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A slippery molecular assembly allows water as a self-erasable security marker.

Thirumalai R, Mukhopadhyay RD, Praveen VK, Ajayaghosh A - Sci Rep (2015)

Bottom Line: While there are many embedded security features available for document safety, they are not immune to forgery.The underlying principle involves the disciplined self-assembly of a tailor-made fluorescent molecule, which initially form a weak blue fluorescence (λem = 425 nm, Φf = 0.13) and changes to cyan emission (λem = 488 nm,Φf = 0.18) in contact with water due to a reversible molecular slipping motion.This simple chemical tool, based on the principles of molecular self-assembly and fluorescence modulation, allows creation of security labels and optically masked barcodes for multiple documents authentication.

View Article: PubMed Central - PubMed

Affiliation: Photosciences and Photonics Group, Chemical Sciences and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology (CSIR-NIIST), Trivandrum 695019, India.

ABSTRACT
Protection of currency and valuable documents from counterfeit continues to be a challenge. While there are many embedded security features available for document safety, they are not immune to forgery. Fluorescence is a sensitive property, which responds to external stimuli such as solvent polarity, temperature or mechanical stress, however practical use in security applications is hampered due to several reasons. Therefore, a simple and specific stimuli responsive security feature that is difficult to duplicate is of great demand. Herein we report the design of a fluorescent molecular assembly on which water behaves as a self-erasable security marker for checking the authenticity of documents at point of care. The underlying principle involves the disciplined self-assembly of a tailor-made fluorescent molecule, which initially form a weak blue fluorescence (λem = 425 nm, Φf = 0.13) and changes to cyan emission (λem = 488 nm,Φf = 0.18) in contact with water due to a reversible molecular slipping motion. This simple chemical tool, based on the principles of molecular self-assembly and fluorescence modulation, allows creation of security labels and optically masked barcodes for multiple documents authentication.

No MeSH data available.


Water responsive hidden barcode as a super security feature.(a) Design principle of forward and reverse barcode using PE derivatives. (b) An ideal two-layer design of hidden barcode over a currency. Layers (L1 and L2) are composed of PE3 and PE1 respectively. (c) Simulated experiment to generate a forward barcode using PE1 coated and PE3 coated papers. The virtual barcode in the initial stages (1–3) remain undetected using a smart phone having barcode reader application. Upon complete wetting of PE1 layer (4) a smart phone with a barcode reader (NeoReader) application can read the encoded message ‘Satyameva Jayate’ meaning ‘Truth Alone Triumphs’.
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f4: Water responsive hidden barcode as a super security feature.(a) Design principle of forward and reverse barcode using PE derivatives. (b) An ideal two-layer design of hidden barcode over a currency. Layers (L1 and L2) are composed of PE3 and PE1 respectively. (c) Simulated experiment to generate a forward barcode using PE1 coated and PE3 coated papers. The virtual barcode in the initial stages (1–3) remain undetected using a smart phone having barcode reader application. Upon complete wetting of PE1 layer (4) a smart phone with a barcode reader (NeoReader) application can read the encoded message ‘Satyameva Jayate’ meaning ‘Truth Alone Triumphs’.

Mentions: In order to further strengthen the security feature of our system, we envisaged barcodes with a three-stage identification protocol. The design of such hidden barcodes depends on control of optical contrast between the fluorescence colours being emitted from the black (binary digit 1) and white (binary digit 0) regions of a designed barcode. If the colour output from both the regions is nearly the same, the barcode remains undetected. Under an appropriate condition, if the fluorescence colour of one of the regions can be changed, the barcode becomes readable and embedded information could be revealed. A combination of the luminous changing PE1 and the permanent blue emitting PE3 can be used to generate a hidden forward barcode. In presence of water, PE1 shows a cyan fluorescence and the barcode becomes readable. Similarly, PE2, which forms a cyan colour film, can be combined with PE1 to generate a readable reverse barcode, which gets masked in presence of moisture (Fig. 4a). In order to establish the idea of barcoding, we carried out a simulated barcode experiment (Supplementary Fig. S18 and Fig. S19). For this purpose two independent films of PE1 and PE3 were prepared on filter papers. Water was dropcast on one of the edges to allow the filter paper to get wet. The changes in emission were recorded by using a camera. Multiple snapshots obtained from the individual films were used to prepare masks corresponding to the black region using PE1 film and white region using PE3 film at different time intervals. A combination of masks prepared from PE1 and PE3 films gave rise to a ‘virtual’ barcode in each case. Initially, this barcode was not readable since the pattern cannot be recognized by the barcode reader application installed in a smartphone (Fig. 4c1). Upon contact with water, the blue barcode pattern becomes visible in cyan colour background under a UV lamp (Fig. 4c2 and 4c3). This is the first manual step of the authenticity check. On complete wetting of the PE1 layer, the barcode reader could read the pattern and decode the embedded information, which is the second step, which is an electronic reading (Fig. 4c4, Supplementary Movie S2). The final protocol is the drying of the barcode, which will temporarily mask the barcode information. In the case of a banknote the hylemetric information derived from the distribution of the fluorescent threads can be encoded inside the barcode, therefore serving as a hallmark for the central organisation that regulates the issue of banknotes as well as reducing its burden of excessive information storage. Each banknote or document with an individual ‘hidden barcode’ design makes the code unbreakable33. From our experiments, we could also confirm that these processes can be repeated any number of times. The barcode pattern recognition can be easily performed with any smart phone fitted with a UV LED and having the required mobile application (NeoReader) and hence can be performed at the point of care. It was also understood via proper simulation that such barcodes can also be prepared with any commercially available cyan or blue fluorescent ink so that the amount of stimuli responsive fluorescent ink (PE1) can be drastically brought down by a clever barcode design (Supplementary Fig. S20). A randomly located barcode defect site can be an added layer of protection. The overall concept of development of optical contrast has been demonstrated in the case of a barcode printed with normal ink having a defect site embedded with PE1 and PE3 films (Supplementary Fig. S21). Apart from this, we have demonstrated that the idea can be further extended to design optically masked logo of valuable products. Such ‘logos’ can be used for the one time verification of the authenticity of valuable objects, which can be tampered after use (Supplementary Movie S3).


A slippery molecular assembly allows water as a self-erasable security marker.

Thirumalai R, Mukhopadhyay RD, Praveen VK, Ajayaghosh A - Sci Rep (2015)

Water responsive hidden barcode as a super security feature.(a) Design principle of forward and reverse barcode using PE derivatives. (b) An ideal two-layer design of hidden barcode over a currency. Layers (L1 and L2) are composed of PE3 and PE1 respectively. (c) Simulated experiment to generate a forward barcode using PE1 coated and PE3 coated papers. The virtual barcode in the initial stages (1–3) remain undetected using a smart phone having barcode reader application. Upon complete wetting of PE1 layer (4) a smart phone with a barcode reader (NeoReader) application can read the encoded message ‘Satyameva Jayate’ meaning ‘Truth Alone Triumphs’.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4419532&req=5

f4: Water responsive hidden barcode as a super security feature.(a) Design principle of forward and reverse barcode using PE derivatives. (b) An ideal two-layer design of hidden barcode over a currency. Layers (L1 and L2) are composed of PE3 and PE1 respectively. (c) Simulated experiment to generate a forward barcode using PE1 coated and PE3 coated papers. The virtual barcode in the initial stages (1–3) remain undetected using a smart phone having barcode reader application. Upon complete wetting of PE1 layer (4) a smart phone with a barcode reader (NeoReader) application can read the encoded message ‘Satyameva Jayate’ meaning ‘Truth Alone Triumphs’.
Mentions: In order to further strengthen the security feature of our system, we envisaged barcodes with a three-stage identification protocol. The design of such hidden barcodes depends on control of optical contrast between the fluorescence colours being emitted from the black (binary digit 1) and white (binary digit 0) regions of a designed barcode. If the colour output from both the regions is nearly the same, the barcode remains undetected. Under an appropriate condition, if the fluorescence colour of one of the regions can be changed, the barcode becomes readable and embedded information could be revealed. A combination of the luminous changing PE1 and the permanent blue emitting PE3 can be used to generate a hidden forward barcode. In presence of water, PE1 shows a cyan fluorescence and the barcode becomes readable. Similarly, PE2, which forms a cyan colour film, can be combined with PE1 to generate a readable reverse barcode, which gets masked in presence of moisture (Fig. 4a). In order to establish the idea of barcoding, we carried out a simulated barcode experiment (Supplementary Fig. S18 and Fig. S19). For this purpose two independent films of PE1 and PE3 were prepared on filter papers. Water was dropcast on one of the edges to allow the filter paper to get wet. The changes in emission were recorded by using a camera. Multiple snapshots obtained from the individual films were used to prepare masks corresponding to the black region using PE1 film and white region using PE3 film at different time intervals. A combination of masks prepared from PE1 and PE3 films gave rise to a ‘virtual’ barcode in each case. Initially, this barcode was not readable since the pattern cannot be recognized by the barcode reader application installed in a smartphone (Fig. 4c1). Upon contact with water, the blue barcode pattern becomes visible in cyan colour background under a UV lamp (Fig. 4c2 and 4c3). This is the first manual step of the authenticity check. On complete wetting of the PE1 layer, the barcode reader could read the pattern and decode the embedded information, which is the second step, which is an electronic reading (Fig. 4c4, Supplementary Movie S2). The final protocol is the drying of the barcode, which will temporarily mask the barcode information. In the case of a banknote the hylemetric information derived from the distribution of the fluorescent threads can be encoded inside the barcode, therefore serving as a hallmark for the central organisation that regulates the issue of banknotes as well as reducing its burden of excessive information storage. Each banknote or document with an individual ‘hidden barcode’ design makes the code unbreakable33. From our experiments, we could also confirm that these processes can be repeated any number of times. The barcode pattern recognition can be easily performed with any smart phone fitted with a UV LED and having the required mobile application (NeoReader) and hence can be performed at the point of care. It was also understood via proper simulation that such barcodes can also be prepared with any commercially available cyan or blue fluorescent ink so that the amount of stimuli responsive fluorescent ink (PE1) can be drastically brought down by a clever barcode design (Supplementary Fig. S20). A randomly located barcode defect site can be an added layer of protection. The overall concept of development of optical contrast has been demonstrated in the case of a barcode printed with normal ink having a defect site embedded with PE1 and PE3 films (Supplementary Fig. S21). Apart from this, we have demonstrated that the idea can be further extended to design optically masked logo of valuable products. Such ‘logos’ can be used for the one time verification of the authenticity of valuable objects, which can be tampered after use (Supplementary Movie S3).

Bottom Line: While there are many embedded security features available for document safety, they are not immune to forgery.The underlying principle involves the disciplined self-assembly of a tailor-made fluorescent molecule, which initially form a weak blue fluorescence (λem = 425 nm, Φf = 0.13) and changes to cyan emission (λem = 488 nm,Φf = 0.18) in contact with water due to a reversible molecular slipping motion.This simple chemical tool, based on the principles of molecular self-assembly and fluorescence modulation, allows creation of security labels and optically masked barcodes for multiple documents authentication.

View Article: PubMed Central - PubMed

Affiliation: Photosciences and Photonics Group, Chemical Sciences and Technology Division, CSIR-National Institute for Interdisciplinary Science and Technology (CSIR-NIIST), Trivandrum 695019, India.

ABSTRACT
Protection of currency and valuable documents from counterfeit continues to be a challenge. While there are many embedded security features available for document safety, they are not immune to forgery. Fluorescence is a sensitive property, which responds to external stimuli such as solvent polarity, temperature or mechanical stress, however practical use in security applications is hampered due to several reasons. Therefore, a simple and specific stimuli responsive security feature that is difficult to duplicate is of great demand. Herein we report the design of a fluorescent molecular assembly on which water behaves as a self-erasable security marker for checking the authenticity of documents at point of care. The underlying principle involves the disciplined self-assembly of a tailor-made fluorescent molecule, which initially form a weak blue fluorescence (λem = 425 nm, Φf = 0.13) and changes to cyan emission (λem = 488 nm,Φf = 0.18) in contact with water due to a reversible molecular slipping motion. This simple chemical tool, based on the principles of molecular self-assembly and fluorescence modulation, allows creation of security labels and optically masked barcodes for multiple documents authentication.

No MeSH data available.