Long-wavelength Peak Research Articles

Phage-modified dual-peak long-period fiber grating biosensor for ultrasensitive, rapid and specific detection of pathogen strains

Herein, we present an ultrasensitive, rapid and specific phage-modified dual-peak long-period fiber grating (Phage-DP-LPFG) biosensor for detecting foodborne pathogens. Compared to the single-peak resonance LPFG with a grating period of 360 μm, the DP-LPFG with a grating period of 163 μm offers enhanced sensitivity to refractive index changes caused by bacterial adsorption. By directionally immobilising phages on the DP-LPFG, the sensor achieves high specificity for target bacterial strains. Upon capturing the target strain, the short-wavelength near-infrared transmission loss peak undergoes a blue shift, whereas the long-wavelength transmission loss peak exhibits a red shift. The shift in spacing between the two peaks (Δλ) increases with higher bacterial capture, enabling the quantification of target strains based on Δλ changes. Using Escherichia coli O157:H7 (E. coli O157:H7) as a model, the Phage-DP-LPFG biosensor demonstrates a linear detection range of 25–108 CFU/mL with a low limit of detection of 8 CFU/mL in 10 min under optimal conditions. The biosensor was also tested on food samples such as fish and milk, showing no notable differences from standard methods but with reduced detection time. It was further extended to the detection of another foodborne pathogen strain Hafnia paralvei (MCCC 1K06097) (H. paralvei (MCCC 1K06097)) with satisfactory results. This study offers a novel approach for the rapid, sensitive and specific detection of trace pathogenic strains in foods.

Sandwich Layer-Modified Ω-Shaped Fiber-Optic LSPR Enables the Development of an Aptasensor for a Cytosensing-Photothermal Therapy Circuit.

The metastasis of cancer cells is a principal cause of morbidity and mortality in cancer. The combination of a cytosensor and photothermal therapy (PTT) cannot completely eliminate cancer cells at one time. Hence, this study aimed to design a localized surface plasmonic resonance (LSPR)-based aptasensor for a circuit of cytosensing-PTT (COCP). This was achieved by coating a novel sandwich layer of polydopamine/gold nanoparticles/polydopamine (PDA/AuNPs/PDA) around the Ω-shaped fiber-optic (Ω-FO). The short-wavelength peak of the sandwich layer with strong resonance exhibited a high refractive index sensitivity (RIS). The modification with the T-shaped aptamer endowed FO-LSPR with unique characteristics of time-dependent sensitivity enhancement behavior for a sensitive cytosensor with the lowest limit of detection (LOD) of 13 cells/mL. The long-wavelength resonance peak in the sandwich layer appears in the near-infrared region. Hence, the rate of increased localized temperature of FO-LSPR was 160 and 30-fold higher than that of the bare and PDA-coated FO, indicating strong photothermal conversion efficiency. After considering the localized temperature distribution around the FO under the flow environment, the FO-LSPR-enabled aptasensor killed 77.6% of cancer cells in simulated blood circulation after five cycles of COCP. The FO-LSPR-enabled aptasensor improved the efficiency of the cytosensor and PTT to effectively kill cancer cells, showing significant potential for application in inhibiting cancer metastasis.

3D printed self-calibrating on-site sensing platform based on bimodal excitation carbon dots for visual 4-nitrophenol detection by means of the localization of inner filter effect and pH regulation

For facile and rapid detection of 4-nitrophenol (4-NP), we synthesize nitrogen-doped carbon dots (N-CDs) through microwave radiation treatment using melamine and o-phenylenediamine as precursors. We employed N-CDs as an ingenious ratiometric fluorescence sensor via a novel bimodal excitation behavior. As the concentration of N-CDs increases, the broad excitation peak splits into two excitation peaks. The blue-shift phenomenon appears at the short-wavelength excitation peak, while the long-wavelength excitation peak presents the red-shift. Consequently, 4-NP can be sensitively detected by N-CDs owing to the localization of inner filter effect (L-IFE) with the detection limit of 83 nM ranging from 0.083 to 80 µM. Moreover, a self-calibrating on-site sensing platform constructed by 3D printing technique realizes the visual 4-NP detection in actual samples based on bimodal excitation behavior and RGB analysis. Our work not only presents a novel perspective for visual 4-NP sensing, but also renders the integration of 3D printing technology and the CDs industry.

Photoluminescence Redistribution of InGaN Nanowires Induced by Plasmonic Silver Nanoparticles

Hybrid nanostructures based on InGaN nanowires with decorated plasmonic silver nanoparticles are investigated in the present study. It is shown that plasmonic nanoparticles induce the redistribution of room temperature photoluminescence between short-wavelength and long-wavelength peaks of InGaN nanowires. It is defined that short-wavelength maxima decreased by 20%, whereas the long-wavelength maxima increased by 19%. We attribute this phenomenon to the energy transfer and enhancement between the coalesced part of the NWs with 10-13% In content and the tips above with an In content of about 20-23%. A proposed Fröhlich resonance model for silver NPs surrounded by a medium with refractive index of 2.45 and spread 0.1 explains the enhancement effect, whereas the decreasing of the short-wavelength peak is associated with the diffusion of charge carriers between the coalesced part of the NWs and the tips above.

A disaggregation-induced emission strategy to obtain dual-emission fluorescence-enhanced probe for visualization of SO2 fluctuation in living cells, tumor tissue and zebrafish

The emergence of disaggregation-induced emission (DIE) probes has provided new insights into the traditional aggregation-caused quenching (ACQ) dyes. However, establishing and achieving promising DIE platforms for biomedical imaging is still a major challenge. In this study, for the first time, we designed a novel DIE platform based on highly planar chromenoquinoline derivatives to obtain dual-emission enhanced SO2 probe. Highly planarized chromenoquinoline derivatives with strong π-π stacking interactions are extremely prone to aggregation, resulting in partial fluorescence quenching. Interestingly, the addition of SO2 to probe DEE-1 caused partial disaggregation of chromenoquinoline derivatives, which evoked the dual-emission enhancement derived from disaggregation-induced emission in the long-wavelength region (λem = 625 nm, 5-fold) and SO2 addition peak in the short-wavelength region (λem = 510 nm, 15-fold). Significantly, these unique probes DEE-1 and DEE-2 were successfully employed for dual-channel imaging of the SO2 fluctuation in living cells, tumor tissue and zebrafish, highlighting the great potential of disaggregation-induced emission strategy. Thus, this work not only provide a dual-emission fluorescence-enhanced tool to investigate and study the signal molecules (SO2), but also deliver clues for the development of more potential probes for other analytes based on the DIE mechanism.

Effect of microstructure-scale features on lignin fluorescence for preparation of high fluorescence efficiency lignin-based nanomaterials

As a natural fluorescent material, the practical application of lignin fluorescence was hindered due to the low fluorescence quantum yield (QY). Inspired by its aggregation fluorescence behavior, the effect of microstructure-scale on lignin fluorescence was studied from two levels, the molecular weight and colloidal sphere. It was demonstrated that with the decrease of lignin microstructure-scale, the non-radiative dissipation and reabsorption effect of lignin fluorescence would be weak, resulting in high emission efficiency. On this basis, hydrogenolysis was used to obtain small molecular fragments and reduce content of reabsorbing groups of lignin, of which the QY was greatly increased by 35 times to about 12%. In addition, the emission peak of lignin was the fluorescence addition of its main structural units. The long-wavelength emission peak was often the illusion from the reabsorption effect but not duo to the formation of conjugated structure. This work provided a potential method for the preparation of high QY lignin and an in-depth understanding of lignin fluorescence.

Unique Property of Nontraditional Intrinsic Luminescence in the Transforming of Solution‐Hydrogel‐Solid and Its Applications

AbstractFor the unusual phenomenon of nontraditional intrinsic luminescence, a systematic fluorescence study is conducted in the phase transformation from solution through hydrogel to solid states. In this process, significant differences are found in fluorescence intensity, peak position, lifetime, and excitation‐dependent emission. In particular, the samples in the hydrogel state show two fluorescent peaks at 480 and 516 nm, respectively, while only one fluorescent peak is detected in the cases of solution (at 516 nm) or solid (at around 450 nm). More interestingly, the longer wavelength peak presents excitation‐dependent fluorescence, and the shorter one is excitation‐independent. These unique fluorescent observations can be ascribed to the fact that the aggregates of amine groups act as the actual fluorescent centers, which are quite sensitive to their surrounding microenvironments. Based on these results, some simulation tests of sensors and intelligent hydrogels in response to water are also studied.

Active near-infrared wavefront engineering employing geometric phase metasurfaces combined with phase-change materials

In recent years, with the remarkable development of micro–nano technology, phase change materials (PCMs) with superior tunable and nonvolatile functionality are integrated into metasurfaces, which has aroused huge interests among scientific communities. However, the imaginary part of refractive index of PCMs in the crystalline phase is large in the near-infrared region (NIR), leading to the strong absorption of device and limiting the development of the PCMs in the NIR. Here, we propose and investigate the hybrid metasurface with asymmetric double-split rings. We use PCM and silica (SiO2) as the composite dielectric layer, which can efficiently reduce the impact of the high imaginary part of the refractive index PCM in the crystalline phase. Moreover, metasurfaces with two types can obtain two different resonances. Furthermore, by inducing the phase change of the PCM, we can move the short-wavelength resonance peak to the position of another long-wavelength resonance peak. Meanwhile, we can add two sets of different phases to two different types of metasurfaces. Thus, the active metasurface based on the PCM can be used to achieve the active wavefront in the NIR. Hence, the proposed metasurface based on the PCM can be applied in tunable beam switching, reconfigurable holography, and other reconfigurable optical components in the NIR.

Diode-pumped wavelength-switchable visible Pr<sup>3+</sup>:YLF laser and vortex laser around 670 nm

Here we developed a novel wavelength-switchable visible continuous-wave (CW) Pr³⁺:YLF laser around 670 nm. In single-wavelength laser operations, the maximum output powers of 2.60 W, 1.26 W, and 0.21 W, the maximum slope efficiencies of 34.7%, 27.3%, and 12.3% were achieved with good beam qualities (<italic>M</italic>² &lt; 1.6) at 670.4 nm, 674.2 nm, and 678.9 nm, respectively. Record-high output power (2.6 W) and record-high slope efficiency (34.7%) were achieved for the Pr³⁺:YLF laser operation at 670.4 nm. This is also the first demonstration of longer-wavelength peaks beyond 670 nm in the ³P₁→³F₃ transition of Pr³⁺:YLF. In multi-wavelength laser operations, the dual-wavelength lasings, including 670.1/674.8 nm, 670.1/679.1 nm, and 675.0/679.4 nm, were obtained by fine adjustment of one/two etalons within the cavity. Furthermore, the triple-wavelength lasings, e.g. 672.2/674.2/678.6 nm and 670.4/674.8/679.4 nm, were successfully demonstrated. Moreover, both the first-order vortex lasers (LG₀⁺¹ and LG₀^-1 modes) at 670.4 nm were obtained by off-axis pumping.

Panchromatic Organoboron Molecules with Tunable Absorption Spectra.

Panchromatic molecules, e. g. organic small molecules with wide absorption spectra, are very desirable for solar energy-related applications. Here, we report the development of a series of organoboron compounds composed of an organoboron core unit, two π-bridging units and two electron-withdrawing end-capping units. All seven molecules have the HOMO localized on the core unit and the LUMO delocalized on the whole conjugated backbone. They exhibit wide absorption spectra consisting of two strong absorption bands with the full width at half maximum of ca. 280 nm. These panchromatic compounds can be used as electron acceptors in organic solar cells. We elucidate the relationship between the chemical structures and opto-electronic properties of these organoboron panchromatic compounds. Increasing the electron-withdrawing capability of the core units results in a downshifted HOMO level as well as blueshifted long-wavelength absorption band with increased extinction coefficient. Extending the π-bridging units causes an increased HOMO level and blueshifted long-wavelength absorption band with increased extinction coefficients. Weakening the electron-withdrawing capability of the end-capping units leads to an upshifted LUMO level and blueshifted long-wavelength absorption peak with decreased extinction coefficient. This work provides insight into the absorption spectrum manipulation of panchromatic molecules and would pave the way for the development of solar energy-related applications.

Tunable and Reconfigurable Dual-Band Chiral Metamirror

Chiral metasurfaces have recently undergone a dramatic development, due to their important applications in optics, chemistry and biology. However, the tunability and reconfigurability of the chiral metasurfaces remain challenges. Then, we proposed an S-shaped metamirror consisting of a MIM (Au-LiNbO3−Au) structure with a dual-band chiral absorption in the near-infrared range. The proposed structure has two resonant wavelengths with a giant chiro-optical effect. The giant chiro-optical effect originates from the different plasmonic resonances induced by the incident circularly polarized light (CPL) with opposite spin states. By tuning the voltage and thus tuning the refractive index of the lithium niobate (LiNbO3), chiral resonant wavelengths can be dynamically adjusted in a large range as desired. Furthermore, by tuning the refractive index of LiNbO3, we can move the short-wavelength resonance peak to the position of another long-wavelength resonance peak. Therefore, the chiral metamirror can be dynamically reconfigured at the position of the long-wavelength resonance peak. The work offers a further step in developing tunable and reconfigurable chirality for possible applications including reconfigurable chiral hologram, chiral-selective absorber and other chiral components in near-infrared region.

Diode pumped Nd:YVO4/LBO/Ba(NO3)2 Raman laser at 563 nm

Radiation at a wavelength of 563 nm was achieved using an all-solid-state laser system based on a diode-pumped actively Q-switched Nd3+:YVO4 laser with intra-cavity second harmonic generation in LBO followed by intra-cavity Raman conversion in Ba(NO3)2. The output power of 101 mW was achieved under a pump power of 5 W and a modulation frequency of 12.7 kHz with a slope conversion efficiency of 19%. The achieved peak power at 563 nm was 0.67 kW, which allows one to use this laser in medical treatment through selective excitation of deoxyhemoglobin into its long-wavelength absorption peak.

A New Approach to the Synthesis of Lead Sulfide Colloidal Quantum Dots in a Mixture of Oleylamine and Oleic Acid

A new approach to the synthesis of lead sulfide colloidal quantum dots has been proposed, which uses a mixture of oleic acid and oleylamine. Colloidal quantum dots of PbS with a long-wavelength excitonic peak in the range from 1.7 to 2.05 μm have been obtained. The effects of temperature, reaction time, and the ratio of lead and sulfur precursors on the spectral characteristics of PbS quantum dots obtained have been studied.

5,10,15,20-tetraphenylporphyrin photoluminescence on nanoporous silicon substrates

Photoluminescence of 5,10,15,20-tetraphenylporphyrin (H2TPP) on nanoporous silicon substrates has been studied. Used nanoporous silicon has a visible PL in the region of H2TPP absorption. Reradiation of porous silicon photoluminescence to the tetraphenylporphyrin long-wavelength peak of the photoluminescence spectrum is observed. The substrate microrelief plays a major role in the formation of tetraphenylporphyrin crystalline structures. The microrelief size of porous silicon was controlled by changing the technological parameters of electrochemical etching.

Novel Phosphonium Dye TDV1 as a Potential Fluorescent Probe to Monitor DNA Interactions with Lysozyme Amyloid Fibrils

The applicability of the novel cationic phosphonium dye TDV1 to monitor the complexation between DNA and pathologically aggregated proteins, amyloid fibrils, was tested using the optical spectroscopy and molecular docking techniques. TDV1 has been found to be highly emissive in buffer solution and is characterized by one well-defined fluorescence peak attributed to the dye monomers. The association of the dye with the double stranded DNA was followed by the enhancement of monomer fluorescence coupled with a bathochromic shift of the emission maximum. The addition of fibrillar lysozyme (LzF) to TDV1-DNA mixture led to the further enhancement of fluorescence intensity of the monomeric dye form coupled with a hypsochromic shift of the emission maximum and an appearance of a second long-wavelength peak. An assumption has been made that the fluorescence enhancement augmenting with increasing the protein concentration in the TDV1/DNA system is produced by the interaction of the free TDV1 monomers with lysozyme fibrils as well as by the LzF-induced conformational alterations of DNA. The long-wavelength peak emerging in the presence of LzF is presumably a consequence of the J-aggregate formation upon the TDV1 association with lysozyme fibrils. The molecular docking studies showed that TDV1 monomers are incorporated into the fibril grooves associating with 7 β-strands in such a way that the dye long axis is parallel to the fibril axis. The most energetically favorable position of TDV1 is the S60-W62/G54-L56 groove in the lysozyme fibril core. In contrast, the TDV1 dimers seem to associate with the more hydrophilic side of the model β-sheet. Cumulatively, the results from the absorption and fluorescence measurements, together with the molecular docking analysis are consistent with the minor groove mode of the TDV1 binding to dsDNA. The electrostatic interactions seem to play a predominant role in the TDV1 complexation with the double stranded DNA, while the hydrophobic interactions and steric hindrances are supposed to be influential in the association of TDV1 with fibrillar lysozyme.

Исследование возможности изготовления напряженных сверхрешеток InAs/GaSb методом газофазной эпитаксии из металлоорганических соединений

AbstractThe first results showing the possibility of manufacturing InAs/GaSb superlattices by the metal-organic chemical vapor deposition (MOCVD) method are presented. The possibility of manufacturing heterostructures with an InAs/GaSb strained superlattice with layer thicknesses of 2–4 nm is experimentally demonstrated. The 77-K electroluminescence spectra of the structures show a long-wavelength peak at around 5 . 0 μm (0 . 25 eV). This peak is probably associated with the strained superlattice because solid solutions that could form on the basis of composite compounds do not provide this carrier-recombination energy.

Optical properties of In0.8Ga0.2As quantum dots in GaAs photovoltaic convertors

In the work, GaAs photovoltaic convertor structures with embedded In0.8Ga0.2As arrays of quantum dots (QDs) have been obtained by metalorganic vapor-phase epitaxy. Spectral characteristic of internal quantum yield showed two spectral peaks at 930 and 985 nm of photosensitivity beyond the GaAs absorption edge. A theoretical calculation of the band transitions in the nanoheterostructure showed that the peak at 930 nm corresponds to the electron–heavy-hole band transition in the wetting layer of QDs, while the long-wavelength peak at 985 nm corresponds to InGaAs QDs. Contributions of both QDs and wetting layer to the total photocurrent of the devices with the different number of QDs have been calculated.

Identification of Short- and Long-Wavelength Emitting Chlorophylls in Cyanobacterial Photosystem I by Plasmon-Enhanced Single-Particle Spectroscopy at Room Temperature.

A peculiarity of cyanobacterial Photosystem I (PSI) is the presence of so-called red chlorophylls absorbing at wavelengths longer than the reaction center P700. The origin and function of these chlorophylls have been debated in literature, but so far no consensus has been reached on either question. Here, we use plasmon-enhanced single-particle fluorescence spectroscopy to elucidate the origin of both short- and long-wavelength emitting species in monomeric PSI from Thermosynechococcus elongatus at room temperature. Polarized fluorescence spectra of single PSI complexes reveal a phase shift in the modulation of the short-wavelength (687 nm) and long-wavelength (717 nm) peaks. Numerical simulations show that this phase shift reflects a spatial angle of 15° between the transition dipole moments of the two forms. Quantum chemical calculations, together with reported X-ray structural and spectroscopic data, were used to assign the chlorophyll a monomer A3 as a candidate for the short-wavelength emitter and the B31-B32 chlorophyll dimer as a candidate for the long-wavelength emitter.

Multilayer Quantum Well–Dot InGaAs Heterostructures in GaAs-based Photovoltaic Converters

GaAs photovoltaic converters containing quantum well-dot (QWD) heterostructures are studied. The QWD properties are intermediate between those of quantum wells (QWs) and quantum dots. The QWDs are obtained by the epitaxial deposition of In0.4Ga0.6As with a nominal thickness of 8 single layers by metal-organic vapor phase epitaxy. QWDs are a dense array of elastically strained islands that localize carriers in three directions and are formed by a local increase in the indium concentration and/ or InGaAs-layer thickness. There are two quantum-well levels of varied nature in structures with QWDs. These levels are manifested in the spectral characteristics of GaAs photovoltaic converters. A short-wavelength peak with a maximum at around 935 nm is associated with absorption in the residual QW, and the long-wavelength peak (1015–1030 nm) is due to absorption in the QWDs. Investigation by transmission electron microscopy demonstrates that an increase in the number of InGaAs layers leads to stronger elastic stresses, which, in turn, increases the carrier confinement energy in the QWDs and lead to a corresponding long-wavelength shift of the internal quantum efficiency spectrum.

Luminescence Spectra of High-Power Violet and Ultraviolet Gallium Nitride-Based LEDs

The electroluminescence spectra of high-power light-emitting diodes (LEDs) based on p–n heterostructures of the InGaN/AlGaN/GaN type emitting in the visible short-wavelength and ultraviolet spectral regions (the range from 370 to 460 nm) are investigated. The shape of spectra is described by a model taking into account a two-dimensional combined density of states and potential fluctuations. Additional long-wavelength peaks are found in emission spectra. The emission power of ultraviolet and violet LEDs reaches 233 mW at a current of 350 mA, and the external quantum yield reaches 23% at the maximum (near a current of 100 mA).