Forged signature threatens the authenticity of personal identity. Here, an effective SERS anti-counterfeiting system is designed for personal signatures. Mixed ligands improve the complexity of Raman spectra and expand the coding capacity. Fourteen distinct combinations are created from mere five ligands, and great expansion is possible with modest expansion of the ligand library. On the other hand, the (Au-aggregate)@Ag@PSPAA nanostructure significantly increases the surface-enhanced Raman scattering (SERS) intensity and stability so that excellent performance is achieved in SERS detection. By integrating these strategies, SERS inks are produced and applied in signature anti-counterfeiting. The resulting spectra are converted to barcodes that are readily detected through a smart phone APP. With these improvements, this work brings SERS one step closer toward practical applications in signature anti-counterfeiting.
Puxian Xiong,Mingying Peng,Jiangkun Cao,Xueliang Li
Mechanoluminescence (ML) is a phenomenon upon external mechanical stimuli and it has found diverse applications such as stress sensing, structure health diagnosis, 3-D signature, energy harvesting etc because of its unique properties of in situ and real-time response to the stimuli. However, ML of most of the state-of-art phosphors primarily appears within the spectral range from ultraviolet to visible, which does not lie in the biological transparent windows, and, therefore, limits its applications in biological field. Here, we report a strong near infrared (NIR) ML from orthorhombic Cmcm perovskite Sr 3 Sn 2 O 7 : Nd 3+ , which is peaked at ~ 900 nm and located exactly within the first optical transparent window of tissues. The ML apparates after gradual discharge of the traps deeper than 0.73 eV triggered by the external mechanical stimuli and subsequently excitation of Nd 3+ to the state of 4 F 3/2 . The rechargable ML presents well repeatable linearity to loaded force at least up to 5000 N, and it can penetrate tissues easily that are thick up to 30 mm such as pigskin and the ceramic disk of hydroxy apatite which is the main constituent of bone. These results demonstrate the potential application for in situ biomechanical sensor. Meanwhile, by recording and processing these ML signals during signing on a pellet sample, for the first time, we provide a novel signature system based on NIR ML. This could raise the security level of existed signature anti-countering to a higher level.
Bioinspired hydrogels have promising prospects in applications such as wearable devices, human health monitoring equipment, and soft robots due to their multifunctional sensing properties resembling natural skin. However, the preparation of intelligent hydrogels that provide feedback on multiple electronic signals simultaneously, such as human skin receptors, when stimulated by external contact pressure remains a substantial challenge. In this study, we designed a bioinspired hydrogel with multiple conductive capabilities by incorporating carbon nanotubes into a chelate of calcium ions with polyacrylic acid and sodium alginate. The bioinspired hydrogel consolidates self-healing ability, stretchability, 3D printability, and multiple conductivities. It can be fabricated as an integrated strain sensor with simultaneous piezoresistive and piezocapacitive performances, exhibiting sensitive (gauge factor of 6.29 in resistance mode and 1.25 kPa–1 in capacitance mode) responses to subtle pressure changes in the human body, such as finger flexion, knee flexion, and respiration. Furthermore, the bioinspired strain sensor sensitively and discriminatively recognizes the signatures written on it. Hence, we expect our ideas to provide inspiration for studies exploring the use of advanced hydrogels in multifunctional skin-like smart wearable devices.
危险品化学品经营许可证（带存储）