GUMBOS and NanoGUMBOS: Applications as Photosensitizers in Dye-sensitized Solar Cells

Renewable energy is a major concern due to increased world energy consumption. In particular, solar energy is a type of renewable energy source that uses devices known as solar cells to convert sunlight to electricity. Specifically, devices referred to as dye-sensitized solar cells (DSSCs) employ dyes to absorb solar energy. Dyes derived from ruthenium complexes have been typically used in DSSCs. Unfortunately, several disadvantages are associated with current ruthenium complex photosensitizers, which can be attributed to limited supply and expense of metals, as well as reduced absorption in the near-infrared region of the electromagnetic spectrum. Accordingly, this dissertation is a discussion of novel dyes referred to as group of uniform materials based on organic salts (GUMBOS) for application as photosensitizers in DSSCs. These GUMBOS are solid phase organic salts composed of bulky ions that have melting points from 25°C to 250°C. Importantly, GUMBOS can be tuned for multiple functions based on selected ions resulting in interesting physiochemical properties. In addition, nanomaterials derived from GUMBOS (nanoGUMBOS) can also result in significant properties. The first part of this dissertation involves the synthesis and characterization of nanoGUMBOS from cyanine dyes. These nanomaterials are prepared via a facile self-assembly approach, and spectral and electrochemical properties are investigated. In one study, controlled properties of cyanine-based nanoGUMBOS are found to be dependent on the counterion associated with the cationic dye. In another study, GUMBOS derived from cyanine dyes with increasing methine chain lengths are synthesized. In addition, binary nanomaterials consisting of two different cyanine methine chain length GUMBOS are prepared. The effect of Förster resonance energy transfer between these latter nanomaterials enhances fluorescence into the near-infrared region of the electromagnetic spectrum. The individual and binary nanoGUMBOS offer possible use as sensitizers that extend into the near-infrared region of the electromagnetic spectrum. The second part of this dissertation entails the incorporation of cyanine-based GUMBOS and nanoGUMBOS into DSSCs. In this study, various preparation methods are used for formation of titanium dioxide semiconductor electrodes. Solar cells comprised of these electrodes and cyanine-based GUMBOS are fabricated, and the performances of these DSSCs are investigated

Social infrastructures for the post-Covid recovery in the UK

The central conflict facing policymakers, the voluntary sector, and communities during the Covid-19 pandemic has been keeping safe from a virus that is transmitted interpersonally while also providing vital support to those in need. The report presents the findings from 12 months of ethnographic, participatory, and quantitative research, which has revealed that people have fallen back on their families, neighbourhoods and communities in order to navigate new challenges and burden. We call these networks of kinship and care within and between families, friends, and communities “social infrastructures” and argue that economic life and pandemic recovery relies on the strength of these foundational relations. In the UK, local and rapid response initiatives saved lives as voluntary sector, religious organisations, and Community Champions built on these relations of care to encourage vaccine uptake. These innovative social projects also helped people to grieve and recover from losses of life and livelihoods. We argue that both short- and long-term investment in these integrated social infrastructures is crucial for the post-Covid recovery in the UK

Detection and diversity of a putative novel heterogeneous polymorphic proline-glycine repeat (Pgr) protein in the footrot pathogen Dichelobacter nodosus

Dichelobacter nodosus, a Gram-negative anaerobic bacterium, is the essential causative agent of footrot in sheep. Currently, depending on the clinical presentation in the field, footrot is described as benign or virulent; D. nodosus strains have also been classified as benign or virulent, but this designation is not always consistent with clinical disease. The aim of this study was to determine the diversity of the pgr gene, which encodes a putative proline-glycine repeat protein (Pgr). The pgr gene was present in all 100 isolates of D. nodosus that were examined and, based on sequence analysis had two variants, pgrA and pgrB. In pgrA, there were two coding tandem repeat regions, R1 and R2: different strains had variable numbers of repeats within these regions. The R1 and R2 were absent from pgrB. Both variants were present in strains from Australia, Sweden and the UK, however, only pgrB was detected in isolates from Western Australia. The pgrA gene was detected in D. nodosus from tissue samples from two flocks in the UK with virulent footrot and only pgrB from a flock with no virulent or benign footrot for >10 years. Bioinformatic analysis of the putative PgrA protein indicated that it contained a collagen-like cell surface anchor motif. These results suggest that the pgr gene may be a useful molecular marker for epidemiological studies

A review and comparison of strategies for multi-step ahead time series forecasting based on the NN5 forecasting competition

Multi-step ahead forecasting is still an open challenge in time series forecasting. Several approaches that deal with this complex problem have been proposed in the literature but an extensive comparison on a large number of tasks is still missing. This paper aims to fill this gap by reviewing existing strategies for multi-step ahead forecasting and comparing them in theoretical and practical terms. To attain such an objective, we performed a large scale comparison of these different strategies using a large experimental benchmark (namely the 111 series from the NN5 forecasting competition). In addition, we considered the effects of deseasonalization, input variable selection, and forecast combination on these strategies and on multi-step ahead forecasting at large. The following three findings appear to be consistently supported by the experimental results: Multiple-Output strategies are the best performing approaches, deseasonalization leads to uniformly improved forecast accuracy, and input selection is more effective when performed in conjunction with deseasonalization

Tunable near-infrared emission of binary nano- and mesoscale GUMBOS

Tuning the emission spectra of organic nanomaterials is of great interest due to possible use in sensing, optoelectronics, and light harvesting applications. Herein, we report the tunable emission of binary organic nanomaterials derived from a group of uniform materials based on organic salts (GUMBOS). In these studies, the cations of cyanine-based GUMBOS are altered by increasing the number of alkyl groups on an attached methine chain. Mixtures of these GUMBOS are used to form binary nanomaterials, which are then characterized by use of UV-vis absorption spectroscopy, fluorescence spectroscopy, and cyclic voltammetry. Based on these studies, it is determined that these binary nanomaterials exhibit broad absorption spectra, as well as tunable emission spectra due to the presence of Förster resonance energy transfer (FRET). This tunable emission of binary nanomaterials suggests potential applications as sensitizers in the visible to near-infrared region of the electromagnetic spectrum. Furthermore, examination of electrochemical properties indicates possible utility for light harvesting and optoelectronic applications. © 2014 the Partner Organisations

Electro-optical characterization of cyanine-based GUMBOS and nanoGUMBOS

© 2014, The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht. Over the last decade in materials science, molecular electronics has emerged as one of the most rapidly developing interdisciplinary research areas with the prospects of ultimate miniaturization and integration of functional organic species with traditional silicon based semiconductor technology. To this end, fundamental studies to investigate the electrical and optical properties of organic nanomaterials deserve special attention. In this work, conductive probe atomic force microscopy (CP-AFM) and Raman spectroscopy have been performed on a new class of ionic materials, referred to as group of uniform materials based on organic salts (GUMBOS) and nanoparticles derived from these GUMBOS, termed as nanoGUMBOS. The GUMBOS investigated in this study are 1,1′-Diethyl-2,2′-cyanine bis (trifluoromethanesulfonyl) imide ([PIC][NTf2]) and 1,1′-Diethyl-2,2′-cyanine bis (pentafluoromethanesulfonyl) imide ([PIC][BETI]), which have been synthesized by use of a facile, template free anion exchange reaction between their respective parent compounds, followed by an ultrasonication assisted, additive free re-precipitation reaction to obtain the nanoscale particles (nanoGUMBOS). The ([PIC][NTf2] nanoGUMBOS were found to self-assemble into distinct diamond-like, trapezoid structures whereas [PIC][BETI] exhibited rod-like structures. [PIC][NTf2] nanoGUMBOS induced ~25 and ~38 times enhancement in the Raman signal intensity as compared to the parent compound [PIC][I] and [PIC][BETI] nanoGUMBOS respectively. In conjunction with the results of Raman spectra, the current-voltage (I-V) data obtained by CP-AFM are also presented as first-time evidence of electrical performance exhibited by these unique class of materials. The results reported in this study are indicative of their potential incorporation into next generation organic thin film applications in optoelectronics, dye-sensitized solar cells, and chemical sensors

Anion-controlled morphologies and spectral features of cyanine-based nanoGUMBOS - An improved photosensitizer

The ability to control the morphologies and spectral properties of organic low-dimensional nanomaterials is of paramount importance. The research reported herein demonstrates a template-free approach to tailored morphological and optical properties for a novel class of pseudoisocyanine (PIC)-based fluorescent organic nanoparticles derived from a group of uniform materials based on organic salts (GUMBOS). The synthesized nanoscale PIC-based particles (termed nanoGUMBOS), [PIC][NTf 2] and [PIC][BETI], exhibit interesting adaptability as a function of the associated anion. The diamond-shaped nanostructures of [PIC][NTf 2] and [PIC][BETI] nanorods exhibit enhanced fluorescence quantum yields relative to the parent compound, [PIC][I]. As supported by fluorescence lifetime measurements, these enhanced spectral properties can be attributed to differences in molecular self-assembly ordering (e.g., H- vs. J-aggregation) and restricted molecular rotation leading to reduced twisted intramolecular charge transfer in the nanoGUMBOS. The electrochemical properties of the PIC-based GUMBOS suggest their potential use in dye-sensitized solar cells. © 2012 The Royal Society of Chemistry

Ionically self-assembled, multi-luminophore one-dimensional micro- and nanoscale aggregates of thiacarbocyanine GUMBOS

Groups of uniform materials based on organic salts (GUMBOS), derived from thiacarbocyanine (TC)-based dyes with increasing methyne chain lengths, were prepared through a single-step metathesis reaction between the iodide form of the TC dye and lithium bis(perfluoroethylsulfonyl)imide as the lipophilic anion source. Ionic self-assembly of these fluorescent hydrophobic GUMBOS resulted in aqueous dispersions of one-dimensional micro- and nanoscale molecular aggregates. Blended binary and ternary aggregates containing multiple TC GUMBOS were also prepared. These nanostructures exhibited a variety of aspect ratios, affording tunable Förster resonance energy transfer (FRET) and aggregation-dependent spectroscopic properties. © 2012 American Chemical Society

Tunable Size and Spectral Properties of Fluorescent NanoGUMBOS in Modified Sodium Deoxycholate Hydrogels

Microstructures of sodium deoxycholate hydrogels were altered considerably in the presence of variable tris(hydroxymethyl)aminomethane (TRIS) concentrations. These observations were confirmed by use of X-ray diffraction, polarized optical microscopy, rheology, and differential scanning calorimetry measurements. Our studies reveal enhanced gel crystallinity and rigidity with increasing TRIS concentrations. The tunable hydrogel microstructures obtained under various conditions have been successfully utilized as templates to synthesize cyanine-based fluorescent nanoGUMBOS (nanoparticles from a group of uniform materials based on organic salts). A systematic variation in size (70–200 nm), with relatively low polydispersity and tunable spectral properties of [HMT][AOT] nanoGUMBOS, was achieved by use of these modified hydrogels. The gel microstructures are observed to direct the size as well as molecular self-assembly of the nanomaterials, thereby tuning their spectral properties. These modified hydrogels were also found to possess other interesting properties such as variable morphologies ranging from fibrous to spherulitic, variable degrees of crystallinity, rigidity, optical activity, and release profiles which can be exploited for a multitude of applications. Hence, this study demonstrates a novel method for modification of sodium deoxycholate hydrogels, their applications as templates for nanomaterials synthesis, as well as their potential applications in biotechnology and drug delivery