Blue-shift Phenomenon Research Articles

Ground Hyper-Spectral Remote-Sensing Monitoring of Wheat Water Stress during Different Growing Stages

Monitoring agricultural drought via ground hyper-spectral remote sensing has always been a hot topic in the fields of agriculture and meteorology. In this study, a greenhouse experiment was conducted on wheat subjected to water stress during its different growth stages, namely tillering, jointing, and milk maturity. An instrument (HOBO ware PRO) used to continuously measure soil moisture was employed to measure the soil water content (SWC). An analytical spectral device (ASD) was utilized to obtain the spectral curve of wheat subject to different water treatment methods. The canopy temperature was obtained using thermal infrared sensors (METER SI-400). The relationships between the SWC, wheat drought stage, canopy temperature, and spectral response characteristics were elucidated. The results showed that the significant differences in spectral characteristics were due to water stress during the different growth stages of wheat. Red-edge parameters of red-valley position (RVP) and red-edge position (REP) both changed by 21 nm for the tillering-stage drought and the jointing-stage drought; however, the RVP and REP values for the milk maturity stage drought and the treatment under no water stress changed by 2 nm. Further, it was proved that the red-edge blue-shift phenomenon was affected not only by the different wheat growth processes, but also by the water stress at different growth stages. Red-edge reflectance clearly reflects wheat water stress at different growth stages. From SWC and canopy temperature analysis results, SWC and canopy temperature had a significant difference between wheat drought at different growth stages, and the canopy temperature at the jointing stage drought had the strongest change. The water index (WI) based on eleven vegetation water indexes exhibited a good performance for distinguishing wheat water stress at different growth stages. In conclusion, ground-based hyperspectral remote sensing can provide a large amount of high temporal and spectral resolution data on vegetation and its surrounding environment, making it an important technical tool for wheat drought monitoring, which has a great significance on the monitoring and early warning of wheat drought, reducing drought-related yield losses, and ensuring food security.

Luminescence properties, crystal field and nephelauxetic effect on (NH4)2NaMF6: Mn4+ (M = Al, Ga and In) red phosphors for warm white light-emitting diodes

In recent years, M (M = Al, Ga and In)-based fluoride red phosphors have received widespread attention. Herein, the red phosphors (NH4)2NaAlF6:Mn4+ (NNAFM), (NH4)2NaGaF6:Mn4+ (NNGFM) and (NH4)2NaInF6:Mn4+ (NNIFM) were synthesized by hydrothermal method, and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometers (EDS). Upon 470 nm light irradiation, the strongest emission peaks of (NH4)2NaMF6:Mn4+ red phosphors were at 637 nm (NNAFM), 636 nm (NNGFM) and 634 nm (NNIFM), respectively. This blue shift phenomenon with the increase of atomic radius was analyzed by crystal field and nephelauxetic effect. Besides, the concentration quenching mechanism, fluorescence lifetime and thermal stability were also discussed. Finally, three kinds of red phosphors were combined with blue chip and yellow phosphor (YAG:Ce3+) to form LED devices for improving their performance. The LED device (blue chip-YAG:Ce3+-NNGFM) possesses high color rendering index (Ra = 90.1), low correlated color temperature (3422 K) and luminous efficiency (41.23 lm W−1).

Optical Properties of the Suwannee River Fulvic Acid Complexation with Thorium Using 3D Fluorescence Spectroscopy

The relationship between the complexation amount of thorium (Th) and Suwannee River fulvic acid (SRFA) and the changes in Th concentration and pH were studied using differential spectroscopy and 3D excitation-emission matrix fluorescence spectroscopy (3D EEM). Experiments were performed at different Th concentrations and pH values. In the differential spectra at different concentrations, four bands of aromatic components appeared, and thorium was complexed with the carboxyl groups in SRFA. The 3D EEM spectra showed a fulvic acid-like fluorescence region, a visible-light fulvic acid region, and the blueshift phenomenon. The fluorescence intensity decreased with increasing thorium concentration and increased with increasing pH. The results showed that the amount of complexation of thorium and SRFA increased with increasing thorium concentration, and high pH was not conducive to the complexation of thorium and SRFA.

Excellent enhancement of thermal stability and quantum efficiency for Na2BaCa(PO4)2:Eu2+ phosphor based on Sr doping into Ca

High thermal stability and quantum efficiency are the two very significant factors for phosphors when concerning all kinds of related applications. Therefore, it is still main research topics as long as referencing to the luminescence phosphors. It is well known that deep trap and large band gap are beneficial to excellent thermal stability. In this work, a series of Na 2 BaCa 1- x Sr x (PO 4 ) 2 :0.03Eu 2+ phosphors have been prepared by traditional solid state reaction. When the Sr 2+ content increases, the emission intensity exhibits a blue shift phenomenon with the highest peak around 448 nm caused by the varied centroid shift ( ε c ) and the crystal field splitting ( ε cfs ). The thermal stability of Na 2 BaCa 0.2 Sr 0.8 (PO 4 ) 2 :0.03Eu 2+ phosphor still approaches to 100.3% of that room temperature at 150 °C, while the external and internal quantum efficiency are greatly enhanced from 19.92% to 62.53%. It is due to the effect of the cation disorder by introducing the high level of Sr ion, which create the deep trap and broaden the bandgap, resulting in the anti-thermal quenching behavior and enhanced quantum efficiency. Moreover, Rietveld refinements, microstructure, decay curves and thermoluminescence are also adopted to shed light on related mechanism of luminous performance. Furthermore, a pc-WLED device has been fabricated through Na 2 BaCa 0.2 Sr 0.8 (PO 4 ) 2 :0.03Eu 2+ blue phosphor mixed with commercial yellow phosphor (SrSi 2 O 2 N 2 :Eu 2+ ) and red phosphor (Sr 2 Si 5 N 8 :Eu 2+ ), which performs a color temperature of 4721 K with a high color rendering index of Ra = 91.9. In view of zero thermal quenching and favorable quantum efficiency, this new phosphor is a prospect candidate for blue phosphors in WLED application. Further, the work provides a new method and reference for the great enhancement of thermal stability and quantum efficiency of luminescence materials. Based on the crystal structure of Na2BaCa(PO4)2:Eu2+ phosphors, the PL, thermal dependent spectra and application in WLED of Na2BaCa0.2Sr0.8(PO4)2:Eu2+ phosphors have been detected. • A series of solid solution Na 2 BaCa x Sr 1 -x (PO 4 ) 2 ( x = 0–1.0) have been synthesized. • The thermal stability of Na 2 BaCa 0.2 Sr 0.8 (PO 4 ) 2 :0.03Eu 2+ is 100.3% of that room temperature at 150 °C. • The external quantum efficiency of Na 2 BaCa 0.2 Sr 0.8 (PO 4 ) 2 :0.03Eu 2+ is improved from 19.92% to 40.78%. • The fabricated white WLED shows the CIE of (0.3532, 0.3561), the CCT of 4721 K and CRI of 91.9.

Optical refraction and absorption spectra in perturbed monolayer PbBiI

We investigate the optical properties of a noncentrosymmetric quantum spin Hall insulator in the presence of electric and magnetic fields. We employ the Kubo formula to engineer the optical redshift and blueshift phenomena through the interplay between the bulk gap, the Rashba-like gap, and the external fields. Intriguingly, for a range of electric (magnetic) fields, the refracted and absorbed lights exhibit direct (indirect) interband optical transitions. Accordingly, for a critical electric field, optical refraction and absorption spectrum decreases gradually and becomes constant, respectively. While for a critical magnetic field, step-like jumps appear in the optical coefficients. All these findings are discussed in the context of symmetry breaking.

Development of Nd (III)-Based Terahertz Absorbers Revealing Temperature Dependent Near-Infrared Luminescence.

Molecular vibrations in the solid-state, detectable in the terahertz (THz) region, are the subject of research to further develop THz technologies. To observe such vibrations in terahertz time-domain spectroscopy (THz-TDS) and low-frequency (LF) Raman spectroscopy, two supramolecular assemblies with the formula [NdIII (phen)3 (NCX)3] 0.3EtOH (X = S, 1-S; Se, 1-Se) were designed and prepared. Both compounds show several THz-TDS and LF-Raman peaks in the sub-THz range, with the lowest frequencies of 0.65 and 0.59 THz for 1-S and 1-Se, and 0.75 and 0.61 THz for 1-S and 1-Se, respectively. The peak redshift was observed due to the substitution of SCN− by SeCN−. Additionally, temperature-dependent TDS-THz studies showed a thermal blueshift phenomenon, as the peak position shifted to 0.68 THz for 1-S and 0.62 THz for 1-Se at 10 K. Based on ab initio calculations, sub-THz vibrations were ascribed to the swaying of the three thiocyanate/selenocyanate. Moreover, both samples exhibited near-infrared (NIR) emission from Nd (III), and very good thermometric properties in the 300–150 K range, comparable to neodymium (III) oxide-based thermometers and higher than previously reported complexes. Moreover, the temperature dependence of fluorescence and THz spectroscopy analysis showed that the reduction in anharmonic thermal vibrations leads to a significant increase in the intensity and a reduction in the width of the emission and LF absorption peaks. These studies provide the basis for developing new routes to adjust the LF vibrational absorption.

The CON−H…+NH2 Blue-Shifting H-Bond Stabilizing Effect on Z Secondary Amides and Cyclic System Conformational Rearrangement through an Alkylamine-Chain Migration Pathway

The paper is focusing on the amide linkage exceptional properties and usage of chemistry (conformational rearrangement, geometrical stereoisomers, spectroscopic blue shift phenomenon, protonation and deprotonation reactions, synthetic scope, and mechanistic implications). Hydrogen-bond-stabilized acylation reactions of a diamine with thioamides or nitriles reveal how substituents influence both the outcome of stereoselectivity and interactions. Inferring the chemical mechanism from the structures of reactants is dissimilar to the appropriate E isomers, the Z form becomes more favored in the secondary amides obtained. One conclusion from the estimation of Z structures, based on the 1H-15N 2D NMR spectra in comparison with the references, is the existence of the intramolecular, blue shifting CON−H…+NH2CH3 hydrogen bonds. The rearrangement of a methylamino residue provided the free base stabilized in the CH3N−H…O=CNH after deprotonation. An essential part of the publication describes systems in a highly stereoselective fashion, so the stereochemical outcome of the product is predictable now.

AlGaN multiple quantum well deep‐ultraviolet micro‐light‐emitting diodes for high color conversion efficiency quantum dots display

AbstractDisplays based on inorganic micro‐light‐emitting diodes (micro‐LEDs) are highly anticipated for next‐generation technologies. AlGaN‐based deep‐ultraviolet (deep‐UV) micro‐LED as the excitation source for quantum dots display with high efficiency was reported in this paper. To achieve optimized electro‐optical performance, deep‐UV micro‐LEDs with different electrodes were fabricated and analyzed in sizes from 200 × 200 to 10 × 10 μm2. At the same forward bias, the devices with Ti/Al‐based electrodes achieved 10 times injection current and three times electroluminescence intensity than those with Cr/Al‐based electrodes. The blueshift phenomenon of deep‐UV light was observed from 292 nm at 2 A/cm2 to 287 nm at 200 A/cm2 with the increasing current density. By the excitation of deep‐UV micro‐LED, quantum dot film achieved high light conversion efficiency and optimized color rendering, as the converted color emission peak was separate from the pumping source. The high energy of deep‐UV photons and the narrow emission bandwidth of QDs resulted in prominent color purity. The forward voltage and electroluminescence intensity uniformity of a 250 × 250 micro‐LED array with each pixel size of 30 × 30 μm2 were further discussed. The optical microscope images of green QD film pumped by a deep‐UV micro‐LED demonstrated its competitive application in the color‐converted display.

Tailoring the electronic, optical and mechanical properties of KMgH3 and RbCaH3 perovskite hydrides without and with Samarium

Perovskite hydrides such as KMgH3 and RbCaH3 have been proven to be an attractive candidate for good application prospects in optoelectronic devices and conversion energy. Doping these perovskites with rare earth has turned into a progressively essential way to improve luminescence and photo-conversion of devices. In this work, the ab-initio calculations have been carried out to explore the structural, electronic, optical, and mechanical properties of both KMgH3 and RbCaH3 without and with Sm based on generalized gradient approximation functional within the framework of DFT including the spin−orbit coupling. It is found that doping the perovskites with Sm depicts substantially modification in electronic behavior leading increased bandgap energy as well as the carrier effective masses with increasing Sm concentrations for the case of KMgH3, while it has been reduced for RbCaH3. In addition, the optical investigation reveals a blue-shift phenomenon from absorption coefficient spectra, which is owing to the Sm doping into KMgH3; combined with a minimum absorption in visible spectrum for pure KMgH3 perovskite. Besides, we denote a maximum absorption in the UV region of the doped RbCaH3. Furthermore, the mechanical analysis exhibits that these perovskites are hard and stiffer, especially KMgH3 hydride systems. These outcomes may conduct and give a reliable reference for experimenters to design novel perovskite hydrides toward improving optoelectronic performances.

Monolithic Multi‐Color Tunable Inorganic Light‐Emitting Diodes (Adv. Electron. Mater. 1/2022)

Blueshift Phenomenon Monolithic red, green, and blue light-emitting diodes (LEDs) can be achieved by exploiting the blueshift phenomenon, caused by the strong band-filling effect at different energy localization states. In article number 2100598, Sung-Nam Lee and colleagues design different-sized red, green, and blue LEDs by controlling the sizes of the LEDs on the same wafer, which can be utilized in micro-LED display applications.

AlGaN-Based Deep-UV Micro-LED Array for Quantum Dots Converted Display With Ultra-Wide Color Gamut

Deep-ultraviolet (Deep-UV) micro light-emitting diodes (Micro-LEDs) array greatly benefits various future applications. In this letter, we fabricated Deep-UV Micro-LEDs with different geometries from <inline-formula> <tex-math notation="LaTeX">$10 \times 10\,\,\mu \text{m}$ </tex-math></inline-formula>² to <inline-formula> <tex-math notation="LaTeX">$200 \times 200\,\,\mu \text{m}$ </tex-math></inline-formula>², and investigated its application on tristimulus quantum dots converted display. As the Micro-LEDs scaling, the smaller-sized devices provided higher brightness under the same injection current density due to the enhanced current spreading uniformity and heat dissipation. For a <inline-formula> <tex-math notation="LaTeX">$10 \times 10\,\,\mu \text{m}$ </tex-math></inline-formula>² device, the maximal optical power density was up to 185 W/cm² at 5 kA/cm², and the peak external quantum efficiency reached 3.43 &#x0025; at 30 A/cm². The device exhibited a minor blue shift phenomenon as the current density increased. Deep-UV Micro-LED stimulated quantum dots display obtained 121&#x0025; of the Rec. 2020 standard in the CIE 1931 color space. This ultra-wide color gamut indicated it as a competitive candidate for future display technology.

Tetraphenylnaphthosiline (TPNS): a potential building block for deep-blue emitter featured aggregation-induced blue-shifted emission

A novel deep-blue building block with aggregate-induced emission was developed for spin-coating undoped devices. The aggregation-induced blue-shift phenomenon of this AIEgen has been reasonably explained by theoretical calculation methods.

On the mechanism of carrier recombination in downsized blue micro-LEDs

The mechanism of carrier recombination in downsized μ-LED chips from 100 × 100 to 10 × 10 μm2 on emission performance was systemically investigated. All photolithography processes for defining the μ-LED pattern were achieved by using a laser direct writing technique. This maskless technology achieved the glass-mask-free process, which not only can improve the exposure accuracy but also save the development time. The multi-functional SiO2 film as a passivation layer successfully reduced the leakage current density of μ-LED chips compared with the μ-LED chips without passivation layer. As decreasing the chip size to 10 × 10 μm2, the smallest chip size exhibited the highest ideality factor, which indicated the main carrier recombination at the high-defect-density zone in μ-LED chip leading to the decreased emission performance. The blue-shift phenomenon in the electroluminescence spectrum with decreasing the μ-LED chip size was due to the carrier screening effect and the band filling effect. The 10 × 10 μm2 μ-LED chip exhibited high EQE values in the high current density region with a less efficiency droop, and the max-EQE value was 18.8%. The luminance of 96 × 48 μ-LED array with the chip size of 20 × 20 μm2 exhibited a high value of 516 nits at the voltage of 3 V.

Multi-peak narrow-band perfect absorber based on two-dimensional graphene array

In this paper, we have investigated an absorber based on two-dimensional hexagonal graphene array and theoretically propose a calculation method for the approximate conductivity of graphene in the terahertz band and its correction term, and we also theoretically explain the phenomenon of blue-shift of the absorption spectrum with increasing graphene chemical potential. The finite difference time domain (FDTD) method shows that this absorber has the advantages of exciting high absorption rate, multi-band, tunable and high figure of merit (FOM). By discussing the analysis of different graphene geometries, we demonstrate the optimality of this result. The bottom layer of our absorber is composed of an Au reflection layer, and the middle layer is a silicon oxide dielectric layer. Four hexagonal two-dimensional graphene is placed at the top. Taking this as the basic unit, an array can be formed. Our absorber has a simple structure, which simplified the processing technology and saves the processing cost greatly. In the near-infrared band from 1600 nm to 1900 nm, our absorbers have absorption peaks of 99.70%, 99.25% and 99.82% at 1667.19 nm, 1691.71 nm and 1773.20 nm, respectively. In addition, the resonance wavelength of the absorber can also be adjusted by adjusting the chemical potential and refractive index of the silicon dioxide layer. The absorber also has the features of polarization and angular insensitivity. Our simulation results show that our absorber's absorption spectrum will change significantly as the ambient refractive index changes, and based on this, we can calculate the sensitivity and the figure of merit (FOM) of our model. We finally calculated the best FOM for the three peaks of our absorber (sorted by resonance wavelength from short to long) is 90.93, 90.96, 107.34, and the sensitivity is 290.25 nm/RIU, 309.95 nm/RIU, 318.50 nm/RIU, respectively. Thus, we trust that our absorbers can be widely used in Near-infrared thermal radiation, optical detector and Near-infrared sensors.

Effects of Different Quick-freezing Methods on Protein Properties of Largemouth Bass( Lateolabrax japonicus )

In this paper, largemouth bass is used as raw material to study the effects of different cooling rates(liquid nitrogen quick freezing(1.81 ℃), freezing liquid quick freezing(0.15 ℃), flat plate quick freezing(0.14 ℃)) in freezing storage(0, 1, 2, 4, 12, 24 weeks), the influence of the physical and chemical properties of sea bass protein, by measuring the salt-soluble protein, sulfhydryl group, carbonyl group, Ca2+-ATPase activity content, surface hydrophobicity, endogenous fluorescence spectrum and protein composition changes in the fish meat, and using double factor variance and correlation analysis study quick-freezing method and storage time to investigate the degeneration of fish protein after freezing. The results showed that with the passage of frozen storage time, the value of salt-soluble protein showed a downward trend: The plate group and liquid nitrogen group had the lowest and the highest at the end of the frozen storage, respectively; the activity values of sulfhydryl and Ca2+-ATPase both increased first and then decreased. The endogenous fluorescence intensity of fibrin increased, resulting in a blue shift phenomenon, and the value of myofibrillar protein carbonyl and surface hydrophobicity increased significantly(P<0.05). The results of SDS-PAGE electrophoresis showed that myofibrillar protein was degraded during the freezing period, while the liquid nitrogen group had a faster cooling rate and a slower degree of protein degradation, while the plate group was the opposite. The volume of ice crystals formed by quick freezing of liquid nitrogen was similar to the distribution of water in the raw material, which was conducive to storage. Compared with liquid nitrogen quick freezing, the time for the formation of the maximum ice crystal zone in the quick freezing of liquid nitrogen was longer than that of liquid nitrogen quick freezing and shorter than that of flat quick freezing, and there was not much difference between the two. The correlation analysis between the two-factor variance and the indicators showed that the quick freezing method had a significant effect on the active sulfhydryl group and the maximum fluorescence intensity of myofibril protein(P<0.05). The freezing time was the main factor affecting the protein of the sea bass. The oxidative modification of amino acid side chain groups in myofibrillar protein was the main factor causing the degradation or aggregation of protein.

Van der Waals heterostructure of graphene Defected&Doped X(X = Au, N) composite ZnO monolayer: A First Principle study

GGA + U(Zn 3d = 10eV, O 2p = 7eV) and van der Waals correction methods (DFT-D2) were used to calculate the surface structural, electronic and optical properties of ZnO composite graphene (Z-G) system via first-principles. The binding energy and Bader charge transfer are calculated. When the composite site is at the top site and the interlayer distance is 2 Å, the ZnO composite graphene (Z-G) interface is the most stable, the energy value is 2.86eV. The Dirac point remained unchanged after intrinsic graphene composite ZnO, indicating that the interaction between intrinsic graphene and ZnO did not affect the excellent electrical conductivity of graphene. By studying the energy band, density of states, and optical properties of ZnO in graphene (ZGC-V) composite ZnO, Au and N doped graphene (ZGC-Au and ZGC-N) composite ZnO. It is found that doped and defected graphene composite ZnO the Dirac points disappeared, the bandgap value is 0.441eV, 0.831eV and 0.203eV, respectively. Electron-hole pair is well separated at the interface of doped and defected graphene composite ZnO. The defected and doped graphene composite ZnO lead to the blue shift phenomenon of light absorption peak, defected graphene composite ZnO absorption peak movement was the maximum of 1.64eV. The change of band gap and optical properties provides a theoretical explanation for the excellent performance of ZnO composite graphene (Z-G) in photocatalysts and ultraviolet light-emitting devices.

Monolithic Multi‐Color Tunable Inorganic Light‐Emitting Diodes

AbstractInorganic light‐emitting diodes (LEDs) possess exceptional advantages for achieving wide wavelength emission ranges. However, certain material limitations should be overcome to alleviate the green gap between InGaN and AlInGaP‐based LEDs. In this study, monolithic red, green, and bluish‐green emissions are achieved by exploiting the blueshift phenomenon, caused by the band‐filling and piezoelectric screening effects. Different‐sized LEDs are designed to control the injection current density on the same wafer. The smaller the size of the LED, the shorter the emission wavelength, resulting in multi‐color emission (from red to bluish‐green). As a result, red, green, and white emissions are individually and simultaneously obtained using dichromatic LED systems, comprising three red and one green LED cell. In addition, a wide range of visible light colors are achieved by adjusting the size of the LEDs and the applies injection current.

Tuning the electronic and optical properties of molybdenite (MoS2) by adsorption of alkali metals and halogens

Electronic and optical properties of nanostructures formed by monolayer of molybdenite and with adsorption of alkali metals (Li, Na, K, Rb, Cs) and halogens (F, Cl, Br, I, At) on MoS2 are investigated by using the first principle calculations based on the density functional theory (DFT). The results suggest strong absorption peaks for pristine MoS2 in certain regions of the visible portion of the spectrum (~380–470 nm) and in the entire ultraviolet region. Structures formed by adsorption of Li, F, Cl, Br, I on MoS2 contribute to the red shift phenomenon where absorption peaks are seen to shift towards the lower energy range of the spectrum. However, a blue shift phenomenon is seen in other structures formed by the adsorption of At, Na, K, Rb, Cs over MoS2, where absorption peaks shift to higher energy range of the spectrum. Furthermore, high absorption is observed in the entire visible region (~400–790 nm) and UV region (below 360 nm) of the spectrum for all the adsorbed nanostructures. The measured dielectric constant is in line with the measured refractive index for all the adsorbed nanostructures.

Energy transfer between two luminescent centers and photoluminescent properties of Ca4-yLa6(AlO4)x(SiO4)6-xO1-x/2: yEu2+apatite structure phosphors

Green-emitting, apatite structure of Ca4-yLa6(AlO4)x(SiO4)6-xO1-x/2: yEu2+ was synthesized by using the high-temperature solid-state method under reducing atmosphere (90%N2–10%H2). Corresponding to the Eu2+ of 4f65 d1→4f7 transition at the excitation wavelength of 335 nm, a broadband emission of 450–700 nm showed. Eu2+ lattice selection in Ca4-yLa6(AlO4)x(SiO4)6-xO1-x/2: yEu2+ phosphor were discussed conjunction with apatite crystal structure characteristics. The design of (AlO4)5-/(SiO4)4- various ratios and Eu2+ doping concentration improved the Eu2+ luminous intensity and the red-shift of optical emission spectra. Energy transfer between the two luminescent centers of Eu(I) and Eu (II) happened, and clearly distinguished by photoluminescence decay curves monitored at 480 nm and 560 nm with the average-lifetime (τ) of Eu(I) are 240.5 ns, Eu (II) are 405.3 ns, respectively. The temperature-dependent emissions along with blue-shift phenomenon were addressed through the transition process of energy level. Eu(I) and Eu(II) lattice sites.

Swing Arm Location-Controllable DNA Walker for Electrochemiluminescence Biosensing.

Here, we described a novel swing arm location-controllable DNA walker based on the DNA tetrahedral nanostructures (DTNs) for nucleic acid detection using the polycyclic aromatic hydrocarbon (PAH) microcrystals (TAPE-Pe MCs) consisting of the nonplanar molecular tetrakis(4-aminophenyl)ethene (TAPE) and planar molecular perylene (Pe) as electrochemiluminescence (ECL) luminophores. Specifically, the swing arm strands and track strands were fixed simultaneously on the DTNs to obtain the location-controllable DNA walker, which possessed an improved reaction efficiency compared to that of a fixed swing arm-based DNA walker due to the quantitative and orderly swing arm on the DTNs. On the other hand, the Pe microcrystals doped by TAPE molecules could decrease the π-π stacking of Pe molecules for the ECL efficiency enhancement, achieving a blue-shifted and intense ECL emission. Therefore, we defined this enhanced and blue-shifted ECL phenomenon as "inhibition of conjugation-driven ECL (IC-ECL)". To prove these principles, a location-controllable DNA walker-based ECL biosensor was developed with microRNA let-7a as target molecules. The ECL biosensor achieved a low detection limit of 4.92 fM within a wide linear range from 10 fM to 100 nM. This approach offers a new insight for ECL efficiency increase and location-controllable strategies with improved reaction efficiency, demonstrating potential in diagnostic analysis.