Luminescent EuIII complexes based on phenanthro-imidazole ligands for white LEDs/OLEDs and temperature sensors: Combined experimental and theoretical investigations

The present theis works deals with molecular designing and synthesis of novel class bipolar or ancillary ligand for europium complexes and explore the possibility of using the same in white LEDs, temperature sensor and OLED applications In chapter 1, a general overview of the development of new-generation optical lanthanide based complexes - introduction, literature survey of recent trends and brief objectives of the thesis was discus. In introduction, the basic concepts of the lanthanides, OLED device materials, LEDs applications and ratiometric thermal sensors were discussed. The main aim and importance of the proposed work of the thesis was summarized in this chapter. In chapter 2, four europium complexes (Eu(TTA)3Phen-Ph-Ph, Eu(TTA)3Phen-mCF3-Ph Eu(TTA)3Phen-pCF3-Ph and Eu(TTA)3Phen-Fl-Ph) were designed and synthesized. The N1-functionalization of the phenanthro-imidazole ring by phenyl, substituted phenyl moiety (CF3, electron withdrawing group), fluorene and their influence on photophysical and electrochemical properties of EuIII complexes were determined by experimental and theoretical analyses. Among all the ligands, fluorene functionalized ligand shows white emission in the solid state. All the complexes (in solid and solution) showed the distinctive emission of EuIII ion at 612 nm, due to electric dipole transition (5D0→7F2). The absence of ligand emissions (solution, thin film and solid) in the PL emission spectra of EuIII complexes indicate that the efficient energy transfer from ligand to central metal ion (antenna effect), confirmed by DFT, TD-DFT. The HOMO-LUMO levels were determined by CV studies. Eu-complex was doped in PMMA matrix to fabricate the composite film devices (Eu(TTA)3Phen-pCF3-Ph shown highest quantum yield 78.7 %). The fluorene functionalized ligand integrated with InGaN LED chip (395 nm, forward bias 20 mA) show the potentiality of the ligand and shown white emission. The obtained efficient red emission from the fabricated LEDs (EuIII complexes coated on InGaN-based near UV LED) shown that the currently synthesized complexes could be a potential red component for warm white LEDs. In chapter 3, A new class of bipolar phenanthroimidazole based (N1 functionalization with Ph, mCF3, pCF3 and Fl) ligands and their efficient -diketonate EuIII complexes have been designed, synthesized, characterized successfully and their photophysical, electrochemical properties have also been investigated. All the ligands and complexes show similar UV-Visible absorption behaviour ( - *, at ~270, ~360 nm). Photoluminescence emission spectra of Eu-complexes and its ligands were carried out in solution form as well as in solid and thin film. The PL study indicates that the Eu-complex emits tunable emission due to incomplete/partial energy transfer (white (solution), red (solid)); whereas fluorene decorated Eu-complex shows narrow band red emission with appropriate CIE color gamut. The obtained PL emission clearly indicates that the efficient energy transfer encountered in case of fluorene based complex. The energy transfer mechanism for all the Eu-complexes was proposed based on combined experimental and theoretical study (DFT, TD-DFT). The PL lifetime of the EuIII complexes also supports the PL emission behaviour. The Judd–Ofelt spectral intensity parameters, electrochemical study and absolute QY (mCF3 based Eu-complex shows better QY of 75.9 %) of the Eu-complexes were also been investigated. White and red LED was fabricated using these complexes with near UV InGaN based LEDs (395 nm). In chapter 4, the efficient -diketonate red emitting carbazole-based EuIII complexes were synthesized and their photophysical, electrochemical properties were also been investigated. The PL study indicating that the efficient energy transfer from ligand to EuIII metal ion (dominant pathway) with appropriate CIE color gamut and time-dependent density functional theory (TD-DFT) also confirms the identical. The Judd-Ofelt theory to the emissive properties of EuIII complexes was investigated. The Eu(TTA)3Phen-Fl-CBZ complex shown better lifetime was found to be 0.64 ms. The absolute PL quantum yield (QY) of the complexes in solid is found to be 77.3 % and it possesses high thermal decomposition temperature (235C). The Judd-Ofelt intensity and related parameters were calculated for two complexes. The electrochemical analysis was shown narrow band gap energy (HOMO and LUMO). The PMMA film study of the complexes showed enhanced results than the solution. The fabricated Eu complexes with 395 nm emitted LED (InGaN) chips under 20 mA forward-bias current shown pure red emission and the corresponding CIE color coordinates are x = 0.66, y = 0.33. The obtained pure red emission is superior as compare to that of the solution and solid form of the complexes and the results are shown the presently investigated complexes find potential application in warm white LEDs. In chapter 5, A new diphenylamine (DPA) and carbazole (CBZ) functionalized ancillary ligands coordinated β-diketonate EuIII complexes shown incomplete or complete energy transfer from ligand to EuIII ion. Solvatochromism study of DPA based complex leads to balancing the primary RGB colors to obtain single molecule white emission. The temperature dependent PL study indicates that the DPA based complex could be used as ratiometric temperature sensor (color changes from blue to yellowish-red via white). In addition shown white emission with 0.34, 0.33 CIE coordinates. In the case of CBZ functionalized bipolar ligand and its corresponding β-diketonate EuIII complex shown efficient energy transfers from the ligand to EuIII center metal ion and emits narrow band red emission with apt CIE color gamut. TD-DFT calculations were performed to know the energies of the singlet (1S) and triplet (3T) levels for the bipolar ligand and shown good overlap between the ligand triplet level and EuIII excited level. The PLQY is found to be 44.4 %, whereas the DPA based complex shown comparatively less QY (supports the inefficient energy transfer). HOMO and LUMO energy levels energies (redox reaction) were calculated from the electrochemical analysis for the Eu-complexes. The synthesized EuIII complex was doped in PMMA with different percentage ratio and found to be concentration variation influence on emission intensity and symmetry. The CBZ-Eu-complex conjugated with near UV LED (395 nm) shown red emission with CIE color coordinates of 0.66, 0.33 and could find potential application in white LEDs. In chapter 6, the effect of functionalization of carbazole with spacer in C1 position and fluorine in N1 position in the phenanthroline-imidazole based bipolar ligand has been designed, synthesised, same is utilized to synthesise Eu(TTA)3Phen-Fl-O-CBZ complex and studied their photophysical properties. In addition, phenyl and fluorene functionalization in N1 position of phenanthro-imidazole ring (with alkoxy spacer) and its influence on photophysical properties of their binuclear Eu- complexes were systematically investigated. The mono and binuclear Eu-complexes emission spectra (pure red emission) clearly indicate that the complete energy transfer from ligand (L) to EuIII ion occurs, since there is no emission from ligand was encountered (confirmed by DFT and TD-DFT calculations). It is found that the spacer molecule can decrease the energy gap of HOMO-LUMO energy levels (2.6 eV) with respect to that of without spacer one and increment in the singlet and triplet energy levels was also observed, consequences efficient energy transfer (L to M). The enhanced QY observed by 1% doping with PMMA as compare with other doping concentrations (14.2%). Binuclear Eu show dominant electric dipole transition of EuIII ion (5D0→7F2, confirms the EuIII ion in the non-centrosymmetric site). The highest QY (59.5 %, for thin film) obtained for the Eu2(TTA)6(L2). The binuclear EuIII complexes were combined with InGaN near UV LED, obtained pure red emission with CIE color coordinate values x = 0.65, y = 0.34 and x = 0.66, y = 0.33 for Eu2(TTA)6(L1) and Eu2(TTA)6(L2), respectively. The obtained results indicate that the synthesized complexes are potential aspirant for light converting devices. In chapter 7, a series of organic chromophores or ancillary ligands (based on phenanthroimidazole) conjugated with triphenylamine or carbazole moieties were designed with and without spacer and studied their excited state photophysical properties by density functional theory and time-dependent density functional theory. The UV absorption analysis shown maxima around λmax 288, which is belongs to the -* transition of the ligands. The excited state photophysical properties reveal that the location of the triplet level found among three (1a-f, 2a-f, 3a-f) series 3a-f shown better energy matching with the excited state (5D0) of EuIII ion and could facilitate the energy transfer from ligand to Eu ion very efficient. In addition, the substituted phenyl moiety (mCF3 and pCF3) at N1-position in the phenanthro-imidazole ligand give additional benefits by reducing the triplet energy comparatively with other substitution that leads to efficient energy transfer from L to Eu ion in the complex could be expected. In addition, HOMO and LUMO calculations given lead that some of the designed ligands can also serve as host materials for triplet dopant in OLEDs. The systematic theoretical study is certainly leads to synthesis of best ligand molecules for Eu complexes. In chapter 8, the present works deals with molecular designing and synthesis of novel class bipolar or ancillary ligand for europium complexes and explore the possibility of using the same in white LEDs, temperature sensor and OLED applications. The observations and the conclusions derived from the present investigations are summarized in this chapter

Relation between body mass index, forced expiratory volume in one second and 6 minute walk test in stable COPD patients

Background: Chronic obstructive pulmonary disease (COPD) is a common respiratory disorder characterized by irreversible, progressive airflow obstruction. It is diagnosed by spirometry which measures FEV1 and bronchoreversibility. Recent focus has been on COPD systemic effects like malnutrition, cardiovascular disorders, diabetes, musculoskeletal disorders, anxiety and depression. A composite index named BODE index (BMI, FEV1, dyspnea, 6MWT) has a better prediction of mortality than FEV1 alone in these patients. Relation between components of BODE like BMI, FEV1 and 6MWT has been an area of interest since it measures nutritional status (BMI), airway obstruction (FEV1) and exercise capacity (6MWT). We tried to evaluate the relation between lower BMI (˂21) and higher BMI groups (>21) with respect to FEV1 and 6MWT.Methods: A cross sectional observation study was conducted in a tertiary care centre. Stable patients of COPD were recruited from to outpatient department of respiratory medicine. BMI, FEV1 and 6MWT were calculated. Patients are made into 2 groups with BMI less than 21 and more than 21. Both FEV1 and 6MWT means were calculated and analyzed to find out any difference between these two groups.Results: There was no statistical difference of FEV1 and 6MWT between lower and higher BMI groups.Conclusions: In COPD patients, FEV1 and 6MWT values were not statistically different between lower and higher BMI groups. Further studies are needed to prove that other anthropometric measurement like fat free mass index can be a better substitute for more accurate assessment of exercise capacity

Inverse Modeling Of Groundwater System Using Coupled PSO-MLPG Techniques

The effective management of groundwater systems relies on the adequate knowledge of its hydro-geological parameters. In large aquifer systems, it is often computationally expensive to estimate the spatially distributed aquifer parameters. Inverse modeling of these parameters are usually required in simulation of flow and contaminant transport in the problem domain for its meaningful system prediction. In the present study, a new approach for inverse modeling is adopted based on Meshless Local Petrov Galerkin (MLPG) flow simulation model which is coupled with Particle Swarm Optimization (PSO) model. MLPG is one of the meshless techniques, which are recently developed to solve many partial differential governing equations in various engineering fields. Here, without using a pre-defined mesh, the system of equations are established for the entire domain. In MLPG, only appropriate distribution of nodes is utilized in the modeling. The nodes are used for approximation of the governing equations by using support domain. This alleviates the huge efforts required in pre-processing for groundwater modeling, as in mesh based methods. The numerical model is developed in 2 dimensions using MATLAB. The standard PSO algorithm is used for optimization and both simulation optimization models are coupled. The model is applied to a hypothetical confined aquifer to compute transmissivity in different zones of the aquifer. The stability of the estimated parameter is investigated by considering different sets of head data, assuming error free head and different sets involving measurement errors. The solutions are compared with other inverse models using the Levenberg-Marquardt Algorithm (LMA) and Genetic Algorithm (GA). The PSO results are comparable with LMA and are better compared to GA estimates. From the results we can say that the model can be applied to obtain optimal estimates of the aquifer parameters in the regional groundwater systems

Mounier-Kuhn syndrome: a rare entity of bronchiectasis

Mounier-Kuhn syndrome (MKS) is a rare clinical and radiologic entity characterized by pathologic dilatation of the trachea and bronchi. The etiology of this disorder is uncertain and the clinical presentation is variable. The diagnosis is usually made on the basis of the characteristic CT scan findings. We report one such case in a 44-year-old man presenting with recurrent lower respiratory tract infections

Milestone Developments and New Perspectives of Nano/Nanocrystal Light Emitting Diodes

Light emitting diode (LED) is a one type of p/n junction semiconductor device which is used in less energy consumption for numerous lighting functions. Because of their high performance and long existence, their eye-catching application is getting increasing numbers in recent times. LEDs are nowadays defined as using the “ultimate light bulb”. In a previous couple of years, its efficiency has been multiplied through converting it to nano size. This new light-emitting has a nano-pixel structure and it affords high-resolution performance and the geometry of the pixel is cylindrical or conical form. Due to the fact that the previous few years, a few impurity-doped nanocrystal LEDs are varying a good deal in trend. Its performance is very excessive and consumes a smaller amount of voltage. Its monochromatic behavior and indicator excellent are shown publicly demanded in the market and in this work, it’s covered evaluations of the fundamental’s standards of LEDs and the specific mixed metallic and nanocrystal shape of emitters. In addition, it covers the upcoming challenges that the current trend is working to resolve to get efficient materials to fulfill the future energy crisis

Nitrogen and sulfur co-doped activated carbon nanosheets for high-performance coin cell supercapacitor device with outstanding cycle stability

Herein, we report the utilization of nitrogen and sulfur dual heteroatoms co-doped activated carbon (NSAC) by hydrothermal method for electrochemical supercapacitors. Various NSACs were made by using a fixed amount of activated carbon and changing the amounts of thioacetamide. From NSAC electrodes, the coin cell configuration was fabricated and the overall electrochemical conduct was evaluated by using cyclic voltammetry, galvanostatic charge-discharge, cycle life, and electrochemical impedance methodologies. The outcomes manifest that co-doping sulfur and nitrogen into the AC improves the electrochemical performance. In comparison to pure activated carbon, the optimized NSAC produced a higher specific capacitance value of 417 F g−1 at 0.7 A g−1 and also demonstrated outstanding charge-discharge cycling stability at 7 mA (5 A g−1), maintaining 76% of its opening capacitance after 60,000 cycles in the CR2032 device configuration. The impedance studies phase angle value of 85° has added evidence of the NSAC’s good capacitor performance. Thus, we believe this work is suitable for practical applications for energy storage devices. Graphical abstract: [Figure not available: see fulltext.]This work was supported by Qatar University through a National Capacity Building Program Grant (NCBP) [QUCP-CAM-20/23-463]. The publication of the article was funded by the Qatar National Library. Statements made herein are solely the responsibility of the authors

UV Induced Photodegradation of Direct Green dye by Tb-doped La10Si6O27 Catalyst

Due to the expansion of industry, the world's population growth has led to increased air and water contamination. Because they are poisonous and non-biodegradable, organic dyes are a significant source of this contamination. Studies have concentrated on photocatalysts to transform organic dyes into innocuous compounds in order to lessen the harm that organic colours cause. In this study, solution combustion technique was employed to prepare rare-earth metal (terbium (Tb)) doped lanthanum silicate phosphor (La10Si6O27) using lanthanum nitrate and fumed silica were utilized as precursors, oxalyldihydrazide was used as fuel, and terbium nitrate was used as a dopant. The photocatalytic activities for the Direct Green-23 (DG23) dye degradation under UV irradiation were studied and found that 59.05% of dyes degraded at 120 min. These findings shows that, La10Si6O27 is a promising material for industrial dye degradation since 59.05% of the dyes were absorbed by the material in 120 min.This work was supported by Qatar University through a National Capacity Building Program Grant (NCBP), [QUCP-CAM-2022-463]. The publication of the article was funded by Qatar National Library

Progressive Review of Functional Nanomaterials-Based Polymer Nanocomposites for Efficient EMI Shielding

Nanomaterials have assumed an imperative part in the advancement of human evolution and are more intertwined in our thinking and application. Contrary to the conventional micron-filled composites, the unique nanofillers often modify the properties of the polymer matrix at the same time, bestowing new functionality because of their chemical composition and their nano dimensions. The unprecedented technological revolution is driving people to adapt to miniaturized electronic gadgets. The sources of electromagnetic fields are ubiquitous in a tech-driven society. The COVID-19 pandemic has escalated the proliferation of electromagnetic interference as the world embraced remote working and content delivery over mobile communication devices. While EMI shielding is performed using the combination of reflection, absorption, and electrical and magnetic properties, under certain considerations, the dominant nature of any one of the properties may be required. The miniaturization of electronic gadgets coupled with wireless technologies is driving us to search for alternate lightweight EMI shielding materials with improved functionalities relative to conventional metals. Polymer nanocomposites have emerged as functional materials with versatile properties for EMI shielding. This paper reviews nanomaterials-based polymer nanocomposites for EMI shielding applications.This work was supported by Qatar University through a National Capacity Building Program Grant (NCBP), [QUCP-CAM-20/23-463]. Statements made herein are solely the responsibility of the authors

Recent Advances in Copper-Based Materials for Sustainable Environmental Applications

In recent years, copper-based nanomaterials have gained significant attention for their practical applications due to their cost-effectiveness, thermal stability, selectivity, high activity, and wide availability. This review focuses on the synthesis and extensive applications of copper nanomaterials in environmental catalysis, addressing knowledge gaps in pollution management. It highlights recent advancements in using copper-based nanomaterials for the remediation of heavy metals, organic pollutants, pharmaceuticals, and other contaminants. Also, it will be helpful to young researchers in improving the suitability of implementing copper-based nanomaterials correctly to establish and achieve sustainable goals for environmental remediation.This work was supported by Qatar University through a National Capacity Building Program Grant (NCBP), [QUCP-CAM-20/23-463]. Statements made herein are solely the responsibility of the authors