Chitnis Dipti, Kalyani N Thejo, Dhoble Sanjay
Department of Physics, RTM Nagpur University, Nagpur, India.
Department of Applied Physics, Laxminarayan Institute of Technology, Nagpur, India.
Luminescence. 2018 Aug;33(5):968-980. doi: 10.1002/bio.3497. Epub 2018 May 31.
We report on the comprehension of novel europium activated hybrid organic Eu(dmh) phen (Eu: europium, dmh: 2,6-dimethyl-3,5-heptanedione, phen: 1,10 phenanthroline) organo-metallic complexes, synthesized at different pH values by the solution technique. Photo physical properties of these complexes in various basic and acidic solvents were probed by UV-vis optical absorption and photoluminescence (PL) spectra. Minute differences in optical absorption peaks with variable optical densities were encountered with the variation in solvent from basic (chloroform, toluene, tetrahydrofuran) to acidic (acetic acid) media, revealing bathochromic shift in the absorption peaks. The PL spectra of the complex in various acidic and basic organic solvents revealed the position of the emission peak at 613 nm irrespective of the changes in solvents whereas the excitation spectrum almost matched with that of the UV-vis absorption data. The optical density was found to be maximum for the complex with pH 7.0 whereas it gradually decreased when pH was lowered to 6.0 or raised to 8.0 at an interval of 0.5, demonstrating its pH sensitive nature. Several spectroscopic parameters related to probability of transition such as absorbance A(λ), Napierian absorption coefficient α(λ), molecular absorption cross-section σ(λ), radiative lifetime (τ ) and oscillator strength (f) were calculated from UV-vis spectra. The relative intensity ratio (R-ratio), calculated from the emission spectra was found to be almost the same in all the organic solvents. The optical energy gap, calculated for the designed complexes were found to be well in accordance with the ideal acceptance value of energy gap of the emissive materials used for fabrication of red organic light-emitting diode (OLED). The relation between Stoke's shift and solvent polarity function was established by Lippert-Mataga plot. This remarkable independence of the electronic absorption spectra of Eu complexes on the nature of the solvent with unique emission wavelength furnishes its potential to serve as a red light emitter for solution processed OLEDs, display panels and solid-state lighting.
我们报道了通过溶液技术在不同pH值下合成的新型铕激活的混合有机Eu(dmh)phen（Eu：铕，dmh：2,6-二甲基-3,5-庚二酮，phen：1,10-菲咯啉）有机金属配合物的相关研究。通过紫外可见吸收光谱和光致发光（PL）光谱探究了这些配合物在各种碱性和酸性溶剂中的光物理性质。随着溶剂从碱性（氯仿、甲苯、四氢呋喃）变为酸性（乙酸）介质，光吸收峰出现了微小差异，光密度也有所变化，吸收峰呈现红移。该配合物在各种酸性和碱性有机溶剂中的PL光谱显示，发射峰位置在613 nm，与溶剂变化无关，而激发光谱几乎与紫外可见吸收数据匹配。发现pH值为7.0时配合物的光密度最大，而当pH值以0.5的间隔降至6.0或升至8.0时，光密度逐渐降低，表明其对pH敏感。从紫外可见光谱计算了几个与跃迁概率相关的光谱参数，如吸光度A(λ)、自然吸收系数α(λ)、分子吸收截面σ(λ)、辐射寿命(τ)和振子强度(f)。从发射光谱计算得到的相对强度比（R-ratio）在所有有机溶剂中几乎相同。计算得到的所设计配合物的光学能隙与用于制造红色有机发光二极管（OLED）的发光材料的理想能隙接受值非常吻合。通过Lippert-Mataga图建立了斯托克斯位移与溶剂极性函数之间的关系。Eu配合物的电子吸收光谱对溶剂性质具有显著的独立性，且具有独特的发射波长，这使其有潜力用作溶液处理OLED、显示面板和固态照明的红色发光体。
