Latent fingermarks on copperplate paper: facile visualization via electrochromism of 1,1′-bis(3-sulfonatopropyl) viologen

Electrochromic platform for the visual detection of the neuroblastoma biomarkers vanillylmandelic acid and homovanillic acid

Vanillylmandelic acid (VMA) and homovanillic acid (HVA) are biomarkers for the diagnosis and course-of-disease monitoring of malignant tumor neuroblastomas, which endanger infants and children. Herein, we demonstrated a proof-of-concept visual detection of VMA and HVA on an electrochromic basis, in which the viologen 1,1'-dibenzyl-4,4'-bipyridinium dichloride was used as a coloration chromophore. It was found that VMA and HVA can be used as effective electron mediators to improve the electrochromic performance of devices. It is interesting to note that VMA and HVA reduce the driving voltage of electrochromic devices (ECDs) down to -1.0 V, which is lower than that (-2.1 V) achieved without these additives, and the coloration of ECDs is undoubtedly dependent on the concentration of VMA and HVA from 0.8 to 10-6 mol L-1. Thus, this study presents an ECD platform as a breakthrough strategy for the facile, routine and portable visual detection of the neuroblastoma biomarkers VMA and HVA with obvious advantages over other detection techniques such as HPLC/MS used in clinical diagnosis.

Electrochromic visualization of latent fingermarks deposited on nonconductive surfaces

Electrochromic visualization of latent fingermarks has already been achieved on conducting surfaces such as stainless steel. However, their enhancement on non-conducting surfaces such as glass via electrochromism has not been reported. Considering the non-conductive nature of substrates, a layer of gold was introduced to the fingermark-bearing surfaces, in which gold was used as the cathodes to assemble electrochromic devices for visualization. The contact between gold nanoparticles of the as-obtained conducting layer in the fingermark region should be affected by the height difference within the fingermark, leading to conductivity differences, which give rise to coloration differences in electrochromic devices. It is demonstrated that 1,1'-dibenzyl-4,4'-bipyridinium dichloride can be used as the electrochromic chromophore for the visualization of latent fingermarks deposited on nonconducting surfaces, and the primary and secondary characteristic information can be obtained. The electrochromic visualization herein solves the problem of electrochromically enhancing latent fingermarks on non-conducting surfaces.

The Flexible Electrochromic Device That Turns Blue Under Both Positive and Negative Application Voltages

Using the photocurable electrolyte solution containing viologen derivative 1,1′-bis- (4-vinylbenzyl)-4,4′-bipyridinium dihexafluorophosphate (EV2+•2PF6−) and its composite of EV2+•2PF6− and triphenylamine derivative N,N′-di(4-((3-(triethoxysilyl)-propyl)imino)methyl)phenyl-N,N′-diphenyl-4,4′-biphenyldiamine (TPB-PSSO) as the electrochromic active layer, respectively, the flexible electrochromic devices (FECDs) were prepared by photocurable technology. The device structure was PET-ITO/photocurable electrolyte solution/PET-ITO. The electrochromic properties of FECDs were investigated. The results show that the FECDs can all undergo a reversible color change, especially the PET-ITO/photocurable electrolyte solution-composite/PET-ITO can undergo polychromatic transition. The FECD based on EV2+•2PF6− can reversibly change between colorless and deep blue, and the FECD based on the composite of TPB-PSSO-EV2+•2PF6− can reversibly change between black blue, light yellow, and sky blue.