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

Identification of Nonlinear Dynamical Systems by a Modified Differential Approximation Technique

Engineerin

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

Development of glass-based microfluidic devices: A review on its fabrication and biologic applications

The advent of glass-based microfluidic devices further revolutionized in microfluidic technology due to the several advantageous properties in terms of photonics, electronics, and thermochemistry, compared to silicon, PDMS and paper. In this review article, we discuss the glass materials in comparison with inorganic, organic polymeric and paper materials for the fabrication of microfluidic devices and the suitability, benefits, applicability of their applications. We highlight the performance enhancement of glass achieved via hybrid fabrication with advanced polymers. For this comprehensive overview of the different materials for the fabrication and applications of microfluidic devices, we consider recent advances in the selected applications of glass material-based microfluidics in sensing and biomedical applications, such as Raman spectroscopy, mass spectroscopy, optical detection methods, embedded glass microfluidics for oil and gas, point-of-care diagnostics, cell analysis, nucleic acid assay, immunoassay analysis and drug delivery. Our review concludes by summarizing the future challenges and developments of these glass-based microfluidic devices

Gallium Nitrate Is Efficacious in Murine Models of Tuberculosis and Inhibits Key Bacterial Fe-Dependent Enzymes

Acquiring iron (Fe) is critical to the metabolism and growth of Mycobacterium tuberculosis. Disruption of Fe metabolism is a potential approach for novel antituberculous therapy. Gallium (Ga) has many similarities to Fe. Biological systems are often unable to distinguish Ga3+ from Fe3+. Unlike Fe3+, Ga3+ cannot be physiologically reduced to Ga2+. Thus, substituting Ga for Fe in the active site of enzymes may render them nonfunctional. We previously showed that Ga inhibits growth of M. tuberculosis in broth and within cultured human macrophages. We now report that Ga(NO3)3 shows efficacy in murine tuberculosis models. BALB/c SCID mice were infected intratracheally with M. tuberculosis, following which they received daily intraperitoneal saline, Ga(NO3)3, or NaNO3. All mice receiving saline or NaNO3 died. All Ga(NO3)3-treated mice survived. M. tuberculosis CFU in the lungs, liver, and spleen of the NaNO3-treated or saline-treated mice were significantly higher than those in Ga-treated mice. When BALB/c mice were substituted for BALB/c SCID mice as a chronic (nonlethal) infection model, Ga(NO3)3 treatment significantly decreased lung CFU. To assess the mechanism(s) whereby Ga inhibits bacterial growth, the effect of Ga on M. tuberculosis ribonucleotide reductase (RR) (a key enzyme in DNA replication) and aconitase activities was assessed. Ga decreased M. tuberculosis RR activity by 50 to 60%, but no additional decrease in RR activity was seen at Ga concentrations that completely inhibited mycobacterial growth. Ga decreased aconitase activity by 90%. Ga(NO3)3 shows efficacy in murine M. tuberculosis infection and leads to a decrease in activity of Fe-dependent enzymes. Additional work is warranted to further define Ga’s mechanism of action and to optimize delivery forms for possible therapeutic uses in humans

Fibronectin Facilitates Mycobacterium tuberculosis Attachment to Murine Alveolar Macrophages

Mycobacterium tuberculosis remains a major cause of pulmonary infection worldwide. Attachment of M. tuberculosis organisms to alveolar macrophages (AMs) represents the earliest phase of primary infection in pulmonary tuberculosis. In this study fibronectin (Fn), an adhesive protein, is shown to bind M. tuberculosis organisms and facilitates attachment of M. tuberculosis to murine AMs. A monoclonal antibody (MAb) specific to the heparin binding domain (HBD) of Fn decreases (125)I-Fn binding to M. tuberculosis; whereas MAbs specific to either the cell binding domain (CBD) or the gelatin binding domain (GBD) have no effect on Fn binding to M. tuberculosis. In the presence of exogenous Fn (10 μg/ml) M. tuberculosis attachment to AMs increased significantly from control levels (means ± standard errors of the means) of 11.5% ± 1.1% to 44.2% ± 4.2% (P < 0.05). Fn-enhanced attachment was significantly decreased from 44.2% ± 4.2% to 10.8% ± 1.2% (P < 0.05) in the presence of anti-Fn polyclonal antibodies. The attachment is also inhibited in the presence of MAbs specific for the HBD and CBD, whereas MAbs specific to GBD did not affect the attachment. Further, an Fn cell binding peptide, Arg-Gly-Asp-Ser (RGDS), decreased the attachment from 44.2% ± 4.2% to 15.3% ± 1.2% (P < 0.05), whereas addition of a control peptide, Arg-Gly-Glu-Ser (RGES) did not affect the attachment (40.5% ± 1.8%). These results suggest that Fn-mediated attachment of M. tuberculosis can occur through the binding of Fn to the AM via the CBD and to M. tuberculosis organisms via the HBD

Nano-Structured Carbon: Its Synthesis from Renewable Agricultural Sources and Important Applications

Carbon materials are versatile in nature due to their unique and modifiable surface and ease of production. Nanostructured carbon materials are gaining importance due to their high surface area for application in the energy, biotechnology, biomedical, and environmental fields. According to their structures, carbon allotropes are classified as carbon nanodots, carbon nanoparticles, graphene, oxide, carbon nanotubes, and fullerenes. They are synthesized via several methods, including pyrolysis, microwave method, hydrothermal synthesis, and chemical vapor deposition, and the use of renewable and cheaper agricultural feedstocks and reactants is increasing for reducing cost and simplifying production. This review explores the nanostructured carbon detailed investigation of sources and their relevant reports. Many of the renewable sources are covered as focused here, such as sugar cane waste, pineapple, its solid biomass, rise husk, date palm, nicotine tabacum stems, lapsi seed stone, rubber-seed shell, coconut shell, and orange peels. The main focus of this work is on the various methods used to synthesize these carbon materials from agricultural waste materials, and their important applications for energy storage devices, optoelectronics, biosensors, and polymer coatings

Versatile Luminescent Europium(III)−β-Diketonate-imidazo-bipyridyl Complexes Intended for White LEDs: A Detailed Photophysical and Theoretical Study

Three ancillary ligands based on imidazo-bipyridyl with phenyl (Ph), naphthyl (Np), and triphenylamine (TPA) substitution were synthesized and secondhand to formulate the consistent europium­(III) ternary complexes using thenoyl­trifluoro­acetone as an anionic ligand. The complete investigation of spectroscopic, photophysical, and electrochemical properties was carried out. The attained results for all the ancillary ligands and their corresponding Eu complexes were compared with one another. All the Eu complexes reveal a broad excitation band ranging from the near-UV to blue region, along with high intense emission and apposite color purity. To further understand the ligand-to-metal energy transfer (ET) process, the geometry of the ligand was optimized and the energy level location (singlet and triplet) was calculated by using DFT and TD-DFT calculations. On the basis of the theoretical calculation, the ET mechanism was proposed. From PL emission spectra in the solid state, complete ET occurs from Ph, Np based ancillary ligands to the Eu³⁺ ion, which yields a pure red emission, whereas the TPA functionalized based Eu complex shows incomplete ET. Fortunately, white emission was observed in the TPA based Eu complex in the solid state. The white LED was fabricated by using a white emitting complex integrated with 395 nm emitted LED (InGaN) chips under 20 mA forward-bias current. The excitation source from LED was fully observed by the complex shown for 3Eu and showed yellowish emission in different concentrations (the similar observation also reflected in solid). However, in the case of 1Eu and 2Eu complexes, they showed close to white emission. The Commission International de I’Eclairage (CIE) chromaticity coordinates are close to the National Television Standard Committee standard value for white emission, and in addition, the complex 3Eu coated with the blue LED chip (460 nm) by PMMA (1:10) showed bright white emission with CIE <i>x</i>, <i>y</i> values of 0.30, 0.33, respectively