An examination of handwritten signatures forged using photosensitive signature stamp.

Signature examination is the most common examination performed by any document examiner. Determination of the authenticity of a handwritten signature on a questioned document is an important task for forensic document examiners in the forensic science field. As a result of continuous developments in technology, a signature stamp can now be created using a photosensitive seal to enable the reproduction of a handwritten signature. These stamps are commonly used in China and several other countries. In this study, 10 types of black photosensitive stamp-pad ink, 10 brands of fountain pen ink, 15 types of black gel ink and six types of black erasable gel ink found on the Chinese domestic market were collected and 10 photosensitive signature stamps were created using the signatures of 10 people. Microscopic analysis, infrared (IR) and fluorescence analyses and microspectrophotometry (MSP) techniques were used to examine the resulting photosensitive signature stamp impressions when applied to printing papers, writing papers and invoice papers. By comparing the printing and spectral characteristics of the photosensitive signature stamp impressions with those of the signatures executed using the fountain pens, gel pens and erasable gel pens, it was possible to determine whether each signature was written or stamped using a photosensitive signature stamp. To validate these results, a 96.7% absolute accuracy and a 99.3% detection rate were achieved over a total of 150 blind tests conducted by five forensic document examiners, thus demonstrating that a combination of the four analysis methods used in this work can provide a more scientific approach and improve the accuracy and the detection rate of the examination process.KEY POINTSA signature stamp is a photosensitive seal made in the style of a handwritten signature.Although microscopic analysis can usually provide better examination results, a comprehensive examination method that includes microscopic analysis and ink composition analysis is required to improve the accuracy and the detection rate of the examination process.This study collected and tested photosensitive stamp-pad inks, fountain pen inks, gel inks and erasable inks.Infrared and fluorescence analyses and microspectrophotometry were able to distinguish the photosensitive ink from both erasable ink and fountain pen ink. Supplemental data for this article are available online at https://doi.org/10.1080/20961790.2021.1898755.

Experimental Research on Class Identification with a New Type of Erasable Gel Pens.

A new type of erasable gel pen ink is becoming increasingly popular because of the modifiable characteristics for writing on documents. This study attempts to distinguish 12 types of blue and black erasable gel pens produced by mainstream stationery manufacturers using infrared (IR) visual analysis, Fourier transform infrared (FTIR) analysis, fluorescence analysis, and microspectrophotometry. The results demonstrate that IR visual, FTIR, and fluorescence analysis can be used to help distinguish each type of erasable gel ink. While microspectrophotometry can be used to effectively differentiate the blue gel inks in this study, there are limitations with respect to distinguishing black erasable gel pens. When these four optical analyses methods were used in combination, the gel inks could be accurately distinguished.

Preparation of perfluoro-1,3-propanedisulfonic acid/silica nanocomposites-encapsulated low molecular weight aromatic compounds possessing a nonflammable characteristic.

Perfluoro-1,3-propanedisulfonic acid/silica [PFPS/SiO(2)] nanocomposites were prepared by the sol-gel reactions of the corresponding disulfonic acid [PFPS] with tetraethoxysilane and silica nanoparticles under alkaline conditions. These fluorinated nanocomposites thus obtained can exhibit no weight loss behavior corresponding to the contents of PFPS in the composites after calcination at 800°C, although the parent PFPS can decompose completely around 270°C. In addition, we succeeded in encapsulation of a variety of low molecular weight aromatic compounds such as bisphenol-A, bisphenol-AF, bisphenol-F, 4,4'-biphenol and 1,1'-bi-2-naphthol into PFPS/SiO(2) nanocomposite cores. (1)H MAS NMR spectra, UV-vis spectra, fluorescence spectra and HPLC measurements of PFPS/SiO(2) nanocomposites-encapsulated bisphenol-A showed the presence of encapsulated bisphenol-A in the composites before and even after calcination at 800°C. Interestingly, it was verified that fluorescence spectra of PFPS/SiO(2) nanocomposites-encapsulated bisphenol-A after calcination at 800°C can exhibit an extremely red-shifted and enhanced fluorescence peak, compared to that before calcination or parent bisphenol-A.