Wavelength Shift Research Articles

Thermo-Optoplasmonic Single-Molecule Sensing on Optical Microcavities.

Whispering-gallery-mode (WGM) resonators are powerful instruments for single-molecule sensing in biological and biochemical investigations. WGM sensors leveraged by plasmonic nanostructures, known as optoplasmonic sensors, provide sensitivity down to single atomic ions. In this article, we describe that the response of optoplasmonic sensors upon the attachment of single protein molecules strongly depends on the intensity of WGM. At low intensity, protein binding causes red shifts of WGM resonance wavelengths, known as the reactive sensing mechanism. By contrast, blue shifts are obtained at high intensities, which we explain as thermo-optoplasmonic (TOP) sensing, where molecules transform absorbed WGM radiation into heat. To support our conclusions, we experimentally investigated seven molecules and complexes; we observed blue shifts for dye molecules, amino acids, and anomalous absorption of enzymes in the near-infrared spectral region. As an example of an application, we propose a physical model of TOP sensing that can be used for the development of single-molecule absorption spectrometers.

Characterization of Fiber Bragg Grating Accelerometer for Underwater Vibration Detection

In this paper, the results of the characterization of a Fiber Bragg Grating (FBG) Accelerometer for detecting vibrations underwater are reported. The FBG Accelerometer, consisting of three FBGs, is utilized to detect underwater vibrations in three-dimensional directions. A water pump, with positions varied from 0 to 10 cm, is employed as the vibration source. Furthermore, the experimental results are presented in the form of the peak wavelength shift reflected by the FBG (ΔλB) and frequency. From the experiment results, it is shown that with increasing distance, ΔλB decreases linearly with successive gradients of 0.0058 nm/cm; 0.0059 nm/cm; and 0.0045 nm/cm. for FBG X, Y, and Z. It is also shown that with increasing distance, there is a decrease in frequency from 50 Hz for FBGs X, Y, and Z to 39 Hz; 38 Hz; and 40 Hz for FBGs X, Y, and Z respectively.

Wide-Range and Multistate Work Functions of Organometallic Halide Perovskite Films Regulated by Ferroelectric Substrates.

Work function of organometallic halide perovskite (OHP) films is one of the most crucial photoelectric properties, which dominates the carrier dynamics in OHP-based devices. Despite surface treatments by additives being widely used to promote crystallization and passivate defects in OHP films, these chemical strategies for modulation of work functions face two trade-offs: homogeneity on the surface versus along the thickness; the range versus the accuracy of modulation. Herein, by using ferroelectric substrates of uniform polarization and subnanometer roughness, homogeneous CH3NH3PbI3 films are fabricated with five states of work functions with large spanning (∼0.8 eV) and high precision (sd ∼ 0.01 eV). We reveal that the ferroelectric polarizations and the smooth surfaces regulate CH3NH3+ orientations and suppress distortions of PbI6 octahedrons. The wide-range and multistate work functions originate from the ordered CH3NH3+ orientations and PbI6 octahedrons, which result in intensity enhancements and wavelength shifts in photoluminescence with a 30-fold increase of photoexcited carrier lifetime.

Two dimensional alkaline earth metal sensors (2D-AEMS) of fluorescent strontium sulfide nanosheets for neurotransmitter drug detection via photo induced electron transfer (PIET)

A new sensing platform has been introduced that provides a powerful solution for fluorescence-based biosensors using photoluminescent nanosheets (NS) using the novel two dimensional alkaline earth metal sensors (2D-AEMS). We have synthesized two-dimensional (2D) fluorescent strontium sulfide (SrS) NS using deep eutectic solvent (DES) as green solvent media by a hydrothermal method. The resulting product of 2D SrS NS to enhance the fluorescence intensity was achieved successfully followed by probe ultrasonication. The optical properties of SrS NS were studied by UV–visible and photoluminescence (PL) spectroscopy. The 2D SrS NS showed a blueish-green fluorescence optimized at λex320 nm/λem390 nm and a quantum yield of 38.6% was calculated. Under optimal conditions, the fluorescent SrS NS effectively detected noradrenaline (NA) by PIET-based fluorescence quenching and wavelength shifts were observed. Our proposed 2D-AEMS of 2D SrS NS fluorescence intensity was quenched in a wide linear range from 1 to 300 µM, with a limit of detection (LOD = 3*3SD/S) of 0.047 µM. The 2D-AEMS (fluorescent SrS NS) was applied to the determination of NA in human urine samples, with good recovery ranging from 98.7-100.08%. Also, the SrS NS fluorescence quenching mechanism in the detection of NA was investigated by zeta potential analysis, UV analysis, and dynamic light scattering (DLS). Our proposed 2D SrS NS fluorescence nanomaterials stand as an innovative platform for generating fluorescence sensors, with extensive potential applications in medical, biological, and life science fields, designed to replace traditional dye fluorescence in the near future.

Optical Anapole Modes of the Hybrid Ring-Disk Nanoantenna for Electric Field Enhancement

A promising design combining low loss, high refractive index dielectric materials with metal nanoparticles, and local plasma resonance is described for ring-disk nanoantenna. A hybrid Au ring Si disk structure with chain gaps is constructed and the distributions of the electric field and near-field enhancement of the electric fields are analyzed by numerical simulation utilizing the multipole decomposition method. The electric field strength can be enhanced efficiently using metals to improve the anapole mode response of dielectric materials with large refractive indexes. Additional enhancement of the electric field is achieved by opening the chain gap to create high-intensity hot spots inside the disk. The chain comprises 14 normal octahedrons and a few tips are created by intersecting octahedrons. The electric field is greatly enhanced at the tips where there are high-intensity hot spots. The effectiveness of this structure as a refractive index sensor is assessed. The scattering cross-section (SCS) and wavelength shifts result in a maximum sensitivity of 210[Formula: see text]nm/RIU. The results validate the design concept and the hybrid structure boasting large electric field enhancement and excellent optical sensing properties have large potential in nonlinear photonics.

Estimation of Li-ion battery SOH based on factors combination of FBG wavelength shift and charge-discharge process

For the purpose of daily battery maintenance, safety forecasting, and energy ladder use, it is crucial to accurately estimate the state of health (SOH) of Li-ion batteries. The external fiber Bragg grating (FBG) sensor is used in this work to collect the signal fluctuations of the wavelength shift in different areas during the Li-ion battery's charge-discharge cycle using a combination of feature analysis and data-driven method, and the characteristics of the wavelength shift and the charge- discharge process in different regions under 125 cycles are statistically analyzed. The reaction degree of Li-ion battery in different areas was compared by wavelength shift value. The wavelength shift factor and charge-discharge process factor related to battery SOH were extracted and trained in the NGO-BP regression model. The experimental results show that the combination of fiber Bragg grating wavelength shift factor and charge-discharge process factor can accurately estimate the SOH of Li-ion battery, and the prediction effect of three areas combination is the best, the goodness of fit R2 is 0.99958, the mean square error MSE is 2.71 × 10−4, the mean absolute error MAE is 1.3373 × 10−2, the root mean square error RMSE is 1.6462 × 10−2, and the mean absolute percentage error MAPE is 1.3679 × 10−2%.The combination of negative electrode and middle area uses fewer sensors to obtain higher prediction accuracy, and its cost performance is the highest. The utilization of fiber Bragg grating wavelength shift factor and charge-discharge process factor has essentially led to the accurate calculation of Li-ion battery SOH, which holds significance for battery health monitoring as well as the design and development of battery management systems.

Electrical field-induced Fano resonance tunability in photonic crystal slabs

The creation of tunable Fano resonances in a photonic crystal structure with a side-coupled nanocavity and a waveguide with a partially transmitting element is investigated in this paper. In the proposed structure, the nanocavity’s central hole is made up of two cylinders with different radii that are nested inside each other. The outer and inner cylinders are made of quartz and liquid crystal, respectively. The performance of this device is analyzed using the three-dimensional finite-difference time-domain. The transmission spectrum, resonance wavelength, and quality factor of the proposed structure are calculated for various applied voltages. It is demonstrated that as the applied voltage increases, the quality factor changes and the Fano resonance wavelength shifts. Based on the findings, a tuning range of 5.2 nm is achievable with an excellent transmission contrast within this range. The presented structure is appropriate for applications such as tunable switches and filters.

"Core-Shell" Wave Function Modulation in Organic Narrowband Emitters.

Efficient red-green-blue primary luminescence with an extraordinarily narrow band and durability is crucial for advanced display applications. Recently, the emergence of multiple-resonance (MR) from short-range atomic interactions has been shown to induce extremely narrow spectral widths in pure organic emitters. However, achieving wide-range color tuning without compromising color purity remains a persistent challenge for MR emitters. Herein, the concept of electronic donor/acceptor "core-shell" modulation is proposed within a boron/nitrogen (B/N) MR skeleton, enabling the rational utilization of intramolecular charge transfer to facilitate wavelength shift. The dense B atoms localized at the center of the molecule effectively compress the electron density and stabilize the lowest unoccupied molecular orbital wave function. This electron-withdrawing core is embedded with peripheral electron-donating atoms. Consequently, doping a single B atom into a deep-blue MR framework led to a profound bathochromic shift from 447 to 624 nm (∼0.8 eV) while maintaining a narrow spectral width of 0.10 eV in this pure-red emitter. Notably, organic light-emitting diodes assisted by thermally activated delayed fluorescence molecules achieved superb electroluminescent stability, with an LT99 (99% of the initial luminance) exceeding 400 h at an initial luminance of 1000 cd m-2, approaching commercial-level performance without the assistance of phosphors.

Size-dependent optoelectronic characteristics of InGaN/GaN red micro-LEDs on 4-inch Si substrates: high pixel density arrays demonstration.

In this study, we explored the size-dependent optoelectronic characteristics of InGaN/GaN red micro-LEDs grown on Si substrates. We successfully demonstrated the fabrication of 4-inch wafer-scale InGaN/GaN micro-LEDs, showcasing the feasibility of large-scale production. Additionally, we presented the binary pixel display with 6 µm pitch, achieving a resolution of 4232 PPI. We also introduced a method of driving the display using PWM to linearly control and counteract the blue shift in peak wavelength caused by the QCSE and band-filling effect. Our research represents a significant milestone in the development of InGaN/GaN red micro-LEDs on Si substrates, establishing them as a key component for full-color micro-LED displays.

Unveiling the Multifaceted Nature of 4‐(4‐Methylphenyl Thio)benzophenone: Electronic Structure and Excited States in Gas Phase and Solvents

AbstractBenzophenone and its derivatives are widely used as UV filters and UV‐ink photoinitiators. The photoinitiating properties of benzophenones depend on their degree of conjugation and delocalization within the molecule. By understanding how conjugation, delocalization, and different substituents affect these properties, benzophenone derivatives can be customized for specific applications. Using quantum mechanical calculations based on B3LYP/6‐311++G(d, p) density functional theory (DFT), chemical reactivity, stability, and photoinitiating capabilities of 4‐(4‐methylphenylthio)benzophenone are analyzed. This includes studying its physical and chemical properties in the gas phase, as well as its excited state electronic transitions, vibrational characteristics, and spectroscopic properties both in gas phase and in various solvents. The DFT‐computed infrared spectra match experimental results. The UV/Visible spectra shows absorption towards longer wavelengths due to extended delocalization of π‐electrons. In different solvents with varying polarity, the absorption spectra exhibit high‐intensity peaks, shift in excitation energy and wavelengths based on the polarity of the solvent. This knowledge allows for the development of novel initiators with customized light absorption, excited state lifetimes, and reaction selectivities, which can enhance processes like UV‐curing, photopolymerization, and other light‐driven reactions.

Dimethyl Dihydrophenazine: A Highly Conjugated Auxochrome in Fluorophores to Improve Photostability, Red-Shift Wavelength, and Enlarge Stokes Shift.

5,10-Dimethyl-5,10-dihydrophenazine (MP) is utilized as an effective auxochrome, leveraging its highly conjugated structure to enhance the photophysical and photochemical properties of fluorophores. As illustrated in the difluoride-boron complex and coumarin fluorophores, the extensive conjugation of MP auxochrome substantially red-shifts the absorption/emission wavelengths and increases Stokes shift due to the intensified intramolecular charge transfer effect; notably, MP auxochrome effectively improves fluorophores' photostability by mitigating photooxidative reactions through enhanced electron density delocalization on nitrogen atoms and increased ionization potential. Importantly, MP-based fluorophores demonstrate applicability in stimulated emission depletion nanomicroscopy, showcasing their utility in lipid droplet labeling.

Harnessing chromatic dispersion for blood cancer detection using photonic crystal fibre sensors

Photonic crystal fibres (PCFs) offer precise control over light propagation, making them promising for sensitive bio-sensing applications. This paper proposes a novel PCF sensor for blood cancer detection, leveraging chromatic dispersion as a key sensing mechanism. Our sensor integrates hemoglobin into a 2D PCF structure, enabling the detection of subtle refractive index changes associated with cancer cells. Numerical simulations reveal significant shifts in the zero-dispersion wavelength and slope variations in the dispersion curves when analyzing blood samples with increasing hemoglobin concentrations, exceeding 80%. This distinct behaviour, absent in healthy samples, demonstrates the potential of dispersion-based sensing for cancer diagnosis. The sensor exhibits a sensitivity of 0.0091249, indicating its capability to detect subtle changes in dispersion properties, exceeding the sensitivity of conventional refractive index-based methods. This work highlights the innovative use of chromatic dispersion in PCF sensors, paving the way for early and accurate blood cancer detection and potentially leading to improved treatment outcomes.

A Near-Infrared Fluorescent Dye with Tunable Emission Wavelength and Stokes Shift as a High-Sensitivity Cysteine Nanoprobe for Monitoring Ischemic Stroke.

Sulfur-substituted dicyanomethylene-4H-chromene (DCM) derivatives based on the intramolecular charge transfer (ICT) mechanism were designed as near-infrared (NIR) fluorescent dyes. Using the Knoevenagel condensation method, the S-DCM-OH(835) fluorescence dye was synthesized, which had an emission wavelength exceeding 800 nm and 220 nm of a Stokes shift. Compared to commercial ICG, S-DCM-OH(835) was not only synchronized in emission wavelength but also far superior in Stokes shifts. These advantages made the design of S-DCM-NIR(835) based on this dye potentially valuable for biological applications. Based on this chemical structure, a fluorescent S-DCM-NIR(835) nanoprobe with a mean diameter of 17.69 nm was fabricated as the NIR imaging nanoprobe. Results showed that the nanoprobe maintained the high-specificity identification of cysteine (Cys) via the Michael addition reaction, with the detection limitation of 0.11 μM endogenous Cys. More importantly, in an ischemic stroke mouse model, the S-DCM-NIR(835) nanoprobe could monitor the Cys concentration change at stroke lesion due to the disruption of Cys metabolism under the ischemic stroke condition. Such a S-DCM-NIR(835) nanoprobe could not only differentiate the severity of the ischemic stroke using response time but also quantify the concentration of Cys in real-time in vivo.

High-performance optical fiber differential urea sensing system for trace urea concentration detection with enhanced sensitivity using liquid crystals

A compact optical fiber differential sensing system consisting of microfiber interferometer (MFI) functionalized urease combined with stearic acid (SA)-doped 4-cyano-4′-pentylbiphenyl (5CB) and two fiber Bragg gratings (FBGs) for urea detection has been proposed and experimentally demonstrated. The SA-doped 5CB plays an important role of sensing signal amplification in urease specific recognition of urea. The hydrolysis reaction between urea and urease at the microfiber surface causes the deprotonation and self-assembly of SA, which further induces the reorientation of 5CB from planar alignment to homeotropic alignment. This process can be captured and transduced into the macroscopic wavelength shift of the MFI and power difference of two FBGs in the differential sensing system. The experimental results show that the differential sensing system can effectively detect urea in artificial urine, where the sensitivity of MFI is 3.85 nm/mM with a detection limit of 0.03 mM and the power difference sensitivity of two FBGs is 15.05 dB/mM with a detection limit of 0.01 mM within low concentration range of 0.01–0.1 mM. Furthermore, the differential sensing system has good selectivity, affordability, and temperature self-compensation. Therefore, the differential sensing system can be used as a sensitive method for urea detection and has potential applications in human health detection.

DPPM-Bridged Binuclear Pt(II) Pincer Complexes: Chemistry, Structure, and Photophysics in Solution Revisited.

A series of luminescent binuclear ([dppm{Pt(NNC)}2]2+) and mononuclear ([PPh3Pt(NNC)]+) complexes containing pincer ligands were synthesized and characterized. Photophysical characteristics of both types of complexes were studied in dichloromethane solution. In the solid phase, the binuclear compounds adopt a syn configuration where the {Pt(NNC)} fragments are held together due to intramolecular Pt-Pt bonding and π-stacking of the pincer ligand aromatic systems. Analysis of the complexes' molecular structure in solution by multinuclear NMR spectroscopy showed that the stacked intramolecular configuration is retained in fluid media, which is in complete agreement with a considerable red shift of the emission wavelength due to formation of the intramolecular Pt-Pt bond, leading to the transformation of an emissive excited state to 3MMLCT. It was also found that triethylamine quenches the emission of both types of complexes; the mechanism of quenching is a combination of dynamic and static channels of excited-state deactivation. In the case of binuclear complexes, deprotonation of the dppm methylene bridge by triethylamine also contributes to the chromophore quenching. To explain the observed chemistry of binuclear complex interactions with Et3N, a chemical equilibrium scheme was suggested, which was confirmed by quantitative monitoring of the 31P signal variations as a function of triethylamine concentration.

Multimode interference methane sensor based on a ZIF-8/PDMS composite film.

A multimode interference methane sensor based on a ZIF-8/PDMS composite film is proposed. The sensing principle is that the refractive index of the ZIF-8/PDMS composite film changes when it adsorbs methane, leading to a measurable optical path difference during the coupling of the cladding higher-order modes and the fundamental mode in the multimode interference fiber (MMI). The environmental methane concentration is then detectable by detecting the wavelength shifts of the interference peaks in the resulted spectrum. Through simulations and experiments aimed at enhancing sensor sensitivity, we optimized three parameters within the sensor structure: the length of the Tapered Single-Mode Fiber (TSMF), the composite film thickness, and the TSMF taper diameter. The experimental results indicate that the sensor's sensitivity reaches a maximum of 0.231 nm%-1. Additionally, the sensor exhibits excellent structural stability and measurement repeatability. The response time is as short as 40 s, and the recovery time ranges between 3 and 5 min. The proposed multimode interferometric methane sensor based on the ZIF-8/PDMS composite film has great potential to support highly sensitive methane concentration detection in many applications.

Anti-crosstalk fiber-optic directional torsion sensor via intensity-modulated Lyot filter

In this paper, a fiber-optic directional torsion sensor based on the intensity modulated Lyot filter is completed to alleviate the crosstalk from ambient temperature and axial strain. The transmission is analyzed and compared with the varied twisted length. The experimental results show that the torsion response of 1.18 dB/° can be achieved by the 45° incident angle and 10-cm twisted length, with tiny wavelength shift (∼0.012 nm/°) and minimum range of π-phase jumping. Meanwhile, the crosstalk is well compressed within 0.006°/με and 0.23°/°C owing to ultralow axial-strain and temperature responses. In addition, an in-field test is performed electrically and the detection limit of 0.08° is witnessed experimentally.

Formaldehyde sensor design: Integrating fiber bundle and concave mirror techniques

This study successfully demonstrates the detection of formaldehyde concentration using a fiber bundle with a concave mirror as a reflector. The setup employs an Optical Stimulated Luminescence (OSL) light source connected to the fiber bundle. Light transmitted through the fiber interacts with the formaldehyde solution sample, reflects off the concave mirror, and is received by the collecting fiber before being analyzed by a spectrometer. The experimental results indicate that the detected light intensity decreases linearly with increasing formaldehyde concentration, without any wavelength shift. This suggests that while the absorption properties of formaldehyde remain constant, the quantity of absorbed light increases proportionally with concentration. The sensor design exhibits excellent sensitivity, linearity, and stability, achieving a sensitivity range of 0%–6% at 5004.62 counts/% with a linearity of 97% and a resolution of 0.037%.

Xác định acetamiprid bằng phương pháp quang học sử dụng dung dịch nano vàng được ổn định bằng Polydiallyldimethylammoni clorua

On this research, the development of a simple, cost-efective and highly sensitive spectrophotometric method for acetamiprid detection based on the localized surface plasmon resonance of polydiallyldimethylammonium chloridestabilized gold nanoparticles. By naked eyes, one can detect acetamiprid by the visual change of gold solution color from red to purple, corresponding to the shift of maximum absorbance wavelength in the UV-Vis spectrum. Quantification of acetamiprid is possible through a linear relationship between the maximum absorbance wavelength and the acetamiprid concentrations in the range of 8×10-8 -2×10-6 M. Under the optimum conditions including pH 5, NaCl concentration of 0.02 M and incubation time 20 min, the present method has high precision (RSD < 5%), very low limit of detection (LOD) of 2.7×10-8 M, limit of quantification (LOQ) of 8.2×10-8 M. This method has been successfully applied to determine acetamiprid in several pesticide samples and vegetable samples. The measurement results of acetamiprid in the pesticide samples of the research method with the HPLC-UV method showed a difference of < 2%, while for the vegetable sample, the difference between the research method and the LC-MS/method method/ MS < 5% shows that the method has high accuracy and reliability.

38‐1: Invited Paper: Micro Light‐Emitting Diode Pixel Circuit and Driving Method Considering Wavelength Shift

We proposed micro light‐emitting diode (μLED) pixel circuits and driving methods. Because the wavelength shift of μLEDs occurs as the current density is varied, we designed pixel circuits based on pulse width modulation (PWM), hybrid PWM and pulse amplitude modulation (PAM), and quaternary digital driving.