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Quantifying contrast of latent fingerprints developed by fluorescent nanomaterials based on spectral analysis
No full textFluorescent nanoparticles (NPs) have been used to develop latent fingerprints with enhanced contrast. However, a method for quantifying the contrast is still lacking, making it impossible to achieve quantitative comparison in the contrast enhancement between different fingerprint developing agents. Here we proposed a new method to quantify the developed contrast using two indexes when fluorescent NPs were used to develop the latent fingerprint. One is the intensity index (I) defined as the ratio between the integrated fluorescence intensities of the signal and background in the fluorescence spectra of the developed fingerprint. Another is the chroma index (C) determined from the color difference between developed fingerprints and their substrates in the chromaticity graph. We defined the developed contrast as the product of the chroma index and the common logarithm of the intensity index (C.lg I), and validated this method using both down- and up-conversion fluorescent NPs and on a variety of different substrates (glass, marble, red paper and money). We showed that the developed contrast quantified by our method effectively reflected the true contrast but the intensity or chroma index alone was not always effective. This work opens up a new avenue to quantifying and enhancing the developed contrast
Excellent stability fuel cell type methanol sensor based on platinum-decorated mesoporous CrN
No full textThis paper has developed a fuel cell type methanol sensor based on platinum-decorated mesoporous chromium nitride (CrN). Mesoporous CrN is prepared by the zinc-oxygen precursor ammonolysis method, and the polyol method is adopted to load Pt on CrN and XC-72R carbon blacks. The sensor device manufactured by the hot-press process is tested at room temperature and without additional external voltage. The Pt/CrN sensor presents better stability compared with the Pt/C. The overall change in response current of the Pt/CrN sensor is relatively small within one month, while the Pt/C sensor deteriorates faster. Furthermore, the sensitivity of Pt/CrN is 0.0402 mu A/ ppm, which is 3.26 times higher than that of Pt/C. The Pt/CrN sensor also displays excellent reproducibility. This study indicates that CrN as a kind of supporting material is provided with good application prospects in methanol gas sensing
Hollow and mesoporous aluminosilica-encapsulated Pt-CoOx for the selective hydrogenation of substituted nitroaromatics
No full textHollow and mesoporous aluminosilica nanoreactors (HMANs) with Pt-CoOx cores (similar to 4.7 nm) and hollow aluminosilica shells (similar to 50 nm) were designed by a selective etching method. The Pt-CoOx@HMANs demonstrate a greatly enhanced activity and selectivity for the hydrogenation of various substituted nitroaromatics compared to Pt@HMANs and Pt-CoOx@SiO2
Harnessing the Intriguing Properties of Magnetic Nanop to Detect and Treat Bacterial Infections
No full textInfections caused by pathogenic bacteria, especially multidrug-resistant bacteria, have become a serious worldwide public health problem. Early diagnosis and treatment can effectively prevent the adverse effects of such infections. Therefore, there is an urgent need to develop effective methods for the early detection, prevention, and treatment of diseases that are caused by bacterial infections. So far, magnetic material nanoparticles (MNPs) have been widely used in the detection and treatment of bacterial infections as detection agents and therapeutics. Therefore, this review describes the recent research on MNPs in bacterial detection and treatment. Finally, a brief discussion of challenges and perspectives in this field is provided, which is expected to guide the further development of MNPs for bacterial detection and treatment
A fast and efficient method for selective extraction of lithium from spent lithium iron phosphate battery
No full textA new recovery method for fast and efficient selective leaching of lithium from lithium iron phosphate cathode powder is proposed. Lithium is expelled out of the Oliver crystal structure of lithium iron phosphate due to oxidation of Fe2+ into Fe3+ by ammonium persulfate. 99% of lithium is therefore leached at 40 degrees C with only 1.1 times the amount of ammonium persulfate without the help of acid treatment. The use of ammonium persulfate also avoids the necessity to remove other metal ions in the later purification process. Various characterization methods including SEM, XPS, XRD are used to explore the experimental leaching mechanism. Theoretical investigations are performed which reveals the E-pH diagram of Fe-P-Li-H2O thermodynamic equilibrium. It confirms the possibility and suggests appropriate pH range allowing direct conversion from lithium iron phosphate to iron phosphate with great energy saving and reduced use of acid and base. Based on the experimental and theoretical results, a green and efficient closed-loop recycling route for lithium iron phosphate is proposed. (C) 2021 Elsevier B.V. All rights reserved
Dramatically enhanced Seebeck coefficient in GeMnTe2-NaBiTe2 alloys by tuning the Spin's thermodynamic entropy
No full textThe emerging material GeMnTe2 provides a rare example to study the spin degree of freedom in thermoelectric transport, as it exhibits an anomalous Seebeck coefficient driven by the spin's thermodynamic entropy. This work presents an unconventional strategy to optimize the thermoelectric performance of GeMnTe2 by manipulating the spin degree of freedom. NaBiTe2 is alloyed into GeMnTe2 to disorder the spin orientation under finite temperature, and the obtained Seebeck coefficient is confirmed to be dramatically enhanced by more than 150%. The measurements of XRD and magnetic susceptibility indicate that the increased Seebeck coefficient is due to the increase of the spin's thermodynamic entropy. Finally, the maximum ZT of 1.06 at 820 K is obtained in Ge0.8Na0.1Bi0.1MnTe2. This work enriches the physical picture of spin degree of freedom in thermoelectric materials
Directional Magnetization Reversal Enables Ultrahigh Energy Density in Gradient Nanostructures
No full textHigh-performance ferromagnetic materials are essential for energy conversion and electronic devices. However, the random and nonuniform magnetization reversal in ferromagnetics limits their performance that can be achieved. Here, through both micromagnetism simulations and experiments, a directional magnetization reversal that initiates first from large grains toward smaller ones is discovered by engineering Nd2Fe14B/alpha-Fe gradient nanostructures. Such directional magnetization reversal enables a rare combination of high magnetization and large coercivity, thus leading to a record-high energy density (26 MG Oe) for isotropic permanent magnetic materials, which is approximate to 50% higher than that of its gradient-free counterpart. The unusual magnetization reversal originates from an ordered arrangement of grain sizes in the gradient material, where the large grains have a lower reversal field than that of the smaller ones. These findings open up new opportunities for developing high-performance magnetic materials
Bionic Adaptive Thin-Membranes Sensory System Based on Microspring Effect for High-Sensitive Airflow Perception and Noncontact Manipulation
No full textRecently airflow sensors based on mechanical deformation mechanisms have drawn extensive attention due to their favorable flexibility and sensitivity. However, the fabrication of highly sensitive and self-adaptive airflow sensors in a simple, controllable, and scalable method still remains a challenge. Herein, inspired by the wing membrane of a bat, a highly sensitive and adaptive graphene/single-walled nanotubes-Ecoflex membrane (GSEM) based airflow sensor mediated by the reversible microspring effect is developed. The fabricated GSEM is endowed with an ultralow airflow velocity detection limit (0.0176 m s(-1)), a fast response time (approximate to 1.04 s), and recovery time (approximate to 1.28 s). The GSEM-based airflow sensor can be employed to realize noncontact manipulation. It is applied to a smart window system to realize the intelligent, open, and close behaviors via a threshold control. In addition, an array of airflow sensors is effectively designed to differentiate the magnitude and spatial distribution of the applied airflow stimulus. The GSEM-based airflow sensor is further integrated into a wireless vehicle model system, which can sensitively capture the flow velocity information to realize a real-time direction of motion manipulation. The microspring effect-based airflow sensing system shows significant potentials in the fields of wearable electronics and noncontact intelligent manipulation
Enhancing the Anticorrosion Performance of Graphene-Epoxy Coatings by Biomimetic Interfacial Designs
No full textThe high conductivity of graphene (G) results in G-based composite coatings with unacceptable corrosion-promotion activity (CPA), which greatly limits their applications in metal protection. Herein, a bioinspired graphene-epoxy (B-G-EP) coating with nacre-like structure is constructed to investigate the interfacial structure-dependent anticorrosion of coatings. The results demonstrate that the highly aligned structure of B-G-EP resolves the contradiction between the anticorrosion capability and CPA of G, which breaks the limitation of the blending rule and provides insight into the preparation of high-performance G-based coatings through biomimetic strategies
Improved oxidation and hot corrosion resistance of Ta-doped NiAlY alloy at 750 degrees C
No full textThe oxidation and hot corrosion behaviors of the NiCrAlY, NiAlY, and Ni-xTa-Al-Y alloys (x = 1, 3, 5, and 10 wt%) were investigated at 750 degrees C. The doped Ta promoted the formation of the protective alpha-Al2O3 scales. The NiTaAlY alloys exhibited an improved oxidation resistance compared with the NiAlY alloy. Under the NaCl-induced hot corrosion test, the addition of Ta reduced the consumption of Al and inhibited the internal corrosion of the alloys. The Ni-xTa-Al-Y alloys (x = 1, 3, 5, and 10 wt%) showed better resistance to the NaCl-induced hot corrosion. Moreover, the hot corrosion mechanism of the tested alloys was also discussed