1,577 research outputs found

    Using Surface-Enhanced Raman Scattering of Gold Nanostars for Encoding Molecular Information

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    Increases in the selling of illicit goods warrant a subsequent need for even more sophisticated methods to prevent counterfeit products from being sold. Surface-enhanced Raman spectroscopy (SERS) has the potential to be a powerful tool to thwart counterfeiters because the unique security tags fabricated with this method are difficult to reproduce without knowing the “secret” recipes used in their preparation. In this work, gold nanostars are used as SERS active substrates since their branched structure allows for strong coupling between the light and plasmonic nanoparticles. As a result, Raman signals of trace amount of chemicals can be easily detected. The gold nanostars were used with different combinations of probe molecules so that unique anti-counterfeiting tags can be created. The reproducibility and uniformity of the SERS spectra for these tags were analyzed using principal component analysis (PCA). These SERS tags have a great potential for a variety of anti-counterfeiting applications

    The Private Sector Combats Products Counterfeiting

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    Exploring new applications for photophysically encoded microcarriers

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    The first goal of this thesis was to investigate the potential of two cationic polysaccharides (PQ-4 and PQ-10) for DNA delivery. We have shown that, compared to PEI based polyplexes, they were less efficient in transfecting cells. However, as they had very low toxicity, further tailoring of the nature and extent of cationic side chains on cationic hydroxyethylcellulose may be a promising avenue to further enhance their DNA delivery properties. As a second goal we investigated the applications of digitally encoded microcarriers for cell based assays. We succeeded to show that encoded microcarriers were suitable to grow cells on. Neither the coating at the surface of the beads (which facilitates the growth of the cells), nor the cells themselves hampered the decoding of the beads, even when the cells covering the microcarriers exhibited green or red fluorescence due to the expression of GFP and RFP respectively. We were able (a) to immobilize DNA, siRNA or adenoviral particles on the surfaces of the encoded microcarriers by the use of polyelectrolytes and, subsequently, (b) to grow cells on top of the nucleic acids/adenoviral particles. The DNA and siRNA immobilized on the surface of the microcarrier were not able to transfect cells. However, we showed that the cells growing on the polyelectrolyte layer could indeed become transduced with adenoviral particles hosted by the polyelectrolyte layer. In conclusion, a proof of principal to use photophysically encoded microcarriers as transfected microarray has been shown. As a third goal we investigated the use of digitally encoded microcarriers as tool to combat counterfeiting of tablets. We showed that the codes in the Memobeads in tables produced by granulation did not deform during tabletting and that the code in the beads remained readable. We also found evidence that, after oral intake, the encoded microparticles are highly unlikely toxic to humans

    SELECTED POSSIBILITES OF USING INFRARED SPECTROSCOPY IN CRIMINALISTICS

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    Infrared spectroscopy is one of the most commonly used spectroscopic methods in criminalistics, through which various kinds of criminalistic traces can be explored. It finds wide application in academic research, but also in research of forensic laboratories in order to obtain results ap- plicable in criminalistic practice. The paper provides information about selected possibilities of using Fourier transform infrared spectroscopy and its modifications in investigation of specific criminalistic traces such as documents, banknotes, cosmetics, blood traces and adhesive materials

    Recent advances in optical metasurfaces for polarization detection and engineered polarization profiles

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    Like amplitude, phase and frequency, polarization is one of the fundamental properties of light, which can be used to record, process and store information. Optical metasurfaces are ultrathin inhomogeneous media with planar nanostructures that can manipulate the optical properties of light at the subwavelength scale, which have become a current subject of intense research due to the desirable control of light propagation. The unprecedented capability of optical metasurfaces in the manipulation of the light’s polarization at subwavelength resolution has provided an unusual approach for polarization detection and arbitrary manipulation of polarization profiles. A compact metasurface platform has been demonstrated to detect polarization information of a light beam and to arbitrarily engineer a polarization profile that is very difficult or impossible to realize with conventional optical elements. This review will focus on the recent progress on ultrathin metasurface devices for polarization detection and realization of customized polarization profiles. Optical metasurfaces have provided new opportunities for polarization detection and manipulation, which can facilitate real-world deployment of polarization-related devices and systems in various research fields, including sensing, imaging, encryption, optical communications, quantum science, and fundamental physics

    Immunological analytical techniques for cosmetics quality control and process monitoring

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    Cosmetics analysis represents a rapidly expanding field of analytical chemistry as new cosmetic formulations are increasingly in demand on the market and the ingredients required for their production are constantly evolving. Each country applies strict legislation regarding substances in the final product that must be prohibited or regulated. To verify the compliance of cosmetics with current regulations, official analytical methods are available to reveal and quantitatively determine the analytes of interest. However, since ingredients, and the lists of regulated/prohibited substances, rapidly change, dedicated analytical methods must be developed ad hoc to fulfill the new requirements. Research focuses on finding innovative techniques that allow a rapid, inexpensive, and sensitive detection of the target analytes in cosmetics. Among the different methods proposed, immunological techniques are gaining interest, as they make it possible to carry out low-cost analyses on raw materials and finished products in a relatively short time. Indeed, immunoassays are based on the specific and selective antibody/antigen reaction, and they have been extensively applied for clinical diagnostic, alimentary quality control and environmental security purposes, and even for routine analysis. Since the complexity and variability of the matrices, as well as the great variety of compounds present in cosmetics, are analogous with those from food sources, immunological methods could also be applied successfully in this field. Indeed, this would provide a valid approach for the monitoring of industrial production chains even in developing countries, which are currently the greatest producers of cosmetics and the major exporters of raw materials. This review aims to highlight the immunological techniques proposed for cosmetics analysis, focusing on the detection of prohibited/regulated compounds, bacteria and toxins, and allergenic substances, and the identification of counterfeits

    MANIPULATION OF NANOSCALE WRINKLES ON TRANSPARNET AND FLEXILBE FILMS FOR MULTI-MODAL STRUCTURL COLORATION

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    Department of Mechanical EngineeringMost materials and devices with structurally switchable color features responsive to external stimuli can actively and flexibly display various colors. However, realizing covert???overt transformation behavior, especially switching between transparent and colored states, is more challenging. Current stimulus-response pattern hiding and displaying technology responds to numerous external stimuli (temperature, light, mechanical stimulation, etc.) and causes a change in dye properties and in the spacing of nanostructures. In this phase change method, it is difficult to completely hide information because patterns are easily expressed due to limited viewing angles or irregular external conditions. Therefore, there is a need for a method of controlling a transparent nanoscale surface that can completely hide information. Thus, we introduce a method of forming traditional buckling-type corrugations using bilayer-like or trilayer film. In addition, the photonic structure is fabricated using an inkjet printing method and completely laminated into the film. Moreover, in this dissertation , we study the principle of structural color in which living organisms have color by a nanostructure without pigment and the characteristics of the nanostructured photonic crystal hidden in it and design a color-changing nanostructure for single and complex structural colors. Nanoscale wrinkles are generated on the ductile top surface of various multilayered substrates by external stimuli, and their geometrical and optical features are determined by the material and structural properties of the laminated films. First, we develop a bilayer-like laminated film with a rigid SiO2-nanoparticle (NP)-encapsulated poly(dimethylsiloxane) (PDMS) composite structure surrounded by soft PDMS as a multidimensional structural color platform. Owing to the similarity in the optical properties of PDMS and SiO2 NPs, this device is fully transparent in the normal state. However, as their mechanical strengths differ considerably, upon compressive loading, buckling-type instability arises on the surface of the laminate, leading to the generation of 1D or 2D wrinkled patterns in the form of gratings. As a result, we demonstrate an application of the device in which quick response codes are displayed or hidden as covert???overt convertible-colored patterns for optical encryption/decryption, showing their remarkable potential for anti-counterfeiting applications. Second, we describe a thin trilayer film that can generate various wrinkles on transparent and flexible films in the presence of external mechanical bending. In particular, the wrinkle wavelength can be controlled on a tens of nanometer scale by modulating the material properties of each layer. This active modulation plays a critical role in determining resulting structural color spectra. In other words, the wrinkles function as a diffraction grating so that the film displays bright structural colors under bending conditions. After the bending stress is released, the wrinkles disappear and the film becomes transparent again. Lastly, we demonstrate that the material and structural patterning technique shows remarkable potential for structural coloration applications such as multimodal displays and novel barcode-based anti-counterfeiting techniques.ope

    Reflective-Physically Unclonable Function based System for Anti-Counterfeiting

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    Physically unclonable functions (PUF) are physical security mechanisms, which utilize inherent randomness in processes used to instantiate physical objects. In this dissertation, an extensive overview of the state of the art in implementations, accompanying definitions and their analysis is provided. The concept of the reflective-PUF is presented as a product security solution. The viability of the concept, its evaluation and the requirements of such a system is explored
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