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.

中文翻译：

---

超小型Euro纳米晶体的直接白光发射

本研究报道了超小型euro纳米晶体（WLEuNCs）的直接白光发射。使用硫脲，油胺（OlAm），油醇（OA）和Eu（III）氧化物在120°C下完成一锅合成WLEuNCs。在250 nm激发时，观察到318、429（覆盖绿色光谱的宽峰）和618 nm的三个发射峰。这些蓝色，绿色和红色发射的组合导致了nano纳米晶体的白光发射。CIE坐标（0.26，0.32）确认近白光发射，量子产率约为7％。发现硫脲在纳米晶体的白光发射中是必不可少的。根据国际照明委员会（CIE）的坐标，合成的纳米晶体显示出轻微的“蓝光效应”。通过将溶液冷却至3-4°C可以纠正这种影响。冷却后，白光发射得到了显着改善（CIE坐标为0.34、0.30），量子产率略有提高（〜10％）。白光发射也可能是由于3.7 eV的宽带隙所致。