All-State Switching of the Mie Resonance of Conductive Polyaniline Nanospheres

Environmental permittivity-asymmetric BIC metasurfaces with electrical reconfigurability

Achieving precise spectral and temporal light manipulation at the nanoscale remains a critical challenge in nanophotonics. While photonic bound states in the continuum (BICs) have emerged as a powerful means of controlling light, their reliance on geometrical symmetry breaking for obtaining tailored resonances makes them highly susceptible to fabrication imperfections, and their generally fixed asymmetry factor fundamentally limits applications in reconfigurable metasurfaces. Here, we introduce the concept of environmental symmetry breaking by embedding identical resonators into a surrounding medium with carefully placed regions of contrasting refractive indexes, activating permittivity-driven quasi-BIC resonances (ε-qBICs) without altering the underlying resonator geometry and unlocking an additional degree of freedom for light manipulation through active tuning of the surrounding dielectric environment. We demonstrate this concept by integrating polyaniline (PANI), an electro-optically active polymer, to achieve electrically reconfigurable ε-qBICs. This integration not only demonstrates rapid switching speeds and exceptional durability but also boosts the system's optical response to environmental perturbations. Our strategy significantly expands the capabilities of resonant light manipulation through permittivity modulation, opening avenues for on-chip optical devices, advanced sensing, and beyond.

Long-term stable pH sensor array with synergistic bilayer structure for 2D real-time mapping in cell culture monitoring

Pursuing accurate, swift, and durable pH sensors is important across numerous fields, encompassing healthcare, environmental surveillance, and agriculture. In particular, the emphasis on real-time pH monitoring during cell cultivation has become increasingly pronounced in the current scientific environment-a crucial element being diligently researched to ensure optimal cell production. Both polyaniline (PANi) and iridium oxide (IrOx) show their worth in pH sensing, yet they come with challenges. Single-PANi-layered pH sensors often grapple with diminished sensitivity and lagging responses, while electrodeposited IrOx structures exhibit poor adhesion, leading to their separation from metallic substrates-a trait undesirable for a consistently stable, long-term pH sensor. This paper introduces a bi-layered PANi-IrOx pH sensor, strategically leveraging the advantages of both materials. The results presented here underscore the sensitivity enhancement of binary-phased framework, faster response time, and more robust structure than prior work. Through this synergistic strategy, we demonstrate the potential of integrating different phases to overcome the inherent constraints of individual materials, setting the stage for advanced pH-sensing solutions.

Proton-Assisted Assembly of Colloidal Nanoparticles into Wafer-Scale Monolayers in Seconds

Underwater adhesion processes in nature promise controllable assembly of functional nanoparticles for industrial mass production; However, their artificial strategies have faced challenges to uniformly transfer nanoparticles into a monolayer, particularly those below 100 nm in size, over large areas. Here a scalable "one-shot" self-limiting nanoparticle transfer technique is presented, enabling the efficient transport of nanoparticles from water in microscopic volumes to an entire 2-inch wafer in a remarkably short time of 10 seconds to reach near-maximal surface coverage (≈40%) in a 2D mono-layered fashion. Employing proton engineering in electrostatic assembly accelerates the diffusion of nanoparticles (over 50 µm2/s), resulting in a hundredfold faster coating speed than the previously reported results in the literature. This charge-sensitive process further enables "pick-and-place" nanoparticle patterning at the wafer scale, with large flexibility in surface materials, including flexible metal oxides and 3D-printed polymers. As a result, the fabrication of wafer-scale disordered plasmonic metasurfaces in seconds is successfully demonstrated. These metasurfaces exhibit consistent resonating colors across diverse material and geometrical platforms, showcasing their potential for applications in full-color painting and optical encryption devices.

Programmable directional color dynamics using plasmonics

Adaptive multicolor filters have emerged as key components for ensuring color accuracy and resolution in outdoor visual devices. However, the current state of this technology is still in its infancy and largely reliant on liquid crystal devices that require high voltage and bulky structural designs. Here, we present a multicolor nanofilter consisting of multilayered 'active' plasmonic nanocomposites, wherein metallic nanoparticles are embedded within a conductive polymer nanofilm. These nanocomposites are fabricated with a total thickness below 100 nm using a 'lithography-free' method at the wafer level, and they inherently exhibit three prominent optical modes, accompanying scattering phenomena that produce distinct dichroic reflection and transmission colors. Here, a pivotal achievement is that all these colors are electrically manipulated with an applied external voltage of less than 1 V with 3.5 s of switching speed, encompassing the entire visible spectrum. Furthermore, this electrically programmable multicolor function enables the effective and dynamic modulation of the color temperature of white light across the warm-to-cool spectrum (3250 K-6250 K). This transformative capability is exceptionally valuable for enhancing the performance of outdoor optical devices that are independent of factors such as the sun's elevation and prevailing weather conditions.

Dynamic Spectral Modulation Enabled by Conductive Polymer-Integrated Plasmonic Nanodisk-Hole Arrays

The electrically driven optical performance modulation of the plasmonic nanostructure by conductive polymers provides a prospective technology for miniaturized and integrated active optoelectronic devices. These features of wafer-scale and flexible preparation, a wide spectrum adjustment range, and excellent electric cycling stability are critical to the practical applications of dynamic plasmonic components. Herein, we have demonstrated a large-scale and flexible active plasmonic nanostructure constructed by electrochemically synthesizing nanometric-thickness conductive polymer onto spatially mismatched Au nanodisk-hole (AuND-H) array on the poly(ethylene terephthalate) (PET) substrate, offering low-power electrically driven switching of reflective light in a wide wavelength range of 550-850 nm. The composite structure of the polymer/AuND-H array supports multiple plasmonic resonance modes with strong near-field enhancement and confinement, which provides an excellent dynamic spectral modulation platform. As a result, the PPy/AuND-H array achieves 18.4% reversible switching of spectral intensity at 780 nm and speedy response time, as well as maintains a stable dynamic modulation range at two-potential cycling between -0.6 and 0.1 V after 200 modulation cycles. Compared to the case of the PPy/AuND-H array, the PANI/AuND-H array obtains a more extensive intensity modulation of 25.1% at 750 nm, which is attributed to the significant differences in the extinction coefficient between the oxidized and reduced states of PANI, but its modulation range degrades apparently after 20 cycles driven at applied voltages between -0.1 and 0.8 V. Additionally, the cycling stability could be further improved by reducing the modulation voltage range. Our proposed electromodulated composite structure provides a promising technological proposal for dynamically plasmonic reconfigurable devices.

Resonant-Cavity-Enhanced Electrochromic Materials and Devices

With rapid advances in optoelectronics, electrochromic materials and devices have received tremendous attentions from both industry and academia for their strong potentials in wearable and portable electronics, displays/billboards, adaptive camouflage, tunable optics, and intelligent devices, etc. However, conventional electrochromic materials and devices typically present some serious limitations such as undesirable dull colors, and long switching time, hindering their deeper development. Optical resonators have been proven to be the most powerful platform for providing strong optical confinement and controllable lightmatter interactions. They generate locally enhanced electromagnetic near-fields that can convert small refractive index changes in electrochromic materials into high-contrast color variations, enabling multicolor or even panchromatic tuning of electrochromic materials. Here, resonant-cavity-enhanced electrochromic materials and devices, an advanced and emerging trend in electrochromics, are reviewed. In this review, w e will focus on the progress in multicolor electrochromic materials and devices based on different types of optical resonators and their advanced and emerging applications, including multichromatic displays, adaptive visible camouflage, visualized energy storage, and applications of multispectral tunability. Among these topics, principles of optical resonators, related materials/devices and multicolor electrochromic properties are comprehensively discussed and summarized. Finally, the challenges and prospects for resonant-cavity-enhanced electrochromic materials and devices are presented.

A Reversible Plasmonic Nanoprobe for Dynamic Imaging of Intracellular pH during Endocytosis

Understanding the pH evolution during endocytosis is essential for our comprehension of the fundamental processes of biology as well as effective nanotherapeutic design. Herein, we constructed a plasmonic Au@PANI core-shell...