Iodine Fluorescence Research Articles

The N,N,N′,N′-tetraphenylbenzidine-based conjugated hypercrosslinked polymers for adsorping iodine and fluorescence sensing 2,4-dinitrophenol, iodine

Although progress has been made in the development of hypercrosslinked polymers (HCPs) for iodine uptake, their fluorescence performance and fluorescence sensing performance are rare due to the lack of conjugated behavior in common HCPs. Herein, the N,N,N′,N′-tetraphenylbenzidine-based conjugated hyper-crosslinked polymers (conjugated TPB-based HCPs) were efficiently fabricated via a one-step Friedel-Crafts arylation reaction by selecting N,N,N′,N′-tetraphenylbenzidine (TPB) and N,N′-diphenyl-N,N′-di(m-tolyl)benzidine (DPDB) as the basic building blocks and p-dimethoxybenzene (DMB) as an external crosslinker which will lead to the formation of the conjugated structures. The derived TPB-based HCPs (denoted as, TPB-DMB and DPDB-DMB) possessed excellent stability and high surface areas, Their iodine adsorption capacities are up to 4.25 and 3.56 g·g−1. The high iodine adsorption is caused by chemical adsorption. The fully conjugated structure and the 3D aryl network give the conjugated TPB-based HCPs excellent luminescence properties and fluorescence sensing properties for 2,4-dinitrophenol and iodine. The fluorescence sensing mechanisms of the conjugated TPB-based HCPs for DNP and I2 includes photo-induced electron process and the resonance energy transfer process. This study provides a viable approach for the development of highly efficient iodine sorbents and fluorescence sensors of DNP and iodine for addressing environmental issues.

The construction of the flexible covalent organic frameworks with phenyl sulfide as linkers used for adsorping iodine and fluorescence sensing picric acid

The efficient capture of radioactive iodine and sensitive detection of picric acid are very important to environmental protection. Herein, we synthesized two new flexible 4,4′-thiodianiline (TDA)-based covalent organic frameworks (TTDA and HTDA) by using simple Schiff-base polycondensation reactions with flexible 4,4′-thiodianiline (TDA) and 2,4,6-tris(4-formylphenoxy)-1,3,5-triazine (TPT − 3 − CHO) and hexa(4-formyl-phenoxy)cyclotriphosphazene (NOP − 6 − CHO). The flexible TDA-based COFs are porous, crystalline, and show high thermal stability and good chemical stability. Due to the high content of heteroatoms, abundant aromatic rings, and orderly network, it is conducive to electron transfer, the as-prepared flexible TDA-based COFs show outstanding dual properties of iodine adsorption and fluorescence sensing. The maximum iodine capacities of TTDA and HTDA are as high as 3.34 and 4.38 g g−1, respectively. The flexible TDA-based COFs can be used for sensing picric acid with low limits of detection (LODs) of 1.25 × 10−9 and 1.67 × 10−9 mol L−1 and high quenching constants (KSV) of 6.00 × 104 and 4.88 × 104 L mol−1, respectively.

The effects of the linker length on iodine adsorption and fluorescence sensing property of the N, O, P containing covalent organic frameworks

AbstractCovalent organic frameworks (COFs) are novel porous organic materials with structural tunable features and have great potential applications in iodine adsorption and fluorescence sensing. We explore the effect of linker length on the function of the COFs prepared through the Schiff base aldehyde‐amine polycondensation with different linkers in lengths. The linker length affects the specific surface area, aperture, pore volume, and electron density of the COFs, thus affecting the ability to bind with other substances. The synthetic HPDA and HDAT in this report showed excellent iodine adsorption of 4.53 and 3.92 g g−1, respectively. Meanwhile, HPDA and HDAT are quite sensitive to the fluorescence sensing of picric acid (PA) and o‐nitrophenol (o‐NP) with their limits of detection of 1.86 × 10−11, 4.69 × 10−11 mol L−1, respectively. HPDA and HDAT can be outstanding adsorbents for iodine and excellent fluorescent sensors for PA and o‐NP, respectively.

Nanoarchitectonics of bipyrazole-based porous organic polymer for iodine absorption and fluorescence sensing picric acid and formation of liquid complex of its (poly)iodide ions

A new bipyrazole-based porous organic polymer, TMBPH, was constructed by a nucleophilic substitution polymerization reaction with π-electron-rich 3,3′,5,5′-tetramethyl-4,4′-bipyrazol (TMBP) and hexachlorocyclotriphosphazene (HCCP). Its Brunauer-Emmett-Teller (BET) and Langmuir surface area are 68.97 and 160.69 ​m2 ​g-1, respectively, and its pore volume is 0.0851 ​cm3 ​g-1. TMBPH has a good thermal stability and displays excellent guest uptake of 5.86 ​g ​g-1 in iodine vapor. Interestingly, TMBPH presents a liquid polyiodide complex because of its high iodine adsorption capacity and low pore volume. TMBPH can also adsorb iodine in the solution, and the absorbed iodine can be released at higher temperatures or in the solution. TMBPH as an adsorbent is recovered and reused easily. Furthermore, fluorescent study indicated that TMBPH exhibits high sensitivity to electron-deficient picric acid (PA) via fluorescence quenching. Thus TMBPH can become an ideal absorbent for I2 and fluorescent sensing material for PA to address environmental issues.

Dual functional N,O,P containing covalent organic frameworks for adsorping iodine and fluorescence sensing to p-nitrophenol and iodine

Abstract Covalent-organic-frameworks (COFs) are emerging porous organic materials with fascinating structural features and potential applications in the fields of iodine capture and spectroscopy. However, no dual-functional COFs with both iodine adsorption and fluorescence sensing have been reported. We herein report the construction of the three dual-functional COFs via Schiff base polycondensations with flexible building blocks cyclophosphazene-based aldehydes (NOP-6-CHO) and benzidine (BD) with different substituent groups (-OCH3 and –OH). The resulting COFs show high thermal stability and exhibit different crystallinity. The specific surface area, pore volume, and crystallinity decrease due to the introduction of the substituent group into the linker. Hydrogen bonding interaction makes the significant improvement of microscopic order degree as well as crystallinity of the COFs. Remarkably, the as-prepared COFs exhibit excellent adsorptive performance for iodine molecules via vapor trapping adsorption, and adsorption capacity reach as high as 4.41, 3.78, and 4.47 g g−1 for HBD, HDASD, and HDOBD, respectively. When suspended in polar organic solvents, the three COFs have high fluorescence under UV light. They can detect p-nitrophenol (p-NP) and iodine with high sensitivity and selectivity.

Multi-responsive fluorescent switches and iodine capture of porous hydrogen-bonded self-assemblies

Porous nanoribbons from gels may act as smart materials for applications in iodine absorption and fluorescence sensing for gaseous nitrobenzene, and could reversibly change its fluorescence color under shearing force and solvent annealing.

Confounding effects of temperature in laser-induced fluorescence concentration measurements with iodine vapor

Laser Induced Fluorescence (LIF) provides a non-invasive, quantitative measurement of fluorescent tracers in complex mixing flows. The common availability of broad linewidth lasers and their use with iodine vapor tracers raises a significant concern about confounded tracer concentration measurements, due to the strong dependence of iodine fluorescence on both tracer concentration and flow temperature. We model the sensitivity of iodine fluorescent response to temperature fluctuations, especially for flows with significant temperature contrasts to ambient conditions, and establish a temperature uniformity requirement that bounds the relative error in tracer concentration measurements. We show that in a conventional laboratory setup, in order to bound the measured concentration error to about 5%, the relative temperature fluctuations in iodine LIF must be approximately an order of magnitude smaller than the desired measurement resolution of relative concentration fluctuations. Iodine LIF should thus be employed with great caution.

Triazine-based conjugated microporous polymers constructing triphenylamine and its derivatives with nitrogen as core for iodine adsorption and fluorescence sensing I2

Abstract Three new triazine-based conjugated microporous polymers with nitrogen as cores containing triphenylamine (TPA), 4,4′,4″-tris(N,N-diphenylamino)triphenylamine (TDATA) and 4,4′,4″-tri[phenyl(m-tonyl)amino]triphenylamine moieties (TMDATA) (TTPA, TTDATA and TTMDATA) were constructed via Friedel-Crafts reaction catalysed by methanesulfonic acid. The resulting CMPs possess high BET surface area of over 308, 491 and 456 m2 g−1, large pore volumes, good stability, and display efficient and reversible guest uptake of 4.92, 4.72 and 4.49 g g−1 in iodine vapour which are higher than that of the CMPs with benzene as core. Two ways to release the adsorbed iodine were explored: either slow release into ethanol or quickly release upon heating (with a high degree of control). Spectral studies make us known that the strong affinity for I2 is mainly due to large porosity, a conjugated π-electron aromatic system, C N bonds, and propeller-like twisted structures. Furthermore, luminescent study indicated that TTPA exhibits high sensitivity to electron-deficient I2 via fluorescence quenching. TTPA shows the largest amount of iodine adsorption and was the first CMP used fluorescence sensing iodine.

Triazine-based conjugated microporous polymers with N,N,N′,N′-tetraphenyl-1,4-phenylenediamine, 1,3,5-tris(diphenylamino)benzene and 1,3,5-tris[(3-methylphenyl)-phenylamino]benzene as the core for high iodine capture and fluorescence sensing of o-nitrophenol

A series of novel triazine-based conjugated microporous polymers were constructed via Friedel–Crafts polymerization.

Rapid diagnostics of urinary iodine using a portable EDXRF spectrometer.

A method for urinary iodine diagnostics using a portable energy-dispersion X-ray fluorescent (EDXRF) spectrometer is proposed. The principle of the method consists in excitation of the sample atoms fluorescence by the energy spectrum intentionally formed from the spectrum of an X-ray tube using an optimized X-ray scheme. The optimization by the criterion of the minimum detection limit for L-series iodine fluorescence lines included the calculation of optimal atomic numbers for materials of a re-radiator and a filter, and their thicknesses, the collimation system parameters, and an X-ray tube voltage. Experimentally achieved detection limits were 45 and 75 μg/L by I-Lα and I-Lβ lines, respectively, at the theoretically extreme value 30 μg/L. This sensitivity is found to be sufficient for urinary iodine diagnostics in the range from 50 to 200 μg/L. The results obtained from different patients have shown the satisfactory convergence for the iodine concentration determination by Lα and I-Lβ fluorescence lines. The simple sample preparation procedure and comparably small sizes of the apparatus allows rapid researches directly in clinical settings.

Composition dependent structural, optical and photosensitive properties of a series of charge-transfer tin halides

A series of organic-inorganic hybrid tin halides formulated as Sn(phen)XmYn (phen = 1,10-phenanthroline, X/Y = Cl, Br, I, m + n = 4) were designed and prepared to study main group metal halides as photosensitive dyes. The colors of compounds are tunable with the change of mole ratio of the halides due to the ligand to ligand charge-transfer (LLCT). Intense visible-range absorption can be obtained by increasing the mole ratio of iodine and intense ultraviolet fluorescence emission can be obtained by increasing the mole ratio of chlorine. DFT calculations suggest that the LLCT occurs from electron-rich halide ion to π* orbit of phen. The iodide materials have narrow energy gap and suitable energy level of the excited state for exciton transfer to TiO2 semiconductor. Photocurrent responses experiments using the compounds treated TiO2 electrodes showed that upon irradiation stable photocurrent generated and Sn(phen)I4 has the best photosensitive behavior.

Superb hydroxyl radical-mediated biocidal effect induced antibacterial activity of tuned ZnO/chitosan type II heterostructure under dark

Reactive oxygen species (ROS) is the most dominating factor for bacteria cell toxicity due to release of oxidative stress. Hydroxyl radical (·OH) is a strong oxidizing ROS that has high impact on biocidal activity. This present paper highlights ·OH influenced antibacterial activity and biocidal propensity of tuned ZnO/chitosan (ZnO/CS) nanocomposite against Pseudomonas putida (P. putida) in the absence of light for the first time. For this purpose, the CS proportion was increased by 25 % (w/w) of ZnO during the preparation of ZnO/CS nanocomposite and a systematic study of different ROS like superoxide anion (O 2 ·− ), hydrogen peroxide (H2O2) and ·OH production as well as their kinetics was carried out both under UV irradiation and in dark by UV–Vis spectroscopy using NBT dye, starch and iodine reaction and fluorescence spectroscopy using terephthalic acid. The decoration of ZnO nanoparticles (ZnO·NPs) with CS tuning was characterized by XRD and FTIR spectroscopy, revealing sustained crystallinity and surface coating of ZnO NP (size about ~24 nm) by CS molecule. The hybridization of ZnO nanoparticles with CS@50 wt% (w/w) resulted superior biocidal activity (81 %) within 3 h in dark mediated by optimum production of ·OH among all ROS. Here we have proposed the enhanced production of ·OH in ZnO/CS due to generation of holes by entrapment of electrons in acceptor level formed in nanocomposite for the first time, and the acceptor levels were probed by Positron annihilation lifetime spectroscopy. The increase in non-positronium (non-Ps) formation probability (I2) in ZnO/CS nanocomposite confirmed the acceptor levels. This work also confirms surface defect-mediated ROS generation in dark, and zinc interstitials are proposed as active defect sites for generation of holes and ·OH for the first time and confirmed by steady-state room temperature photoluminescence spectroscopy. Finally, a plausible mechanism was hypothesized focusing on hole generation in ZnO NP and hole transfer from CS for the first time, and a heterostructure of type II was proposed.

Combined SRCT & FXCT – The next steps

One of the goals in developing synchrotron radiation x-ray computed tomography (SRCT) for biomedical specimens, is allowing particular tissues and cell types to be marked in the images. This is equivalent to the staining in histology, which enables researchers to visualise and measure tissue structure and biochemical processes within the specimen. Some progress in this direction for SRCT is being made, using a variety of contrast agents that alter the natural x-ray attenuation of the marked tissue [1]. However there are limits to the usefulness of these attenuation altering techniques. Often high concentrations of potentially disruptive chemicals are required with reduced compatibility for in-vivo studies. Another image highlighting technique which might prove more sensitive is x-ray fluorescence imaging. In this case usually endogenous elemental markers are visualised. We would like to develop a lower resolution, but wider field of view means of three-dimensional (3-D) fluorescence imaging compatible with SRCT. We have previously proposed a technique in which x-ray fluorescence CT (FXCT) and SRCT data can be collected simultaneously [2]. This work resulted in proof of concept modelling, and a simple experiment test system. We show data here which demonstrate a two-dimensional (2-D) reconstruction of an iodine fluorescence map from a phantom. Measurements were performed with a fixed beam modulating mask using the Imaging and Medical beam line (IMBL) at the Australian Synchrotron. Fluorescence data was obtained during a CT scan using a single point detector, while transmission data was simultaneously collected using an area detector. A maximum likelihood expectation maximisation (MLEM) iterative algorithm was used to reconstruct the fluorescence map. We report on technique development and now believe compressive sensing (CS) imaging techniques suit SRCT and may overcome the issues encountered so far in combining SRCT and FXCT.

Laser fluorescence complex for online iodine-129 and iodine-127 detection in gaseous media using a tunable diode laser

This letter reports on the development of a laser fluorescence complex for high-sensitivity real-time selective detection of 127I and 129I molecular iodine isotopologues in gaseous media. A diode laser tunable in the range of 631–638 nm is used as an excitation source of molecular iodine fluorescence. Sensitivities of detection of molecular iodine isotopologues and boundary relations for simultaneous detection of 127I and 129I were evaluated. It is shown that practical realization of the methods for the detection of molecular iodine isotopologues using a developed laser fluorescence complex provides an opportunity to control these isotopologues in gaseous technological media formed during the reprocessing of spent nuclear fuel and in the atmospheric air.

Investigations of Peripheral Propulsive Deceleration Jets on a Mars Science Laboratory Aeroshell

The objective to send more massive landed missions to the surface of Mars necessitates further research and development for ways to adequately decelerate the lander, such as propulsive deceleration. Experimental measurements using planar laser-induced iodine fluorescence provide qualitative visualizations and quantitative propulsive decelerator jet mole fraction measurements over a 0.22% scaled Mars Science Laboratory aeroshell. Peripheral (off-centerline) sonic and supersonic propulsive decelerator jet models, with jet exit velocities of Mach 1.0 and 2.66, were studied in Mach 12 flow and compared with numerical results obtained using computational fluid dynamics. Experimental visualizations were obtained for various thrust coefficients ranging from 0.5 to 3.0 in increments of 0.5. Experimental results indicate that, for both sonic and supersonic jets, the bow shock is preserved between the peripheral jets and, as thrust coefficient increases, the bow shock is pushed farther from the aeroshell forebody, with the supersonic jets having a greater shock standoff distance than sonic models at thrust coefficient greater than 2.0. Comparisons of the experimental visualizations to computed streamlines and shock locations show good agreement. Computed propulsive decelerator jet mole fractions for both sonic and supersonic thrust coefficient of 1.5 closely match experimental results through the jet cores and in cross-sectional cuts.

Propulsion Deceleration Studies Using Planar Laser-Induced Iodine Fluorescence and Computational Fluid Dynamics

Future high-mass spacecraft entering the thin Martian atmosphere will exceed the capabilities of supersonic and subsonic parachutes and will incorporate other means of deceleration. Propulsive deceleration is one technology that is being considered. The interaction of the spacecraft aerodynamics with the propulsion deceleration jets has been shown to cause a decrease in drag coefficient with increasing thrust coefficient, which is not desirable for deceleration. Planar laser-induced iodine fluorescence images for a single-propulsion deceleration jet showed a lifting of the vehicle bow shock away from the aeroshell. Flowfield calculations showed that this lifting provided a shielding effect, preventing the freestream mass and momentum flux from reaching the aeroshell surface, creating a low-pressure region between the jet boundary and the aeroshell. With four peripheral propulsive deceleration jets, planar laser-induced fluorescence images and computational fluid dynamics calculations showed that the vehicle bow shock is maintained between the jets as the thrust coefficient is increased. This bow shock is responsible for greater drag preservation with the peripheral jets. The calculations also showed that high pressure is maintained between the peripheral jets. These results suggest that using a few peripheral propulsion-deceleration jets located near the aeroshell shoulder would provide the greatest drag preservation when using propulsive deceleration.

Polarized fluorescence of jet-cooled molecular iodine

The degree of polarized fluorescence of molecular iodine 127I2 cooled in a supersonic jet under rotationally selective excitation in the electronic transition B3Π0u+-X1Σg+ has been measured and calculated. It was found that the interaction of the angular momentum of the molecule with the nuclear spins of iodine atoms leads to a considerable depolarizing effect. This effect is most pronounced for small rotational quantum numbers of the angular momentum that are comparable with the total nuclear spin of the iodine molecule, which is equal to 5.

In situ detection of atomic and molecular iodine using Resonance and Off-Resonance Fluorescence by Lamp Excitation: ROFLEX

Abstract. We demonstrate a new instrument for in situ detection of atmospheric iodine atoms and molecules based on atomic and molecular resonance and off-resonance ultraviolet fluorescence excited by lamp emission. The instrument combines the robustness, light weight, low power consumption and efficient excitation of radio-frequency discharge light sources with the high sensitivity of the photon counting technique. Calibration of I2 fluorescence is achieved via quantitative detection of the molecule by Incoherent Broad Band Cavity-enhanced Absorption Spectroscopy. Atomic iodine fluorescence signal is calibrated by controlled broad band photolysis of known I2 concentrations in the visible spectral range at atmospheric pressure. The instrument has been optimised in laboratory experiments to reach detection limits of 1.2 pptv for I atoms and 13 pptv for I2, for S/N = 1 and 10 min of integration time. The ROFLEX system has been deployed in a field campaign in northern Spain, representing the first concurrent observation of ambient mixing ratios of iodine atoms and molecules in the 1–350 pptv range.

Molecular Iodine Fluorescence Spectra Generated with Helium-Neon Lasers for Spectrometer Calibration

Gas-phase molecular iodine laser-induced fluorescence (LIF) spectra were recorded out to 815 nm at 1 cm(-1) resolution using green, yellow, and red helium-neon (HeNe) lasers as excitation sources. Nine previously unreported I(2) B←X absorption transitions accessed by these lasers were identified, and specific rovibronic transition assignments were made for two hundred LIF peaks--more than sixty per laser. These I(2) LIF peaks can be used to calibrate the vacuum wavenumber coordinate of spectrometers to better than 0.1 cm(-1) accuracy. In particular, green HeNe excitation of the I(2) R(106) 28-0 transition leads to strong fluorescence well suited for calibration, with a rotational doublet spacing of 15 cm(-1) and a doublet-to-doublet spacing of 190 cm(-1). Calibration by HeNe I(2) LIF may be an especially valuable technique for Raman spectroscopy applications.

X-ray fluorescence camera for imaging of iodine media in vivo

X-ray fluorescence (XRF) analysis is useful for measuring density distributions of contrast media in vivo. An XRF camera was developed for carrying out mapping for iodine-based contrast media used in medical angiography. Objects are exposed by an X-ray beam from a cerium target. Cerium K-series X-rays are absorbed effectively by iodine media in objects, and iodine fluorescence is produced from the objects. Next, iodine Kalpha fluorescence is selected out by use of a 58-microm-thick stannum filter and is detected by a cadmium telluride (CdTe) detector. The Kalpha rays are discriminated out by a multichannel analyzer, and the number of photons is counted by a counter card. The objects are moved and scanned by an x-y stage in conjunction with a two-stage controller, and X-ray images obtained by iodine mapping are shown on a personal computer monitor. The scan pitch of the x and y axes was 2.5 mm, and the photon counting time per mapping point was 2.0 s. We carried out iodine mapping of non-living animals (phantoms), and iodine Kalpha fluorescence was produced from weakly remaining iodine elements in a rabbit skin cancer.