Paper spray ionization (PSI) mass spectrometry (MS) is an emerging tool for ambient reaction monitoring via microdroplet reaction acceleration. PSI-MS was used to accelerate and monitor the time course of the reaction of dansyl chloride with aniline, in acetonitrile, to produce dansyl aniline. Three distinct PSI arrangements were explored in this study representing alternative approaches for sample loading and interaction; conventional single tip as well as two novel setups, a dual-tip and a co-axial arrangement were designed so as to limit any on-paper interaction between reagents. The effect on product abundance was investigated using these different paper configurations as it relates to the time course and distance of microdroplet travel. It was observed that product yield increases at a given distance and then decreases thereafter for all PSI configurations. The fluorescent property of the product (dansyl aniline) was used to visually inspect the reaction progress on the paper substrate during the spraying process. Amongst the variety of sample loading methods the novel dual-tip arrangement showed an increased product yield and microdroplet density, whilst avoiding any on-paper interaction between the reagents.
Furocoumarin (furo[3,2-c]coumarin) derivatives have been synthesized from single step, high yielding (82-92%) chemistry involving a 4-hydroxycoumarin 4 + 1 cycloaddition reaction. They are characterized by FTIR, 1H-NMR, and, for the first time, a comprehensive UV-Vis and fluorescence spectroscopy study has been carried out to determine if these compounds can serve as useful sensors. Based on the fluorescence data, the most promising furocoumarin derivative (2-(cyclohexylamino)-3-phenyl-4H-furo[3,2-c]chromen-4-one, FH), exhibits strong fluorescence (ФF = 0.48) with long fluorescence lifetime (5.6 ns) and large Stokes' shift, suggesting FH could be used as a novel fluorescent chemosensor. FH exhibits a highly selective, sensitive and instant turn-off fluorescence response to Fe3+ over other metal ions which was attributed to a charge transfer mechanism. Selectivity was demonstrated against 13 other competing metal ions (Na+, K+, Mg2+, Ca2+, Mn2+, Fe2+, Al3+, Ni2+, Cu2+, Zn2+, Co2+, Pb2+ and Ru3+) and aqueous compatibility was demonstrated in 10% MeOH-H2O solution. The FH sensor coordinates Fe3+ in a 1:2 stoichiometry with a binding constant, Ka = 5.25 × 103 M-1. This novel sensor has a limit of detection of 1.93 µM, below that of the US environmental protection agency guidelines (5.37 µM), with a linear dynamic range of ~28 (~2-30 µM) and an R2 value of 0.9975. As an exemplar application we demonstrate the potential of this sensor for the rapid measurement of Fe3+ in mineral and tap water samples demonstrating the real-world application of FH as a "turn off" fluorescence sensor.
Aiming for new glycolipids with enhanced chemical stability and close structural similarity to natural cell membrane lipids for the development of a drug delivery system, we have synthesized double amide analogs of glyco-glycerolipids. The synthesis applied a Staudinger reaction based coupling of a 1,3-diazide with fatty acid chlorides. While the concept furnished the desired glucosides in reasonable yields, the corresponding lactosides formed a tetrahydropyrimidine based 1:1 coupling product instead. This unexpected coupling result likely originates from steric hindrance at the iminophosphorane intermediate and provides an interesting core structure for potentially bioactive surfactants. The assembly behavior of both glycolipid types was investigated by optical polarizing microscopy, DSC and surface tension studies.
The exciting discovery of the semiconducting-like properties of deoxyribonucleic acid (DNA) and its potential applications in molecular genetics and diagnostics in recent times has resulted in a paradigm shift in biophysics research. Recent studies in our laboratory provide a platform towards detecting charge transfer mechanism and understanding the electronic properties of DNA based on the sequence-specific electronic response, which can be applied as an alternative to identify or detect DNA. In this study, we demonstrate a novel method for identification of DNA from different shrimp viruses and bacteria using electronic properties of DNA obtained from both negative and positive bias regions in current-voltage (I-V) profiles. Characteristic electronic properties were calculated and used for quantification and further understanding in the identification process. Aquaculture in shrimp industry is a fast-growing food sector throughout the world. However, shrimp culture in many Asian countries faced a huge economic loss due to disease outbreaks. Scientists have been using specific established methods for detecting shrimp infection, but those methods do have their significant drawbacks due to many inherent factors. As such, we believe that this simple, rapid, sensitive and cost-effective tool can be used for detection and identification of DNA from different shrimp viruses and bacteria.
The discovery of semiconducting behavior of deoxyribonucleic acid (DNA) has resulted in a large number of literatures in the study of DNA electronics. Sequence-specific electronic response provides a platform towards understanding charge transfer mechanism and therefore the electronic properties of DNA. It is possible to utilize these characteristic properties to identify/detect DNA. In this current work, we demonstrate a novel method of DNA-based identification of basidiomycetes using current-voltage (I-V) profiles obtained from DNA-specific Schottky barrier diodes. Electronic properties such as ideality factor, barrier height, shunt resistance, series resistance, turn-on voltage, knee-voltage, breakdown voltage and breakdown current were calculated and used to quantify the identification process as compared to morphological and molecular characterization techniques. The use of these techniques is necessary in order to study biodiversity, but sometimes it can be misleading and unreliable and is not sufficiently useful for the identification of fungi genera. Many of these methods have failed when it comes to identification of closely related species of certain genus like Pleurotus. Our electronics profiles, both in the negative and positive bias regions were however found to be highly characteristic according to the base-pair sequences. We believe that this simple, low-cost and practical method could be useful towards identifying and detecting DNA in biotechnology and pathology.
Three fluorescent organic compounds-furocoumarin (FC), dansyl aniline (DA), and 7-hydroxycoumarin-3-carboxylic acid (CC)-are mixed to produce almost pure white light emission (WLE). This novel mixture is immobilised in silica aerogel and applied as a coating to a UV LED to demonstrate its applicability as a low-cost, organic coating for WLE via simultaneous emission. In ethanol solution and when immobilised in silica aerogel, the mixture exhibits a Commission Internationale d'Eclairage (CIE) chromaticity index of (0.27, 0.33). It was observed that a broadband and simultaneous emission involving coumarin carboxylic acid, furocoumarin and dansyl aniline played a vital role in obtaining a CIE index close to that of pure white light.
Large (mega) Stokes shift molecules have shown great potential in white light emission for optoelectronic applications, such as flat panel display technology, light-emitting diodes, photosensitizers, molecular probes, cellular and bioimaging, and other applications. This review aims to summarize recent developments of white light generation that incorporate a large Stokes shift component, key approaches to designing large Stokes shift molecules, perspectives on future opportunities, and remaining challenges confronting this emerging research field. After a brief introduction of feasible pathways in generating white light, exemplifications of large Stokes shift molecules as white light candidates from organic and inorganic-based materials are illustrated. Various possible ways to design such molecules have been revealed by integrating the photophysical mechanisms that are essential to produce red-shifted emission upon photoexcitation, such as excited state intramolecular proton transfer (ESIPT), intramolecular charge transfer (ICT), excited state geometrical relaxation or structural deformation, aggregation-induced emission (AIE) alongside the different formations of aggregates, interplay between monomer and excimer emission, host-guest interaction, and lastly metal to ligand charge transfer (MLCT) via harvesting triplet state. Furthermore, previously reported fluorescent materials are described and categorized based on luminescence behaviors on account of the Stokes shifts value. This review will serve as a rationalized introduction and reference for researchers who are interested in exploring large or mega Stokes shift molecules, and will motivate new strategies along with instigation of persistent efforts in this prominent subject area with great avenues.
There are various approaches to enhancing the catalytic properties of TiO₂, including modifying its morphology by altering the surface reactivity and surface area of the catalyst. In this study, the primary aim is to enhance the photocatalytic activity by changing the TiO₂ nanotubes' architecture. The highly ordered infrastructure is favorable for a better charge carrier transfer. It is well known that anodization affects TiO₂ nanotubes' structure by increasing the anodization duration which in turn influence the photocatalytic activity. The characterizations were conducted by FE-SEM (fiend emission scanning electron microscopy), XRD (X-ray diffraction), RAMAN (Raman spectroscopy), EDX (Energy dispersive X-ray spectroscopy), UV-Vis (Ultraviolet visible spectroscopy) and LCMS/MS/MS (liquid chromatography mass spectroscopy). We found that the morphological structure is affected by the anodization duration according to FE-SEM. The photocatalytic degradation shows a photodegradation rate of k = 0.0104 min-1. It is also found that a mineralization of Simazine by our prepared TiO₂ nanotubes leads to the formation of cyanuric acid. We propose three Simazine photodegradation pathways with several intermediates identified.
A coumarin-terminated self-assembled monolayer on silver particles (C-SAM) from the reduction of silver ions in the presence of compound 3 was successfully prepared by utilizing phase transfer method, and analyzed by FTIR, SEM-EDS, UV-Visible and a particle sizer. The fluorescence behavior of coumarin termini was carried out in ethanol and chloroform with emission wavelength determined at 386 nm, suggesting an interaction between the carbonyl group and the solvent media. The dispersion was then investigated in acidic and basic conditions, showing a direct proportional correlation between the emission and the pH of the aqueous. These results were consistent for interpreting hydrogen bonds, particularly between the carbonyl group with either proton of the alcohol (C=O----H-O-R) or positive species in acidic conditions (C=O----H(+)). The interactions were possible only when the coumarin terminal rearranged in the monolayer and the carbonyl exerted towards the solvent media, while the rest of the molecules were separated from the solvents.
In the title compound, C(10)H(9)N(3)O(3), there is a small twist between the benzene and triazole rings [dihedral angle = 6.32 (7)°]; the carb-oxy-lic acid residue is almost coplanar with the benzene ring to which it is attached [O-C-C-C torsion angle = 1.49 (19)°]. The main deviation from coplanarity of the non-H atoms is found for the hy-droxy group which is almost perpendicular to the remaining atoms [N-C-C-O torsion angle = -75.46 (16)°]. In the crystal, the presence of O-H⋯O (between carboxyl groups) and O-H⋯N (between the hy-droxy group and the triazole ring) hydrogen bonds leads to supra-molecular chains along [03[Formula: see text]]. The chains are connected into sheets via C-H⋯O(hy-droxy) inter-actions.
In the title mol-ecule, C(14)H(9)N(3)O(3), the dihedral angle between the quinoxaline and benzene rings is 77.13 (9)°. The mol-ecule is twisted about the ether-benzene O-C bond, with a C-O-C-C torsion angle of -102.8 (2)°. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds, forming layers in the ab plane, with one nitro O atom accepting two such inter-actions. The layers stack along the c-axis direction via weak C-H⋯π inter-actions.
In the crystal structure of the title compound, C(18)H(12)N(2)O, the dihedral angle between the two fused-ring systems is 84.3 (1) °; the C-O-C angle at the ether O atom is 117.31 (18)°.
There are two mol-ecules in the asymmetric unit of the title compound, C(14)H(10)N(2)O: the dihedral angles between their aromatic ring planes are 47.4 (4) and 46.8 (3)°. In the crystal structure, mol-ecules are linked by N-H⋯N hydrogen bonds from the secondary nitro-gen N-H donor to the tertiary N-atom acceptor of a symmetry-related neighbour, resulting in hydrogen-bonded chains. The two independent chains both propagate in [100].
The dihedral angle between the two aromatic ring systems in the title compound, C(15)H(12)N(2)O, is 42.6 (1)°. The angle at the O atom is widened to 117.7 (1)°.
The aromatic ring systems in the title compound, C(14)H(10)N(2)O, form a dihedral angle of 63.8 (1)°, resulting in an opening up of the ether-O atom angle to 118.2 (1)°.
The dihedral angle between the two aromatic ring systems in the title compound, C(15)H(12)N(2)O, is 79.4 (1)°. The angle at the O atom is widened to 116.93 (9)°.
The dihedral angle between the two aromatic ring systems in the title compound, C(15)H(12)N(2)O, is 85.9 (1)°; The angle at the O atom is widened to 118.2 (2)°. The quinoxalin-yloxy part of the mol-ecule lies on a mirror plane and the tolyl group is disordered over two positions about the mirror plane.
: In this work the influence of carbon nano-dots (CNDs) on absorption of ultra violet (UV) spectra in hybrid PVA based composites was studied. The FTIR results reveal the complex formation between PVA and CNDs. The shifting was observed in XRD spectrum of PVA:CNDs composites compared to pure PVA. The Debye-Scherrer formula was used to calculate the crystallite size of CNDs and crystalline phases of pure PVA and PVA:CNDs composites. The FESEM images emphasized the presence and dispersion of C-dots on the surface of the composite samples. From the images, a strong and clear absorption was noticed in the spectra. The strong absorption that appeared peaks at 280 nm and 430 nm can be ascribed to the n-π* and π-π* transitions, respectively. The absorption edge shifted to lower photon energy sides with increasing CNDs. The luminescence behavior of PVA:CNDs composite was confirmed using digital and photo luminescence (PL) measurements. The optical dielectric constant which is related to the density of states was studied and the optical band gap was characterized accurately using optical dielectric loss parameter. The Taucs model was used to determine the type of electronic transition in the samples.