tree modelling. We then use a Decision Support Tool to generate location and size options for Marine Protected Areas to protect these stocks, based on the priorities of the various stakeholders, notably the minimisation of fishing effort displacement. Variations of conservation/fishing priorities are simulated, as well as differential priorities for individual species, with a focus on protecting nursery grounds and spawning areas. Prioritizing high CPUE cells results in a smaller closed area that displaces the most fishing effort, whereas prioritizing low fishing effort results in a larger closed area that displaces the least fishing effort. The final result is a complete software package that produces maps of predicted species CPUE from limited survey data, and allows disparate stakeholders and policymakers to discuss management options within a mapping interface

A study of TiO2 binder-free paste prepared for low temperature dye-sensitized solar cells

A binder-free titania paste was prepared by chemical modification of an acidic TiO2 sol with ammonia. By varying the ammonia concentration, the viscosity of the acidic TiO2 suspension increased, thereby allowing uniform films to be cast. The photoelectrochemical performance of TiO2 electrodes, cast as single layers, was dependent on the thermal treatment cycle. Fourier transform infrared spectroscopy was used to characterize the extent of residual organics and found that acetates from the TiO2 precursor preparation were retained within the electrode structure after thermal treatment at 150 °C. Electrodes of nominal thickness 4 lm produced an energy conversion efficiency as high as 5.4% using this simple thermal treatment

Electrochemical and optical aspects of cobalt meso-carbazole substituted porphyrin complexes

A series of cobalt (II) porphyrin complexes modified with carbazole rings at one or more meso positions of the macrocycle were synthesized and characterized as to their spectroscopic and basic electrochemical properties in non-aqueous media. The effect of the number and position (syn and anti) of carbazole groups on the complexes properties were investigated. The comparison was made to cobalt (II) porphyrin containing mesityl groups at the meso-positions. The relation between the site of redox processes in cobalt meso-carbazole substituted porphyrins were analysed. It was shown that the conjugated π-ring system of the porphyrin macrocycle, the cobalt central metal ion and the carbazole peripheral substituents are redox-active

Photoelectrochemical cells based on inherently conducting polymers

This review of photoelectrochemical cells (PECs) based on inherently conducting polymers (ICPs) deals with the mechanisms of operation and the various factors that influence the overall efficiency of PECs. The factors addressed include ICP composition and oxidation state, the use of nanostructured surfaces and interfaces, and the PEC electrolyte and redox mediator

Electrotactic ionic liquid droplets

To our knowledge, this work describes the first example of electro-guided, self-propelled droplets composed solely of an ionic liquid (IL), namely trihexyl(tetradecyl)phosphonium chloride ([P6,6,6,14][Cl]). These self-propelled droplets travel along an aqueous-air boundary to desired destinations within the fluidic network. Electrotactic movement of the droplets is due to asymmetric electro-stimulated release of a constituent of the IL droplet, the [P6,6,6,14]+ ion, which is a very efficient cationic surfactant, through electrochemically generated Cl- gradients. The direction and speed of movement can be controlled by switching the impressed voltage (typically 5 - 9V) ON or OFF, and by changing the polarity of the electrodes in contact with the electrolyte solution. The Cl- gradients required for droplet movement are electrochemically generated using 3D printed electrodes which are embedded within the fluidic channels. On demand creation of these Cl- gradients electrochemically allows reversible droplet movement over expended periods of time, and provides a means for precise control over the droplet trajectory