Hot electron and thermal effects in plasmonic catalysis of nanocrystal transformation

Plasmonic metal nanoparticles have the ability to harvest visible light and cause effective energy conversion, and they are considered as promising catalysts to drive chemical reactions. Although plasmonic catalysis has been widely used to mediate the reaction of organic molecules, the mechanism of contribution of thermal and hot carriers remains unclear. The catalysis of hot carriers is normally proposed as the dominant role of plasmonic catalysis, while the contribution of plasmonic thermal effects is often ignored, since the molecules on the metal surface are unstable at high temperatures. Here, plasmon catalytic nanocrystal transformation including oxidation reaction and optimization of the crystal structure is employed to investigate the plasmonic contributions of hot electron and thermal effects in plasmonic catalysis. It is found that the transformation rate and the corresponding product are very different with and without the assistance of hot electron catalysis. The thermal effect plays a dominant role in plasmon-catalyzed material transformation, and hot electrons can promote the oxidation reaction by facilitating the generation of active oxygen. The investigation provides insight into the specific role of hot electron and thermal effects in plasmonic catalysis, which is critically important for exploiting the highly localized fast plasmonic thermal effect and for designing energy-efficient plasmonic catalysts.

Growth of β-NaYF4:Eu3+ Crystals by the Solvothermal Method with the Aid of Oleic Acid and Their Photoluminescence Properties

Lanthanide-doped hexagonal β-NaYF₄ crystals have received much attention in recent years due to their excellent photoluminescence properties. However, lanthanide-doped β-NaYF₄ crystals with micron and submicron scales as well as uniform morphology have received less attention. In this study, Eu³⁺-doped β-NaYF₄ (β-NaYF₄:Eu³⁺) crystals of micron and submicron size scales were synthesized using the solvothermal method with ethylene glycol as the solvent. The β-NaYF₄:Eu³⁺ crystals were highly crystallized. A comparison of the characteristics of the β-NaYF₄:Eu³⁺ crystals synthesized with and without the use of oleic acid as a surfactant was conducted. It was found that the utilization of oleic acid as a surfactant during their synthesis greatly decreased their particle size from micron to submicron scale, while adding a small amount of ethanol further reduced their particle size. In addition, they exhibited much smoother surfaces and more uniform morphologies, which were hexagonal prism bipyramids. The microstructural characteristics and photoluminescence properties of the β-NaYF₄:Eu³⁺ crystals were studied in detail. Results showed that β-NaYF₄:Eu³⁺ crystals prepared with the aid of oleic acid as a surfactant during their synthesis exhibited stronger photoluminescence.

Highly Luminescent Dual Mode Polymeric Nanofiber-Based Flexible Mat for White Security Paper and Encrypted Nanotaggant Applications

Increasing counterfeiting of important data, currency, stamp papers, branded products etc., has become a major security threat which could lead to serious damage to the global economy. Consequences of such damage are compelling for researchers to develop new high-end security features to address full-proof solutions. Herein, we report a dual mode flexible highly luminescent white security paper and nanotaggants composed of nanophosphors incorporated in polymer matrix to form a nanofiber-based mat for anti-counterfeiting applications. The dual mode nanofibers are fabricated by electrospinning technique by admixing the composite of NaYF₄ :Eu³⁺ @NaYF₄ :Yb³⁺ , Er³⁺ nanophosphors in the polyvinyl alcohol solution. This flexible polymer mat derived from nanofibers appears white in daylight, while emitting strong red (NaYF₄ :Eu³⁺ ) and green (NaYF₄ :Yb³⁺ , Er³⁺ ) colors at excitation wavelengths of 254 nm and 980 nm, respectively. These luminescent nanofibers can also be encrypted as a new class of nanotaggants to protect confidential documents. These obtained results suggest that highly luminescent dual mode polymeric nanofiber-based flexible white security paper and nanotaggants could offer next-generation high-end unique security features against counterfeiting.

Rice oil as a green source of capping ligands for GdF3 nanocrystals

The thermal decomposition of triglycerides allows control of the amount of ligands in the synthesis of GdF₃ nanocrystals.

One-pot synthesis of 2-thenoyltrifluoroacetone surface functionalised SrF2:Eu3+ nanoparticles: trace level detection of water

Trace level detection of water by 2-thenoyltrifluoroacetone Surface functionalised fluorescent lanthanide (Eu³⁺) doped SrF₂ nanoparticles.