Broadband Plasmonic Antenna Enhanced Upconversion and Its Application in Flexible Fingerprint Identification

Abstract

photons can be efficiently converted into electron oscillations in plasmonic nanostructures. [1] The use of plasmonic antennas could substantially enhance the efficiency of many optoelectronic devices by utilizing long-wavelength light beyond the visible region, which accounts for more than a half of the total solar energy. [2] For example, Xiong and co-workers recently developed a flexible near-infrared (NIR) photovoltaic device whose external quantum efficiency (at ≈800 nm) was improved from 24.2% to 38.4% by coupling Si nanowires (NWs) with a Ag-nanoplate-based plasmonic antenna that exhibits a surface plasmon extinction band ranging from 550 to 1100 nm. [2a] Most current plasmonic antennas, however, only enable light trapping in the visible region and within a narrow range. [1c,3] Therefore, for many applications, broadband plasmonic antennas that can work in the NIR region, are highly desired.Upconversion (UC) is an anti-Stokes-type emission process in which the sequential absorption of two or more photons leads to the emission of light at a shorter wavelength than the excitation wavelength. [4] In recent years, rare earth (RE) ion-doped upconversion nanocrystals (UCNCs) have demonstrated great potential in bioimaging and biosensing, infrared photodynamic therapy, 3D display and multiplexing, Plasmonic antennas based on metallic nanostructures that can trap longwavelength light can be used to substantially enhance the efficiency of optoelectronic devices by utilizing light beyond the visible region. This study experimentally and theoretically demonstrates that a silver nanowire network (AgNW-net) plasmonic antenna exhibits superwide surface plasmon extinction because of the strong plasmon coupling between AgNWs, providing the ability to trap light spanning the entire solar spectrum. As a proof-of-concept demonstration, the AgNW-net is used to greatly improve the luminescence of lanthanide-doped upconversion nanocrystals (UCNCs) under dual wavelength excitation and the periodic alternating multilayer structure of AgNWs/ UCNCs is further successfully introduced to improve the absolute luminescence intensity of AgNWs/UCNCs composite films. Furthermore, evidence has been provided that this improvement is attributable to excitation field enhancement rather than Purcell effect or plasmon-enhanced energy transfer. Finally, an upconversion flexible fingerprint identification technology is developed based on AgNW-net/UCNCs/polyvinyl alcohol composite materials, which allows us extracting fingerprints on various uneven bending surfaces.

The upconversion quantum yield (UCQY): a review to standardize the measurement methodology, improve comparability, and define efficiency standards

“… eUCQY [ 141 ] LiYF 4 : Er 3+ ,Yb 3+ Powder L: ~2.0 µm (Octahedral) - *>0.1 980 (*Gauss) - 2.1 (*350-750) - A, B, C?, D?, F?, H?, I, J C? eUCQY [ 142 ] SrF 2 : (14.2%)Er 3+ Powder -(*Varied) - *>0.1 980 (*Gauss) 25 63 0.17 (*350-700) 0.28 (*350-700) 6.8 x10 −3 4.4 x10 −3 A, B, C?, D?, F, H?, I, J C? eUCQY [ 143 ] SrF 2 : (2%)Yb 3+ ,(2%)Er 3+ Powder 100-300 nm (Spherical and pseudo-cubic) - *>0.1 980 (*Gauss) 10 2.8 (*400-900) 0.28 A, B, C?, D?, F, H?, I, J C?…”

Plasmon‐Enhanced Blue Upconversion Luminescence by Indium Nanocrystals

“…Experimental results have shown that a maximum of up to tenfold blue upconversion luminescence enhancement is achieved at the optimal 3 nm working distance between InNCs and UCNPs. This is reasonable since the surface plasmon of Au or Ag resonances with visible light (520–660 nm) at longer wavelengths, which can travel longer distance (>10 nm) while that of InNCs is trapped within a smaller range due to the short surface plasmon wavelength, characterized by the typical UV absorption at 265 nm …”

“…Among them, surface plasmon resonance (SPR) has proved to be a facile and efficient method for enhancing upconversion emissions, by resonating with either the excitation or emission process . For example, since the first demonstration that coating upconversion nanoparticles with gold nanocrystals or nanoshells can drastically enhance upconversion luminescence, Ag nanostructures and Au nanorods have also been utilized for this purpose and the enhancement factor keeps increasing . However, this strategy usually enhances green and red upconversion emissions (i.e., 520–660 nm) since the SPR bands of Au and Ag nanostructures usually locate within the visible to near infrared range, which is not compatible for enhancing short‐wavelength luminescence such as blue or UV emission.…”

Steady State Luminescence Enhancement in Plasmon Coupled Core/Shell Upconversion Nanoparticles

“…Recent reports reveal that the upconversion luminescence can be efficiently enhanced by coupling UCNPs with plasmonic metal nanostructures . Due to the emission and absorption band match between the UCNPs and surface plasmon in grating nanohole array, nanoparticle and photonics crystal, the upconversion intensity can be dramatically enhanced by several to thousand folds . Lu et al reported a nanosilver grating which couples efficiently with UCNPs and got an enhancement factor of 16 for the green emission under the excitation of 1 kW cm −2 .…”