An ideal anti-counterfeiting technique has to be inexpensive, mass-producible, nondestructive, unclonable and convenient for authentication. Although many anti-counterfeiting technologies have been ...developed, very few of them fulfill all the above requirements. Here we report a non-destructive, inkjet-printable, artificial intelligence (AI)-decodable and unclonable security label. The stochastic pinning points at the three-phase contact line of the ink droplets is crucial for the successful inkjet printing of the unclonable security labels. Upon the solvent evaporation, the three-phase contact lines are pinned around the pinning points, where the quantum dots in the ink droplets deposited on, forming physically unclonable flower-like patterns. By utilizing the RGB emission quantum dots, full-color fluorescence security labels can be produced. A convenient and reliable AI-based authentication strategy is developed, allowing for the fast authentication of the covert, unclonable flower-like dot patterns with different sharpness, brightness, rotations, amplifications and the mixture of these parameters.
A better understanding of the redox process of lithium polysulfide (LPS) on carbon surfaces is helpful for designing Li/S batteries with better performance. The “shuttle mechanism” can explain the ...low coulomb efficiency and self-discharge of a Li/S battery, but it cannot explain the fact that battery performance is strongly affected by electrolyte volume and sulfur load. This paper aims to reveal the main redox process of LPS on the surface of carbon by examining the cathodic behavior with different electrolyte volume and sulfur load. Scanning electron microscopy (SEM) images and impedance spectra of the cathode before and after the first discharge were compared, and it was found that the discharge process is the continuous dissolution of sulfur composited with carbon into the electrolyte to form LPS. At the same time, LPS re-precipitates sulfur on the surface of the cathode through a disproportionation reaction to form a solid film. Cyclic voltammetry (CV) curves showed that the solid film passivates the electrode, and the electrode is activated only when the potential is swept negatively and Li
2
S is generated. When a lean electrolyte is used, there is fluctuation in the CV curves, which proves that the dissolution-reprecipitation of sulfur is the main process of the cathode. The discharge–charge curves of cathodes with different sulfur load were compared, and it was found that there is wavy fluctuation in the discharge curve when the sulfur load increases, which proves again that the sulfur reaction dominates the electrode process.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Cadmium sulfide (CdS) as one of the most common visible-light-responsive photocatalysts has been widely investigated for hydrogen generation. However, its low solar–hydrogen conversion efficiency ...caused by fast carrier recombination and poor catalytic activity hinders its practical applications. To address this issue, we develop a novel and highly efficient nickel–cobalt phosphide and phosphate cocatalyst-modified CdS (NiCoP/CdS/NiCoPi) photocatalyst for hydrogen evolution. The dual-cocatalysts were simultaneously deposited on CdS during one phosphating step by using sodium hypophosphate as the phosphorus source. After the loading of the dual-cocatalysts, the photocurrent of CdS significantly increased, while its electrical impedance and photoluminescence emission dramatically decreased, which indicates the enhancement of charge carrier separation. It was proposed that the NiCoP cocatalyst accepts electrons and promotes hydrogen evolution, while the NiCoPi cocatalyst donates electrons and accelerates the oxidation of sacrificial agents (e.g., lactic acid). Consequently, the visible-light-driven hydrogen evolution of this composite photocatalyst greatly improved. The dual-cocatalyst-modified CdS with a loading content of 5 mol % showed a high hydrogen evolution rate of 80.8 mmol·g–1·h–1, which was 202 times higher than that of bare CdS (0.4 mmol·g–1·h–1). This is the highest enhancement factor for metal phosphide-modified CdS photocatalysts. It also exhibited remarkable stability in a continuous photocatalytic test with a total reaction time of 24 h.
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IJS, KILJ, NUK, PNG, UL, UM
Impurity doping is an effective approach to tuning the optoelectronic performance of host materials by imparting extrinsic electronic channels. Herein, a family of lanthanide (Ln
) ions was ...successfully incorporated into a Bi:Cs
AgInCl
lead-free double-perovskite (DP) semiconductor, expanding the spectral range from visible (Vis) to near-infrared (NIR) and improving the photoluminescence quantum yield (PLQY). After multidoping with Nd, Yb, Er and Tm, Bi/Ln:Cs
AgInCl
yielded an ultrabroadband continuous emission spectrum with a full width at half-maximum of ~365 nm originating from intrinsic self-trapped exciton recombination and abundant 4f-4f transitions of the Ln
dopants. Steady-state and transient-state spectra were used to ascertain the energy transfer and emissive processes. To avoid adverse energy interactions between the various Ln
ions in a single DP host, a heterogeneous architecture was designed to spatially confine different Ln
dopants via a "DP-in-glass composite" (DiG) structure. This bottom-up strategy endowed the prepared Ln
-doped DIG with a high PLQY of 40% (nearly three times as high as that of the multidoped DP) and superior long-term stability. Finally, a compact Vis-NIR ultrabroadband (400~2000 nm) light source was easily fabricated by coupling the DiG with a commercial UV LED chip, and this light source has promising applications in nondestructive spectroscopic analyses and multifunctional lighting.
A high yield of the dimer-type heterostructure of Ag/ZnO nanocrystals with different Ag contents is successfully prepared through a simple solvothermal method in the absence of surfactants. The ...samples are characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, UV−vis spectroscopy, and IR spectroscopy. The results show that all samples are composed of metallic Ag and ZnO; Ag nanoparticles locate on the surface of ZnO nanorods; the binding energy of Ag 3d5/2 for the Ag/ZnO sample with a Ag content of 5.0 atom % shifts remarkably to the lower binding energy compared with the corresponding value of pure metallic Ag because of the interaction between Ag and ZnO nanocrystals; the concentration of oxygen vacancy for the as-synthesized samples varies with the increasing Ag content, and the Ag/ZnO sample with a Ag content of 5.0 atom % has the largest density of oxygen vacancy. In addition, the relationship between their structure and photocatalytic property is investigated in detail. It is found that the photocatalytic property is closely related to its structure, such as heterostructure, oxygen defect, and crystallinity. The presence of metallic Ag nanoparticles and oxygen vacancy on the surface of ZnO nanorods promotes the separation of photogenerated electron−hole pairs and thus enhances the photocatalytic activity.
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IJS, KILJ, NUK, PNG, UL, UM
Hierarchical porous plasmonic metamaterials consisting of periodic nanoholes with tunable diameter and uniformly distributed mesopores over the bulk are developed as a new class of 3D ...surface‐enhanced Raman spectroscopy (SERS) substrates. This multiscale architecture not only facilitates efficient cascaded electromagnetic enhancement but also provides an enormous number of Raman‐active binding sites, exhibiting excellent reproducibility and ultrasensitive detection of aromatic molecules down to 10−13 M.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
An unclonable plasmonic anti‐counterfeiting strategy is demonstrated, which involves the use of molecule‐embedded metal@silica core–shell nanoparticles as information carriers. A ...shadow‐mask‐lithography‐assisted self‐assembly is developed for the fabrication of the plasmonic security labels. The produced security labels show multiple sets of coding information that are highly unique, technically unreplicable, and can be robustly decoded by portable microscopes within seconds.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The excitation of surface plasmons in metallic nanostructures provides an opportunity to localize light at the nanoscale, well below the scale of the wavelength of the light. The high local ...electromagnetic field intensities generated in the vicinity of the nanostructures through this nanofocusing effect are exploited in surface enhanced Raman spectroscopy (SERS). At narrow interparticle gaps, so‐called hot‐spots, the nanofocusing effect is particularly pronounced. Hence, the engineering of substrates with a consistently high density of hot‐spots is a major challenge in the field of SERS. Here, a simple bottom‐up approach is described for the fabrication of highly SERS‐active gold core‐satellite nanostructures, using electrostatic and DNA‐directed self‐assembly. It is demonstrated that well‐defined core‐satellite gold nanostructures can be fabricated without the need for expensive direct‐write nanolithography tools such as electron‐beam lithography (EBL). Self‐assembly also provides excellent control over particle distances on the nanoscale. The as‐fabricated core‐satellite nanostructures exhibit SERS activities that are superior to commercial SERS substrates in signal intensity and reproducibility. This also highlights the potential of bottom‐up self‐assembly strategies for the fabrication of complex, well‐defined functional nanostructures with future applications well beyond the field of sensing.
A dense array of core‐satellite gold nanostructures is fabricated as a low‐cost surface enhanced Raman spectroscopy (SERS) substrate through a combined electrostatic and DNA‐directed self‐assembly. These core‐satellite nanostructures show strong and highly reproducible SERS activity, superior to those of a commercial Klarite SERS substrate, and an ability target analytes (e.g., benzenethiol), at concentrations down to 1 × 10−9M.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Surface-enhanced Raman spectroscopy (SERS) has attracted increasing interest for chemical and biochemical sensing. Several studies have shown that SERS intensities are significantly increased when an ...optical interference substrate composed of a dielectric spacer and a reflector is used as a supporting substrate. However, the origin of this additional enhancement has not been systematically studied. In this paper, high sensitivity SERS substrates composed of self-assembled core-satellite nanostructures and silica-coated silicon interference layers have been developed. Their SERS enhancement is shown to be a function of the thickness of silica spacer on a more reflective silicon substrate. Finite difference time domain modeling is presented to show that the SERS enhancement is due to a spacer contribution via a sign change of the reflection coefficients at the interfaces. The magnitude of the local-field enhancement is defined by the interference of light reflected from the silica-air and silica-silicon interfaces, which constructively added at the hot spots providing a possibility to maximize intensity in the nanogaps between the self-assembled nanoparticles by changing the thickness of silica layer. The core-satellite assemblies on a 135 nm silica-coated silicon substrate exhibit a SERS activity of approximately 13 times higher than the glass substrate.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A magnetic tunnel junction (MTJ) is the core component in memory technologies, such as the magnetic random-access memory, magnetic sensors and programmable logic devices. In particular, MTJs based on ...two-dimensional van der Waals (vdW) heterostructures offer unprecedented opportunities for low power consumption and miniaturization of spintronic devices. However, their operation at room temperature remains a challenge. Here, we report a large tunnel magnetoresistance (TMR) of up to 85% at room temperature (
T
= 300 K) in vdW MTJs based on a thin (< 10 nm) semiconductor spacer WSe
2
layer embedded between two Fe
3
GaTe
2
electrodes with intrinsic above-room-temperature ferromagnetism. The TMR in the MTJ increases with decreasing temperature up to 164% at
T
= 10 K. The demonstration of TMR in ultra-thin MTJs at room temperature opens a realistic and promising route for next-generation spintronic applications beyond the current state of the art.
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