Optical Contrast Research Articles

High-Performance Complementary Electrochromic Batteries using Nb18W16O93 by the Synergistic Effects of Aqueous Al3+/K+ Dual-Ion.

Multivalent ions, especially Al3+ in aqueous electrolyte contributes to higher capacity and color contrast for more sustainable post-lithium electrochromism and energy storages. However, the lack of suitable cathodic and anodic electrochromic materials is a major challenge for Al-ion electrochromic batteries, which limits their optical contrast and lifespan. Herein, we report that Wadsley-Roth phase Nb18W16O93 with open structure achieves Al3+ intercalation/extraction reversibly. The complementary electrochromic energy storage devices based on Nb18W16O93 coupled with Prussian blue using hybrid Al3+/K+ aqueous electrolytes show a fast response, a high capacity and a large coloring efficiency. The superior performances are due to the cations of Al3+ and K+ selectively insert/extract in the electrode of Nb18W16O93 and Prussian blue, respectively. This work provides an effective strategy for high-performance and low-cost electrochromic batteries with higher sustainability.

High‐Performance Complementary Electrochromic Batteries using Nb18W16O93 by the Synergistic Effects of Aqueous Al3+/K+ Dual‐Ion

AbstractMultivalent ions, especially Al3+ in aqueous electrolyte contributes to higher capacity and color contrast for more sustainable post‐lithium electrochromism and energy storages. However, the lack of suitable cathodic and anodic electrochromic materials is a major challenge for Al‐ion electrochromic batteries, which limits their optical contrast and lifespan. Herein, we report that Wadsley‐Roth phase Nb18W16O93 with open structure achieves Al3+ intercalation/extraction reversibly. The complementary electrochromic energy storage devices based on Nb18W16O93 coupled with Prussian blue using hybrid Al3+/K+ aqueous electrolytes show a fast response, a high capacity and a large coloring efficiency. The superior performances are due to the cations of Al3+ and K+ selectively insert/extract in the electrode of Nb18W16O93 and Prussian blue, respectively. This work provides an effective strategy for high‐performance and low‐cost electrochromic batteries with higher sustainability.

Simultaneously Detecting the Power and Temperature of a Microwave Sensor via the Quantum Technique

This study introduces a novel method for the simultaneous detection of microwave sensor power and temperature, leveraging nitrogen-vacancy (NV) centers as a robust quantum system. Through precise measurement of the optical detection magnetic resonance contrast in NV centers, the microwave power is accurately determined. Furthermore, the temperature of the sensor is obtained by monitoring the variations in zero-field splitting and thorough spectral analysis. This method enables the efficient real-time acquisition of synchronized data on both microwave power and temperature from the sensor, facilitating concurrent monitoring without the necessity of additional sensing devices. Finally, we verified that the magnetic sensitivity of the system is approximately 1.2 nT/Hz1/2, and the temperature sensitivity is around 0.38 mK/Hz1/2. The minimum resolution of microwave power is about 20 nW. The experimental results demonstrate that this quantum measurement technique provides stable and accurate data across a wide range of microwave power and temperature conditions. These findings indicate substantial potential for this technique in advanced applications such as aerospace, medical diagnostics, and high-frequency communications. Future studies will aim to extend the industrial applicability of this method by refining quantum control techniques within NV center systems.

SCC/PVA Hydrogel with Self‐Healing Capability for Electrochromic Device

AbstractCracking caused by aging or repeated bending can severely affect the lifetime of electrochromic devices. In this work, a self‐healing electrochromic hydrogel was developed with poly (vinyl alcohol) (PVA)‐sodium carboxymethyl chitosan (SCC) semi‐inter transfer network as the matrix, viologen bromide (HPV2+2Br−) as the electrochromic substance, and borax as the cross‐linking agent. The self‐healing properties of hydrogel stem from the dynamic and reversible borate bonds between borax and PVA molecular chains. As the voltage changes, the color of the device transitions from colorless to light purple and then to dark purple. The optical contrast at 600 nm reaches approximately 51 %. At room temperature, the disconnected hydrogel can fully restore its original state after 30 minutes of contact, effectively addressing issues related to cracks and damage in flexible electrochromic devices. This research holds significant implications for enhancing the reliability and stability of flexible electrochromic devices.

Organic Dye Molecule Intercalated Prussian Blue for Simultaneously Enhancing Coloration Efficiency and Energy Storage Capacity in Electrochromic Battery.

The dual-functional device combining electrochromic properties and energy storage has gained numerous attentions in the field of energy-saving smart electronics. However, achieving simultaneous optimization of coloration efficiency and energy storage capacity of materials poses a significant challenge. This study presents a novel approach by incorporating methyl orange into Prussian blue channels (PB-MO films) to adjust the internal electronic structure of Prussian blue. This modification allows the active layer to simultaneously improve the electrochromic and energy storage performance. The introduction of methyl orange not only alters the ratio of Fe3+/Fe2+ within the framework through the coordination reaction of Fe3+ with methyl orange, but also improves the reaction kinetics after intercalating organic dye molecules, including charge transfer resistance, diffusion capability of ions and capacitive contribution. The PB-MO films demonstrate remarkable properties: high optical contrast (81.4% at 670nm), excellent coloration efficiency (265 cm2C-1), and significant specific capacity (84 mAh m-2 at 0.05 A m-2), outperforming pure PB films. The PB-MO films are ideally suited for applications in displays and intelligent energy storage fields, boasting both high coloration efficiency and substantial energy storage capacity, thus advancing promote the development of dual-functional electrochromic devices.

Regulation of Br on molecular aggregation, film morphology and electrochromic performance of polythiophene derivatives

In this work, five polythiophene derivatives were synthesized through electrochemical copolymerization of 3,3-bis(bromomethyl)-3,4-dihydro-2H-thieno[3,4-b] (Deng et al., 2023; Li et al., 2020) [1,4]dioxepine (ProDOT-Br) and 3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b] (Deng et al., 2023; Li et al., 2020) [1,4]dioxepine (ProDOT-Me) at different mass ratios. DFT results prove that the layer spacing of conjugated blocks was increased from 5.94 Å for PProDOT-Me to 8.89 Å for PProDOT-Br due to the introduction of Br atom into side chain. And, the diverse film morphologies, such as fibre shape, cellular shape, flat shape, etc, were obtained by changing Br content in polymer. Additionally, through optimizing Br content, PBM(1,2) achieved enhanced electrochromic properties relative to two reference polymers [PProDOT-Br and PProDOT-Me], such as high optical contrast (ΔT = 76 %), fast response time (0.5 s), high transparency, and good stability. Finally, the flexible electrochromic device (8 cm × 4 cm) based on PBM(1,2) was constructed, which achieves rapid color change from purple to transparent blue. The results indicate that introducing various contents of Br atom into side chain is an effective strategy for regulating molecular microstructure and optimizing electrochromic properties of conjugated polymers.

SKYQUANT 3D: Quantifying Vascular Anatomy With an Open-Source Workflow for Comprehensive Analysis of Volumetric Optoacoustic Angiography Data.

Efficient visualization of the vascular system is of key importance in biomedical research into tumor angiogenesis, cerebrovascular alterations, and other angiopathies. Optoacoustic (OA) angiography offers a promising solution combining molecular optical contrast with high resolution and deep penetration of ultrasound. However, its hybrid nature implies complex data collection and processing workflows, with significant variability in methodologies across developers and users. To streamline interoperability, we introduce SKYQUANT 3D, a Python-based set of instructions for the Thermo Fisher Scientific Amira/Avizo 3D Visualization & Analysis Software. Our workflow simplifies the batch processing of volumetric optoacoustic angiography images, extracting meaningful quantitative information while also providing statistical analysis and graphical representation of the results. Quantification performance of SKYQUANT 3D is demonstrated using functional preclinical and clinical in vivo 3D OA angiographic tests involving ambient temperature variations and repositioning of the imaged limb.

Flexible polyaniline/carbon quantum dots films for enhanced electrochromic performance

Polyaniline (PANI) conducting polymers exhibit potential electrochromic properties. However, the electrochromic response of PANI films in the infrared (IR) ranges is restricted by their dense structure. Herein, the polyaniline/carbon quantum dots (PANI/CQDs) films were synthesized with sulfuric acid (SA) and CQDs as the dopants. The tetrahedral structures of SA contribute to the formation of highly oriented lamellar PANI. The synergistic effect between CQDs and PANI promotes the loose and porous surface morphology, thereby improving the electrochromic performance of PANI film. The PANI/CQDs porous film for the polymerization charge of 0.5C (PANI/CQDs-5) shows the optimal electrochromic properties and IR modulation capacity, achieving an optical contrast (ΔT) values of 53 % at 850 nm, and with the emittance variation (Δε) values of 0.41, 0.46 and 0.42 in 3–5 μm, 8–14 μm, and 2.5–25 μm, respectively. Furthermore, the switching time of the PANI/CQDs-5 films for coloration and blanching are 2.5 s and 3.6 s, respectively, with over 95 % retention after 100 cycles. Theoretical calculations verified that PANI/CQDs composite films displayed outstanding electron and ion transfer kinetics, facilitating superior electrochromic properties.

Effects of fluorine atom numbers on electrochromic properties of the benzothiadiazole-based D-A polymers

In this work, two fluorinated D-π-A-π-D type monomers, F-EDOT and FF-EDOT, were facilely synthesized by donor-acceptor-donor method via Stille coupling reaction, with monofluorinated benzothiadiazole and difluorinated benzothiadiazole as the acceptor units and 3,4-ethylenedioxythiophene (EDOT) as the donor units. The electrochemical polymerization behavior of the fluorinated monomers, electrochemical and electrochromic properties of the corresponding fluorinated D-A polymers were compared to study the effects of different fluorine atom numbers on the optoelectronic properties of the monomers and their resultant D-A polymers. The results show that the introduction of more F atoms into the conjugated backbone increases the oxidation potential of monomers, both of them have low initial oxidation potential (0.65 V/0.70 V). As in the case of monomers, the substitution of more F atoms also leads to the decreased HOMO energy level of the polymers, thus leading to the increased band gap energy of P(FF-EDOT) (1.39 eV). This result can be attributed to the deviation of planarity and the reduced effective conjugate length. As prepared fluorinated D-A polymers also have good adhesion on the electrode surface, favorable redox activity, and outstanding redox stability (the redox activity of P(F-EDOT) remains 99 % after 1000 cycles). At the same time, the fluorinated D-A polymers also show distinguish electrochromic properties under various external potentials; both the optical contrast and coloration efficiency decreased with the increase of F atom numbers, and the corresponding response time increased. As a result, both the fluorinated D-A polymers show light green in the neutral state, P(F-EDOT) shows more obvious electrochromic performance in the near infrared region (optical contrast: 35.02 %, coloration efficiency: 159.94 cm2 C−1, and quick response time: 0.2 s), accompanied with excellent discoloration stability and optical memory effect. The study of novel fluorinated-based electrochromic materials further expands the selection of acceptor units and the application prospect of electrochromic materials.

Ti3C2Tx‐MXene‐Based Color‐Indicative All‐Organic Electrochromic Supercapacitors

An all‐organic multifunctional solid‐state electrochromic supercapacitor has been designed by utilizing 2D‐MXene and a combination of viologen and polythiophene. The 2D MXene is synthesized using selective etching method and properly characterized; afterward, it is doped in ethyl viologen (EV) and a solid‐state electrochromic supercapacitor device is prepared having poly‐3‐hexylthiophene (P3HT) as complementary electrode. The prepared device gives high optical contrast (OC) (≈85%) and coloration efficiency (CE) (≈340 cm2 C−1) with ≈1 s of switching time in the visible spectrum at 515 nm. A similar color modulation is observed in NIR region also. Along with high electrochromic properties, the device takes almost 23.1 s for discharging and 6.7 s for charging, giving high Columbic efficiency due to the pseudocapacitor‐type charge storage property providing necessary electrons for the redox reaction to occur. The current study proposes a new MXene‐based recipe for designing multifunctional electrochromic supercapacitors with a promise for practical use.

Novel donor-acceptor-donor type electrochromic polymers based on 1,3-indandione modified triphenylamine derivatives as new acceptor units

Two donor (D)-acceptor (A)-donor (D) type of conjugated monomers, ITPA and ICTPA, consisted of 1H-indene-1,3(2H)-dione (IN)- or 2-(3-oxo-2,3-dihydroinden-1-ylidene)-malononitrile (INCN)-substituted triphenylamine as the acceptor unit, were synthesized by Stille coupling reaction and Knovenagel condensation reaction, and their corresponding polymers (PITPA and PICTPA) were prepared by electrochemical polymerization. Both ITPA and ICTPA hade low initial oxidation potential of 0.70 V and 0.76 V, respectively, which was conducive to achieve high-quality polymer films. In comparison with FTPA which was not substituted by IN unit, ITPA and ICTPA exhibited the distinct red-shifted and dual absorption bands due to the stronger electron-withdrawing ability of IN and INIC units. Moreover, the electrochromic results demonstrated that PITPA possessed much higher optical contrast of 41 %, higher coloration efficiency (CE) of 445.5 cm2 C−1 at 1100 nm with extremely fast response time as low as 0.3 s, and a promising optical memory behavior compared with its counterpart without IN unit. These results suggested that the introduction of IN unit into triphenylamine could improve the electrochromic performance of the conjugated polymers and also provide a new strategy to develop novel and high-performance electrocheomic polymers.

Yellow-transmissive blue electrochromic polymers based on triphenylamine and ProDOT derivatives

Electrochromic polymer with yellow hue is few relative to those with other two primary colors due to its optical absorption at short wavelength of ≈ 450 nm. Triphenylamine (TPA) and its derivatives (TPAs) as chromogenic groups are frequently used to construct neutral yellow electrochromic polymers, however, those polymers based on TPAs usually exhibit low transmittance at oxidation state due to the residual absorption at short wavelength. Here, three neutral yellow electrochromic polymers (PBBE-1, PBBE-2 and PBBE-3) with different content ratios of ProDOT-10, TPA-4 and benzene were synthesized by Suzuki coupling reaction. With ProDOT-10 content in polymeric chain increasing, the oxidation potentials of polymers decrease gradually. Due to the twisted molecular structure, the absorption peaks of polymers almost remain unchanged when ProDOT-10 content in polymer reaches critical value, which provide an effective method for preparing neutral yellow electrochromic polymers. During oxidation process, PBBE-1 turns to black; PBBE-2 turns to dark blue; PBBE-3 turns to light grey, further to light blue. Through optimizing TBA-4/ProDOT-10 ratio, the electrochromic properties of polymers have been improved, such as optical contrast, response time and coloration efficiency. Especially, PBBE-3 possesses 40 % optical contrast at 435 nm, which is higher than reported TPAs based polymers at short wavelengths.

Photonic crystal topological interface state modulation for nonvolatile optical switching

Phase change materials (PCMs), characterized by high optical contrast (Δn>1), nonvolatility (zero static power consumption), and quick phase change speed (∼ns), provide new opportunities for building low-power and highly integrated photonic tunable devices. Optical integrated devices based on PCMs, such as optical switches and optical routers, have demonstrated significant advantages in terms of modulation energy consumption and integration. In this paper, we theoretically verify the solution for a highly integrated nonvolatile optical switch based on the modulation of the topological interface state (TIS) in the quasi-one-dimensional photonic crystal (quasi-1D PC). The TIS exciting wavelength changes with the crystalline level of the PCM. The extinction ratio (ER) of the topological optical switch is over 18 dB with a modulation length of 9 μm. Meanwhile, the insertion loss (IL) can be controlled within 2 dB. Furthermore, we have analyzed the impact of fabrication errors on the device’s performance. The obtained results show that, the topological optical switch, which changes its “on/off” state by modulating TIS, exhibits enhanced robustness to the fabrication process. We provide an interesting and highly integrated scheme for designing the on-chip nonvolatile optical switch. It offers great potential for designing highly integrated on-chip optical switch arrays and nonvolatile optical neural networks.

Reusing the Wasted Energy of Electrochromic Smart Window for Near-Zero Energy Building.

Electrochromic smart windows (ESWs) are an effective energy-saving technology for near-zero energy buildings. They consume electric energy unidirectionally during a round-trip coloring-bleaching process, with the energy involved in the bleaching process being wasted. It is highly desirable to reuse this wasted electric energy directly and/or transfer it into other energy storage equipment, further enhancing the overall efficiency of electric energy usage. Herein, a zinc anode-based ESW (ESW-PZ) is reported that not only has fascinating visible-near-infrared (VIS-NIR) dual-band electrochromic performance (a high optical contrast of 63%) but also showcases good energy storage characteristics (a wide voltage window of 2.6V and a high energy density of 127.5 µWh cm-2). The buildings utilizing ESW-PZ to modulate indoor environments demonstrated an average annual energy saving of 366MJ m-2 based on energy simulations, which is about 16% of the total energy consumption. Impressively, a high utilization efficiency of 90% (855 mWh m-2) of the wasted electric energy is realized through an ingenious circuit-switching strategy, which can be reused to power small household appliances.

Intellectual fitting of hard X-ray resonant reflectance maps obtained for low-contrast oxide multilayers across L absorption edges of Eu and Gd

The present work describes an intellectual computational approach to X-ray resonant reflectometry – a synchrotron-based method aimed at non-destructive characterization of epitaxial nanoscale multilayers with low optical contrast between the sublayer materials. Resonant reflectance from specially designed bilayer structures was measured as a function of grazing angle and photon energy across the L absorption edges of rare earth elements and then modeled with the aid of a specially developed software utilizing OpenCL high speed computations performed on a graphical processing unit. The map fitting was carried out in the blind mode in which the spectral shapes of the optical constants of the sublayers were reconstructed by the fitting routine without initial knowledge of the chemical composition and without using any reference spectra. The model uses stepped Lorentzian line shape for the imaginary part of the scattering length density and the Kramers-Kronig consistent line shape for the corresponding real part. Epitaxially grown Eu2O3 / Gd3Ga5O12 bilayers were used as a test bench system to demonstrate the benefits of the proposed 2D mapping technique over conventional X-ray reflectometry. To increase reliability, the map fitting was carried out simultaneously at the absorption edges of two different chemical elements. The derived shapes and positions of the absorption peaks were used to uniquely identify rare earth elements within the corresponding sublayers and provide information on their oxidation states. The method was experimentally tested on the bilayers having different material order to show that not only the chemical composition but also the layer sequence can be effectively reconstructed in the automatic way from the 2D resonant reflectance maps.

Calibrated absolute optical contrast for high-throughput characterization of horizontally aligned carbon nanotube arrays

Horizontally aligned carbon nanotube (HACNT) arrays hold significant potential for various applications in nanoelectronics and material science. However, their high-throughput characterization remains challenging due to the lack of methods with both high efficiency and high accuracy. Here, we present a novel technique, Calibrated Absolute Optical Contrast (CAOC), achieved through the implementation of differential principles to filter out stray signals and high-resolution calibration to endow optical contrast with physical significance. CAOC offers major advantages over previous characterization techniques, providing consistent and reliable measurements of HACNT array density with high throughput and non-destructive assessment. To validate its utility, we demonstrate wafer-scale uniformity assessment by rapid density mapping. This technique not only facilitates the practical evaluation of HACNT arrays but also provides insights into balancing high throughput and high resolution in nanomaterial characterization.

Hunting for Monolayer Black Phosphorus with Photoluminescence Microscopy

Monolayer black phosphorus (BP) holds great promise for naturally hyperbolic polaritons and correlated states in rectangular moiré superlattices. However, preparing and identifying high-quality monolayer BP are challenging due to its instability and high transparency, which limits extensive studies. In this study, we developed a method for rapidly and nondestructively identifying monolayer BP and its crystal orientation simultaneously using modified photoluminescence (PL) microscopy. The optical contrast of monolayer BP has been significantly increased by at least twenty times compared to previous reports, making it visible even on a transparent substrate. The polarization dependence of optical contrast also allows for the in situ determination of crystal orientation. Our study facilitates the identification of monolayer BP, expediting more extensive research on and potential industrial applications of this material.

Monte Carlo simulation of spatial frequency domain imaging for breast tumors during compression.

Near-infrared optical imaging methods have shown promise for monitoring response to neoadjuvant chemotherapy (NAC) for breast cancer, with endogenous contrast coming from oxy- and deoxyhemoglobin. Spatial frequency domain imaging (SFDI) could be used to detect this contrast in a low-cost and portable format, but it has limited imaging depth. It is possible that local tissue compression could be used to reduce the effective tumor depth. To evaluate the potential of SFDI for therapy response prediction, we aim to predict how changes to tumor size, stiffness, and hemoglobin concentration would be reflected in contrast measured by SFDI under tissue compression. Finite element analysis of compression on an inclusion-containing soft material is combined with Monte Carlo simulation to predict the measured optical contrast. When the effect of compression on blood volume is not considered, contrast gain from compression increases with the size and stiffness of the inclusion and decreases with the inclusion depth. With a model of reduction of blood volume from compression, compression reduces imaging contrast, an effect that is greater for larger inclusions and stiffer inclusions at shallower depths. This computational modeling study represents a first step toward tracking tumor changes induced by NAC using SFDI and local compression.

A pan-cancer dye for solid-tumour screening, resection and wound monitoring via short-wave and near-infrared fluorescence imaging.

The efficacy of fluorescence-guided surgery in facilitating the real-time delineation of tumours depends on the optical contrast of tumour tissue over healthy tissue. Here we show that CJ215-a commercially available, renally cleared carbocyanine dye sensitive to apoptosis, and with an absorption and emission spectra suitable for near-infrared fluorescence imaging (wavelengths of 650-900 nm) and shortwave infrared (SWIR) fluorescence imaging (900-1,700 nm)-can facilitate fluorescence-guided tumour screening, tumour resection and the assessment of wound healing. In tumour models of either murine or human-derived breast, prostate and colon cancers and of fibrosarcoma, and in a model of intraperitoneal carcinomatosis, imaging of CJ215 with ambient light allowed for the delineation of nearly all tumours within 24 h after intravenous injection of the dye, which was minimally taken up by healthy organs. At later timepoints, CJ215 provided tumour-to-muscle contrast ratios up to 100 and tumour-to-liver contrast ratios up to 18. SWIR fluorescence imaging with the dye also allowed for quantifiable non-contact wound monitoring through commercial bandages. CJ215 may be compatible with existing and emerging clinical solutions.

Applicability of energy-theta mapping in resonant soft X-ray reflectometry to probe depth dependence of oxidation state and crystallographic environment in iron oxide multilayers

In the present paper we discuss applicability of the synchrotron method of resonant x-ray reflectometry to non-destructive depth profiling of multilayer heterostructures with low optical contrast between the sublayers. The two-dimensional mapping approach comprising evaluation and measurement of reflectance as a function of photon energy and grazing angle is shown to provide a convenient way to effectively utilize the enhancement of optical contrast between the sublayers that exists at the absorption edges of chemical elements due to particular spectral shape peculiarities related to oxidation state, crystallographic environment and magnetization. In the present study the evaluation of the resonant X-ray reflectivity maps is performed using a specially developed modeling and fitting software. Estimation of the photon energy / grazing angle combinations at which the reflectance is most sensitive to the minor changes in the physical properties of the sublayers is illustrated by the example of ferroic-on-semiconductor nanoscale heterostructures composed of nanoscale film of metallic iron oxidized from either top or bottom side. The subtle differences in resonant soft x-ray reflectance caused by variation of the oxide film thickness, oxidation state and crystallographic environment are discussed. The presented approach is applicable to a large class of heterostructures composed of sublayers that can be distinguished only by the differences in their near edge X-ray absorption fine structure.