Zhao Haiquan, Qin Xingchen, Zhao Lei, Dong Shumin, Gu Lianghong, Sun Wen, Wang Dongsheng, Zheng Yonghao
School of Optoelectronic Science and Engineering of UESTC , University of Electronic Science and Technology of China , Chengdu 610054 , China.
Department of Chemistry and Biochemistry , California State University Northridge , Northridge , California 91330-8262 , United States.
ACS Appl Mater Interfaces. 2020 Feb 19;12(7):8952-8960. doi: 10.1021/acsami.0c00462. Epub 2020 Feb 5.
Secret information recorded by traditional single-encrypted invisible inks is easily cracked because the inks can switch only between "NONE" and "TRUTH". Developing double-encrypted systems makes the information reversibly switchable between "FALSE" and "TRUTH", which is helpful to ensure the safety of the secret information during transport. Here, we prepared heat-developed invisible inks by hydrochromic molecules donor-acceptor Stenhouse adducts (DASAs) and oxazolidines (OXs) and promoted the invisible inks from single to double encryption. DASAs coordinate with water molecules and form stable colorless cyclic DASA·HO molecules, which lose coordinated water molecules after heating and switch to colored linear DASAs. In contrast, OXs are colored with water and are colorless after heating. Single-encrypted secrecy was realized by DASA invisible inks. The information is invisible under the encrypted state and becomes bright purple after heating. Vapor treating re-encrypted the information in ∼5 min. Furthermore, the single-encryption was promoted to double-encryption by a DASA/OX invisible inks system. Heating and vapor treating switch the information between the "FALSE" and "TRUTH" reversibly. The DASA/OX invisible ink system is applied for secrecy of texts, graphic images, and quick response (QR) codes.
传统的单加密隐形墨水记录的秘密信息很容易被破解，因为这些墨水只能在“无”和“真相”之间切换。开发双加密系统可使信息在“假”和“真相”之间可逆切换，这有助于确保秘密信息在传输过程中的安全。在此，我们通过热致变色分子供体-受体斯滕豪斯加合物（DASAs）和恶唑烷（OXs）制备了热显影隐形墨水，并将隐形墨水从单加密提升为双加密。DASAs与水分子配位并形成稳定的无色环状DASA·HO分子，加热后失去配位水分子并转变为有色线性DASAs。相比之下，OXs遇水显色，加热后无色。通过DASA隐形墨水实现了单加密保密。信息在加密状态下不可见，加热后变为亮紫色。蒸汽处理在约5分钟内对信息进行重新加密。此外，通过DASA/OX隐形墨水系统将单加密提升为双加密。加热和蒸汽处理可使信息在“假”和“真相”之间可逆切换。DASA/OX隐形墨水系统应用于文本、图形图像和二维码的保密。
