Preparation of photoluminescent nanocomposite ink for detection and mapping of fingermarks

Abstract

Simple and efficient detection and mapping method based on a strong turn‐on fluorescent pigment was developed for fingerprint analysis. We present a phosphor powder characterized by strong emission which is useful to achieve better fingerprint detection on multicolored or photoluminescent surfaces, such as currency notes characterized by optically changeable inks and highly fluorescent positions, because it offers better contrast and reduce the difficulty of background interference. Novel photochromic ink was prepared to establish a fingerprinted colorless film onto cellulose documents with green emission for anticounterfeiting applications as illustrated by photoluminescence spectra. Inorganic/organic nanoscale composite ink was prepared from rare‐earth doped aluminate phosphor nanoparticles (PNPs; 27–49 nm) dispersed in a polyacrylic acid binding agent. PNPs were dispersed efficiently in polyacrylic acid to generate a colorless mark. The produced photochromic inks were spray‐coated onto off‐white paper sheets enclosing invisible fingermarks, and then exposed to thermofixation. Photochromic film was detected on paper surface presenting a transparent appearance under visible daylight and switchable to green under UV light. The CIE Lab parameters and photoluminescence spectra were studied under visible light and ultraviolet irradiation. The fingerprinted sheets showed fluorescence band at 517 nm upon excitation at 366 nm, showing a bathochromic shift and reversible photochromism without fatigue. The morphologies of pigment phosphor particles and fingerprinted sheets were inspected. The rheological properties of ink and mechanical behavior of the fingerprinted paper samples were explored. Highlights Novel smart ink with alkaline‐earth aluminate and polyacrylic acid was developed. Dual‐mode fluorescent photochromism was presented for latent fingerprint analysis. Off‐white fingerprinted films under daylight showed color change to green under UV. Fluorescence band monitored at 517 nm upon excitation at 366 nm. Fluorescent fingermark on paper sheets demonstrated good photostability.

Tunable Photochromism of Spirooxazine in the Solid State: A New Design Strategy Based on the Hypochromic Effect

“…As everyone has their unique fingerprint, which cannot be shared, forged, or misplaced, thus the fingerprint has been widely used in many fields such as banknotes, passports, and identity cards for confirming people's identity. [ 39 ] Herein, we develop a novel anti‐counterfeiting method with high security and authentication by a rational combination of the unique feature of fingerprint and the excellent performance of solid photochromic materials. As shown in Figure 5d, a finger was dusted with ≈1 mg of photochromic powder of SO4 , and then stamped on the scotch tape to afford a fussy fingerprint, in which the information was collected and stored.…”

Dual‐mode security authentication of SrAl2O4:Eu,Dy phosphor encapsulated in electrospun cellulose acetate nanofibrous films

“…These results suggest that the light energy detained by Dy 3+ transfers to Eu 2+ throughout the 4f 6 5D 1 ↔4f 7 transition of Eu 2+ [24]. Dy 3+ caused the formation of traps, allowing dark‐time light releases, and ultimately causes Eu 2+ to return to the ground state [31]. The emission intensity at 514 nm enlarged with increase in UV‐illumination duration (10–50 s).…”

“…According to the methods reported by Snari et al [31] and Al‐Qahtani et al [36], Al 2 O₃ (2 mol), SrCO 3 (1.0 mol), H 3 BO 3 (0.2 mol), Eu 2 O 3 (0.02 mol), and Dy 2 O 3 (0.03 mol) were admixed by stirring in 450 ml of absolute ethanol for 3 h. After heating at 90°C for 2 h and being ground for 3 h, the admixture was ultrasonicated (25 kHz) for 60 min. After sintering at 1300°C for 3 h in a reduction carbon atmosphere, the provided powder was milled and sieved into a micropowder of LdSA (12–19 μm).…”

“…Lanthanide-activated phosphor nanomaterials have been presented as interesting photochromic agents [25][26][27]. Recently, many lanthanidedoped phosphor nanomaterials of different colour emissions have been presented such as CaAl 2 O 4 :Eu 2+ ;Nd 3+ (blue emitter), CaS:Eu 2+ ; Tm 3+ ;Ce 3+ (reddish emitter), and SrAl 2 O 4 :Eu 2+ ;Dy 3+ (green emitter) [28][29][30][31]. Due to their photostability and quick responsiveness, inorganic phosphors, such as LdSA, have been shown to play a crucial function in the creation of photochromic products.…”

Recent advances in photoresponsive printing inks for security encoding applications

“…To make fingerprints onto an off‐white paper to easily detectable, Snari et al [98] sprayed them with a unique photochromic ink. Dual‐mode fingerprint detection at a crime scene was seen when ink was prepared using lanthanide‐doped aluminate nanoparticles.…”