Sandwiched WS2/MoTe2/WS2 Heterostructure with a Completely Depleted Interlayer for a Photodetector with Outstanding Detectivity.

Photodetectors based on two-dimensional van der Waals (2D vdW) heterostructures with high detectivity and rapid response have emerged as promising candidates for next-generation imaging applications. However, the practical application of currently studied 2D vdW heterostructures faces challenges related to insufficient light absorption and inadequate separation of photocarriers. To address these challenges, we present a sandwiched WS2/MoTe2/WS2 heterostructure with a completely depleted interlayer, integrated on a mirror electrode, for a highly efficient photodetector. This well-designed structure enhances light-matter interactions while facilitating effective separation and rapid collection of photocarriers. The resulting photodetector exhibits a broadband photoresponse spanning from deep ultraviolet to near-infrared wavelengths. When operated in self-powered mode, the device demonstrates an exceptional response speed of 22/34 µs, along with an impressive detectivity of 8.27 × 1010 Jones under 635 nm illumination. Additionally, by applying a bias voltage of -1 V, the detectivity can be further increased to 1.49 × 1012 Jones, while still maintaining a rapid response speed of 180/190 µs. Leveraging these outstanding performance metrics, high-resolution visible-near-infrared light imaging has been successfully demonstrated using this device. Our findings provide valuable insights into the optimization of device architecture for diverse photoelectric applications.

Perturbative countersurveillance metaoptics with compound nanosieves.

The progress of metaoptics relies on identifying photonic materials and geometries, the combination of which represents a promising approach to complex and desired optical functionalities. Material candidate options are primarily limited by natural availability. Thus, the search for meta-atom geometries, by either forward or inverse means, plays a pivotal role in achieving more sophisticated phenomena. Past efforts mainly focused on building the geometric library of individual meta-atoms and synthesizing various ones into a design. However, those efforts neglected the powerfulness of perturbative metaoptics due to the perception that perturbations are usually regarded as adverse and in need of being suppressed. Here, we report a perturbation-induced countersurveillance strategy using compound nanosieves mediated by structural and thermal perturbations. Private information can be almost perfectly concealed and camouflaged by the induced thermal-spectral drifts, enabling information storage and exchange in a covert way. This perturbative metaoptics can self-indicate whether the hidden information has been attacked during delivery. Our results establish a perturbative paradigm of securing a safer world of information and internet of things.

Flexible Nanowire Cluster as a Wearable Colorimetric Humidity Sensor.

Wearable plasmonic devices combine the advantages of high flexibility, ultrathinness, light weight, and excellent integration with the optical benefits mediated by plasmon-enhanced electric fields. However, two obstacles severely hinder further developments and applications of a wearable plasmonic device. One is the lack of efficient approach to obtaining devices with robust antimotion-interference property, i.e., the devices can work independently on the morphology changes of their working structures caused by arbitrary wearing conditions. The other issue is to seek a facile and high-throughput fabrication method to satisfy the financial requirement of industrialization. In order to overcome these two challenges, a functional flexible film of nanowire cluster is developed, which can be easily fabricated by taking the advantages of both conventional electrochemical and sputtering methods. Such flexible plasmonic films can be made into wearable devices that work independently on shape changes induced by various wearing conditions (such as bending, twisting and stretching). Furthermore, due to plasmonic advantages of color controlling and high sensitivity to environment changes, the flexible film of nanowire cluster can be used to fabricate wearable items (such as bracelet, clothes, bag, or even commercial markers), with the ability of wireless visualization for humidity sensing.

Scalable, full-colour and controllable chromotropic plasmonic printing.

Plasmonic colour printing has drawn wide attention as a promising candidate for the next-generation colour-printing technology. However, an efficient approach to realize full colour and scalable fabrication is still lacking, which prevents plasmonic colour printing from practical applications. Here we present a scalable and full-colour plasmonic printing approach by combining conjugate twin-phase modulation with a plasmonic broadband absorber. More importantly, our approach also demonstrates controllable chromotropic capability, that is, the ability of reversible colour transformations. This chromotropic capability affords enormous potentials in building functionalized prints for anticounterfeiting, special label, and high-density data encryption storage. With such excellent performances in functional colour applications, this colour-printing approach could pave the way for plasmonic colour printing in real-world commercial utilization.

A centimeter-scale sub-10 nm gap plasmonic nanorod array film as a versatile platform for enhancing light-matter interactions.

Strongly coupled plasmonic nanostructures with sub-10 nm gaps can enable intense electric field enhancements which greatly benefit the various light-matter interactions. From the point view of practical applications, such nanostructures should be of low-cost, facile fabrication and processing, large-scale with high-yield of the ultrasmall gaps, and easy for integration with other functional components. However, nowadays techniques for reliable fabrication of these nanostructures usually involve complex, time-consuming, and expensive lithography procedures, which are limited either by their low-throughput or the small areas obtained. On the other hand, so far most of the studies on the sub-10 nm gap nanostructures mainly focused on the surface-enhanced Raman scattering and high-harmonic generations, while leaving other nonlinear optical properties unexplored. In this work, using a scalable process without any lithography procedures, we demonstrated a centimeter-scale ordered plasmonic nanorod array film (PNRAF) with well-defined sub-10 nm interparticle gaps as a versatile platform for strongly enhanced light-matter interactions. Specifically, we showed that due to its plasmon-induced localized electromagnetic field enhancements, the Au PNRAF could exhibit extraordinary intrinsic multi-photon avalanche luminescence (MAPL) and nonlinear saturable absorption (SA). Furthermore, the PNRAF can be easily integrated with semiconductor quantum dots (SQDs) as well as wide bandgap semiconductors to strongly enhance their fluorescence and photocurrent response, respectively. Our method can be easily generalized to nanorod array films consisting of other plasmonic metals and even semiconductor materials, which can have multiple functionalities derived from different materials. Overall, the findings in our study have offered a potential strategy for design and fabrication of nanostructures with ultrasmall gaps for future photonic and optoelectronic applications.

Antibody modified gold nano-mushroom arrays for rapid detection of alpha-fetoprotein.

Localized surface plasmon resonance (LSPR) combined with immunoassay shows greatly potential in fast detection of tumor markers. In this paper, a highly sensitive LSPR substrate has been fabricated and modified for direct detection of alpha-fetoprotein (AFP). The biosensor was prepared by interference lithography, and modified by covalently immobilizing anti-AFP on the surface of gold nano-mushroom arrays (GNMA). The modification process was investigated by Vis-NIR reflectance spectra and cyclic voltammogram measurements. We revealed the optical properties of the modified GNMA by measuring the Vis-NIR reflectance spectra and simulating its electric intensity field distribution under light illumination. The GNMA substrate was highly sensitive, with a refractive index sensitivity of ~465 nm/RIU. The substrate can be applied to label-free detection of AFP, with the linear range and the limit of detection determined to be 20-200 ng/mL and 24 ng/mL (S/N=3), respectively. We also demonstrated its clinical application by directly detecting AFP in human serum samples. It is expected that our biosensor could be integrated on microfluidic chips for high-throughput detection in portable early diagnosis, post-operative and point-of-care (POC) in clinical applications.

Gold nanoarray deposited using alternating current for emission rate-manipulating nanoantenna.

We have proposed an easy and controllable method to prepare highly ordered Au nanoarray by pulse alternating current deposition in anodic aluminum oxide template. Using the ultraviolet-visible-near-infrared region spectrophotometer, finite difference time domain, and Green function method, we experimentally and theoretically investigated the surface plasmon resonance, electric field distribution, and local density of states enhancement of the uniform Au nanoarray system. The time-resolved photoluminescence spectra of quantum dots show that the emission rate increased from 0.0429 to 0.5 ns-1 (10.7 times larger) by the existence of the Au nanoarray. Our findings not only suggest a convenient method for ordered nanoarray growth but also prove the utilization of the Au nanoarray for light emission-manipulating antennas, which can help build various functional plasmonic nanodevices.