Thirumalai Rajasekaran, Mukhopadhyay Rahul Dev, Praveen Vakayil K, Ajayaghosh Ayyappanpillai
Photosciences and Photonics Group, Chemical Sciences and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology (CSIR-NIIST), Trivandrum 695019, India.
Academy of Scientific and Innovative Research (AcSIR), CSIR-National Institute for Interdisciplinary Science and Technology (CSIR-NIIST), Trivandrum 695019, India.
Sci Rep. 2015 May 5;5:9842. doi: 10.1038/srep09842.
Protection of currency and valuable documents from counterfeit continues to be a challenge. While there are many embedded security features available for document safety, they are not immune to forgery. Fluorescence is a sensitive property, which responds to external stimuli such as solvent polarity, temperature or mechanical stress, however practical use in security applications is hampered due to several reasons. Therefore, a simple and specific stimuli responsive security feature that is difficult to duplicate is of great demand. Herein we report the design of a fluorescent molecular assembly on which water behaves as a self-erasable security marker for checking the authenticity of documents at point of care. The underlying principle involves the disciplined self-assembly of a tailor-made fluorescent molecule, which initially form a weak blue fluorescence (λem = 425 nm, Φf = 0.13) and changes to cyan emission (λem = 488 nm,Φf = 0.18) in contact with water due to a reversible molecular slipping motion. This simple chemical tool, based on the principles of molecular self-assembly and fluorescence modulation, allows creation of security labels and optically masked barcodes for multiple documents authentication.
保护货币和有价文件免遭伪造仍然是一项挑战。虽然有许多用于文件安全的嵌入式安全特征，但它们并非不会被伪造。荧光是一种敏感特性，它会对诸如溶剂极性、温度或机械应力等外部刺激做出响应，然而由于多种原因，其在安全应用中的实际应用受到了阻碍。因此，迫切需要一种简单且特定的、难以复制的刺激响应安全特征。在此，我们报告了一种荧光分子组装体的设计，在该组装体上，水充当一种自擦除安全标记，用于在护理点检查文件的真实性。其基本原理涉及一种特制荧光分子的有序自组装，该分子最初形成微弱的蓝色荧光（发射波长λem = 425 nm，荧光量子产率Φf = 0.13），由于可逆的分子滑移运动，与水接触时会变为青色发射（发射波长λem = 488 nm，荧光量子产率Φf = 0.18）。这种基于分子自组装和荧光调制原理的简单化学工具，可用于创建安全标签和光学掩蔽条形码，以实现对多份文件的认证。
