Strong Absorption Research Articles

Trimodal Multiplexed Lateral Flow Test Strips Assisted with a Portable Microfluidic Centrifugation Device.

During the COVID-19 pandemic, the use of lateral flow assays (LFAs) expanded significantly, offering testing beyond traditional health care. Their appeal lies in the ease of use, affordability, and quick results. However, LFAs often have lower sensitivity and specificity compared with ELISA and PCR tests. Efforts to improve LFAs have increased detection times and complexity, limiting their use in large-scale point-of-care settings. To address this, we propose a novel approach using probes that generate multiple signals to enhance the sensitivity and selectivity. This concept also allows multiplexed LFAs to detect multiple analytes concurrently. We developed a trimodal probe that integrates fluorescence, color, and magnetism into a single nanohybrid. The strong plasmonic absorption and high fluorescence of Au nanoparticles and polymer dots enable qualitative and semiquantitative diagnosis, while the magnetic signal facilitates accurate quantitative measurements. As proof-of-concept targets, we selected CYFRA 21-1 and CA15-3, biomarkers for lung and breast cancer, respectively. This trimodal LFA demonstrated a remarkable detection limit of 0.26 ng/mL for CYFRA 21-1 and 2.8 U/mL for CA15-3. To the best of our knowledge, this is the first platform of a trimodal LFA with multiplexing ability. The platform's accuracy and reliability were validated using clinical serum samples, showing excellent consistency with electrochemiluminescence immunoassay results. This universal concept can be applied to other targets, paving the way for the next-generation LFAs.

Multilayer thin film mid-infrared broadband absorber with high visible light transmittance

Few reports on absorbers achieve both high transmittance of visible light and strong absorption of mid-infrared light. Here a multilayered absorber with high visible light transmittance and strong broadband absorption in the mid-infrared band is proposed. The absorber is four-layer films of ITO/SiO2/ITO/SiO2 successively deposited on single-sided conductive glass by electron beam evaporation technology. The experiment shows that the integral transmittance in the 400–800 nm range is 82.8 %, and the integral absorption in the 3–5 μm band is 88.2 %.

Infrared Spectroscopy of Live Cells Using High-Aspect-Ratio Metal-on-Dielectric Metasurfaces.

Fourier transform infrared (FTIR) spectroscopy is widely used for molecular analysis. However, for the materials situated in an aqueous environment, a precondition for live biological objects such as cells, transmission-based FTIR is prevented by strong water absorption of mid-infrared (MIR) light. Reflection-based cellular assays using internal reflection elements (IREs) such as high-index prisms or flat plasmonic metasurfaces mitigate these issues but suffer from a shallow probing volume localized near the plasma membrane. Inspired by the recent introduction of high-aspect-ratio nanostructures as a novel platform for manipulating cellular behavior, we demonstrate that the integration of plasmonic metasurfaces with tall dielectric nanostructures dramatically enhances the sensing capabilities of FTIR spectroscopy. We also demonstrate the ability of a metal-on-dielectric metasurface to transduce intracellular processes, such as protein translocation to high-curvature membrane regions during cell adhesion, into interpretable spectral signatures of the reflected light.

Intramolecular Charge Transfer and Spin-Orbit Coupled Intersystem Crossing in Hypervalent Phosphorus(V) and Antimony(V) Porphyrin Black Dyes.

Porphyrin dyes with strong push-pull type intramolecular charge transfer (ICT) character and broad absorption across the visible spectrum are reported. This combination of properties has been achieved by functionalizing the periphery of hypervalent and highly electron-deficient phosphorus(V) and antimony(V) centered porphyrins with electron-rich triphenylamine (TPA) groups. As a result of the large difference in electronegativity between the porphyrin ring and the peripheral groups, their absorption profiles show several strong charge transfer transitions, which in addition to the porphyrin-centered π → π* transitions, make them panchromatic black dyes with high absorption coefficients between 200 and 800 nm. Time-resolved optical and electron paramagnetic resonance (EPR) studies show that the lowest triplet state also has ICT character and is populated by spin-orbit coupled intersystem crossing.

Unveiling the optoelectronic features and physical stability of novel Cs2HgPdI6: Computational insights

In recent years, researchers have been devoted to search for novel stable halide perovskite materials with outstanding photovoltaic performance. Herein, through density functional theory (DFT) calculations, we uncover for the first time the crystal stability, structural parameters, optoelectronic features, and photovolatic performance of Cs2HgPdI6. The Jahn−Teller-distorted Cs2HgPdI6 is detected by its structural feature. The stability of novel Cs2HgPdI6 is completely ensured by means of the DFT calculations. Accurate electronic structure calculations show that Cs2HgPdI6 exhibits an appropriate fundamental gap (1.278 eV). This band gap is mainly determined by the interaction between the I-5p and Pd-4d orbitals. Additionally, Cs2HgPdI6 has good carrier mobility and an ultra-low exciton binding energy. Meanwhile, it also exhibits relatively weak anisotropic optical properties and strong visible-light absorption. The large theoretical conversion efficiency of 31.7 % is illustrated for Cs2HgPdI6. Overall, our research highlights the great potential of this novel compound for photovoltaic applications.

Ultrablack surface with omnidirectional high absorption.

Black surface plays an important role in solar-thermal conversion systems and space optical systems. Despite the significant efforts in developing a black surface with strong broadband absorption, realizing scalable omnidirectional high absorption ultrablack surfaces remains challenging. Here, we report an ultrablack surface based on a structural black paint (SBP), realized by femtosecond (fs) laser fabrication of high aspect ratio microstructure mold followed by mold transferring on black paint coating. The SBP exhibits extremely low hemispheric reflectance (R < 1.2%) in the solar spectrum at a normal incident angle; even at an 80° incident angle, the SBP also has good anti-reflection performance (R < 9%). Based on such properties, we further show the enhanced solar-thermal performance over commercial black paints. Our approach holds promises for scalable and cost-effective manufacturing of ultrablack surface, with potential applications in solar-thermal conversion efficiency improvement and space optical system stray light suppression.

The cluster analysis of traditional Chinese medicine authenticity identification technique assisted by chemometrics

This study explore the authenticity identification technique of traditional Chinese medicine (TCM) using chemometrics in conjunction with cluster analysis. A clustering Gaussian mixture model was constructed and applied for the data clustering analysis of four types of TCM. Chemical measurements combined with discrete wavelet transform (DWT), Fourier transform infrared spectroscopy (FTIR), and Fourier self-deconvolution (FSD) were utilized for the detailed differentiation of Bupleurum scorzonerifolium, Bupleurum yinchowense, Bupleurum marginatum, and Bupleurum smithii Wolff var. parvifolium. Differences in the attenuated total reflection-FTIR (ATR-FTIR) spectra among the four TCMs were observed. Utilizing clustering algorithms, the one-dimensional DWT of the infrared spectra of samples was employed for the authentication of Chinese herbal medicines. The model demonstrates optimal performance throughout 2000 rounds of network training. The accuracy (88.6 %), sensitivity (86.5 %), and specificity (82.7 %) of the model constructed in this study significantly surpassed those of the CNN model: accuracy (67.7 %), sensitivity (70.4 %), and specificity (68.5 %) (P < 0.05). By setting the cluster size K = 5 and the number of Gaussian mixture model components to 5, the model effectively fits the actual number of categories within the dataset. Infrared spectroscopy analysis revealed distinct carbon-oxygen stretching vibration absorption peaks between 1025 and 1200 cm−1 for Bupleurum scorzonerifolium, Bupleurum yinchowense, Bupleurum marginatum, and Bupleurum smithii Wolff var. parvifolium, indicating strong absorption peaks of carbohydrates. A comprehensive structural information analysis revealed a similarity of above 0.982 among the four types of TCM. Combined with chemometrics and intelligent algorithm-based cluster analysis, successful and accurate authentication of TCM authenticity was achieved, providing an effective methodology for quality control in TCM.

Benchtop IR Imaging of Live Cells: Monitoring the Total Mass of Biomolecules in Single Cells.

Absolute quantity imaging of biomolecules on a single cell level is critical for measurement assurance in biosciences and bioindustries. While infrared (IR) transmission microscopy is a powerful label-free imaging modality capable of chemical quantification, its applicability to hydrated biological samples remains challenging due to the strong IR absorption by water. Traditional IR imaging of hydrated cells relies on powerful light sources, such as synchrotrons, to mitigate the light absorption by water. However, we overcome this challenge by applying a solvent absorption compensation (SAC) technique to a home-built benchtop IR microscope based on an external-cavity quantum cascade laser. SAC-IR microscopy adjusts the incident light using a pair of polarizers to precompensate the IR absorption by water while retaining the full dynamic range. Integrating the IR absorbance over a cell yields the total mass of biomolecules per cell. We monitor the total mass of the biomolecules of live fibroblast cells over 12 h, demonstrating promise for advancing our understanding of the biomolecular processes occurring in live cells on the single-cell level.

Improved UV Photoresponse Performance of ZnO Nanowire Array Photodetector via Effective Pt Nanoparticle Coupling.

Ultraviolet (UV) photodetectors (PDs) based on nanowire (NW) hold significant promise for applications in fire detection, optical communication, and environmental monitoring. As optoelectronic devices evolve towards lower dimensionality, multifunctionality, and integrability, multicolor PDs have become a research hotspot in optics and electronic information. This study investigates the enhancement of detection capability in a light-trapping ZnO NW array through modification with Pt nanoparticles (NPs) via magnetron sputtering and hydrothermal synthesis. The optimized PD exhibits superior performance, achieving a responsivity of 12.49 A/W, detectivity of 4.07 × 1012 Jones, and external quantum efficiency (EQE) of 4.19 × 103%, respectively. In addition, the Pt NPs/ZnO NW/ZnO PD maintains spectral selectivity in the UV region. These findings show the pivotal role of Pt NPs in enhancing photodetection performance through their strong light absorption and scattering properties. This improvement is associated with localized surface plasmon resonance induced by the Pt NPs, leading to enhanced incident light and interfacial charge separation for the specialized configurations of the nanodevice. Utilizing metal NPs for device modification represents a breakthrough that positively affects the preparation of high-performance ZnO-based UV PDs.

Self-Driven Graphene Photodetector Arrays Enabled by Plasmon-Induced Asymmetric Electric Field.

Gap surface plasmon (GSP) modes enhance graphene photodetectors (GPDs)' performance by confining the incident light within nanogaps, giving rise to strong light absorption. Here, we propose an asymmetric plasmonic nanostructure array on planar graphene comprising stripe- and triangle-shaped sharp tip arrays. Upon light excitation, the noncentrosymmetric metallic nanostructures show strong light-matter interactions with localized field close to the surface of tips, causing an asymmetric electric field. These features can accelerate the hot electron generation in graphene, forming a directional diffusion current. Accordingly, the artificial GPDs exhibit a wavelength-dependence behavior covering the wavelength range from 0.8 to 1.6 μm, with three photoresponse maxima corresponding to the nanostructures' resonances. Additionally, the polarization-dependent GPDs can realize a responsivity of ∼25 mA/W and a noise equivalent power of ∼0.44 nW/Hz1/2 at zero bias when excited at the resonance of 1.4 μm. Overall, our study offers a new strategy for preparing compact and multifrequency infrared GPDs.

Visible-Photo-Assisted Phase Switching of Antiferroelectric-to-Ferroelectric Orders in an I3--Intercalated 2D Perovskite.

Antiferroelectric (AFE) has emerged as a promising branch of electroactive materials, due to their intriguing physical attributes stemming from the electric field-induced antipolar-to-polar phase transformation. However, the requirement of an extremely high electric field strength to switch adjacent sublattice polarization poses great challenges for exploiting molecular AFE system. Although photoirradiation is striking as a noncontact and nondestructive manipulation tool to optimize physical properties, the optical control of antiferroelectricity is still unexplored. Here, by adopting light-sensitive triiodide I3- anion into the 2D perovskite family, we have designed the first I3--intercalated molecular AFE of (t-ACH)2EA2Pb3I10(I3)0.5·((H3O)(H2O))0.5 (1, t-ACH = trans-4-aminomethyl-1-cyclohexanecarboxylate, EA = ethylammonium). The I3--intercalating gives an ultra-narrow bandgap of 1.65 eV with strong absorption. In terms of AFE structure, theanti-parallel alignment of electric dipoles results in a spontaneous polarization of 4.3 µC/cm2. Strikingly,1merely shows AFE behaviour in the dark even under ultrahigh voltage, while the field-induced ferroelectric state can be facilely obtained upon visible illumination. Suchunprecedented photo-assisted phase switching ascribes to the incorporation of photoactive I3- anions, which reduce the AFE-to-ferroelectric switching barrier for 1. This pioneering work on the photo-assisting transformation of ferroic orders paves a new way to develop future photoactive materials with significant potential applications.

Visible‐Photo‐Assisted Phase Switching of Antiferroelectric‐to‐Ferroelectric Orders in an I3‐‐Intercalated 2D Perovskite

Antiferroelectric (AFE) has emerged as a promising branch of electroactive materials, due to their intriguing physical attributes stemming from the electric field‐induced antipolar‐to‐polar phase transformation. However, the requirement of an extremely high electric field strength to switch adjacent sublattice polarization poses great challenges for exploiting molecular AFE system. Although photoirradiation is striking as a noncontact and nondestructive manipulation tool to optimize physical properties, the optical control of antiferroelectricity is still unexplored. Here, by adopting light‐sensitive triiodide I3‐ anion into the 2D perovskite family, we have designed the first I3‐‐intercalated molecular AFE of (t‐ACH)2EA2Pb3I10(I3)0.5·((H3O)(H2O))0.5 (1, t‐ACH = trans‐4‐aminomethyl‐1‐cyclohexanecarboxylate, EA = ethylammonium). The I3‐‐intercalating gives an ultra‐narrow bandgap of 1.65 eV with strong absorption. In terms of AFE structure, the anti‐parallel alignment of electric dipoles results in a spontaneous polarization of 4.3 µC/cm2. Strikingly, 1 merely shows AFE behaviour in the dark even under ultrahigh voltage, while the field‐induced ferroelectric state can be facilely obtained upon visible illumination. Such unprecedented photo‐assisted phase switching ascribes to the incorporation of photoactive I3‐ anions, which reduce the AFE‐to‐ferroelectric switching barrier for 1. This pioneering work on the photo‐assisting transformation of ferroic orders paves a new way to develop future photoactive materials with significant potential applications.

Rational Design of A-Site Cation for High Performance Lead-Free Perovskite X-Ray Detectors.

Design of hypotoxic lead-free perovskites, e.g. Bismuth(Bi)-based perovskites, is much beneficial for commercialization of perovskite X-ray detectors due to their strong radiation absorption. Nevertheless, the design principles governing the selection of A-site cations for achieving high-performance X-ray detectors remain elusive. Here, seven molecules (methylamine MA, amine NH3, dimethylbiguanide DGA, phenylethylamine PEA, 4-fluorophenethylamine p-FPEA, 1,3-propanediamine PDA, and 1,4-butanediamine BDA) and calculated their dipole moments and interaction strength with metal halide (BiI3) are selected. The first-principles calculations and related spectroscopy measurements confirm that organic molecules (DGA) with large dipole moments can have strong interactions with perovskite octahedron and improve the carrier transport between the organic and inorganic clusters. Consequently, zero-dimensional single crystal (SC) (DGA)BiI5∙H2O is synthesized. The (DGA)BiI5∙H2O SCs demonstrate an exceptional carrier mobility-lifetime product of 6.55×10-3cm2V-1, resulting in the high sensitivity of 5879.4µCGyair -1cm-2, featuring a low detection limit (4.7nGyairs-1) and remarkable X-ray irradiation stability even after 100 days of aging at a high electric field (100Vmm-1). Furthermore, the (DGA)BiI5∙H2O SCs for imaging, achieving a notable spatial resolution of 5.5lpmm-1 are applied. This investigation establishes a pathway for systematically screening A-site cations to design low-dimensional SCs for high-performance X-ray detection.

Multi-scale structural design of multilayer magnetic composite materials for ultra-wideband microwave absorption

Broadband microwave absorbing (MA) materials have important applications in reducing electromagnetic radiation pollution and realizing low scattering characteristics. However, current MA materials with single-layer structure generally cannot meet this requirement due to the difficulty in achieving good impedance matching. Here, we design a multilayer-structured MA material, which consists of a wave transmitting layer, a carbon-magnetic material composite absorbing layer, a strong magnetic absorbing layer and a reflector layer. Hollow Co/CoFe@C composite particles prepared using CoCoPBA as templates are used as fillers to design carbon-magnetic material composite absorbing layer. The Co/CoFe bimagnetic phases enhance permeability while the hollow structure optimizes permittivity, which endows this absorbing layer with strong microwave absorption ability with a reflection loss of -47.18 dB. The introduction of a strong magnetic absorbing layer that combines FeSiAl with high permeability and SmFeB with high coercivity further significantly improves the overall impedance matching of the material. Benefitting from the multi-scale structural design, the obtained multilayer MA material achieves strong microwave absorption in both low and high frequency ranges, and the effective absorption bandwidth reaches 12.85 GHz, far superior to the traditional single-layer MA material.

Machine Learning Phenotyping and GWAS Reveal Genetic Basis of Cd Tolerance and Absorption in Jute

Cadmium (Cd) is a dangerous environmental contaminant. Jute (Corchorus sp.) is an important natural fiber crop with strong absorption and excellent adaptability to metal-stressed environments, used in the phytoextraction of heavy metals. Understanding the genetic and molecular mechanisms underlying Cd tolerance and accumulation in plants is essential for efficient phytoremediation strategies and breeding novel Cd-tolerant cultivars. Here, machine learning (ML) and hyperspectral imaging (HSI) combining genome-wide association studies (GWAS) and RNA-seq reveal the genetic basis of Cd resistance and absorption in jute. ML needs a small number of plant phenotypes for training and can complete the plant phenotyping of large-scale populations with efficiency and accuracy greater than 90%. In particular, a candidate gene for Cd resistance (COS02g_02406) and a candidate gene (COS06g_03984) associated with Cd absorption are identified in isoflavonoid biosynthesis and ethylene response signaling pathways. COS02g_02406 may enable plants to cope with metal stress by regulating isoflavonoid biosynthesis involved in antioxidant defense and metal chelation. COS06g_03984 promotes the binding of Cd2+ to ETR/ERS, resulting in Cd absorption and tolerance. The results confirm the feasibility of high-throughput phenotyping for studying plant Cd tolerance by combining HSI and ML approaches, facilitating future molecular breeding.

The effect of conduction loss on microwave absorption performance of Fe-doped NiCo2O4 spinel oxide

Strong absorption and large bandwidth are two contributors to material’s electromagnetic wave absorbing performance. While spinel ferrite materials have garnered extensive attention in the realm of microwave absorption, their relatively low conductivity remains a practical challenge.In this work, NiCo2-xFexO4 (x = 0, 0.04, 0.06 and 0.08) precursor was prepared by hydrothermal and after-sintered method. It was found that Fe doping exhibit excellent EM absorption properties. Specially, when the Fe content is 0.08, the maximum reflection loss -48.90 dB at 15.40 GHz and the maximum effective bandwidth 4.20 GHz are achieved. More importantly, the absorption frequency can be broadened from Ku to C band even to S band with proper adjusting Fe content. Doping with Fe enhances conduction loss and make a significant contribution to dielectric loss, as a result, the impedance matching degree of the Fe-NiCo2O4 composite is influenced by the synergistic effect of its dielectric and magnetic properties. This work provides a simple way for enhancing the microwave absorption capabilities of ferrite materials and provides insight into understanding conduction loss in microwave absorption.

Infrared optical properties of SiGeSn and GeSn layers grown by molecular beam epitaxy

The infrared optical properties of thick GeSn films (&amp;gt;500 nm) having 10% Sn concentration and of SiGeSn layers, utilized for the growth of strain-relieved, direct-gap GeSn films by molecular beam epitaxy, are investigated. Two growth methods are used: a graded-growth structure and a stepped-growth structure that help us to illustrate the properties of the GeSn and SiGeSn layers. Interestingly, there can be strong absorption in SiGeSn films throughout the infrared. We observe an increase in infrared absorption with increasing Sn concentration up to 21% Sn and in films, where the Sn is held constant at 18%, with increasing Si concentration up to 30%. Cavity effects in the infrared transmission measurement of stepped-growth structures are observed and associated with reflections at growth interfaces. Si–Si bond formation is proposed to occur at high Si concentrations in SiGeSn films, and the bandgap in SiGeSn films appears to decrease with increasing Si and Sn concentrations.

Interlayer engineered bilayered V₂O₅ NPs as saturable absorbers for infrared ultrashort pulse generation

Interlayer engineering offers a promising approach to modifying the structure of layered vanadium-based oxides, enhancing their saturable absorption effect and making them a desirable choice for developing infrared wavelength-range photonics devices. This experimental work synthesizes interlayer vanadium pentoxide (V2O5) using hydrothermal techniques to produce an excellent saturable absorber (SA). The interlayer engineering strategy enhances strong saturable absorption and self-defocusing effects in V2O5-based SA, enabling the generation of ultrashort pulses in the infrared region. Their superior nonlinear optical characteristics are demonstrated by a modulation depth of 13.9 % and saturation intensity of 0.42 GW cm−1, respectively. By utilizing a transmission coupling fiber-based V2O5-SA inside an Er-doped fiber laser cavity, a passively Q-switched (PQS) laser with a narrow pulse width of 2.78 μs and signal-to-noise ratio (SNR) ∼50 dB is realized for the first time. Furthermore, we explore a V2O5 NPs-SA long-term stability and high damage threshold. The results not only offer additional proof of the capable potential of interlayer V2O5 as a photo-bleaching absorber for realizing pulsed lasers in the NIR band but also cover the method for advancing their probable applications in optoelectronic devices.

Impact of Pd2+ and Sn4+ co-doping ZnO nanoflakes toward high-performing Schottky diode based on the generation of intermediate bands within the energy gap

Pd:Sn/ZnO nanohybrid was prepared by chemical co-precipitation route and identified using XRD, EDX, SEM, and TEM techniques. The microstructure analysis emphasized the polycrystalline nature in which Pd and Sn ions were substituted inside ZnO framework to form the nanocomposite. The surface morphology was appeared in 2D nanoflakes with large specific surface area. The optical parameters including Eg, n, and k were deduced from T% and R% spectra through wavelength range 300–1400 nm. The thin film showed strong optical absorption inside the UV region with a value of Eg = 3.10 eV. The Ag/Pd:Sn/ZnO/p-Si/Al Schottky diode was fabricated by thermal evaporation technique, and its electronic and photodetector properties were investigated from I–V and C–V measurements. The fabricated device exhibited non-ideal behavior with high rectification ratio RR = 935 and a relatively small Rs lies between 2365 and 2755 Ω. Under illumination impacts, the photodiode exhibited high photosensitivity and responsivity attributed to the large photo-induced charge carriers.

Ultrasonic spray synthesis, photoelectric properties and photovoltaic performances of chalcogenide CaSnS3

Chalcogenide perovskites are promising lead-free, stable absorber materials for solar cells. This work reports the synthesis of orthorhombic phase pure CaSnS3 thin films by facile low temperature sulfurization of solution-processed CaSnO3 oxide precursors. Structural characterization confirms complete anion exchange to produce crystalline CaSnS3 films with vertically aligned rod-like grains. Optical studies show strong visible light absorption with direct bandgap of 1.72 eV, ideal for photovoltaics. Electrical measurements indicate p-type conductivity with hole concentration of 1.2×1017 cm-3 and mobility around 8 cm2V-1s-1 at room temperature. First-principles DFT calculations corroborate the p-type electronic structure. Prototype CaSnS3 solar cells are fabricated with TiO2 electrode, demonstrating power conversion efficiency of 2.5% under AM1.5G, open-circuit voltage of 0.55 V, short circuit current density of 11.5 mA/cm2 and fill factor of 0.62. The cells also exhibit remarkable ambient shelf stability over 6 months. The comprehensive results validate the photovoltaic potential of these earth abundant, sustainable chalcogenide perovskites synthesized via scalable low-cost solution methods. Further interface engineering can enable enhanced efficiencies.