Multifunctional N,S-doped and methionine functionalized carbon dots for on−off−on Fe^(3+)and ascorbic acid sensing,cell imaging,and fluorescent ink applying

Fluorescent carbon dots(CDs)have been identified as potential nanosensors and attracted tremendous research interests in wide areas including anti-counterfeiting,environmental and biological sensing and imaging in considering of the attractive optical properties.In this work,we present a CDs based fluorescent sensor from polyvinylpyrrolidone,citric acid,and methionine as precursors by hydrothermal approach.The selective quantifying of Fe^(3+)and ascorbic acid(AA)are based on the fluorescent on-off-on process,in which the fluorescent quenching is induced by the coordination of the Fe^(3+)on the surface of the CDs,while the fluorescence recovery is mainly attributed to redox reaction between Fe^(3+)and AA,breaking the coordination and bringing the fluorescence back.Inspired by the good water solubility and biocompatibility,significant photostability,superior photobleaching resistance as well as high selectivity,sensitivity,and interference immunity,which are constructed mainly from the N,S-doping and methionine surface functionalization,the CDs have not only been employed as fluorescence ink in multiple anticounterfeiting printing and confidential document writing or transmitting,but also been developed as promising fluorescence sensors in solution and solid by CDs doped test strips and hydrogels for effectively monitoring and removing of Fe^(3+)and AA in environmental aqueous solution.The CDs have been also implemented as effective diagnostic candidates for imaging and tracking of Fe^(3+)and AA in living cells,accelerating the understanding of their function and importance in related biological processes for the prevention and treatment specific diseases.

Information encryption with a high information-carrying capacity based on a stimulus-responsive hydrogen-bonded organic framework and a smartphone

Information-carrying capacity has become an important factor in the development of encryption and anti-counterfeiting.Herein,a hydrogen-bonded organic framework(HOF-PyTTA)was developed as novel anti-counterfeiting ink without rare metals and a smartphone-based APP was written for encryption and anti-counterfeiting.We found that the fluorescence of HOF-PyTTA can be quenched by Fe^(3+)ions and recovered by the addition of ascorbic acid.And the fluorescence of HOF-PyTTA can be enhanced by the increasing concentrations of ethanol.Based on these stimulus-response properties,four anti-counterfeiting models with gradually increased security were studied.Mode one was printed by HOFs ink and decrypted by UV light.Mode two was based on HOF-PyTTA and CsPbBr_(3)inks(or HOF-PyTTA-Fe^(3+))which are used to separately print the genuine and pirated information.A decryption reagent was applied to get the genuine information.Furthermore,we successfully construct a dynamic information encryption anti-counterfeiting model using a fluorescence array in combination with an information encryption anticounterfeiting APP.The circular array is printed by several concentrations of HOF-PyTTA ink and different RGB thresholds are set with the help of the information encryption anti-counterfeiting APP,to obtain distinct encrypted anti-counterfeiting information,thus accomplishing a high information-carrying capacity.

Arbitrated quantum signature scheme based on reusable key

An arbitrated quantum signature scheme without using entangled states is proposed.In the scheme,by employing a classical hash function and random numbers,the secret keys of signer and receiver can be reused.It is shown that the proposed scheme is secure against several well-known attacks.Specifically,it can stand against the receiver’s disavowal attack.Moreover,compared with previous relevant arbitrated quantum signature schemes,the scheme proposed has the advantage of less transmission complexity.

Binary phase hopping based spreading code authentication technique

Civil receivers of Global Navigation Satellite System (GNSS) are vulnerable to spoofing and jamming attacks due to their signal structures. The Spreading Code Authentication (SCA) technique is one of the GNSS message encryption identity authentication techniques. Its robustness and complexity are in between Navigation Message Authentication (NMA) and Navigation Message Encryption (NME)/Spreading Code Encryption (SCE). A commonly used spreading code authentication technique inserts unpredictable chips into the public spreading code. This method changes the signal structure, degrades the correlation of the spreading code, and causes performance loss. This paper proposes a binary phase hopping based spreading code authentication technique, which can achieve identity authentication without changing the existing signal structure. Analysis shows that this method can reduce the performance loss of the original signal and has good compatibility with the existing receiver architecture.