An electronic nose can detect highly volatile chemicals in foods, drugs, and environments, but it is still very much a challenge to detect the odors from crystalline compounds (e.g., solid explosives) with a low vapor pressure using the present chemosensing techniques in such way as a dog's olfactory system can do. Here, we inkjet printed silver nanoparticles (AgNPs) on cellulose paper and established a Raman spectroscopic approach to detect the odors of explosive trinitrotoluene (TNT) crystals and residues in the open environment. The layer-by-layer printed AgNP paper was modified with p-aminobenzenethiol (PABT) for efficiently collecting airborne TNT via a charge-transfer reaction and for greatly enhancing the Raman scattering of PABT by multiple spectral resonances. Thus, a Raman switch concept by the Raman readout of PABT for the detection of TNT was proposed. The AgNPs paper at different sites exhibited a highly uniform sensitivity to TNT due to the layer-by-layer printing, and the sensitive limit could reach 1.6 × 10(-17) g/cm(2) TNT. Experimentally, upon applying a beam of near-infrared low-energy laser to slightly heat (but not destruct) TNT crystals, the resulting airborne TNT in the open environment was probed at the height of 5 cm, in which the concentration of airborne species was lower than 10 ppt by a theoretical analysis. Similarly, the odors from 1.4 ppm TNT in soil and 7.2, 2.9, and 5.7 ng/cm(2) TNT on clothing, leather, and envelope, respectively, were also quickly sensed for 2 s without destoying these inspected objects.
The effects of welding energy on the mechanical and microstructural characteristics of ultrasonic-welded pure copper plates were investigated. Complex dynamic recrystallization and grain growth occurred inside the weld zone during ultrasonic welding. At a low welding energy, a thin band of straight weld interfaces was observed and had an ultra-fine grain structure. With an increase in welding energy, the weld interface progressively changed from flat to sinusoidal, and eventually turned into a convoluted wavy pattern, bearing similarities to shear instabilities, as observed in fluid dynamics. The lap shear load of the joints initially increased and then remained stable as the welding energy increased. The tensile characteristics of the joints significantly depended on the development of plastic deformation at the interface. The influence of the microstructure on the hardness was also discussed.
White-light-emitting materials for the applications in display and lighting have widely been prepared by the rare earth with high photoluminescent efficiency and stability, but the short resource, high cost, and serious environmental concerns are the insurmountable barriers of rare-earth-based materials. Here, we report that strong laser ablation of common organosilica colloid can produce white-light-emitting silica nanoparticles. The instant high temperature and pressure induced by strong laser simultaneously caused the reduction of partial silica and the pyrolysis of carbon chains in the interior of silica nanoparticles, in which the rapid crystallizations of the silicon and carbon vapor led to the formations of silicon dots and diamond-like carbon dots in the silica matrix. Significantly, the resultant silica nanoparticles containing different sized silicon and diamond dots exhibited a wide fluorescence spectrum to display bright white light under UV excitation. Moreover, the light emission diode (LED) device prepared by using the ablated silica nanoparticles as light source gave off the warm white light with Commission Internationale de l'Eclairage (CIE) coordinates (0.34, 0.32). The strategy reported here opens a new window to the exploration of white-light-emitting materials through the very simple, inexpensive, and environment-friendly pathway.
Abstract:The effects of vibration amplitude on the interface reaction and mechanical strength of the Cu/Al joints were systematically investigated in ultrasonic spot welding (USW) experiments. The appropriate vibration amplitude (22.5 µm) was beneficial for obtaining a sound joint. The formation of the continuous intermetallic compounds (IMC) layer accelerated with a higher vibration amplitude. The lap shear tensile strength of the Cu/Al joints decreased when the thickness of the intermetallic layer was greater than 1 µm at various amplitudes. With the increase in welding time, a crack occurred in the copper side owing to the occurrence of the eutectic reaction, α-Al + θ → L, at the periphery of the nugget. The remarkable decline of ultrasonic power curves occurred at various amplitude levels upon the formation of a crack in the copper side.
RATIONALE: Laser-ablation electrospray ionization mass spectrometry (LAESI-MS) was applied to analyze fresh meat species without sample pretreatment. The study demonstrates that the LAESI-MS technique is a promising, rapid and accurate method for meat identification using a protocol combining principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA). METHODS: A focused IR-laser was used for meat sample ablation at a wavelength of 2940 nm. The ablated particulates were carried through a transfer PTFE tube using air as carrier gas, delivered to the electrospray plume and ionized. A TOF-MS was used to detect the ion signal. The raw mass spectra were analyzed using the PCA and PLS-DA protocol. RESULTS: Five fresh meat samples, chicken, duck, pork, beef and mutton, were identified by the developed LAESI-MS technique using the protocol combining PCA and PLS-DA. The discrimination accuracy of all meat species is 100%, and the score plot also shows good identifying ability. CONCLUSIONS: Five fresh meat samples were analyzed using the LAESI-MS technique. Each set of raw mass data was collected within 30 s and analyzed by the PCA and PLS-DA protocol. Eighteen, 19, 18, 17, and 15 markers for chicken, duck, pork, beef, and mutton, respectively, have been selected successfully for meat identification. The results demonstrate that LAESI-MS is a new reliable and rapid method for meat identification. Copyright © 2016 John Wiley & Sons, Ltd.The consumption of meat keeps constantly increasing in the world. As reported by Sans et al., meat consumption rose worldwide from 23.1 kg per person per year in 1961 to 42.20 kg per person per year in 2011. [1] As a result, the safety of meat has drawn extensive attention by society. Consumers are increasingly concerned about the quality of the meat they eat due to the many meat scandals which have occurred recently. [2] In order to detect fraudulent species in meat, many techniques have been developed. Enzyme-linked immunosorbent assay (ELISA) and polymerase chain reaction (PCR) methods are routinely used for the specification of meat. [3] The ELISA method can be used as a fast qualitative or quantitative technique. One hundred meat samples and meat products have been analyzed for species determination by the ELISA method. The results showed that 22.0% of the samples were not in compliance with Turkish Food Codex, violating consumer rights and presenting a potential public health risk. [4] However, using an ELISA it is difficult to analyze different species in a single run, and also is quite expensive. [3] PCR methods are widely applied to identify meat species in routine laboratories. Only 0.1% of raw pork in poultry was detected by the PCR method. [5] However, the PCR method is not widely implemented in food control programs due to complex operation or financial reasons.Recently, mass spectrometry has become an important tool for the identification of meat due to its intrinsic high sensitivity and high specificity. Matrix-assisted laser desorption ionizat...
Crop straw, as a widely used biomass resource, can be processed to produce renewable energy and green products. However, about 70% of straw were burned in the open air, causing serious environmental pollution and air pollution. In order to reduce the burden on the environment, the different straw management strategies are comparatively studied and evaluated by applying the life-cycle assessment (LCA) method. Within the system boundary from cradle to grave, three alternative scenarios, including straw particleboard, straw cement-bonded particleboard, and straw direct combustion power generation, are compared with the current common treatment (straw open burning). e comprehensive inventory analysis on each treatment scenario is carried out indepth, and the corresponding resource consumption and environmental impact of each treatment scenario are calculated, respectively. e LCA results showed that the environmental impacts of reusing crop straw to produce straw particleboard and cement-bonded particleboard (Scenario 1 and Scenario 2) is significantly reduced by 6% and 10%, by comparison with the use of wood resource. Greenhouse gas emissions from straw direct combustion power generation (Scenario 3) processes are reduced by 30% compared with coal power generation. From the environmental point of view, the scenario of straw particleboard product has the smallest impact on the environment, while straw open burning is not an advisable way due to the highest environmental impact from the highest greenhouse gas emissions and acidification effects. From the perspective of energy consumption, the energy consumption for the combustion power generation is the smallest in all scenarios. It is suggested that governments are supposed to construct reasonable scenarios for the straw disposition based on the local development status and condition. e research results can provide scientific guidance for the management strategy of the comprehensive utilization of straw resources.
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