3D Hotspots Platform for Plasmon Enhanced Raman and Second Harmonic Generation Spectroscopies and Quantitative AnalysisYang, Zhen‐Wei; Meng, Ling‐Yan; Lin, Jia‐Sheng; Yang, Wei‐Min; Radjenovic, Petar; Shen, Shao‐Xin; Xu, Qing‐Chi; Yang, Zhi‐Lin; Tian, Zhong‐Qun; Li, Jian‐Feng
doi: 10.1002/adom.201901010pmid: N/A
Constructing plasmonic hotspots in metal nanostructures is essential for plasmon‐enhanced spectroscopies (PESs), but their application in quantitative analysis is a long‐standing challenge. Herein, highly uniform, reproducible, stable, and sensitive 3D hotspots platform substrates are assembled on hydrophobic silicon wafers using a drop of solution containing silica coated surface plasmon resonance (SPR) active nanoparticles (NPs). Plasmon‐enhanced second harmonic generation (PESHG) and surface‐enhanced Raman scattering (SERS) experimental signals increase sharply with the increase of droplet evaporation time, which is attributed to the rapid increase of 3D hotspots generated by gradual decrease of distance between adjacent NPs. Compared with 3D bare metal NP substrate, 3D metal shell‐isolated nanoparticles (SHINs) substrate demonstrates much more stable PESHG and SERS signals attributing to the protecting SiO2 shells. Besides that, uniform distribution of 3D “hotspots” on the hydrophobic substrate can facilitate the quantitative analysis of an analyte using SERS. Experimental and theoretical results demonstrate that the 3D hotspots platform has the potential to be developed as a plasmon‐enhanced substrate for linear and nonlinear spectroscopies with practical sensing applications.
Fabrication of Pixelated Organic Light‐Emitting Transistor (OLET) with a Pure Red‐Emitting Organic SemiconductorOh, Sangyoon; Kim, Jin Hong; Park, Sang Kyu; Ryoo, Chi Hyun; Park, Soo Young
doi: 10.1002/adom.201901274pmid: N/A
A pure red‐emitting organic light‐emitting transistor (OLET) is successfully fabricated using a π‐extended dicyanodistyrylbenzene‐type organic semiconductor material (Hex‐4‐TFPTA), which shows outstanding charge transport and solid‐state luminescence at the same time. Based on the structural (X‐ray) and photophysical analyses, it is found that the appropriate molecular stacking and highly allowed S1→S0 transition of Hex‐4‐TFPTA created the ambidextrous balance between electrical mobility (µe, FET ≈ 1 cm2 V−1 s−1) and solid‐state luminescent quantum yield, even in the deep‐red (DR) region (ΦF = 28%). Remarkably, the color purity of the red Hex‐4‐TFPTA thin film (0.70, 0.30) is close to the National Television System Committee (NTSC) standard primary red (0.67, 0.33) in Commission Internationale de I'Eclairage (CIE) color space. Moreover, in this work, micropixelated areal OLET emission is demonstrated for the first time by patterning the organic layer via a novel soft‐lithographic technique called “patterned taping.”
White Light‐Emitting Electrochemical Cells Based on Deep‐Red Cu(I) ComplexesFresta, Elisa; Weber, Michael D.; Fernandez‐Cestau, Julio; Costa, Rubén D.
doi: 10.1002/adom.201900830pmid: N/A
The synthesis and characterization, as well as photoluminescent and electrochemical features of a series of ionic copper(I) complexes—, i.e., [Cu(N^N)(P^P)]+, where N^N is 4,4′‐diethylester‐2,2′‐biquinoline (dcbq) and P^P is bis‐triphenylphosphine, bis[2‐(diphenylphosphino)phenyl)ether] (POP), or 4,5‐bis(diphenylphosphino)‐9,9‐dimethylxanthene (Xantphos)—are reported along with their application to achieve both deep‐red and white light‐emitting electrochemical cells (LECs). In short, the first deep‐red Cu(I)‐based LECs featuring high irradiances (≈100 µW cm−2) and excellent color stability (x/y CIE color coordinates of 0.66/0.32) over days are reported. This is achieved by comparing the electroluminescent behavior of this series of complexes with respect to the irradiance and stability, as well as the impact of introducing supporting electrolytes on the device performance. This is rationalized using spectroscopic and electrochemical studies. Finally, the first white‐emitting LEC is manufactured with red‐emitting copper(I) complexes, achieving x/y CIE color coordinates of 0.31/0.32 and a high color rendering index of 92.
Filterless Polarization‐Sensitive 2D Perovskite Narrowband PhotodetectorsLi, Lu; Jin, Long; Zhou, Yunxi; Li, Junze; Ma, Jiaqi; Wang, Shuai; Li, Wancai; Li, Dehui
doi: 10.1002/adom.201900988pmid: N/A
Polarization‐sensitive narrowband photodetectors can respond to a narrow spectral range of light together with the ability to sense the polarization of light. Traditionally, expensive filters combined with polarizers are utilized to realize the polarization‐sensitive narrowband photodetections. To reduce the cost and simplify optical system, here a polarization‐sensitive narrowband photodetector based on 2D perovskite single crystals without any additional optical components is reported. The photodetector shows a linear dichroic ratio of 1.56 at 552 nm under the oblique incident angle of 45° and the full width at half maximum of 20 nm. Moreover, the photodetector exhibits a high external quantum efficiency of 120% and a peak specific detectivity of 1.23 × 1010 Jones under the normal illumination. This polarization‐sensitive narrowband photoresponse can be ascribed to the charge collection narrowing mechanism assisted by the enhanced self‐trapped states in 2D perovskites and the large anisotropic crystal structure between different crystal directions. In particular, the device configuration is specially designed so that the absorption anisotropy takes place between the in‐plane and out‐of‐plane directions and photogenerated carriers transport along the in‐plane direct to avoid the large organic barrier along the out‐of‐plane direction, resulting in the polarization‐sensitive narrowband photodetections with high performance.
Nonreciprocal Transmission in Nonlinear PT‐Symmetric Metamaterials Using Epsilon‐Near‐Zero Media Doped with DefectsJin, Boyuan; Argyropoulos, Christos
doi: 10.1002/adom.201901083pmid: N/A
Nonreciprocal transmission forms the basic operation mechanism of optical diodes and isolators and requires the tantalizing task of breaking the Lorentz reciprocity law. In this work, strong nonreciprocal transmission is demonstrated by using a compact nonlinear parity‐time (PT) symmetric system based on epsilon‐near‐zero (ENZ) materials photonically doped with gain and loss defects and separated by an ultrathin air gap. The nonlinear response of this scalable configuration is triggered at relatively low optical intensities due to the strong electric field confinement in the defects. The extreme asymmetric field distribution achieved upon excitation from opposite incident directions, combined with the enhanced nonlinear properties of the proposed system, results in a pronounced self‐induced nonreciprocal transmission. Cascade configurations with optimized geometrical dimensions are used to achieve self‐induced nonreciprocal transmission with a maximum contrast, ideal for the design of new all‐optical diodes. The presented robust nonreciprocal response occurs by operating at a frequency slightly shifted off the exceptional point but without breaking the PT‐symmetric phase, different compared to previous works. The findings of this work can have a plethora of applications, such as nonreciprocal ultrathin coatings for the protection of sources or other sensitive equipment from external pulsed signals, circulators, and isolators.
Wafer‐Scale Polymer‐Based Transparent Nanocorals with Excellent Nanoplasmonic Photothermal Stability for High‐Power and Superfast SERS ImagingWu, Kaiyu; Nguyen, Long Quang; Rindzevicius, Tomas; Keller, Stephan Sylvest; Boisen, Anja
doi: 10.1002/adom.201901413pmid: N/A
Polymer‐based surface‐enhanced Raman spectroscopy (SERS) substrates offer distinctive advantages such as low‐cost and high optical transparency which allows direct detection of trace chemicals on target surfaces and easy microfluidic integration. However, incident‐laser‐induced localized surface plasmon resonances can generate heat that deform the polymer and significantly reduce the intensities of recorded SERS signals. Herein, a novel wafer‐scale polymer‐based transparent nanocoral (WTNC) SERS substrate with 3D electromagnetic “hotspots” is presented. Its fabrication is simple and lithography‐free. The novel SERS substrate demonstrates excellent nanoplasmonic heat resistance, high SERS sensitivity, and unmatched SERS signal uniformity with a relative standard deviation of ≈6% across 80 mm. Excellent photothermal stability is achieved by highly crosslinking SU‐8, a negative epoxy photoresist, raising its initial degradation temperature to ≈230 °C, much higher than the glass transition temperature of state‐of‐the‐art thermalplasts used in SERS substrates, including polyethylene terephthalate and poly(methyl methacrylate). The WTNC substrate can withstand very high laser irradiance of up to 300 kW cm−2, enabling superfast SERS imaging of analytes in extremely small quantities. A high resolution SERS image containing 10 201 spectra of ≈44 amol trans‐1,2‐bis(4‐pyridyl)ethylene is obtainable in <5 min. The WTNC substrate pushes the state‐of‐the‐art in polymer‐based SERS substrates and has great potential for rapid routine analyses.