Fluorescence Emission Intensity Research Articles

Reversible Acid-Base Long Persistent Luminescence Switch Based on Amino-Functionalized Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) with long persistent luminescence (LPL) have attracted extensive research attention from researchers due to their potential applications in information encryption, anticounterfeiting technology, and security logic. In contrast to short-lived fluorescent materials, LPL materials offer a visible response that can be easily distinguished by the naked eye, thereby facilitating a much clearer visualization. However, there are few reports on functional LPL MOF materials as probes. In this article, two amino-functional LPL MOFs (VB4-2D and VB4-1D) were synthesized. They both exhibited adjustable fluorescence and phosphorescence from blue to green and from cyan to green, respectively. Notably, the MOFs emitted bright and adjustable LPL upon the removal of the different radiation sources. The basic amino functional groups in the MOFs exhibited acid and ammonia sensitivity, and fluorescence and phosphorescence emission intensities can be burst and restored in two atmospheres, respectively, which can be cycled multiple times. Furthermore, LPL intensity undergoes switching between two different conditions as well, which can be visually discerned by the naked eye, enabling visual sensing of volatiles by LPL. This combination of photoluminescence and the visual LPL switching behavior of acids and bases in functional MOFs may provide an effective avenue for stimulus response, anticounterfeiting, and encryption applications.

Protein aggregation monitoring in cells under oxidative stress: a novel fluorescent probe based on a 7-azaindole-BODIPY derivative.

The development of new fluorescent probes as molecular sensors is a critical step for the understanding of molecular mechanisms. BODIPY-based probes offer versatility due to their high fluorescence quantum yields, photostability, and tunable absorption/emission wavelengths. Here, we report the synthesis and evaluation of a novel 7-azaindole-BODIPY derivative to probe hydrophobic proteins as well as protein misfolding and aggregation. In organic solvents, this compound shows two efficiently interconverting emissive excited states. In aqueous environments, it forms molecular aggregates with unique photophysical properties. The complex photophysics of the 7-azaindole-BODIPY derivative was explored for sensing applications. In the presence of albumin, the compound is stabilized in hydrophobic protein regions, significantly increasing its fluorescence emission intensity and lifetime. Similar effects occur in the presence of protein aggregates but not with other macromolecules like pepsin, DNA, Ficoll 40, and coconut oil. Fluorescence lifetime imaging microscopy (FLIM) and two-photon fluorescence microscopy on breast (MCF-7) and lung (A549) cancer cells incubated with this compound display longer fluorescence lifetimes and higher emission intensity under oxidative stress. Synchrotron FTIR micro spectroscopy confirmed that the photophysical changes observed were due to protein misfolding and aggregation caused by the oxidative stress. These findings demonstrate that this compound can serve as a fluorescent probe to monitor protein misfolding and aggregation triggered by oxidative stress.

Mechanistic insights into diversified photoluminescence behaviours of BF2 complexes of N-benzoyl 2-aminobenzothiazoles.

Many BF2 complexes of heteroaromatics are well known for their dual-state emission (DSE) properties. However, AIE and ACQ effects have also been observed in certain cases. To date, no rational explanations have been proposed for these uncommon photoluminescence (PL) behaviours. The current research prepared four BF2 complexes of N-benzoyl 2-aminobenzothiazoles with diversified photoluminescence (PL) properties as model compounds and utilized quantum chemical calculation tools to address this issue. Theoretical calculations revealed that the electron-donating groups (EDGs) at the para-position of the exocyclic phenyl ring exert significant influence on their ground-state electronic structures and vertical excitation features. Potential energy curve (PEC) analysis showed that the exocyclic phenyl ring and NMe2 could not function as effective rotors due to elevated energy barriers. Only the NPh2 of BFBB-3 could spontaneously rotate ∼60° to induce the formation of an emissive twisted intramolecular charge transfer (TICT) state. The two-channel model involving both vibronic relaxation and S0/S1 surface crossing revealed that the drastic narrowing of the S1/S0 energy gap in the region approaching minimun energy conical intersection (MECI) led to the generation of a dark state in BFBB-1. The small energy barrier to access the dark-state region makes the resulting fast internal conversion a competitive channel for excited-state deactivation. In contrast, the presence of EDGs in BFBB-2 and 4 inhibits this pathway, thereby resulting in intense fluorescence emissions in solution. In addition, crystallographic analysis illustrated that the F atoms perpendicular to the polyheterocycle promoted a slipped face-to-face packing mode and enhanced intermolecular interactions. The efficiencies of their solid-state emissions are mainly affected by the degree of π-π overlaps.

Structural modulation of aggregation-induced emission luminogens for NIR-II fluorescence imaging/photoacoustic imaging of tumors.

Concurrent near-infrared-II (NIR-II) fluorescence imaging (FLI) and photoacoustic imaging (PAI) holds tremendous potential for effective disease diagnosis owing to their combined benefits and complementary features, in particular on the basis of a single molecule. However, the simultaneous guarantee of high-quality NIR-II FLI and PAI is recognized to be challenging impeded by the competitive photophysical processes at the molecular level. Herein, a simple organic fluorophore, namely T-NSD, is finely engineered with facile synthetic procedures through delicately modulating the rigidity and electron-withdrawing ability of the molecular acceptor. The notable advantages of fabricated T-NSD nanoparticles include a large Stokes shift, intense fluorescence emission in the NIR-II region, and anti-quenching properties in the aggregated states, which eventually enable the implementation of dual-modal NIR-II FLI/PAI in a 4T1 tumor-xenografted mouse model with reliable performance and good biocompatibility. Overall, these findings present a simple strategy for the construction of NIR-II optical agents to allow multimodal disease diagnosis.

Cellulose nanocrystals from celery stalk as quercetin scaffolds: A novel perspective of human holo-transferrin adsorption and digestion behaviours.

In this study, cellulose nanocrystals (CNCs) were synthesized from celery stalks to be used as the platform for quercetin delivery. Additionally, CNCs and CNCs-quercetin were characterized using the results of scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and zeta potential, while their interactions with human holo-transferrin (HTF) were also investigated. We examined their interaction under physiological conditions through the exertion of fluorescence, resonance light scattering, synchronized fluorescence spectroscopy, circular dichroism, three-dimensional fluorescence spectroscopy, and fluorescence resonance energy transfer techniques. The data from SEM and TEM exhibited the spherical shape of CNCs and CNCs-quercetin and also, a decrease was detected in the size of quercetin-loaded CNCs from 676 to 473 nm that indicated the intensified water solubility of quercetin. The success of cellulose acid hydrolysis was confirmed based on the XRD results. Apparently, the crystalline index of CNCs-quercetin was reduced by the interaction of CNCs with quercetin, which also resulted in the appearance of functional groups, as shown by FTIR. The interaction of CNCs-quercetin with HTF was also demonstrated by the induced quenching in the intensity of HTF fluorescence emission and Stern-Volmer data represent the occurrence of static quenching. Overall, the effectiveness of CNCs as quercetin vehicles suggests its potential suitability for dietary supplements and pharmaceutical products.

Shedding light on the use of graphene oxide-thiosemicarbazone hybrids towards the rapid immobilisation of methylene blue and functional coumarins.

Coumarins, methylene blue derivatives, as well as related functional organic dyes have become prevalent tools in life sciences and biomedicine. Their intense blue fluorescence emission makes them ideal agents for a range of applications, yet an unwanted facet of the interesting biological properties of such probes presents a simultaneous environmental threat due to inherent toxicity and persistence in aqueous media. As such, significant research efforts now ought to focus on their removal from the environment, and the sustainable trapping onto widely available, water dispersible and processable adsorbent structures such as graphene oxides could be advantageous. Additionally, flat and aromatic bis(thiosemicarbazones) (BTSCs) have shown biocompatibility and chemotherapeutic potential, as well as intrinsic fluorescence, hence traceability in the environment and in living systems. A new palette of graphene oxide-based hierarchical supramolecular materials incorporating BTSCs were prepared, characterised, and reported hereby. We report on the supramolecular entrapping of several flat, aromatic fluorogenic molecules onto graphene oxide on basis of non-covalent interactions, by virtue of their structural features with potential to form aromatic stacks and H-bonds. The evaluations of the binding interactions in solution by between organic dyes (methylene blue and functional coumarins) and new graphene oxide-anchored Zn(ii) derivatised bis(thiosemicarbazones) nanohybrids were carried out by UV-Vis and fluorescence spectroscopies.

Fluorescent probes for investigating the internalisation and action of bioorthogonal ruthenium catalysts within Gram-positive bacteria.

Bioorthogonal reactions are extremely useful for the chemical modification of biomolecules, and are already well studied in mammalian cells. In contrast, very little attention has been given to the feasibility of such reactions in bacteria. Herein we report modified coumarin dyes for monitoring the internalisation and activity of bioorthogonal catalysts in the Gram-positive bacterial species Bacillus subtilis. Two fluorophores based on 7-aminocoumarin were synthesised and characterised to establish their luminescence properties. The introduction of an allyl carbamate (R2N-COOR') group onto the nitrogen atom of two 7-aminocoumarin derivatives with different solubility led to decreased fluorescence emission intensities and remarkable blue-shifts of the emission maxima. Importantly, this allyl carbamate group could be uncaged by the bioorthogonal, organometallic ruthenium catalyst investigated in this work, to yield the fluorescent product under biologically-relevant conditions. The internalisation of this catalyst was confirmed and quantified by ICP-OES analysis. Investigation of the bacterial cytoplasm and extracellular fractions separately, following incubation of the bacteria with the two caged dyes, facilitated their localisation, as well as that of their uncaged form by catalyst addition. In fact, significant differences were observed, as only the more lipophilic dye was located inside the cells and importantly remained there, seemingly avoiding efflux mechanisms. However, the uncaged form of this dye is not retained, and was found predominantly in the extracellular space. Finally, a range of siderophore-conjugated derivatives of the catalyst were investigated for the same transformations. Even though uptake was observed, albeit less significant than for the non-conjugated version, the fact that similar intracellular reaction rates were observed regardless of the iron content of the medium supports the notion that their uptake is independent of the iron transporters utilised by Gram-positive Bacillus subtilis cells.

Lightening flavin by amination for fluorescent sensing.

Monitoring of reactive oxygen species (ROS), such as O2˙-, etc., in organisms is of great significance, not only for their essential role in biological processes, but their excessive production may also result in many diseases. Flavin (FL) is a fluorophore that naturally exists in flavoenzymes, and its fluorescent emission (FE) becomes negligible when reduced. This enables the application of FL derivatives as fluorescent sensors for ROS. We presented a theoretical investigation to address the impact of amino substitution on the photophysical properties of aminoflavins (AmFLs). Resulting from the interplay of electronic and positional effects, amination at C8 enhances the electronic coupling between the ground state and the first singlet excited state by enlarging the adiabatic energy change of the electronic transitions and the emission transition dipole moments, weakens the vibronic coupling by decreasing the contribution of isoalloxazine to the frontier molecular orbitals, redshifts the absorption band, and enhances the fluorescent emission drastically in 8AmFL. The theoretically estimated fluorescent emission intensity of 8AmFL is ∼40 times that of FL, suggesting its potential application as a fluorescent sensor.

A novel ratiometric fluorescence probe based on the FRET-ICT mechanism for detecting fluoride ions and viscosity

Fluoride ion is not only important for dental health, but also a contributing factor in a variety of diseases. At the same time, fluoride ions and cell viscosity are both important to the physiological environment of mitochondria. We developed a dual-response ratiometric fluorescent probe BDF based on Förster resonance energy transfer (FRET) and intramolecular charge transfer (ICT) mechanism for the detection of F− and viscosity. BDF has an outstanding intramolecular energy transfer efficiency of 97.7% and shows excellent performance for fluorine ion detection. In addition, when the system viscosity increases, the fluorescence emission intensity of BDF is greatly heightened, indicating the possibility of viscosity detection. Finally, based on the fluorescence properties of BDF, we used the probe to detect F− in the toothpaste sample and image exogenous fluoride ions in HeLa cells.

Fluorescent composite beads: An advanced tool for environmental monitoring and harmful pollutants removal from water

The quality and safety of water sources have been significantly impacted by various pollutants, including trace elements. To address this concern, this study utilized composite beads made of alginate and carbon quantum dots (CDs) for detecting and removing As(III) and Se(IV) ions in tap water. Fluorescent CDs were hydrothermally synthesized and incorporated into an alginate-Ca2+ matrix through a straightforward procedure. Characterization analyses revealed distinct properties of the composite beads, containing varying amounts of CDs, compared to the pristine beads. Optimal adsorption parameters (30 mg of adsorbent, 10 mg/L of initial pollutant concentration, 35 °C, and 180 min of contact time) for the beads containing 30 w/w-% of CDs (Alg@CDs30) were determined through a fractional factorial design. These composite beads exhibited the highest adsorption capacity for both metals, achieving a removal rate of 94.5% for As(III) and 98.0% for Se(IV) in tap water. Kinetic and isothermal analyses indicated that the adsorption of both metals on Alg@CDs30 involves a combination of chemisorption and diffusion processes. Recycling experiments demonstrated that the composite beads could be reused up to 20 times without a noticeable loss of adsorption efficiency. Regarding the sensing property, our experiments revealed a significant reduction in the fluorescence emission intensity of Alg@CDs30 upon interaction with As(III) and Se(IV), confirming its ability to detect both ions in tap water, with limits of detection (LOD) of 2.6 ± 0.5 μg/L for As(III) and 1.1 ± 0.2 μg/L for Se(IV). The alginate-Ca2+ matrix s contributed to the stability of the CDs' fluorescence. These results confirm the potential of Alg@CDs beads as effective tools for the simultaneous monitoring and removal of hazardous metal ions from real water samples.

Assembly of three new triphenylamine functionalized MOFs for the fluorescent sensing of nitrobenzene

The detection of nitrobenzene (NB) is very important because it has a series of irreversible effects on human health. Metal-organic frameworks (MOFs) show potential applications in this field due to their tunable and porous structures. In this work, three new MOFs, namely [Mn3(TCA)2(DMF)4]·DMF (JOU-28), [Cd21(TCA)14(H2O)9]·21DMF·21H2O (JOU-29), and [Cd3Cl3(TCA)(DMF)2]·H2O (JOU-30), were successfully prepared by solvothermal method (H3TCA = 4,4′,4″-tricarboxytriphenylamine; DMF = N,N′-Dimethylformamide). Single crystal X-ray diffractions showed that JOU-28 was a 3D porous supramolecular structure based on 2D coordination networks, while both JOU-29 and JOU-30 were 3D porous structures based on 1D chains. Due to its strong fluorescence emission, JOU-29 was selected as a representative to study the NB sensing performance. A linear relationship between the NB concentration and the fluorescence emission intensity of JOU-29 could be obtained as I0/I = 0.952 + 8089[NB]. This result showed that JOU-29 can be used for quantitative detection of NB. Further studies revealed that the fluorescence quenching of JOU-29 may be due to the fluorescence resonance transfer effect and the competitive absorption. This work provides clues for the design and synthesis of fluorescent MOFs for NB detection.

Regulation of fluorescence, morphology, surface wettability and function of naphthalimide-based self-assembly system by metal coordination

Three naphthalimide-based supramolecular gelators (N1, N2 and N3) that contained one, two, or three naphthalimide groups, respectively, were designed and synthesized, and the self-assembly processes of the three gelators were studied using different technique. Their self-assembly behavior could be regulated through the number of terminal branches. More importantly, their self-assembled structure, fluorescence behavior and surface wettability and function could be regulated through metal coordination, and helical nanofibers could be formed by gel N2 with Cd2+, Co2+, Eu3+, Tb3+, Mn2+, Ni2+ and Hg2+. The fluorescence emission intensities of these gels could change with different degrees under the addition of different metal ions, and a super-hydrophilic surface could be obtained from xerogel N3 in the presence of Co2+, Eu3+, Mn2+ and Tb3+. Specifically, gelator N3 could selectively and sensitively respond to Fe2+ in the solution and gel state with a response time of 0.5 s and a low limit of detection of 1.84 nM. This work provided a new regulation method for the supramolecular self-assembly process.

Functionalized Phytochemicals-Embedded Carbon Dots Derived from Medicinal Plant for Bioimaging Application.

Precise visualization of biological processes necessitates reliable coloring technologies, and fluorescence imaging has emerged as a powerful method for capturing dynamic cellular events. Low emission intensity and solubility of intrinsic fluorescence are still challenging, hindering their application in the biomedical field. The nanostructurization and functionalization of the insoluble phytochemicals, such as chlorophyll and curcumin, into carbon dots (CDs) were conducted to address these challenges. Due to their unique fluorescence characteristics and biocompatibility, CDs derived from medicinal plants hold promise as bioimaging agents. Further, the nitrogen in situ functionalization of the as-synthesized CDs offered tunable optical properties and enhanced solubility. The surface modification aims to achieve a more positive zeta potential, facilitating penetration through biological membranes. This work provides valuable insights into utilizing functionalized phytochemical-embedded carbon dots for bioimaging applications. The doping of nitrogen by adding urea showed an alteration of surface charge, which is more positive based on zeta potential measurement. The more positive CD particles showed that Andrographis paniculata-urea-based CDs were the best particles to penetrate cells than others related to the alteration of the surface charge and the functional group of the CDs, with the optimum dose of 12.5 μg/mL for 3 h of treatment for bioimaging assay.

Impacts of ultraviolet and photosynthetically active radiations on photosynthetic efficiency and antioxidant systems of the cyanobacterium Spirulina subsalsa HKAR-19.

This study summarizes the response of cyanobacterium Spirulina subsalsa HKAR-19 under simulated light conditions of photosynthetically active radiation (PAR), PAR+UV-A (PA), and PAR+UV-A+UV-B (PAB). Exposure to UV radiation caused a significant (P < 0.05) decrease in chlorophyll a, phycocyanin, and total protein. In contrast, total carotene content increased significantly (P < 0.05) under PA and PAB with increasing irradiation time. The photosynthetic efficiency of photosystem II also decreased significantly in PA and PAB radiation. We havealso recorded a decrease in the fluorescence emission intensity of phycocyanin under PA and PAB exposure. The phycocyanin fluorescence shifted towards shorter wavelengths (blue-shift) after 72h of PA and PAB exposure. Intracellular reactive oxygen species (ROS) levels increased significantly in PA and PAB. Fluorescence microscopic images showed an increase in green fluorescence, indicating ROS generation in UV radiation. We havealso quantified ROS generation using green and red fluorescence ratio represented as G/R ratio. A 2-6-foldincrease in antioxidative enzymes activity was observed to overcome the damaging effects caused by UV stress as compared to untreated control cultures. The lipid peroxidation was assessed in terms of malondialdehyde content which increases significantly (P < 0.05) as the duration of exposure increases. These results suggest that a combined effect of PAR, UV-A, and UV-B was more deleterious than an individual one.

Assembly of two luminescent cadmium(II) 4,4'-phosphini Co-dibenzoate coordination polymers

Two new cadmium(II) coordination polymers [Cd(HL)(H2O)]·1.5H2O (1) and [Cd(HL)(4-bpmp)0.5]·2H2O (2) (H3L = 4,4'-phosphinicobis-dibenzoic acid, and 4-bpmp = N,N'-bis(4-pyridylmethyl)piperazine) have been synthesized by self-assembly of CdCl2 with 4,4'-phosphinicobis-dibenzoate, and N,N'-bis(4-pyridylmethyl)piperazine through solvothermal/hydrothermal method. Their structures were confirmed by X-ray single crystal diffraction, infrared spectrometer (IR), and powder X-ray diffraction (PXRD) and TGA techniques. Both compounds are in Pī space group and exhibited a 2D networks constructed from dinuclear [Cd2(POO)2] or paddle-wheel [Cd2(COO)2(POO)2] units, respectively. In 2, the Cd2+ is five-coordinated and shows a rare tetragonal pyramidal geometry. At room temperature, the compounds exhibit moderately intense blue and green fluorescence emission with peaks at 381 nm and 509 nm, respectively.&#x0D; KEY WORDS: Cadmium(II) compounds, Photoluminescence, Carboxyphosphinate ligand&#x0D; Bull. Chem. Soc. Ethiop. 2024, 38(1), 85-98. DOI: https://dx.doi.org/10.4314/bcse.v38i1.7

Efficient Expression in the Prokaryotic Host System, Purification and Structural Analyses of the Recombinant Human ACE2 Catalytic Subunit as a Hybrid Protein with the B Subunit of Cholera Toxin (CTB-ACE2).

Angiotensin-converting enzyme 2 (ACE2) has a specific interaction with the coronavirus spike protein, enabling its entry into human cells. This membrane enzyme converts angiotensin II into angiotensin 1-7, which has an essential role in protecting the heart and improving lung function. Many therapeutic properties have been attributed to the human recombinant ACE2 (hrACE2), especially in combating complications related to diabetes mellitus and hypertension, as well as, preventing the coronavirus from entering the target tissues. In the current study, we designed an appropriate gene construct for the hybrid protein containing the ACE2 catalytic subunit and the B subunit of cholera toxin (CTB-ACE2). This structural feature will probably help the recombinant hybrid protein enter the mucosal tissues, including the lung tissue. Optimization of this hybrid protein expression was investigated in BL21 bacterial host cells. Also, the hybrid protein was identified with an appropriate antibody using the ELISA method. A large amount of the hybrid protein (molecular weight of ~ 100kDa) was expressed as the inclusion body when the induction was performed in the presence of 0.25mM IPTG and 1% sucrose for 10h. Finally, the protein structural features were assessed using several biophysical methods. The fluorescence emission intensity and oligomeric size distribution of the CTB-ACE2 suggested a temperature-dependent alteration. The β-sheet and α-helix were also dominant in the hybrid protein structure, and this protein also displays acceptable chemical stability. In overall, according to our results, the efficient expression and successful purification of the CTB-ACE2 protein may pave the path for its therapeutic applications against diseases such as covid-19, diabetes mellitus and hypertension.

Imidazole-based solid-state fluorescence switch: Stimuli-responsive emission, mechanochromism and acidochromism

Stimuli modulated fluorescence properties of imidazole-based molecular probe (E)-2-(5,5-dimethyl-3-(4-(1,4,5-triphenyl-1H-imidazole-2-yl)styryl)cyclohex-2-en-1-ylidene)malononitrile (Ph-ISO) in the solid state is presented. Not only did the probe display aggregation induced emission (AIE) activity with intense solid-state fluorescence emission, but also exhibited several repetitive cycles of reversible mechanochromism as well as acidochromism. The solid-state emission is ascribed to the intermolecular interactions in the highly twisted conformation of Ph-ISOviamultiple C–H---N and C–H---π interactions as confirmed by the single crystal X-ray analysis. The applied mechanical stress in the form of grinding results in the transformation of crystalline state to the amorphous state with a red shifted emission band attributed to attaining more planar conformation vs twisted conformation, with extended molecular conjugation. While reversible mechanochromism makes the probe suitable for rewritable papers, the switchable acidochromism is useful for theon-sitemonitoring of pH differences in biological and environmental media.

Interaction studies of water-soluble Zn(II) complex with calf thymus DNA using biophysical and molecular docking methods"

The binding between a fluorescent water-soluble Zn(II) complex of {2-[N-(2-hydroxyethylammonioethyl) imino methyl] phenol} and calf thymus DNA (ct-DNA) was investigated using spectroscopic techniques. The complex was prepared and identified by FT-IR, and 1H NMR spectroscopies. The significant changes in the absorption and the circular dichroism spectra of ct-DNA in the presence of the Zn(II) complex implied the interaction between the Zn(II) complex and ct-DNA. Upon addition of ct-DNA, the fluorescence emission intensity of the Zn(II) complex was increased and indicated the interaction between the Zn(II) complex and ct-DNA was occurred. The binding constant values (Kb) resulted from fluorescence spectra clearly showed the Zn(II) complex affinity to ct-DNA. The fluorescence studies also approved the static enhancement mechanism in the Zn(II) complex-DNA complexation process. The thermodynamic profile exhibited the exothermic and spontaneous formation of ct-DNA-Zn(II) complex system via hydrogen bonds and van der Waals forces. The competitive fluorescence investigation by methylene blue (MB), and Hoechst 33258 demonstrated that the Zn(II) complex could replace the DNA-bound Hoechst and bind to the minor groove binding site in ct-DNA. The viscosity changes were negligible, representing the Zn(II) complex binding to DNA via the groove binding mode. Molecular docking simulation affirmed that the Zn(II) complex is located in the minor groove of ct-DNA near the DG12, DA17, DA18, and DG16 nucleobases.

Eosin-Y containing electrospun fibers for optical ammonia sensing based on wavelength shift

Sensors in recent days have been in great demand in industrial zones of simple, low-cost sensors for effectively sensing various gases. This research work develops electrospinning fibers for optical ammonia sensing based on the wavelength shift. The optical sensing fibers were produced approach by the electrospinning technique. The addition of cellulose acetate (CA) matrix with doped Eosin-Y is an NH3 fluorophore. The same light emitting diode (LED) light source was used to excite NH3-sensitive dyes at 380 nm peak wavelength. Display the eosin Y emission spectrum, with a maximum wavelength of 582 nanometers. The observed red emission wavelength shift and fluorescence intensity at 582 nm decreased with increasing concentrations of NH3. The emission spectrum of eosin-Y fluorescence at 582 nanometers is changed with increasing NH3 concentrations ranging from 0 to 500 parts per million. In this work, according to the experiment results, the sensitivity of NH3 sensors is 7.73. Finally, the electrospinning fibers for optical NH3 sensing developed as a result of this research enable effective sensing of NH3 concentrations in practical applications in a variety of fields, including medical and industrial.

Sequential Recognition of Bisulfate and Acetate by a Ruthenium(II) Complex: Experimental and Theoretical Studies

AbstractNew complex [RuLCl2(PPh3)] (L=N,N‐bis(2‐hydroxy‐5‐nitrobenzaldehyde)‐2,2’‐diaminodiethylamine) was prepared and characterized analytically and was employed as a luminescent chemosensor for the detection of anions. The results show that [RuLCl2(PPh3)] can detect HSO4− and AcO− selectively and in sequential order in H2O‐CH3CN (8 : 2, v/v) at pH 7.0. The spectral binding, titration, and interference analyses reveal that the addition of HSO4− to [RuLCl2(PPh3)] results in an intense fluorescence emission (IF/I0=6.55). This shows that HSO4− interacts suitably with the complex to switch ON the fluorescence which could be explained by inhibition of a PET mechanism as the above addition forms [RuLCl(HSO4)(PPh3)] in the excited state. Selectivity interaction of complex [RuLCl2(PPh3)] with HSO4− results in the formation of [RuLCl(HSO4)(PPh3)] in water but the system exhibits negligible change in its emission except for AcO−, which enhances fluorescence intensity. For the addition of AcO− to [RuLCl2(PPh3)], the system [RuLCl(AcO)(PPh3)] is formed, however, the adding of HSO4− to [RuLCl(AcO)(PPh3)] does not show any change in the intensity, suggesting that there exists a logic gate function for the addition of HSO4− followed by AcO− to [RuLCl2(PPh3)]. This finding is interesting because [RuLCl2(PPh3)] can act as a fast selective chemosensor for the sequential detection of HSO4− and AcO−.