Nonradiative Energy Transfer Research Articles

The effect of polarity and hydrogen bonding on the electronic and vibrational structure of the salicylate anion in acetonitrile and water: implicit and explicit solvation approaches.

This study investigates the fluorescence quenching of the salicylate anion in water compared to acetonitrile (ACN) and the stability of its keto structure in ACN using DFT and TD-DFT methods at the 6-311++G(d,p) basis set. Computational simulations in implicit and explicit environments of ACN and water reveal the effects of solvent polarity and hydrogen bonding on enol [Od-H⋯Oa] and keto [Od⋯H-Oa] tautomerization, fluorescence quenching, and the spectral profile of the salicylate anion. Implicit solvation models show a barrier height of approximately 1.9 kcal mol-1 in ACN and 3.6 kcal mol-1 in water for enol-keto tautomerization in the ground state, with no barrier in the excited state, leading to an ESIPT reaction in both solvents, but only ground state proton transfer in ACN. Simulated absorption spectra for both enol and keto forms are similar in both solvents, while the emission spectrum is red-shifted in water. Explicit solvation studies indicate greater stabilization of the salicylate anion in water than in ACN, with a blue shift in absorption and emission spectra and varying oscillator strengths. Solvent molecule positioning affects enol-keto stabilization in the ground state, but only the keto structure is stabilized in the excited state. Simulated IR spectra in water show a blue shift in Od-H stretching frequency and increased water molecule vibrational frequencies, suggesting non-radiative excitation energy transfer from salicylate ions to water molecules via n → σ* intermolecular hydrogen bonding interactions. This mechanism explains the fluorescence quenching observed in water and results align with experimental data, indicating hydrogen-bonded keto form stabilization both in water and ACN.

Step-wise changes in the excited state lifetime of [Eu(D2O)9]3+ and [Eu(DOTA)(D2O)]- as a function of the number of inner-sphere O-H oscillators.

Lanthanide luminescence is dominated by quenching by high-energy oscillators in the chemical environment. The rate of non-radiative energy transfer to a single H2O molecule coordinated to a Eu3+ ion exceeds the usual rates of emission by an order of magnitude. We know these rates, but the details of these energy transfer processes are yet to be established. In this work, we study the quenching rates of [Eu(D2O)9]3+ and [Eu(DOTA)(D2O)]- in H2O/D2O mixtures by sequentially exchanging the deuterons with protons. Flash freezing the solutions allows us to identify species with various D/H contents in solution and thus to quantify the energy transfer processes to individual OH-oscillators. This is not possible in solution due to fast exchange in the ensembles present at room temperature. We conclude that the energy transfer processes are accurately described, predicted, and simulated using a step-wise addition of the rates of quenching by each O-H oscillator. This documents the sequential increase in the rate of the energy transfer processes in the quenching of lanthanide luminescence, and further provides a methodology to identify isotopic impurities in deuterated lanthanide systems in solution.

EuIII and TbIII upconversion intermediated by interparticle energy transfer in functionalized NaLnF4 nanoparticles.

Lanthanide (LnIII)-doped sodium gadolinium tetrafluoride (NaGdF4) nanoparticles have been excelled as attractive upconversion systems for anti-counterfeiting or energy conversion for instance, with a special interest in the visible upconversion of EuIII and TbIII. The core@shell architecture has enabled the bright upconversion of EuIII and TbIII in this matrix by interfacial energy transfer sensibilized by the TmIII/YbIII pair. Another approach to enable EuIII and TbIII upconversion could be the interparticle energy transfer (IPET) between LnIII-doped sensitizer and acceptor nanoparticles. Yet, the low molar absorptivity of the LnIII through 4f ↔ 4f electronic transitions and the large distance between the nanoparticles are shortcomings that should decrease the energy transfer efficiency. On the other hand, it is feasible to predict that the association of organic ligands displaying large molar absorptivity on the acceptor nanoparticle surface could help to overcome the absorption limitation. Inspired by this exciting possibility, herein, we present the EuIII/TbIII upconversion intermediated by IPET between the donor TmIII, YbIII-doped NaGdF4 nanoparticle and the acceptor LnIII-doped NaGdF4 (Ln = Eu and/or Tb) nanoparticles functionalized with a series organic ligands on the surface (tta- = thenoyltrifluoroacetonate, acac- = acetylacetonate, or 3,5-bbza- = 3,5-dibromebenzoate). Either in solid state or in suspension, upon excitation at 980 nm, visible EuIII/TbIII upconversion could be observed. This emission comes from the absorption of the TmIII, YbIII pair in the donor nanoparticle, followed by IPET from the TmIII excited levels to the ligand singlet/triplet states on the acceptor nanoparticle surface, ligand-to-EuIII/TbIII energy transfer, and upconversion emission. Spectroscopic evidences from the analysis of the donor level lifetimes indicate the contribution of non-radiative energy transfer for the IPET mechanism; the radiative mechanism also contributes for the IPET. Moreover, the design herein introduced enables the development of luminescence temperature probes with relative thermal sensitivity as high as 1.67% K-1 at 373 K. Therefore, this new upconversion pathway opens an avenue of possibilities in an uncharted territory to tune the visible upconversion of LnIII ions.

Enhancing the inherent NIR photoluminescence in SrLaLiTeO6 through Cr3+-Yb3+ co-substitution for high performance pc-LEDs.

Until now, double perovskite tellurates have not been reported to exhibit inherent NIR photoluminescence. Therefore, the current study's revelation of inherent NIR luminescence in SrLaLiTeO6 double perovskite centered at 970 nm under 340 nm excitation is particularly intriguing. This phenomenon is attributed to the photoluminescence of Te4+ ions. This study also examines the NIR luminescence of Cr3+-Yb3+ co-doped SrLaLiTeO6. The host and SrLaLiTeO6:3%Cr3+, y%Yb3+ (y = 1, 2, 4, 6, 8, 10 mol%) were synthesized using the solid-state ceramic route. The successful incorporation of Cr3+ and Yb3+ ions into the host lattice was confirmed through XRD, Raman, and diffuse reflectance spectral analyses. Under 270 nm excitation, the photoluminescence (PL) of SrLaLiTeO6:Cr3+ exhibits a blueshift of the PL band to 965 nm due to the 4T2(4F) → 4A2g(4F) emission component of Cr3+ ions. The excited-state lifetime of SrLaLiTeO6:0.5%Cr3+ was measured at 36 μs, but this decreased to 26 μs as the Cr3+ concentration reached 10 mol%, primarily due to the enhancement of non-radiative energy transfer between Cr3+ ions. Incorporating Yb3+ into the system results in additional spectral lines with an enhanced intensity in the range of 970 nm to 1125 nm when excited at 270 nm. These emission lines correspond to the 2F5/2 → 2F7/2 transitions of Yb3+ ions, indicating an efficient energy transfer from Cr3+ to Yb3+. Furthermore, the study also reveals that Yb3+ emission is observed even without Cr3+ ions in SrLaLiTeO6 under 340 nm excitation, suggesting the possibility of energy transfer from the host to Yb3+ ions. The thermal stability and crystal field parameters of the synthesized phosphors are also explained in detail. To explore the potential of these phosphors in practical applications, phosphor-converted NIR LEDs were fabricated using SrLaLiTeO6, SrLaLiTeO6:3% Cr3+, and SrLaLiTeO6:3% Cr3+, 1%Yb3+.

High performance metal-semiconductor-metal ultraviolet photodetector based on mixed-dimensional TiO2/CsPbBr3 heterostructures

Zero-dimensional (0D) and one-dimensional (1D) mixed heterostructure semiconductors can bring superior electrical and optoelectronic performances due to the synergistic advantages of different dimensionalities. Here, a metal-semiconductor–metal (MSM) ultraviolet (UV) photodetector based on 1D-0D TiO2/CsPbBr3 heterostructure semiconductor is constructed, which exhibits excellent photodetection performance. A back-to-back Schottky contact is formed in the MSM (Au/TiO2/Au) structure due to the large band-energy bending resulted from the abundant surface-states at 1D-TiO2 surface. Under an applied voltage, a small saturation current flows through the device. Benefiting from the decoration of CsPbBr3 QDs, the dark current of MSM photodetectors can be further suppressed, and producing the improved on/off ratio (I light/I dark), photoresponsivity (R λ ), and detectivity (D*). PL properties study suggested that an energy transfer is occurred between the 0D-CsPbBr3 and 1D-TiO2. The TiO2/CsPbBr3 heterojunctions are beneficial for photo-induced charge transfer in hetero-interface because of the type-II energy-band alignment, but not non-radiative energy transfer from 0D-CsPbBr3 to 1D-TiO2. On the whole, this study depicts a fascinating coupling architecture of mixed-dimensional materials toward implementing low-cost and high-performance optoelectronic devices.

Luminescence and Excited State Dynamics of Tb1-XEuxAl3(BO3)4 (x=0.01-0.20)

The room temperature luminescence spectra and emission decay curves of undoped and Eu3+-doped TbAl3(BO3)4 crystals, grown using the flux growth technique, are presented and discussed. The experimental results show that excitation of the Tb3+ excited states gives rise to 5D0 emission from the Eu3+ ion, and therefore non-radiative energy transfer involving the two ions is operative. Analysis of the experimental data indicates that the excitation of the Tb3+ donor ion gives rise to fast energy migration in the 5D4 level of the Tb3+ subset of cations, followed by the energy transfer process populating the 5D0 level of Eu3+. Upon increasing the Eu3+ acceptor concentration, the mainly green emission intensity and the decay time of the 5D4 level decrease, whilst the red emission of 5D0 becomes dominant. The experimental data are interpreted on the basis of the trigonal huntite-type structure of the double borate crystals under investigation.

Effect of Chloramphenicol as Antibiotic on the Structure and Function of Pepsin and Its Mechanism of Action.

The interaction between chloramphenicol (CHL) and pepsin (PEP), as well as the impact of CHL on PEP conformation, were investigated using spectroscopic techniques and molecular docking simulations in this study. The experimental results demonstrate that CHL exhibits a static quenching effect on PEP. The thermodynamic parameters indicate that the reaction between CHL and PEP is spontaneous, primarily driven by hydrogen bonding and van der Waals forces. Moreover, the binding distance of r<7 nm suggests the occurrence of Förster's non-radiative energy transfer between these two molecules. In the synchronous fluorescence spectrum, the maximum fluorescence intensity of PEP produced a redshift phenomenon, indicating that CHL was bound to tryptophan residues of PEP. The addition of CHL induces changes in the secondary structure of PEP, as confirmed by the observed alterations in peak values in three-dimensional fluorescence spectra. The UV spectra reveal a redshift of 3 nm in the maximum absorption peak, indicating a conformational change in the secondary structure of PEP upon addition of CHL. Circular dichroism analysis demonstrates significant alterations in the α-helix, β-sheet, β-turn, and random coil contents of PEP before and after CHL incorporation, further confirming its ability to modulate the secondary structure of PEP.

Synthesis and study of luminescence properties of a deep red-emitting phosphor K2 LiAlF6 :Mn4+ for plant cultivation.

Light is the most important component in plant growth and development. This study synthesised a novel Mn4+ -doped K2 LiAlF6 red-emitting phosphor using the coprecipitation method. We observed that on addition of dopant Mn4+ ions to the host K2 LiAlF6 , its phase changed from rhombohedral to cubic due to the change in the lattice position of the atoms. When the atoms are excited at 468 nm, the K2 LiAlF6 :Mn4+ phosphor exhibited a red emission band ranging from 630 to 700 nm, centred at 638 nm, which matched well with the absorption spectra of phytochrome PR. The critical quenching content of Mn4+ ions was ~3mol%. The critical distance between Mn4+ ions was determined to be 19.724 Å, and non-radiative energy transfer among the nearest-neighbour Mn4+ ions was the mechanism used for the concentration quenching effect. The Commission International de l'Eclairage (CIE) chromaticity coordinates of the K2 LiAlF6 :0.03 Mn4+ sample were (x = 0.7162, y = 0.2837). The luminescence mean decay time was calculated to be 8.29 ms. These results demonstrated the promising prospect of K2 LiAlF6 :Mn4+ as a red-emitting phosphor for application in red light-emitting diodes for plant cultivation.

Structure, luminescence properties and anti-thermal quenching of a novel Eu3+-activated red phosphor based on the negative thermal expansion material In0.5Sc1.5(MoO4)3

A new Eu3+-doped phosphor was synthesized by the high-temperature solid-state method based on In0.5Sc1.5(MoO4)3 with negative thermal expansion characteristics in the wide temperature range. The phosphor was pure phase, and the Eu3+ occupied the Sc3+-site. The main emission peak of the phosphor was located at 615 nm, which was attributed to the 5D0-7F2 energy level transition of Eu3+, and the fluorescence lifetime was between 297 and 493 μs. Its quenching concentration was 8 mol%, and the non-radiative energy transfer mechanism between Eu3+ ions was mainly exchange interaction. Under the excitation of 246 nm, the luminous intensity of phosphor was thermically enhanced after 348 K and showed near-zero thermal quenching characteristic. It could be attributed to the positive thermal expansion of phosphor change into two-dimensional negative thermal expansion. At 465 nm excitation, it also exhibited the anti- thermal quenching property and the luminous intensity remained 103.4 % at 423 K of that at the room temperature. The internal quantum efficiency of In0.5Sc1.5(MoO4)3: 8 mol% Eu3+ phosphor was 57.8 %, while the overall color purity was as high as 99.52 %. The LED device packaged it with a commercial LED chip could emit bright red light. Its comprehensive luminous properties were better than the commercial red phosphor Y2O3: Eu3+. The results showed that In0.5Sc1.5(MoO4)3: Eu3+ was a new red phosphor with good luminous performance and anti-thermal quenching characteristic.

Assessment of the Binding of Pseudallecin A to Human Serum Albumin with Multi-Spectroscopic Analysis, Molecular Docking and Molecular Dynamic Simulation.

The binding of pseudallecin A (PA), a potential antibiotic with strong inhibitory activities against Gram-positive Escherichia coli and Gram-negative Staphylococcus aureus, to human serum albumin (HSA) was explored. The interaction between them was assessed by multi-spectroscopic analysis, binding site competitive analysis, molecular docking and molecular dynamic simulation, showing the results as follows: PA effectively quenched the innate fluorescence of HSA by a static quenching process, formed a complex at a molar ratio of approximately 1 : 1 and performed an effective non-radiative energy transfer; the binding of PA to HSA was a spontaneous exothermic reaction driven by enthalpy with strong affinity and had a slight effect on the conformation of HSA; PA bound at site III of HSA and hydrogen bonds were the major binding forces to maintain the stability of the PA-HSA complex. Molecular dynamic simulation was performed to calculate the root mean square deviation (RMSD), root mean square fluctuation (RMSF) and radius of gyration (Rg) for this complex and effectively supported the spectroscopic outcome. These results meant that the delivery and distribution of PA as a water-insoluble molecule can be efficiently accomplished via HSA in human blood and, it has a good potential for future drug application and pharmacological development.

Versatile properties of BaGd2ZnO5:Ho3+ nanomaterial: Compatible towards solid state lightening, anti-counterfeiting and biomedical applications

For the first time, BaGd2ZnO5:Ho3+ (1–11 mol %) nanophosphor (BGZO:Ho3+ NPs) is prepared using combustion synthesis by utilizing glycine as fuel. Phase purity is evaluated using Rietveld refinement and X-ray diffraction. Through crystallographic analysis, the orthorhombic symmetry type with Pbnm (62) space group has been determined. The size of the non-uniformly aggregated particles examined by morphological analysis ranges from 37 to 53 nm. Asignificant photoluminescence (PL) emission observed at 551 nm (green colour) for the 5S2+5F4→5I8 transition. Due to non-radiative energy transfer via cross-relaxation, concentration quenching is observed beyond 9 mol %. Thechromaticity coordinates of BGZO:9Ho3+ NPs is(x = 0.2870, y = 0.7016) suggested that it would be suitable for green emission in white light emitting diode applications. In this case, a flexible light-emitting polydimethylsiloxane (PDMS) material serves as the framework for an anti-counterfeiting (AC) technique. Thrombosis is considered as a major threat to the society as it leads to death and disability. Despite, several risk factors oxidative stress has been considered as the key contributor of thrombosis. The most promising NPs were subsequently investigated for their ability to reduce oxidative stress and thrombosis. It is perceived that NPs demonstrated antioxidant properties by scavenging DPPH (2, 2-diphenyl-1-picrylhydrazyl). In addition, the phosphor inhibited platelet aggregation induced by Adenosine di-phosphate (ADP). The overall results clearly indicated that BGZO:Ho3+ NPs opens up a new avenue in forensic applications.

Application of non-radiative energy transfer from Tb3+ to Nd3+ for pumping a 6 μm solid-state laser

It has been shown that the sensitization scheme involving non-radiative energy transfer from Tb3+ to Nd3+ in selenide glass is suitable for pumping a mid-infrared Nd3+ ion laser. Stimulated emission corresponding to a novel laser transition 4I11/2–4I9/2 of Nd3+ ions was demonstrated at liquid nitrogen temperature. Using an intracavity CaF2 prism, the laser was tunable from 5.56 to 6.01 μm. Output energy up to 16 mJ has been obtained.

Assessing Partial Inhibition of Ribonuclease A Activity by Curcumin through Fluorescence Spectroscopy and Theoretical Studies.

Molecular interactions and controlled expression of enzymatic activities are fundamental to all cellular functions in an organism. The active polyphenol in turmeric known as curcumin (CCM) is known to exhibit diverse pharmacological activities. Ribonucleases(RNases) are the hydrolytic enzymes that plays important role in ribonucleic acid (RNA) metabolism. Uncontrolled and unwanted cleavage of RNA by RNases may be the cause of cell death leading to disease states. The protein ribonuclease A (RNase A) in the superfamily of RNases cleaves the RNA besides its role in different diseases like autoimmune diseases, and pancreatic disorders. Interaction of CCM with RNase A have been reported along with the possible role of CCM to inhibit the RNase A enzymatic activity. The interaction strength was found to be 104M-1 order from spectroscopic results. Quenching of RNase A fluorescence by CCM was 104M-1 order. Non-radiative energy transfer from RNase A (donor) to CCM (acceptor) suggested a distance of 2.42nm between the donor-acceptor pair. Circular dichroism studies revealed no structural changes in RNase A after binding. Binding-induced conformational variation in protein was observed from synchronous fluorescence studies. Agarose gel electrophoresis revealed a partial inhibition of the RNase A activity by CCM though not significant. Molecular docking and molecular dynamics studies suggested the residues of RNase A involved in the interaction with supporting the experimental finding for the partial inhibition of the enzyme activity. This study may help in designing new CCM analogues or related structures to understand their differential inhibition of the RNase A activity.

Evaluation of the Binding Properties of A New Phenylurea Appended Carbazole Compound to Pepsin/Trypsin by Computational and Multi-Spectral Analysis.

A novel carbazole compound, named 1-(9-ethyl-9H-carbazol-3-yl)-3-phenylurea (Cpu) was synthesized and its binding properties with protease enzymes (pepsin and trypsin) has been examined by steady-state fluorescence measurements, UV/vis absorption, infrared (FT-IR) and circular dicroism (CD) spectroscopies and also computational methods. The fluorescence experimental results indicated that the quenching mechanism of enzyme by Cpu is static process. The thermodynamic parameters (both negative ΔH/ΔS) and molecular docking results suggested that the binding of Cpu to pepsin/trypsin were driven by hydrogen bonds and van der Waals forces. Based on Förster's theory, the binding distance (r) between pepsin/trypsin and Cpu was calculated to be 3.072/2.784nm, which implies that non-radiative energy transfer occurs from enzyme to Cpu. Furthermore, absorption, CD, and FT-IR spectral analysis provided an evidence that the presence of Cpu induced notable changes in the secondary structures and microenvironmental of both pepsin and trypsin, supporting its significant influence on these enzymes.

Solid State Synthesis and Characterization of Yb3+/Ho3+ Doped GdPO4 Nanophosphor for Luminescence Properties

A reliable solid-state method for synthesizing GdPO4:Yb3+/Ho3+ nanophosphor is presented, exhibiting both up and down conversion luminescent properties. The peaks were observed at 460, 550, 640, and 750 nm after excitation at 300 nm, which is followed by nonradiative resonance energy transfer (ET) with the P-O charge transfer band of Ho3+ ions. A significant up-conversion nanophosphors by enhancing Ho3+ ion emissions is accomplished. The Ho3+ ion peaks at 542 and 635 nm were identified using a strong 980 nm laser source, leading to well-crystalline nanoparticles. The present results demonstrated an enormous potential of GdPO4:Yb3+/Ho3+ for high-quality, widespread luminescence. Due to their significant quantum yield when excited at a wavelength of 300 nm, these materials exhibit a diverse array of potential applications and hold considerable potential for advancement across several industries.

High thermal stability of warm white emitting single phase GdPO4: Dy3+/ Sm3+ phosphor for UV excited wLEDs

Highly thermally stable warm white light emission has been obtained from a single component phosphor; GdPO4: Dy3+/Sm3+. A series of GdPO4: Sm3+ (1%)/Dy3+ (x%) (x = 0.1, 0.5, 1 and 2) phosphors have been synthesized by the co-precipitation method. The crystal structure and phase purity of the samples obtained were verified by X-ray diffraction. Photoluminescence spectra, luminescence lifetimes are used to study the effect of Dy3+ concentration and the energy transfer from Dy3+ to Sm3+ as a function of excitation wavelength. The nearest-neighbor contributed to the non-radiative energy transfer from Dy3+ to Sm3+ in GdPO4, under 273 and 363 nm excitation. A warm white light was obtained from all phosphors excited at 273 nm and for 1 and 2% of Dy3+ in GdPO4:Sm3+ under 363 nm excitation. Temperature-dependent luminescence properties are determined for GdPO4: Sm3+ (1%), Dy3+ (1%) under 273 nm and 363 nm excitation. The studied phosphor has a good luminescence thermal stability and the determined activation energy for thermal quenching is 1.26 and 0.75 eV for 273 nm and 363 nm excitation wavelengths, respectively. The effect of the Dy3+ concentration as an activator ion responsible for the white emission light, at a fixed concentration of Sm3+ as a red emission compensator in the Dy3+ emission spectrum, was discussed. The low color temperature and high thermal stability indicate that the studied material is a promising solid-state emitting phosphors for the UV chip excited warm wLED applications.

Novel blue-emitting glass CaO-B2O3-2SiO2: Eu2+, Ce3+ with energy transfer

In this paper, CaO-B2O3-2SiO2: Eu[Formula: see text] and CaO-B2O3-2SiO2: Eu[Formula: see text], Ce[Formula: see text] fluorescent glasses have been synthesized by a conventional melt-quenching method. First, under 350[Formula: see text]nm excitation, the CaO-B2O3-2SiO2: Ce[Formula: see text] luminescent glass emits light at about 400[Formula: see text]nm, and the optimum dosage is 0.3[Formula: see text]mol%. Then, under 400[Formula: see text]nm UV excitation, the CaO-B2O3-2SiO2: Eu[Formula: see text] luminescent glasses showed a strong emission with a peak around 460[Formula: see text]nm and a half wavelength of 95[Formula: see text]nm. The results showed that the luminescence of this glass was greatest when the doping amount was 0.3[Formula: see text]mol% and gradually decreased with increase of the doping amount. After calculation and analysis, it was found that this was due to the nonradiative energy transfer between Eu[Formula: see text] ions. The mechanism of energy transfer was dipole–dipole interaction. Finally, Ce[Formula: see text]/Eu[Formula: see text] co-doped luminescent glasses were also successfully prepared with strong emission. The existence of energy transfer was demonstrated by theoretical and practical measurement data. CaO-B2O3-2SiO2: Ce[Formula: see text], Eu[Formula: see text] can be used as blue fluorescent glass for white light illumination.

Hydroxychloroquine-Loaded Chitosan Nanoparticles Induce Anticancer Activity in A549 Lung Cancer Cells: Design, BSA Binding, Molecular Docking, Mechanistic, and Biological Evaluation.

The current study describes the encapsulation of hydroxychloroquine, widely used in traditional medicine due to its diverse pharmacological and medicinal uses, in chitosan nanoparticles (CNPs). This work aims to combine the HCQ drug with CS NPs to generate a novel nanocomposite with improved characteristics and bioavailability. HCQ@CS NPs are roughly shaped like roadways and have a smooth surface with an average size of 159.3 ± 7.1 nm, a PDI of 0.224 ± 0.101, and a zeta potential of +46.6 ± 0.8 mV. To aid in the development of pharmaceutical systems for use in cancer therapy, the binding mechanism and affinity of the interaction between HCQ and HCQ@CS NPs and BSA were examined using stopped-flow and other spectroscopic approaches, supplemented by molecular docking analysis. HCQ and HCQ@CS NPs binding with BSA is driven by a ground-state complex formation that may be accompanied by a non-radiative energy transfer process, and binding constants indicate that HCQ@CS NPs-BSA was more stable than HCQ-BSA. The stopped-flow analysis demonstrated that, in addition to increasing BSA affinity, the nanoformulation HCQ@CS NPS changes the binding process and may open new routes for interaction. Docking experiments verified the development of the HCQ-BSA complex, with HCQ binding to site I on the BSA structure, primarily with the amino acids, Thr 578, Gln 579, Gln 525, Tyr 400, and Asn 404. Furthermore, the nanoformulation HCQ@CS NPS not only increased cytotoxicity against the A549 lung cancer cell line (IC50 = 28.57 ± 1.72 μg/mL) compared to HCQ (102.21 ± 0.67 μg/mL), but also exhibited higher antibacterial activity against both Gram-positive and Gram-negative bacteria when compared to HCQ and chloramphenicol, which is in agreement with the binding constants. The nanoformulation developed in this study may offer a viable therapy option for A549 lung cancer.

Effective role of Co-dopants (Dy3+, Sm3+) on Tunable multicolour emission of Tb3+ doped telluroborate glasses for Natural White light applications

In the current work the efficacy of incorporation of Dy3+ and Sm3+ ions into Tb3+ doped new telluroborate glass as well as their interactions was investigated. In this study, Tb3+ ions were employed as activators and sensitizers for both Dy3+ and Sm3+ ions emissions, which emanate from the excited states of Dy3+ (4F9/2) and Sm3+ (4G5/2) ions through a non-radiative energy transfer process. To validate the emission gamut of the prepared glasses, distinct emission colours were inspected with the CIE 1931 chromaticity analysis and the appropriate correlated colour temperature (CCT) values were estimated. The emission decay profile relating to the Tb3+ ions (5D4 state) of the glasses was investigated. The energy transfer efficiency, which stems from Tb3+ ion to Dy3+ and Sm3+ ions were found to be 49 and 54% respectively. The IH model was successfully used to analyse the interaction mechanism.

Luminescence studies of high color purity red-emitting [formula omitted] phosphor prepared by microwave-assisted synthesis technique

A set of red-emitting phosphor materials (Ca1−xAl4O7:Eux3+, x = 0, 0.01, 0.03, 0.05, 0.07, 0.09, 0.11, 0.13) were synthesized through microwave-assisted combustion synthesis for the first time. The crystal structures and phase purity of Eu3+ ions-activated calcium dialuminate (CaAl4O7) phosphor were investigated by XRD study and Rietveld refinement analysis were performed. The prepared phosphors exhibit monoclinic crystal structure having C2/c space group. From the radius difference percentage calculation, the occupancy of Eu3+ ions in Ca2+ sites was confirmed which is in better harmony with the refinement result. Morphological analysis was investigated through SEM study. Structural characteristics and the presence of the functional groups were analysed though FTIR study. The optical band gap (Eg) was determined to be 5.46 eV by studying the UV–VIS reflectance spectra. PL measurements were carried out for the prepared material to study the luminescent behaviour. The presence of charge transfer band was observed in the excitation spectra. It is found that the prepared phosphor materials exhibits emission rich in red at 611 nm with fixed excitation wavelength at 393 nm. The concentration quenching and energy transfer kinetics were analysed by employing Blasse and Dexter’s formula that attributed the non-radiative energy transfer to the dipole-dipole (d-d) interactions. Local site symmetry was analysed to study the symmetry of the environment in the neighbourhood of Eu3+ ions in the host matrix. To analyse the colorimetric performance of the phosphor materials, the correlated color temperature (CCT), color purity were calculated by using the CIE chromaticity co-ordinates (CIE 1931). The calculated CCT value shows the appearance of the emitted color of the phosphor in the warmer region. CaAl4O7:Eu3+ phosphor manifests high color purity which was found to be 97.39 %. The PL decay time measurement were performed for Ca1−xAl4O7:Eux3+ (x = 0.07) phosphor to obtain the decay lifetime. The estimated decay time (1.44 ms) indicates that the prepared phosphor material has a good potency to be utilized as a red-emitting phosphor for wLED, display technology and other applications.