Counterfeiting and inverse engineering of security and confidential documents, such as banknotes, passports, national cards, certificates, and valuable products, has significantly been increased, which is a major challenge for governments, companies, and customers. From recent global reports published in 2017, the counterfeiting market was evaluated to be $107.26 billion in 2016 and forecasted to reach $206.57 billion by 2021 at a compound annual growth rate of 14.0%. Development of anticounterfeiting and authentication technologies with multilevel securities is a powerful solution to overcome this challenge. Stimuli-chromic (photochromic, hydrochromic, and thermochromic) and photoluminescent (fluorescent and phosphorescent) compounds are the most significant and applicable materials for development of complex anticounterfeiting inks with a high-security level and fast authentication. Highly efficient anticounterfeiting and authentication technologies have been developed to reach high security and efficiency. Applicable materials for anticounterfeiting applications are generally based on photochromic and photoluminescent compounds, for which hydrochromic and thermochromic materials have extensively been used in recent decades. A wide range of materials, such as organic and inorganic metal complexes, polymer nanoparticles, quantum dots, polymer dots, carbon dots, upconverting nanoparticles, and supramolecular structures, could display all of these phenomena depending on their physical and chemical characteristics. The polymeric anticounterfeiting inks have recently received significant attention because of their high stability for printing on confidential documents. In addition, the printing technologies including hand-writing, stamping, inkjet printing, screen printing, and anticounterfeiting labels are discussed for introduction of the most efficient methods for application of different anticounterfeiting inks. This review would help scientists to design and develop the most applicable encryption, authentication, and anticounterfeiting technologies with high security, fast detection, and potential applications in security marking and information encryption on various substrates.

Light-controlling of phase separation in temperature-responsive polymer solutions by using light-responsive materials for reversible controlling physical and chemical properties of the media with an out-of-system stimulus with tunable intensity.

Graphene oxide (GO) nanosheets were simultaneously modified and reduced with ethylenediamine (EDA). Then, EDAtreated GO (RGO-NH2) was exposed to iterative alkylation and amidation reactions to synthesize poly(amidoamine) (PAMAM)-grafted GO nanosheets. Reactions were continued until 4 th generation of PAMAM were grafted onto GO layers (RGO-4.0GD). FT-IR results approved the synthesis of different structures, while TGA curves showed that reactions occurred non-ideal and PAMAM was not grafted as expected. Also, XRD patterns showed that there is a resistance against the intercalation of nanolayers named stitching. According to Raman spectra, modification progression resulted in more disorder structure of graphene layers due to grafting PAMAM generations whereas reduction occurred continuously. Morphological studies were performed according to SEM and TEM images. Results showed that treated-GO nanosheets restacks together, while distinguishable edge of nanolayers was observed.

in Wiley Online Library (wileyonlinelibrary.com).Tailor-made polystyrene nanocomposite with mixed free and clay-attached polystyrene chains was synthesized using atom transfer radical polymerization. Vinylbenzyl trimethylammonium chloride having a double bond, which could be incorporated into polystyrene chains by a grafting through process, was used as a nanoclay modifier. Conversion and molecular weight evaluation was carried out using gas chromatography and gel permeation chromatography, respectively. The thermogravimetric analysis results confirmed the elevated thermal stability of the nanocomposites in comparison with the neat polystyrene sample. Additionally, the T g increases by clay loading was confirmed by differential scanning calorimetry (DSC). The difference in the degradation temperature of CABr bond in attached and free polystyrene chains was well revealed in DSC thermograms. Finally, a lower clay loading resulted in an exfoliated structure as proved by X-ray diffraction and transmission electron microscopy results.

An initiator containing modifier, 4-hydroxybutyl 2-bromopropionate (CBr), was synthesized by the reaction of 1,4-butanediol and alpha-bromoisobutyryl bromide. Subsequently, graphene oxide was functionalized with CBr to yield initiator-anchored graphene (GCBr). Then, GCBr was used as the precursor for ATRP of styrene.

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Smart polymers with extraordinary characteristics are studied in drug-delivery applications. In the current study, temperature-responsive hybrid core−shell nanoparticles were synthesized by precipitation polymerization of N-isopropylacrylamide and vinyl-modified silica nanoparticles. These temperature-responsive hybrid core−shells were prepared with different cross-linking densities by using 2, 4, and 8 mol % of N,N-methylene bisacrylamide (MBA). Hydrolysis of the silica cores of the hybrid core−shells resulted in hollow poly(Nisopropylacrylamide) (PNIPAM) nanogels. Functionalization of silica nanoparticles with vinylcontaining silane modifier of 3-(trimethoxysilyl) propyl methacrylate (MPS) in two different contents was proven by Fourier transform infrared spectroscopy. Preparation of the hybrid PNIPAM nanogels and etching of the silica cores were studied using thermogravimetric analysis and also electron microscopy imaging. Sensitivity of the PNIPAM nanogel samples to temperature was studied using ultraviolet−visible (UV−vis) spectroscopy. In addition, dynamic light scattering was used for investigation of the squeezing and expansion of the hybrid and hollow samples against variation of temperature. The UV−vis spectroscopy results display higher absorption intensities in higher contents of MPS modifier and MBA cross-linker. The swelling content of the nanogels with hollow cavities was higher than that of the hybrid samples. The hybrid nanogels with 2 and 8 wt % silica content and different cross-linking densities and also their hollow nanoparticles were used for loading and release of doxorubicin (DOX). The release characteristics of the DOX-loaded nanogels were studied at different temperatures using UV−vis spectroscopy. The DOX release was higher at temperatures lower than the gel collapse temperature of the PNIPAM network. Although the nanogels with hollow cavities displayed higher loading capacities, the release percentage was higher for the hybrid PNIPAM nanogels, which was confirmed by the experimental release profiles and mathematical models. The most appropriate fitting of the DOX release data from the PNIPAM nanogel samples was observed for the Korsmeyer−Peppas model. Cytotoxicity studies on HeLa cell line showed that drug-loaded hollow samples showed higher toxicity due to loading of a higher amount of DOX.