Direct White Light Emission from Ultrasmall Europium Nanocrystals

Abstract

Direct white light emission from ultrasmall europium nanocrystals (WLEuNCs) is reported in the present study. The one-pot synthesis of WLEuNCs was done using thiourea, oleyl amine (OlAm), oleyl alcohol (OA), and Eu (III) oxide at 120 °C. Upon excitation at 250 nm, three emission peaks at 318, 429 (broad peak covering green spectrum of light), and 618 nm were observed. The combination of these blue, green, and red emissions resulted in white light emission from the europium nanocrystals. The CIE coordinates (0.26, 0.32) confirm near white light emission with a quantum yield of ∼7%. The role of thiourea was found to be indispensable in emission of white light from nanocrystals. As per Commission Internationale de L'Eclairage (CIE) coordinates, as synthesized nanocrystals exhibited a slight "bluing effect". This effect was rectified by cooling the solution to 3−4 °C. Upon cooling, there was substantial improvement in white light emission (CIE coordinates 0.34, 0.30) along with a slight enhancement in quantum yield (∼10%). The white light emission might also be due a wide band gap of 3.7 eV.

White light emitting silsesquioxane based materials: the importance of a ligand with rigid and directional arms

“…39 This enhanced QY can be ascribed to the excellent complexing properties of the terpyridine as well as to the absence of π-π stacking interactions with consequent self-quenching phenomena. 27 The low QY observed for Ter-POSS@4Cu is in agreement with the one observed in literature and can be justified by the almost complete quenching of the emission band of the ligand. 40 The slight emission is attributed to the appearance of the novel and less intense band centered at ca.…”

“…This behaviour was previously observed in the presence of ultra-small europium nanocrystals and was ascribed to a combination of blue, green and red emissions. 27 In our case, the absence of the broad band due to formation of excimers allows evidencing the two contributions at ca 400 and 500 nm. These two contributions (in the blue and green region of the visible spectrum) together with those of the europium complex (with its typical emission in the red) can explain the resulting intense white light emission.…”

“…White light materials are often prepared from combinations of several components displaying complementary emission colours as blue and yellow (BY), blue and red (BR) or, more recently, blue, green and red (BGR). 27 Organic materials are the most widely used in the synthesis of WLED. [28][29][30] Most organic WLEDs are synthetized by mixing different organic polymers with unique optical properties.…”

Two luminescent film sensors constructed from new lanthanide coordination polymers for ratiometric detection of Zn2+ and NH3 in water and their white emission properties

“…44–47 In past decades, many types of white light materials were reported, such as organic polymers, metal-doped inorganic materials, small organic molecules, quantum dots and nanocrystals, as well as metal complexes. 48–50 For white emission lanthanide coordination polymer materials, the white emission is often obtained by adjusting the ratio of the three primary colors of red, green and blue originating from the emissions characteristic of Tb 3+ , Eu 3+ and the organic ligand either by a co-doping strategy or by tuning the excitation wavelength or temperature. 51 As is well known, it is easy to achieve the color-tuning behaviors of lanthanide complexes through changing the type and proportion of the Ln 3+ ion, yet this method may result in a considerable waste of rare earth resources.…”

One-Pot Phosphine-Free Route for Single-Component White Light Emitting CdSexSy Alloy Nanocrystals

“…Recently, white light emitting (WLE) materials have been a subject of notable scientific interest on account of their versatile and extensive applications in artificial lighting and display devices. − Currently, incandescent bulbs and fluorescent lamps employing mercury vapor are used heavily for lighting applications giving rise to an environmental concern. Surface passivated inorganic semiconductor nanocrystals have emerged as a new technology platform with the potential to replace commercially used lamps.…”