Large Blue Shift Research Articles

An ultra-fast, NIR, mitochondria-targeted fluorescent probe for sulfur dioxide based on benzopyrylium and its imaging of in living cells

Near-infrared emission, is a significant influencing contributor to the detection and visualization of biomolecules and their associated target analytes by fluorescent probes in vivo. SO2 is a critical component of reactive sulfur species (RSS), playing an irreplaceable influence towards various physiological activities. Excessive inhalation of SO2 can cause irreparable respiratory damage, which also is associated with cardiovascular disease, lung cancer and neurological disorders. In this work, we have rationally developed a NIR (690 nm) fluorescence probe 1 based on benzopyrylium towards SO2. The probe 1 can ratiometricly detect SO2 in ultra-fast time (10 s) and overcome physiological interferences from long-term exposure of biothiols. The probe 1 displayed a large blue-shift of 210 nm along with the obvious fluorescence transition from red to blue. The sensing mechanism was proved to be the π-conjugated system of benzopyrylium unit in probe 1 was broken duo to the active CC double bond attacked by SO2. Fortunately, the probe 1 can serve as an effective cell-permeable molecular tool to detect and visualize dynamic equilibrium of SO2 in mitochondria of living cells.

Changes in the Electronic Transitions of Polyethylene Glycol upon the Formation of a Coordinate Bond with Li+, Studied by ATR Far-Ultraviolet Spectroscopy.

This study investigates the electronic transitions of complexes of lithium with polyethylene glycol (PEG) by the absorption bands of solvent molecules via attenuated total reflectance spectroscopy in the far-UV region (ATR-FUV). Alkali-metal complexes are interesting materials because of their functional characteristics such as good ionic conductivity. These complexes are used as polymer electrolytes for Li batteries and as one of the new types of room-temperature ionic liquids, termed solvation ionic liquids. Considering these applications, alkali-metal complexes have been studied mainly for their electrochemical characteristics; there is no fundamental study providing a clear understanding of electronic states in terms of electronic structures for the ground and excitation states near the highest occupied molecular orbital-lowest occupied molecular orbital transitions. This study explores the electronic transitions of ligand molecules in alkali-metal complexes. In the ATR-FUV spectra of the Li-PEG complex, a decrease in intensity and a large blue shift (over 4 nm) were observed to result from an increase in the concentration of Li salts. This observation suggests the formation of a complex, with coordinate bonding between Li+ and the O atoms in PEG. Comparison of the experimental spectrum with a simulated spectrum of the Li-PEG complex calculated by time-dependent density functional theory indicated that changes in the intensities and peak positions of bands at approximately 155 and 177 nm (pure PEG shows bands at 155, 163, and 177 nm) are due to the formation of coordinate bonding between Li+ and the O atoms in the ether molecule. The intensity of the 177 nm band depends on the number of residual free O atoms in the ether, and the peak wavelength at approximately 177 nm changes with the expansion of the electron clouds of PEG. We assign a band in the 145-155 nm region to the alkali-metal complex because we observed a new band at approximately 150 nm in the ATR-FUV spectra of very highly concentrated binary mixtures.

Experimental and Theoretical Studies of the Environmental Sensitivity of the Absorption Spectra and Photochemistry of Nitenpyram and Analogs

Neonicotinoid (NN) pesticides have widespread use, largely replacing other pesticides such as the carbamates. Hence, there is a need to understand their environmental fates at a molecular level in various media, especially water. We report here the studies of a nitroenamine NN, nitenpyram (NPM), in aqueous solution where the absorption cross sections in the actinic region above 290 nm are observed to dramatically decrease compared to those in nonaqueous solvents. Quantum chemical calculations show that addition of a proton to the tertiary amine nitrogen in NPM breaks the conjugation in the chromophore, shifting the absorption to shorter wavelengths, consistent with experiment. However, surprisingly, adding a proton to the secondary amine nitrogen leads to its immediate transfer to the NO2 group, preserving the conjugation. This explains why the UV absorption of ranitidine (RAN), which has a similar chromophore but only secondary amine nitrogens, does not show a similar large blue shift in water. Photolysi...

Investigation of Surface Plasmon Resonance (SPR) in MoS2- and WS2-Protected Titanium Side-Polished Optical Fiber as a Humidity Sensor.

In this paper, we report the effects of a side-polished fiber (SPF) coated with titanium (Ti) films in different thicknesses, namely 5 nm, 13 nm, and 36 nm, protected by a thin layer of transition metal dichalcogenides (TMDCs) such as molybdenum disulfide (MoS2) and tungsten disulfide (WS2), which provide ultra-sensitive sensor-based surface plasmon resonance (SPR) covering from the visible to mid-infrared region. The SPF deposited with Ti exhibits strong evanescent field interaction with the MoS2 and WS2, and good optical absorption, hence resulting in high-sensitivity performance. Incremental increases in the thickness of the Ti layer contribute to the enhancement of the intensity of transmission with redshift and broad spectra. The findings show that the optimum thickness of Ti with 36 nm combined with MoS2 causes weak redshifts of the longitudinal localized surface plasmon resonance (LSPR) mode, while the same thickness of Ti with WS2 causes large blueshifts. The redshifts are possibly due to a reduced plasmon-coupling effect with the excitonic region of MoS2. The observed blueshifts of the LSPR peak position are possibly due to surface modification between WS2 and Ti. Changing the relative humidity from 58% to 88% only elicited a response in Ti/MoS2. Thus, MoS2 shows more sensitivity on 36-nm thickness of Ti compared with WS2. Therefore, the proposed fiber-optic sensor with integration of 2D materials is capable of measuring humidity in any environment.

Environment-Sensitive Near-Infrared Probe for Fluorescent Discrimination of Aβ and Tau Fibrils in AD Brain

The early noninvasive diagnosis of Alzheimer's disease targeted β-amyloid (Aβ) plaques or Tau tangles is a major challenge because of the coshared β-sheet structure of the target. In contrast to tailoring probes to specific amyloids, here, we showed that near-infrared (NIR) environment-sensitive probe 18 could fluorescently discriminate Aβ and Tau from artificial aggregates to pathological change in the brain tissue. The biological evaluation demonstrated that the substantial fluorescence enhancement, large blueshift in the emission upon interactions with the aggregates, and the high binding affinity significantly contributed to the fluorescent discrimination. A simplified Ooshika-Lippert-Mataga equation provided an effective means of correlating 18 with the static relative permittivity (ε0) of proteins, elucidating the origin of the distinction capabilities, and quantitatively estimating the dielectric properties of proteins. Moreover, 18 possessed high bioavailability, including sufficient blood-brain barrier penetration, in vivo NIR imaging, and ex vivo histology in living mice.

Galactic-scale Broad Absorption Line Outflow in the Quasar SDSS J144842.45+042403.1

Abstract We report a clear detection of He i*λλ2946, 3189, and 3889 broad absorption line (BAL) in the low-ionization BAL (LoBAL) quasar SDSS J144842.45+042403.1. We also detected new BALs, including Lyα, C ii, and Si iv, as well as optical emission lines, such as Hα, Hβ, and [O iii]. Using photoionization simulations, we constrained the physical conditions of the outflow to a hydrogen column density of N H ≈ 1021.3 cm−2, an ionization parameter of U ≈ 10−1.4, and a hydrogen number density of n H ≈ 103.6 cm−3, and located its radial distance at r abs ∼ 1.52 kpc from the central engine. The photoionization model predicts the presence of a Lyman limit system with H i column density of N H i ∼ 3.0 × 1017–1.2 × 1018 cm−2, which is confirmed by the GALEX photometry. Interestingly, we found that the [O iii] emission line doublet has an outflow component at a large blueshift of v ∼ 1700 km s−1 and a width of FWHM ∼ 5000 km s−1. Assuming that we are witnessing the same outflow in both emission and absorption lines, we estimate the global covering fraction of the emission line outflow to be ∼4%, its mass-loss rate to be ∼70 M ⊙ yr−1 and its kinetic luminosity to be ∼3.2 × 1044 erg s−1. SDSS J1448+0424 is a representative example of a significant fraction of LoBAL quasars, which deserves further studies to understand the connection between the growth of supermassive black holes and the evolution of their host galaxies.

A novel colorimetric and fluorescent probe based on indolium salt for detection of cyanide in 100% aqueous solution

We reported a novel indolium salt -based colorimetric and fluorescent probe N1 for cyanide. The probe N1 showed a bleaching solution and fluorescence quenching toward CN− in 100% aqueous solution over other anions. In UV-vis and fluorescent spectrometry method, a large blue shift (261 nm), color bleaching and fluorescence quenching was observed. The minimum detection limit on fluorescence response of the probe N1 towards CN− was 3.34 × 10−7 mol/L. This probe N1 operates via intramolecular charge transfer (ICT) mechanism, because the nucleophilic attacking of CN− to the indol CN, the ICT progress was blocked with color changed and fluorescence quenched, which is further confirmed by 1H NMR, MS and DFT studies. Therefore, the synthesized probe would be a promising device for the detection of cyanide.

Luminescence Tuning of Layered Rare-Earth Hydroxides (LRHs, R = Tb, Y) Composites with 3-Hydroxy-2-naphthoic Acid and Application to the Fluorescent Detection of Al3.

Tunable luminescence (quenching or blue shift) of HNA/OS-LRH composites (HNA is 3-hydroxy-2-naphthoic acid; OS is the anionic surfactant of 1-octanesulfonic acid sodium; LRHs are layered rare-earth hydroxides, R = Tb3+, Y3+) in the solid state and delaminated state is reported, which is utilized as an effective fluorescent probe for detecting metal ions. HNA/OS species are intercalated into LRH layers to generate composites of HNA xOS1- x-LTbH ( x = 0.10, 0.15, 0.20 , 0.25) and HNA yOS1- y-LYH ( y = 0.05, 0.10, 0.15, 0.20, 0.25, 0.30). In the solid state, LYH composites exhibit green emissions (from 493 to 504 nm) with a large blue shift in comparison to the 542 nm emission of free HNA- anions, while in the delaminated state in formamide (FM), the composites display blue emission (480 nm) relative to the green emission (512 nm) of an HNA soltuion in FM. However, LTbH composites display coquenched luminescence in both the solid state and delaminated state. Also, HNA0.25OS0.75-1:1-LYH, HNA0.25OS0.75-1:2-LYH, and HNA0.05OS0.95-1:1-LYH (1:1 and 1:2 are HNA:NaOH molar ratios) show significantly elongated fluorescence lifetimes of 15.35, 14.37, and 12.72 ns, respectively, in comparison with free HNA-Na (6.44 ns), and their quantum yields of 23.40%, 21.97%, and 22.31%, respectively, are much larger than that of free HNA-Na (4.86%). The LTbH composite (HNA0.25OS0.75-1:1-LTbH) has also a relatively higher quantum yield of 12.46%. The HNA0.25OS0.75-1:1-LYH colloid exhibits excellent recognition selectivity for Al3+ over other metal ions (Mg2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+, and Hg2+) with distinct fluorescence sensitization. It shows an intense change in its fluorescence emission when it is bound to Al3+ ions, giving a lower detection limit of 6.32 × 10-6 M. This is novel research on the fluorescence chemosensing of LRH composites.

Tunable dual emission in type-I/type-II CdSe/CdS/ZnSe nanocrystals

We have used wet chemical methods to fabricate colloidal CdSe/CdSm/ZnSen core/intermediate/shell (C/I/S) nanocrystals (NCs), where m = 1 and 2 and n = 1–4 are the number of monolayers. The growth was monitored by using Raman and UV–vis spectroscopy, which demonstrated the formation of correct CdSe/CdSm/ZnSen C/I/S NCs. X-ray diffraction studies proved single-phase NCs crystallized in the zincblende-type structure. Photoluminescence (PL) studies have indicated that after photoexcitation C/I/S NCs generate simultaneously type-I and type-II emissions, namely EI and EII, associated with CdSe/CdSm and CdSm/ZnSen structures, respectively. For a specific value of m = 2, we have found the redshift of both EI and EII emissions when n is increased from 1 to 4. The PL studies versus the laser-excitation power (Pex) up to about four orders of magnitude allow us to identify the origin of two emissions. A large blueshift of the EII peak is ascribed to the band bending effect resulting from the spatially separated photoexcited carriers in type-II NCs. It appears that the dependence of the EII peak on the cube root of Pex (Pex1/3) is linear while that of the EI peak on Pex1/3 is almost constant. In this work, we also point out that the emission intensity (I) of EI and EII can be tuned by changing the values of n and Pex, where I obeys a power law I∝Pexk, with k = 0.7–1.0 dependent on the emission type. The nature of these phenomena is discussed in comparison with previous studies on C/S and C/I/S nanoheterostructures.

Outflows & Feedback from Extremely Red Quasars

AbstractFeedback from accreting supermassive black holes is often invoked in galaxy evolution models to inhibit star formation, truncate galaxy growth, and establish the observed black-hole/bulge mass correlation. We are studying outflows and feedback in a unique sample of extremely red quasars (ERQs) during the peak epoch of galaxy formation (at redshifts 2.3 < z < 3.4). We identified ERQs in the Sloan Digital Sky Survey III (SDSS-III) Baryon Oscillation Spectroscopic Survey (BOSS) quasar catalog based on their extremely red i–W3 colors, but we find that ERQs typically have a suite of other extreme properties including 1) a high incidence of blueshifted broad absorption lines, 2) broad emission lines with unusually large rest equivalent widths (REWs), peculiar “wingless” profiles, and frequent large blueshifts (reaching ˜8740 km s-1), and 3) characteristically very broad and blueshifted [OIII] 4959,5007Å lines that trace ionized outflows at speeds up to ˜6700 km s-1. We propose that these ERQs represent a young quasar population with powerful outflows on the precipice of causing important disruptive feedback effects in their host galaxies.

PH-Dependent fibril maturation of a Pmel17 repeat domain isoform revealed by tryptophan fluorescence

The pre-melanosomal protein (Pmel17) aggregates within melanosomes to form functional amyloid fibrils that facilitate melanin polymerization. The repeat domain (RPT) of Pmel17 fibrillates under strict acidic melanosomal pH. Alternative splicing results in a shortened repeat domain (sRPT), which also forms amyloid fibrils. Here, we explored the effects of pH and protein concentration on sRPT aggregation by monitoring the intrinsic fluorescence of the sole tryptophan at position 381 (381W). 381W emission properties revealed changes of local environment polarity for sRPT fibrils formed at different pH. At pH 4, fibrils formed rapidly with no lag phase. A high 381W intensity was observed with a slight blue shift (10 nm). These fibrils underwent further structural rearrangements at intermediate pH (5–6), mirroring that of melanosome maturation, which initiates at pH 4 and increases to near neutral pH. In contrast, typical sigmoidal kinetics were observed at pH 6 with slower rates and 381W exhibited quenched emission. Interestingly, biphasic kinetics were observed at pH 5 in a protein concentration-dependent manner. A large 381W blue shift (23 nm) was measured, indicating a more hydrophobic environment for fibrils made at pH 5. Consistent with 381W fluorescence, Raman spectroscopy revealed molecular level perturbations in sRPT fibrils that were not evident from circular dichroism, transmission electron microscopy, or limited proteolysis analysis. Finally, sRPT fibrils did not form at pH ≥7 and preformed fibrils rapidly disaggregated under these solution conditions. Collectively, this work yields mechanistic insights into pH-dependent sRPT aggregation in the context of melanosome maturation.

Distinctive effects on fluorescence quantum yields of 4-substituted N-methylphthalimides by inclusion complexation with β-cyclodextrins

The inclusion constants K for the complexation of 4-substituted N-methylphthalimides with β-cyclodextrins [β-CD and 2,6-di-O-methylated β-CD (DM-β-CD)] were determined from the fluorescence spectra that were enhanced by the inclusion. The structures of the 1:1 inclusion complexes were characterized using 2D ROESY NMR measurements. 4-Substituted N-methylphthalimides showed higher stability for the inclusion complexes formed with the methylated β-CD compared with those with native β-CD (KDM-β-CD/Kβ-CD = 1.2–2.1); this is attributed to the enhanced hydrophobic interaction due to the methylation of the rim OH groups. 4-Substituted N-methylphthalimides having donor–acceptor (D–A) characteristics showed large blue shifts of the fluorescence maxima. In addition, we determined the fluorescence quantum yields (Φ values) for the inclusion complexes using quantum measurement apparatus equipped with a half-moon unit. The Φ values of the D–A N-methylphthalimides were significantly enhanced by the inclusion of β-CDs. The results suggested that the hydrogen-bonding interaction of the OH groups of the β-CD rim with N-methylphthalimides is not operative and that the enhancement of the quantum yield upon inclusion is attributable to the local polarity around the phthalimides inside the hydrophobic CD cavity.

Formation and UV-Vis Studies of Lead Sulfide Nanoparticles

An elegant technique of synthesizing semiconductor lead sulfide nanoparticles (PbS-NPS) embedded in Langmuir-Blodgett (LB) films is presented here. Stearic acids have been used as a matrix to form and grow the quantum-sized PbS. Pure Y-type Pb-salts of stearic acid (SA) LB films were prepared at a dipping speed of 15 mm/min and surface pressure of 28 mN/m. PbS-NPs were formed inside LB films of SA by exposure the LB films to hydrogen sulfide (H2S) gas. The preparation of PbS-NPs is discussed in terms of particle formation and growth. The presence of PbS-NPs was investigated by UV-visible absorption. It was found that the PbS-NPs within SA LB films indicated a large blue shift of the optical absorption edge. The estimation of the size distribution performed by optical measurements allows one to attribute the particle range a few nanometers. This figure seems to depend upon the reaction conditions as well as the quality of the initial LB films.

Plasmonic and Photothermal Immunoassay via Enzyme-Triggered Crystal Growth on Gold Nanostars.

Immunoassay is commonly used for the detection of disease biomarkers, but advanced instruments and professional operating are often needed with current techniques. The facile readout strategy for immunoassay is mainly limited to the gold nanoparticles-based colorimetric detection. Here, we show that photothermal nanoparticles can be applied for biosensing and immunoassay with temperature as readout. We develop a plasmonic and photothermal immunoassay that allows straightforward readout by color and temperature based on crystal growth, without advanced equipment. It is demonstrated that alkaline phosphatase-triggered silver deposition on the surface of gold nanostars causes a large blue shift in the localized surface plasmon resonance of the nanosensor, accompanied by photothermal conversion efficiency changes. This approach also allows dual-readout of immunoassays with high sensitivity and great accuracy for the detection of prostate-specific antigen in complex samples. Our strategy provides a promising way for point-of-care testing and may broaden the applicability of programmable nanomaterials for diagnostics.

A ratiometric fluorescent probe for the detection of endogenous hydroxyl radicals in living cells

A new ratiometric fluorescent probe (4) for monitoring hydroxyl radicals (•OH) has been designed and synthesized. The ratiometric sensing of probe 4 toward •OH is realized by the oxidation of the dicyanovinyl group of probe 4 to afford the corresponding epoxide, which can further reaction with •OH to give a coumarin derivative as the final product. The above reaction interrupts the large π-conjugated system of probe 4 and exhibits a remarkable large blue shift of 160 nm in the emission spectra of the sensing system. Probe 4 exhibits high selectivity toward •OH over other reactive oxygen species and reactive nitrogen species. Preliminary study shows that probe 4 can be employed to monitor endogenous •OH in living cells with a ratiometric fluorescent imaging manner.

Counterion-controlled spectral tuning of the protonated Schiff-base retinal

Color vision is based on the ability of different opsin proteins to tune the absorption band of their chromophore, the retinal protonated Schiff base (RPSB). Two main mechanisms proposed for this tunability are geometric and electrostatic. Here we probe the latter effect experimentally and by a quantum chemical calculation of the absorption by an isolated complex containing the retinal chromophore and molecules with a strong dipole moment. Betaine complexation causes an anomalously large blue shift. The shift provides direct evidence that the strong charge-transfer character of the electronic transition is the cause of the opsin shift, and shows that the electric field of the counterion is responsible for the color tuning, which allows absorption of light in the blue region of the visible spectrum by opsin proteins.

Reddish orange to blue tunable emission from rare earth β-diketonate Eu(TTA)3 dpphen complex for solid state lighting applications

This work reports synthesis and characterization of novel Eu(TTA)3 dpphen (Eu-Europium, TTA- 2-Thenoyltrifluoroacetone, dpphen-4,7-diphenyl,1,10-phenanthroline) complex which has potential to tune its emission from reddish-orange to blue colour. Its crystalline nature was revealed by X-ray diffractogram while, the structure formation and molecular bonding of the complex was declared by FTIR spectra. TGA/DTA analysis divulges high thermal stability. UV–visible absorption spectra of the complex in various solvents show two distinct peaks referring to the π → π∗ and n → π∗ optical transitions in the rare earth ions and β-diketonate moieties. Also, various optical transition parameters were evaluated from these results. Under excitation wavelength of 380 nm, the complex in solid state illustrates characteristic reddish-orange light emission registered at 613 nm with narrow full width at half maxima, attributed to f-f transition of central Eu3+ ions. However, solvated complex in various organic solvents such as chloroform, dichloromethane and toluene revealed a red shift by 1 nm with intense sharp emission, peaking at 614 nm. Conversely, solvated complex in acetic and formic acid displays a large blue shift of about 136 and 135 nm, respectively. Various photo physical and photometric properties of the complex reveal its prospective as tunable emissive material that can be coated on flexible substrates for solid state lighting applications.

Performance of Fluorescent Cell-Labeling Dyes under Simulated Europa Mission Radiation Doses.

We investigated the performance of several commonly used fluorescent dyes after exposure to a simulated Europa mission total ionizing radiation dose of 300 krad (3 kGy) applied using a 60Co source. Dyes irradiated in aqueous solution or as lyophilized powders were evaluated for absorbance and emission spectra, quantum yield, and where appropriate, ability to label cells or nucleic acids. Although some dyes showed significant increase or decrease in quantum yield with the dose, their spectra and cell-labeling properties remained essentially unchanged after irradiation in powder form. Irradiation in aqueous solution led to significantly greater changes, including a large blue shift in the DNA intercalator propidium iodide. These results suggest that many fluorescent probes are appropriate for use in astrobiological missions to Europa, but that SYTO9 and propidium iodide should be used with caution or not mixed with each other, as is commonly done in "Live/Dead" labeling applications.

Evolution and Tailoring of DUV Plasmonic Properties in Al Nanoparticle Arrays by UV Irradiation

Ultraviolet irradiation was used to tailor the surface plasmon band of the densely distributed aluminium nanoparticle arrays fabricated by gas-phase deposition. We showed that the broad surface plasmon resonance band of the as-prepared sample could be tuned to a sharp and strong resonance band in the deep ultraviolet optical range, with a large blue shift of the peak wavelength. The evolution of the surface plasmon resonance properties was attributed to the ultraviolet irradiation-improved surface oxidation of the nanoparticles, which eliminated the near-field couplings between the closely spaced nanoparticles by increasing their interspacing.

Thermal and Plasmonic Stabilization of Silver Nanostructures Using a Bilayer Anchoring Technique.

In this work, we demonstrate how to suppress the shape instability of silver (Ag) nanotriangular pyramids following high-temperature annealing without a coating or encapsulation, thus producing a more stable optical plasmonic system. Nanosphere lithography (NSL) was used to fabricate large-area arrays of nanotriangular pyramids of Ag on glass substrates. By using a combination of morphology and spectroscopic studies it was found that exposure of this system to high temperatures of 473 K and beyond in air led to a rapid change in nanostructure shape, and thus, the surface area, with a substantial change to the original plasmonic character. On the other hand, NSL nanotriangular pyramids made from bilayers of Ag on Co or Co on Ag showed much smaller changes in shape and area following annealing up to 573 K in air. In the case of pure Ag, the NSL nanotriangular pyramid changed into a more spherical shape with an overall decrease of ∼24% in its surface area following annealing at 573 K. This lead to a large blue shift of over ∼287 nm or ∼39% in the location of the dipolar plasmonic resonance. On the other hand, the triangular shape of Ag was retained in both the metal bilayer cases, with much smaller area changes of ∼10 and ∼9%, for the Ag deposit when on Co and when under Co, respectively. Consequently, the plasmonic shifts were substantially smaller, of ∼65 nm or about 9%, in these bilayer systems. The mechanism for this stabilization was attributed to the higher surface energy of Co and much lower diffusivity of Co as well as Ag on Co that resulted in an anchoring of the Ag shape to its original state. The plasmonic quality factor for the bimetal NSL nanotriangular pyramids also showed substantially improved stability over pure Ag, further indicating that this anchoring approach is a viable pathway to produce pristine Ag surfaces for high-temperature plasmonic applications.