Reversible metallisation of soft UV patterned substrates

Soft UV (365 nm) patterning of ortho-nitrobenzyl functionalized thiol-on-gold self-assembled monolayers (SAMs) using acid catalysis, produces surfaces which can be used for the selective electro-deposition of copper. Exploiting the difference in the reduction peak potential between the photolysed and the masked regions of the SAM allows copper to be deposited selectively on those areas that have been exposed to the light. The copper can be removed by raising the electrode potential. The process is fully reversible so that depositing a pattern of copper, and removing it again is something that can be repeated many times. The copper deposited on the photolysed regions, like copper deposited on bare gold, forms a film of copper oxide, and so it is presumably formed on top of the SAM. Preliminary results for two-photon photocleavage show that it is also possible to implement patterning with sub-wavelength features

Programmable Assembly of DNA-Functionalized Liposomes by DNA

This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Nano, copyright © American Chemical Society after peer review and technical editing by publisher. To access the final edited and published work see http://dx.doi.org/10.1021/nn1030093Bionanotechnology involves the use of biomolecules to control both the structure and property of nanomaterials. One of the most studied examples is DNA-directed assembly of inorganic nanoparticles such as gold nanoparticles (AuNPs). However, systematic studies on DNA-linked soft nanoparticles, such as liposomes, are still lacking. We herein report the programmable assembly and systematic characterization of DNA-linked liposomes as a function of liposome size, charge, fluidity, composition, DNA spacer, linker DNA sequence, and salt concentration for direct comparison to DNA-directed assembly of AuNPs. Similar to the assemblies of AuNPs, sharp melting transitions were observed for liposomes where the first derivative of the melting curve full width at half-maximum (fwhm) is equal to or less than 1 °C for all of the tested liposomes, allowing sequence specific DNA detection. We found that parameters such as liposome size, charge, and fluidity have little effect on the DNA melting temperature. Cryo-TEM studies showed that programmable assemblies can be obtained and that the majority of the liposomes maintained a spherical shape in the assembled state. While liposome and AuNP systems are similar in many aspects, there are also important differences that can be explained by their respective physical properties.University of Waterloo || Natural Sciences and Engineering Research Council |

Nature's lessons in design: nanomachines to scaffold, remodel and shape membrane compartments.

Compartmentalisation of cellular processes is fundamental to regulation of metabolism in Eukaryotic organisms and is primarily provided by membrane-bound organelles. These organelles are dynamic structures whose membrane barriers are continually shaped, remodelled and scaffolded by a rich variety of highly sophisticated protein complexes. Towards the goal of bottom-up assembly of compartmentalised protocells in synthetic biology, we believe it will be important to harness and reconstitute the membrane shaping and sculpting characteristics of natural cells. We review different in vitro membrane models and how biophysical investigations of minimal systems combined with appropriate theoretical modelling have been used to gain new insights into the intricate mechanisms of these membrane nanomachines, paying particular attention to proteins involved in membrane fusion, fission and cytoskeletal scaffolding processes. We argue that minimal machineries need to be developed and optimised for employment in artificial protocell systems rather than the complex environs of a living organism. Thus, well-characterised minimal components might be predictably combined into functional, compartmentalised protocellular materials that can be engineered for wide-ranging applications

Perylene-Based Liquid Crystals as Materials for Organic Electronics Applications

Columnar phases formed by the stacking of disclike molecules with an intimate π–π overlap forms a 1D pathway for the anisotropic charge migration along the columns. Columnar phases have great potential in organic electronic devices to be utilized as active semiconducting layers in comparison to organic single crystals or amorphous polymers in terms of processability, ease of handling, and high charge carrier mobility. Intelligent molecular engineering of perylene and its derivatives provided access to tune the physical properties and self-assembly behavior. The columnar phase formed by perylene derivatives has great potential in the fabrication of organic electronic devices. There are several positions on the perylene molecule, which can be functionalized to tune its self-assembly, as well as optoelectronic properties. Thus, many liquid-crystalline molecules stabilizing the columnar phase, which are based on perylene tetraesters, perylene diester imides, and perylene bisimides, have been synthesized over the years. Their longitudinal and laterally extended derivatives, <i>bay</i>-substituted derivatives exhibiting a columnar phase, are reported. In addition, several liquid-crystalline oligomers and polymers based on perylene derivatives were also reported. All such modifications provide an option to tune the energy levels of frontier molecular orbitals with respect to the work function of the electrodes in devices and also the processability of such materials. In this feature article, we attempt to provide an overview of the molecular design developed to tune the applicable properties and self-assembly of perylene derivatives as well as recent developments related to their application in the fabrication of organic solar cells, organic light-emitting diodes, and organic field-effect transistors

Microwave-Assisted Method for the Synthesis of Perylene Ester Imides as a Gateway Toward Unsymmetrical Perylene Bisimides

A high yielding microwave-assisted synthetic method to obtain unsymmetrical perylene diester monoimide (PEI) by treating the perylene tetrester (PTE) with a requisite amine is reported. Perylene-based molecules are widely used in the construction of self-assembled supramolecular structures because of their propensity to aggregate under various conditions. In comparison to perylene bisimides (PBIs), PEIs are less studied in organic electronics/self-assembly due to the synthetic difficulty and low yields in their preparation. PEIs are less electron deficient and have an unsymmetric structure in comparison to PBIs. Further, the PEIs have a higher solubility than PBIs. The present method is applicable with a wide range of substrates like aliphatic, aromatic, benzyl amines, PTEs, and <i>bay</i>-annulated PTEs. This method provides a tuning handle for the optical/electronic properties of perylene derivatives and also provides an easy access to unsymmetrical PBIs from the PEIs

Nonsymmetrical cholesterol dimers constituting regioisomeric oxadiazole and thiadiazole cores: an investigation of the structure-property correlation

Three series of chiral nonsymmetrical dimers were prepared by connecting promesogenic cholesterol to a bent structure derived from a substituted 1,3,4-oxadiazole or 1,2,4-oxadiazole or 1,3,4-thiadiazole moiety. These two mesogenic segments are interconnected through spacers of varying lengths and parity. The structures of the bent achiral unit were systematically varied with different central heterocyclic cores to understand the influence of bent angles on the thermal and gelation behavior. The bent angle of the achiral unit, which is determined by the heterocyclic core, has a major role in the stabilization of frustrated phases. Dimers based on the 1,3,4-oxadiazole unit with a more bent structure stabilized frustrated phases like blue phases and twist grain boundary phases. The bent system with a wider bent angle preferred to stabilize chiral nematic and smectic A phases. It is interesting to note that an increased bent structure reduced the mesophase stability as in the case of dimers based on the 1,3,4-oxadiazole unit, where many compounds exhibited monotropic phases. In the case of dimers with a wider bent angle, enantiotropic mesomorphism was observed. All the compounds showed blue light emission in the solution. Among these chiral dimers, only the compounds based on the 1,3,4-oxadiazole unit showed the gelation ability, which emphasizes how small structural changes like bent angle, dipole moment and the type of heteroatom in the heterocyclic unit affect the macroscopic self-assembly. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique

Neuropsychiatric co-morbidities in non-demented Parkinson′s disease

Objective: To evaluate neuropsychiatric co-morbidities (depression, psychosis and anxiety) in non-demented patients with Parkinson′s disease (PD). Background: Non-motor symptoms like neuropsychiatric co-morbidities are common in Parkinson′s disease and may predate motor symptoms. Currently there is scarcity of data regarding neuropsychiatry manifestations in Indian patients with PD. Methods: In this cross-sectional study consecutive 126 non-demented patients with PD (MMSE ≥25) were enrolled. They were assessed using Unified Parkinson′s disease rating scale (UPDRS), Hoehn & Yahr (H&Y) stage, Schwab and England (S&E) scale of activity of daily life. Mini-international neuropsychiatric interview (MINI) was used for diagnosis of depression, psychosis and anxiety. Beck′s depression inventory (BDI), Brief psychiatric rating scale (BSRS) and Hamilton rating scale for anxiety (HAM-A) scales were used for assessment of severity of depression, psychosis and anxiety respectively. Results: Mean age and duration of disease was 57.9 ± 10.9 years and 7.3 ± 3.6 years respectively. At least one of the neuropsychiatric co-morbidity was present in 64% patients. Depression, suicidal risk, psychosis and anxiety were present in 43.7%, 31%, 23.8% and 35.7% respectively. Visual hallucinations (20.6%) were most frequent, followed by tactile (13.5%), auditory (7.2%) and olfactory hallucinations (1.6%). Patients with depression had higher motor disability (UPDRS-motor score 33.1 ± 14.0 vs 27.3 ± 13.3; and UPDRS-total 50.7 ± 21.8 vs 41.0 ± 20.3, all p values <0.05). Patients with psychosis were older (63.6 ± 8.0 years vs 56.1 ± 11.1 years, p < 0.05) and had longer duration of illness (8.6 ± 3.4 years vs 6.9 ± 3.5, p < 0.05). Conclusions: About two third patients with Parkinson′s disease have associated neuropsychiatric co-morbidities. Depression was more frequent in patients with higher disability and psychosis with longer duration of disease and older age. These co-morbidities need to be addressed during management of patients with PD

Photoisomerization behavior of photochromic amide-based azobenzene dyes exhibiting H-bonding effect: Synthesis and characterization

Amide linkage was introduced into azo compound at para position and its optical storage properties were investigated. Synthesized compounds showed liquid crystalline behavior when electron withdrawing group was inserted in the chemical structure. UV/Vis study showed that the photoisomerization effect in solution occurred at 18-24 sec (E-Z) and 5-11 hours (Z-E), whereas in solids it occurred at 30 sec (E-Z) and 5 hours (Z-E). Photoisomerization effect of amide based azodyes in the presence of hydrogen bonding is discussed for the first time. Effect of terminal electronic withdrawing groups on hydrogen bonding is speculated to be the reason behind the surprising behavior. Strong evidence for the structure property relations reported here is useful for applications such as optical storage device in which one can tune the structure according to one’s requirement