Radiation-based security

The problems presented in different security areas are varied but the solutions that have been offered are generally based upon the same principles. Employing radiation to locate and identify explosives or contraband has been most obvious at airports but other locations are now receiving equal attention. Neutron and X-ray interrogation are the systems most frequently employed. However, the more recently developed approaches such as multi-view dual-energy imaging and the use of high-speed diffraction measurements are the most likely systems to become widely available. This review looks briefly at the neutron and X-ray based systems that have been developed indicating their mode of operation and their advantages and disadvantages. It then summarizes the current state-of-the-art. The paper finishes by looking in some detail at one of the most promising areas of development—in-line diffraction measurements.     

Time-encoded bio-fluorochromic supramolecular co-assembly for rewritable security printing

Innovative fluorescence security technologies for paper-based information are still highly pursued nowadays because data leakage and indelibility have become serious economic and social problems. Herein, we report a novel transient bio-fluorochromic supramolecular co-assembly mediated by a hydrolytic enzyme (ALP: alkaline phosphatase) towards rewritable security printing. A co-assembly based on the designed tetrabranched cationic diethynylanthracene monomer tends to be formed by adding adenosine triphosphate (ATP) as the biofuel. The resulting co-assembly possesses a time-encoded bio-fluorochromic feature, upon successively hydrolyzing ATP with ALP and re-adding new batches of ATP. On this basis, the dynamic fluorescent properties of this time-encoded co-assembly system have been successfully enabled in rewritable security patterns via an inkjet printing technique, providing fascinating potential for fluorescence security materials with a biomimetic mode.

Rewritable security printing has been successfully achieved based on a biofuel-driven transient supramolecular co-assembly mediated by an enzyme, providing fascinating potential for artificial functional materials with a biomimetic mode.     

Use of stable isotopes as surrogates for radionuclides for security studies

During the past decade, interest has increased in qualifying and quantifying the threat posed to the public by the illegal use of radionuclides. In order to take investigations beyond the laboratory bench into more realistic scenarios, environmental and safety considerations dictate that these studies be performed on stable and benign surrogates. This paper discusses some of these studies, specifically the use of cerium dioxide for actinide ceramics and calcium and natural strontium ceramics for those based on ⁹⁰Sr.     

Amperometric sensing of hydrogen peroxide vapor for security screening

Rapid detection of the hydrogen peroxide precursor of peroxide explosives is required in numerous security screening applications. We describe a highly sensitive and selective amperometric detection of hydrogen peroxide vapor at an agarose-coated Prussian-blue (PB) modified thick-film carbon transducer. The sensor responds rapidly and reversibly to dynamic changes in the level of the peroxide vapor, with no apparent carry over and with a detection limit of 6 ppbv. The remarkable selectivity of the PB-based screen-printed electrode towards hydrogen peroxide leads to effective discrimination against common beverage samples. For example, blind tests have demonstrated the ability to selectively and non-invasively identify concealed hydrogen peroxide in drinking cups and bottles. The attractive performance of the new microfabricated PB-based amperometric peroxide vapor sensor indicates great potential for addressing a wide range of security screening and surveillance applications. Figure Experimental setup (left) with three electrode electrochemical Hydrogen Peroxide sensor hanging above container of “unknown” liquid. Schematic (right) demonstrating fundamental principles of operation of the sensor.     

Bio-inspired approaches to sensing for defence and security applications

Interdisciplinary research in biotechnology and related scientific areas has increased tremendously over the past decade. This rapid pace, in conjunction with advances in microfabricated systems, computer hardware, bioengineering and the availability of low-powered miniature components, has now made it feasible to design bio-inspired materials, sensors and systems with tremendous potential for defence and security applications. To realize the full potential of biotechnology and bio-inspiration, there is a need to define specific requirements to meet the challenges of the changing world and its threats. One approach to assisting the defence and security communities in defining their requirements is through the use of a conceptual model. The distributed or intelligent autonomous sensing (DIAS) system is one such model. The DIAS model is not necessarily aimed at a single component, for instance a sensor, but can include a system, or even a system of systems in the same way that a single organism, a multi-cellular organism or group of organisms is configured. This paper provides an overview of the challenges to and opportunities for bio-inspired sensors and systems together with examples of how they are being implemented. Examples focus on both learning new things from biological organisms that have application to the defence and security forces and adapting known discoveries in biology and biochemistry for practical use by these communities.     

Neutron activation analysis of concrete for cross-border nuclear security

The dissolution of the Soviet Union coupled with the growing sophistication of international terror organizations has brought about a desire to ensure that a sound infrastructure exists to interdict smuggled nuclear material prior to leaving its country of origin. To combat the threat of nuclear trafficking, radiation portal monitors (RPMs) are deployed around the world to intercept illicit material while in transit by passively detecting gamma and neutron radiation. Portal monitors in some locations have reported abnormally high background counts. The higher background data has been attributed, in part, to the naturally occurring radioactive materials (NORM) in the concrete surrounding the portal monitors. Higher background increases the minimum detectable activity (MDA) and can ultimately lead to more material passing through the RPMs undetected. This work employed two different neutron activation analysis (NAA) methods for the purpose of developing a process to characterize the concrete surrounding the RPMs. Thermal neutron instrumental NAA (INAA) and fast NAA (FNAA) were conducted on six samples from three different composition concrete slabs. Comparator standards and quality control materials were used to help ensure that the methods were both precise and accurate. The combination of INAA and FNAA accounted for 84–100% of the total elemental composition of the samples. Knowing the composition of the concrete will allow RPM customers to choose suitable materials prior to installation, thereby increasing the ability of the monitors to detect radiological and nuclear materials.     

The role of spectroscopy versus detection for border security

Countries around the world are deploying radiation portal monitor systems to interdict the illicit shipment of radioactive material crossing international borders. Because of their high efficiency for gamma-ray detection, most deployed systems are based on plastic scintillators and are non-spectroscopic in capability. Spectroscopic portal monitor systems are undergoing engineering development for near term deployment. The ability to identify the detected radionuclides may allow improved operational handling of radiation alarms, particularly those from the normal commerce of naturally occurring radioactive material. The goal for improved systems is to increase the sensitivity to threats while reducing the operational impact of nuisance alarms.     

Applications of aptamers for chemistry analysis,medicine and food security

Since aptamer and its in vitro selection process called SELEX were independently described by Ellington and Gold in 1990, extensive research has been undertaken and numerous isolated aptamers for various targets have been applied. Aptamers can bind to a wide range of targets that include small organic molecules, inorganic compounds, haptens and even whole cells with high binding affinity and specificity. Aptamers for a wide range of targets have been selected currently. In addition, aptamers are thermo stable and can also be regenerated easily within a few minutes denaturation, which makes them easy to store or handle. These advantages make aptamers extremely suitable for applications based on molecular recognition as analytical, diagnostic and therapeutic tools. In this review, the recent applications of aptamers for chemistry analysis, medicine and food security, along with the future trend will be discussed.     

食品安全分析样品前处理-快速检测联用方法研究进展

综述了近年来传感器、可视化分析、便携光谱、酶联免疫检测及便携气相色谱等食品安全快速检测技术的研究现状,以及食品安全分析中样品前处理-快速检测联用技术的研究进展,为发展选择性好、准确度高、可定量的新型食品安全快速检测技术提供参考。     

Laser desorption ionization mass spectrometric imaging of mass barcoded gold nanoparticles for security applications

Patterns created by the inkjet printing of functionalized gold nanoparticles (NPs) can be selectively detected by laser desorption/ionization imaging mass spectrometry (LDI-IMS). These patterns can only be visualized by mass, providing a robust yet tunable system for potential anti-counterfeiting applications.     

DNA-based logic gates operating as a biomolecular security device

The first example of a nucleic acid-based molecular keypad lock has been constructed by taking advantage of the sequence-specific recognition ability of DNA and solid-phase substrates.     

Visible-light-excited long-lived organic room-temperature phosphorescence of phenanthroline derivatives in PVA matrix by H-bonding interaction for security applications

Organic room-temperature phosphorescence (RTP) materials are very attractive, but there is still a challenge to achieve RTP for their practical applications under visible light excitation (λ > 400 nm) because of the implement for the most organic RTP is under ultraviolet light. Herein, a simple tactics for inhibiting the vibrational dissipation of three amorphous phenanthroline derivatives by doping them into polyvinyl alcohol (PVA) matrix was utilized to afford visible-light excitation RTP. By using this method, on account of the mutual H-bonding and confinement effect with PVA matrix, a series of organic RTP materials with blue-green phosphorescence emission were obtained under visible-light excitation. The afterglow colors of RTP materials can be adjusted by co-doping the available fluorescence dyes (RhB or Rh6G) into the PVA films through a triplet-to-singlet Förster resonance energy transfer. However, the H-bonding is easily broken by water molecules resulting in the RTP phenomenon disappears. Hence, Aphen-epoxy resin composite system was constructed to overcome this drawback. It is shown that the composite still has good phosphorescence properties after soaking in water for 7 days. The superior RTP of the amorphous phenanthroline derivatives in processable polymer matrices endows these materials with a highly potential for the night warning clothing coating and information encryption.     

High-fidelity determination of security threats via a Boolean biocatalytic cascade

The ability to assess diverse security threats using a biochemical logic network system is demonstrated. The new biocatalytic cascade, emulating a NOR logic gate, is able to identify the presence of explosive compounds and nerve agents by providing a simple and rapid 'YES'/'NO' alert.     

元素成像技术在安检领域的研究进展

元素成像作为一种快速、直观的无损检测技术,在核工业、航空航天、新能源、地质、考古、先进制造等多个领域得到广泛应用。其中的X射线凭借较强的穿透物体的能力,太赫兹和毫米波凭借对人体无接触、低损害的特点,在安检领域得到了广泛应用。本文对这三种成像技术的数据集和近几年的图像处理技术进行了总结和归纳,为该领域的进一步深入应用提供了有力的技术支撑。     

Ultra-sensitive measurements of <Superscript>233</Superscript>U by accelerator mass spectrometry for national security applications

By making modifications to our previously established measurement setup, we increased our abundance sensitivity for ²³³U by three orders of magnitude and can now measure ²³³U/²³⁸U ratios as low as 10⁻¹³. Because ²³³U has separate production pathways than ²³⁶U, it can provide valuable information on the particular source of anthropogenic uranium in a sample. We demonstrated the utility of our improved capability by using ²³³U to distinguish separate sources of anthropogenic uranium in a set of samples collected from a contaminated site. In the future, we plan to apply our new capability to characterizing ²³³U in a wide range of uranium materials.     

Responsive hyperbranched poly(formyl-1,2,3-triazole)s toward quadruple-modal information security protection

Science China Chemistry - Secrecy has received tremendous attention in modern information society. Innovative polymer-based fluorescent materials with multiple mode emission are quite desirable to...     

Biocomputing security system: concatenated enzyme-based logic gates operating as a biomolecular keypad lock

A biomolecular security system mimicking a keypad lock device was developed using enzyme-based concatenated AND logic gates resulting in the implication logic network.     

Generation and mid-IR measurement of a gas-phase to predict security parameters of aviation jet fuel

The worldwide use of kerosene as aviation jet fuel makes its safety considerations of most importance not only for aircraft security but for the workers’ health (chronic and/or acute exposure). As most kerosene risks come from its vapours, this work focuses on predicting seven characteristics (flash point, freezing point, % of aromatics and four distillation points) which assess its potential hazards. Two experimental devices were implemented in order to, first, generate a kerosene vapour phase and, then, to measure its mid-IR spectrum. All the working conditions required to generate the gas phase were optimised either in a univariate or a multivariate (SIMPLEX) approach. Next, multivariate prediction models were deployed using partial least squares regression and it was found that both the average prediction errors and precision parameters were satisfactory, almost always well below the reference figures.     

Enhanced self-host blue emission of CaSrSb2O7 materials via Bi3+ ion doping for high CRI WLEDs,security inks and flexible displays

Luminescent materials are indispensable in our daily lives and have already been widely applied in various fields. Herein, novel self-host blue-emitting CaSrSb₂O₇ and CaSrSb₂O₇:Bi³⁺ phosphors with orthorhombic space group Imma (74) were successfully prepared. The phase purity, elemental composition, morphology, luminescent behaviors, etc. were investigated in detail. To compare the luminescence properties of rare-earth-activated phosphors, the self-host blue-emitting CaSrSb₂O₇ phosphor with unique performance exhibited a good quantum yield (QY) of 39.81%, and its emission intensity and QY could also be improved by doping Bi³⁺ ions. The CaSrSb₂O₇:Bi³⁺ phosphor was located in the pure blue region with the Commission Internationale de I'Eclairage chromaticity coordinate of (0.151, 0.058) and good color purity of 89.35%. For identifying its potential applications, the packaged white light-emitting diode device emitted a high color rendering index value of 93.66 under a forward current of 300 mA, and it would be further applied in security inks and flexible displays owing to its strong emission by the naked eyes. These results suggest that novel self-host blue-emitting CaSrSb₂O₇:Bi³⁺ phosphors could be used in multifunctional applications.     

Molecular logic circuits and a security keypad lock based on a novel colorimetric azo receptor with dual detection ability for copper(II) and fluoride ions

A novel azoimine dye-based colorimetric chemosensor (1) has been designed and synthesised for dual recognition of copper(II) and fluoride ions in aqueous media. Significantly, the outstanding dual-ion recognition properties along with the excellent reversibility prompted us to consider 1 as an ideal candidate for fabrication of multiple logic circuits. According to the response profile of 1 towards Cu²⁺ and F^? inputs, we developed a unique tunable system integrated with one INHIBIT logic gate as well as one OR gate. Also, 1 behaved as a molecular keypad lock with sequential addition of Cu²⁺ and F^? inputs. In accession, a reversible ‘Write–Read–Erase–Read’ function with complementary ‘IMP/INH’ logic gate has been demonstrated through a feedback loop using F^? and trifluoroacetic acid as two chemical inputs. To the best of our knowledge, this is the first report where the symmetrical bis azo-azomethine dye has been exploited as a molecular keypad lock.