Green Region Research Articles

Synthesis of TiO2/Al2O3 Double-Layer Inverse Opal by Thermal and Plasma-Assisted Atomic Layer Deposition for Photocatalytic Applications.

In comparison to conventional nano-infiltration approaches, the atomic layer deposition (ALD) technology exhibits greater potential in the fabrication of inverse opals (IOs) for photocatalysts. In this study, TiO2 IO and ultra-thin films of Al2O3 on IO were successfully deposited using thermal or plasma-assisted ALD and vertical layer deposition from a polystyrene (PS) opal template. SEM/EDX, XRD, Raman, TG/DTG/DTA-MS, PL spectroscopy, and UV Vis spectroscopy were used for the characterization of the nanocomposites. The results showed that the highly ordered opal crystal microstructure had a face-centered cubic (FCC) orientation. The proposed annealing temperature efficiently removed the template, leaving the anatase phase IO, which provided a small contraction in the spheres. In comparison to TiO2/Al2O3 plasma ALD, TiO2/Al2O3 thermal ALD has a better interfacial charge interaction of photoexcited electron-hole pairs in the valence band hole to restrain recombination, resulting in a broad spectrum with a peak in the green region. This was demonstrated by PL. Strong absorption bands were also found in the UV regions, including increased absorption due to slow photons and a narrow optical band gap in the visible region. The results from the photocatalytic activity of the samples show decolorization rates of 35.4%, 24.7%, and 14.8%, for TiO2, TiO2/Al2O3 thermal, and TiO2/Al2O3 plasma IO ALD samples, respectively. Our results showed that ultra-thin amorphous ALD-grown Al2O3 layers have considerable photocatalytic activity. The Al2O3 thin film grown by thermal ALD has a more ordered structure compared to the one prepared by plasma ALD, which explains its higher photocatalytic activity. The declined photocatalytic activity of the combined layers was observed due to the reduced electron tunneling effect resulting from the thinness of Al2O3.

A Simple Molecular Design Strategy for Pure-Red Multiple Resonance Emitters.

Though the flourishment of materials with multiple resonance (MR) in blue to green regions, red-emissive MR emitters are still rare in literatures, which definitely should be resolved for further applications. Herein, we report a simple molecular design strategy for the construction of pure-red MR emitters by conjugate charge transfer, which could greatly enhance the π-conjugation degree and charge-transfer property of the target molecule while maintaining the basic feature of MR, leading to a significant redshift of more than 128 nm compared to the selected parent MR core. The proof-of-concept emitter PPZ-BN exhibited a pure-red emission with a dominant peak at 613 nm and a small full-width-at-half-maximum of 0.16 eV (48 nm). The optimized organic light-emitting diode showed a high external quantum efficiency of 26.9 %, a small efficiency roll-off, and an excellent operation stability (LT99) of more than 43 hours at an initial luminance of 10 000 cd m-2 .

A Simple Molecular Design Strategy for Pure‐Red Multiple Resonance Emitters

AbstractThough the flourishment of materials with multiple resonance (MR) in blue to green regions, red‐emissive MR emitters are still rare in literatures, which definitely should be resolved for further applications. Herein, we report a simple molecular design strategy for the construction of pure‐red MR emitters by conjugate charge transfer, which could greatly enhance the π‐conjugation degree and charge‐transfer property of the target molecule while maintaining the basic feature of MR, leading to a significant redshift of more than 128 nm compared to the selected parent MR core. The proof‐of‐concept emitter PPZ‐BN exhibited a pure‐red emission with a dominant peak at 613 nm and a small full‐width‐at‐half‐maximum of 0.16 eV (48 nm). The optimized organic light‐emitting diode showed a high external quantum efficiency of 26.9 %, a small efficiency roll‐off, and an excellent operation stability (LT99) of more than 43 hours at an initial luminance of 10 000 cd m−2.

Artificial synapse based on carbon quantum dots dispersed in indigo molecular layer for neuromorphic applications

Conventional computers are limited in their performance due to the physical separation of the memory and processing units. To overcome this, parallel computation using artificial synapses has been thought of as a possible replacement in computing architecture. The development of nanoelectronic devices that can show synaptic functionalities is very important. Here, we report the robust synaptic functionalities of carbon quantum dots embedded in two terminal indigo-based organic synapses. The carbon quantum dots (CQDs) are prepared using an easy-to-do process from commercial jaggery. The CQDs have a size range between 3.5 and 4.5 nm with excellent light emission in the green region. CQD+indigo-based devices show extremely stable memory characteristics, with ON and OFF states differing by more than 10 Mohm. Devices show excellent long-term potentiation and long-term depression characteristics, with both synaptic weight updates following a double exponential behavior. The extent of nonlinearity is explained using the nonlinearity factor. The linear increase in memory is established with repeated learning and forgetting (or potentiation and depression) curves. This study gives a robust way to make an artificial synapse work efficiently at room temperature with excellent memory and synaptic behavior.

Synthesis and emission characteristics of rare earth ions (Eu3+ and Tb3+) doped calcium orthogermanate phosphors

In this study, rare earth ions (Eu3+ and Tb3+) doped calcium orthogermanate (Ca2GeO4) phosphors were synthesized through the high temperature solid-state route. PL (Photoluminescence), FTIR (Fourier transform infrared spectroscopy), SEM (Scanning electron microscopy), EDS (Energy dispersive spectroscopy) and PXRD (Powder X-ray diffraction) techniques were used to characterize all the prepared powder samples. The PXRD results of the samples give an orthorhombic phase system. The SEM-EDS measurements are used to confirm the doping of europium and terbium ions into the Ca2GeO4 lattice. The vibrational characteristics of the proposed phosphors are investigated from FTIR spectra. As per the PL studies, the Eu3+ and Tb3+ activated Ca2GeO4 phosphors are exhibited a prominent red emission at 610 nm and bright green emission at 547 nm under 244 nm and 229 nm excitation wave lengths respectively. The obtained results are ascribed to the ED (Electric Dipole) transition and MD (Magnetic Dipole) transitions 5D0 → 7F2 and 5D4 → 7F5 of europium and terbium ions respectively. The CIE diagram illustrates the emission colors of the synthesized phosphors which are given as red and green emission regions. Based on obtained results, the prepared phosphors may be suitable for solid state light and display devices.

Fast Neutron Irradiation on GaN-Based Light-Emitting Diodes From Near-Ultraviolet to Green Spectral Ranges

Neutron irradiation effects were compared for GaN-based multi-quantum well (MQW) light emitting diodes (LEDs) with emission wavelength in the near-ultraviolet (NUV), blue and green spectral regions. Optical output power, current-voltage and peak wavelength were analyzed in detail before and after irradiation. Three colors of LEDs showed an increase and then a decrease in optical output power with the increase of neutron fluence ranging from 1.0×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> to 1.0×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">14</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> . The enhanced light emission performance is attributed to the increase of carrier injection for neutron irradiated MQWs. In addition, the formation of tunneling conductivity channels in the p-doped AlGaN electron block layer (EBL) induced by neutrons is considered as the main factor that dominates the performance degradation. Among the three colors of LEDs, the order of severity for the optical and electrical properties influenced by this medium-fluence neutron irradiation is green, blue, and NUV LEDs, in turn becoming more serious. The NUV LEDs rely heavily on the EBL due to their poor carrier confinement in relatively shallow GaN/AlGaN MQWs, so an increase of carrier injection or leakage induced by neutrons has significant influence on device performance. As the green LEDs have deep quantum wells, the strong confinement of carriers leads to their being least sensitive to neutron irradiation. So we believe that design of LEDs with deep quantum wells to enhance the carrier confinement ability will be helpful to improve their radiation tolerance. The findings not only enrich the understanding of the influence mechanism of neutron irradiated GaN-based UV/visible LEDs, but are also helpful to radiation hardened design.

Optical absorption and photoluminescence properties of Cucurbita maxima dye adsorption on TiO2 nanoparticles

Dye-sensitised solar cells (DSSCs) are 3rd generation photovoltaic device that imitate photosynthesis in plants. The fundamental concept of a DSSCs is that the photoanode is covered by the dye as a sensitiser. Natural dyes from plant-based extracts have gained attention as alternatives to toxic and expensive commercial dye sensitisers. Various studies have been conducted on the use of natural plant dye extracts for DSSCs . However, more fundamental studies on their adsorption on TiO2 photoanode nanoparticles are still not well understood. In this study, we investigated the crystal structure, optical absorption, and photoluminescence properties of TiO2, Cucurbita maxima, and Cucurbita maxima dyes adsorbed on TiO2 nanoparticles as potential materials for DSSCs. Raman spectra confirmed the anatase phase of the TiO2 nanoparticles. The particle size of 12 ± 2 nm was confirmed through the transmission electron microscope. The optical absorption properties of Cucurbita maxima show two distinct absorption bands: blue visible (450–500 nm) and red visible (635–674 nm). The photoluminescence spectra of the dye extract and its adsorption onto the TiO2 nanoparticles showed two prominent peaks in the blue and red regions of the electromagnetic spectrum. No significant peak is observed in the green region of the electromagnetic spectrum. These studies shed more light on the fundamental properties of chlorophyll adsorption on TiO2 nanoparticles and their optical and photoluminescence properties for applications as sensitisers in DSSCs.

The Skill of Self-Management for School Principals in Digital Education

School self-management has come to be seen as a participatory and collaborative process between all school teachers and the surrounding community and its institutions. This quantitative study examines reality using the self-management of school principals. The sample of the study involved 215 principals of schools in the green line region of Palestine. A questionnaire was emailed and posted on social media (Facebook and WhatsApp) to collect data. The Statistical Package for Social Sciences was used to analyze the data. The findings of the study were: (i) self-management faces great challenges in its application; (ii) principals do not involve teachers and society in decision-making. (iii) The inability of school principals to set the general objectives of the curriculum due to a lack of experience; (iv) Some principals were unable to create teachers who carried out their duties through self-management.

Influence of annealing temperature on structural, optical and electrical properties of zinc silicate (Zn2SiO4) nanophosphors

Zinc Silicate (Zn2SiO4) nanophosphors have been successfully synthesized by co-precipitation route. The structural, optical and electrical properties of Zn2SiO4 nanophosphors have been thoroughly investigated. The structural studies made using X-ray diffraction measurements exhibited that with increase in the annealing temperature of Zn2SiO4 nanophosphors, the crystallite size is found to increase from 20 to 28 nm and indicate higher lattice parameter with improved crystallinity with annealing temperature. FT-IR studies confirm presence of ZnO4 and SiO4 vibrational modes and confirm the formation of Zn2SiO4 nanophosphors with optimum visibility for annealed temperature of 1000 °C. The UV–Vis spectroscopy measurements reveal the maximum absorption peak associated with lowest bandgap of 5.53 eV is achieved for Zn2SiO4 nanophosphors at annealing temperature of 1000 °C. The photoluminescence emission spectra reveal that the Zn2SiO4 nanophosphors are self-luminescing in green spectral region at 520 nm and the emission intensity decreases with increase in annealing temperature. The color correlated temperatures (CCT) studies shows that the samples of Zn2SiO4 nanophosphors can be utilised for achieving cool white light applications and maximum CCT is achieved for Zn2SiO4 nanophosphor annealed at temperature of 1000 °C. The dielectric measurements reveal presence of interfacial polarization and following Maxwell–Wagner polarization & Koop's characteristics in Zn2SiO4 nanophosphors. In addition, highest permittivity and low dielectric loss is observed for Zn2SiO4 nanophosphors annealed at 900 °C and 1100 °C. The impedance Cole-Cole plots reveal non-Debye type relaxation in all Zn2SiO4 nanophosphors and decrease in the radius of the semicircles with increase in annealing temperature. A high resistive nature is observed for Zn2SiO4 nanophosphor annealed at 1100 °C. These results help in understanding the potential usage of these Zn2SiO4 nanophosphors for white light as well as microelectronic device applications.

Photoluminescent studies of trivalent terbium activated magnesium metaphosphate phosphors

ABSTRACT The solution combustion route is used to synthesize a series of MgP2O6:Tb3+(0.5–3.5 mole %) phosphors. X-ray diffraction and Rietveld refinement analysis have verified the crystal purity (monoclinic symmetry) with space group P21/n and refined lattice parameters (a = 11.12 Å, b = 8.268 Å, and c = 9.902 Å), respectively. The excitation and emission features of the synthesized material (luminescent properties) are monitored using photoluminescence spectroscopy. The emission spectrum, recorded at excitation 215 nm, shows the most prominent emission peak at 545 nm, which is responsible for green colour emission. The CIE coordinates indicate that phosphors emit in the green light region. The synthesized material has conventional application in solid-state lighting under UV excitation (215 nm).

How ligand coordination and superatomic-states accommodate the structure and property of a metal cluster: Cu4(dppy)4Cl2vs. Cu21(dppy)10 with altered photoluminescence

We have synthesized two copper nanoclusters (NCs) with a protection of the same ligand diphenylphosphino-2-pyridine (C17H14NP, dppy for short), formulated as Cu4(dppy)4Cl2 and Cu21(dppy)10, respectively. The former one bears a distorted tetrahedron Cu4 core with its six edges fully protected by chlorine and dppy ligands, while the latter presents a symmetric Cu21 core on which ten dppy molecules function as monolayer protection via well-organized monodentate or bidentate coordination. Interestingly, the Cu4(dppy)4Cl2 cluster exhibits a strong yellow emission at ∼577 nm, while Cu21(dppy)10 displays dual emissions in purple (∼368 nm) and green (∼516 nm) regions respectively. In combination with TD-DFT calculations, we demonstrate the origin of altered emissions and unique stability of the two copper nanoclusters pertaining to the ligand coordination and metallic superatomic states.

Luminescence studies of lanthanides (Europium and Terbium) doped Sr2SiO4 phosphor

Polycrystalline Eu3+ and Tb3+ activated Sr2SiO4 phosphor synthesized through the solid state technique. The prepared powders have been studied by Photoluminescence studies, Fourier transform infrared spectroscopy, Scanning electron microscopy, Energy dispersive X-ray analysis and X-ray diffraction. Photoluminescence properties of Eu3+ and Tb3+ incorporated Sr2SiO4 phosphors have been studied. From the emission spectrum, europium doped phosphors show strong line at 613 nm, which is ascribed to the 5D0 → 7F2 transition of Eu3+ ions and terbium doped samples show maximum line at 547 nm, it is ascribed to the 5D4 → 7F5 transition of Tb3+ ions. Powder XRD profiles of the phosphors confirms the orthorhombic structure. EDAX provides information about the components which are presented in the chemical compound viz. Sr, Si, O, Eu and Tb. The formation of synthesized samples is verified further by FTIR spectroscopy. The CIE color coordinates are obtained lying in red and green region.

Investigation of structural, morphological and photoluminescence properties in ZnO: Co2+ nanostructures prepared by solution combustion technique using Mimosa pudica leaf extract as a fuel

Novel solution combustion technique was equipped for the synthesis of ZnO:Co2+ (1–11 mol%) nanostructures using mimosapudica (MP) leaf extract as a fuel. The prepared sample exhibits highly crystalline structure showing mushroom like morphological features. This might be due to the experimental reaction took place at the time of synthesis and evident that morphology was highly dependant on concentration of leaf extract. The obtained product of ZnO:Co2+ through MP leaf extract was examined through several characterization techniques. The packing diagram obtained using Rietveld refinement data shows the formation of hexagonal wurtzite structure having crystallite size 43–68 nm, cell volume ∼ 47.58 Å3 and density of atoms ∼ 8.42 × 1022 atoms percm3. From FTIR spectra the absorption peak in the range 500–650 cm−1exhibits the Zn-O stretching frequency having the high orientation of ZnO wurtzite structure. The energy band gap increases with Co2+ ion concentration in ZnO. The Photoluminescence (PL) emission spectra was observed in blue and green region at 422–435 & 524 nm respectively due to the presence of Zinc and oxygen vacancies. The CIE coordinate value reflecting in blue and green region confirms that the ZnO:Co2+ can be used as a one of the component in production of artificial white light LEDs/solid state display applications.

Gemological and Luminescence Characteristics of Taaffeites from Mogok, Myanmar

Taaffeite is a rare gem that has been found in different localities such as Tanzania, Sri Lanka, China, and Mogok, Myanmar. In this study, thirty-two taaffeite samples from Mogok, Myanmar, were investigated by conventional gemological testing, laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), Raman spectrometry, and fluorescence spectrometry. Through microscopic observations, various types of inclusions were observed in these taaffeites, including irregular inclusions, orange and brown intrusions, black dotted and flake inclusions, healed fissures, tubular inclusions, fingerprint inclusions, and multi-phase inclusions. The Raman spectra demonstrated that the inclusions were mainly calcite, forsterite, celestite, graphite, dolomite, and transparent tubular or columnar inclusions filled with CO2. In previous studies, taaffeite showed inert or chalky fluorescence under long-wave ultraviolet (LWUV) light and inert fluorescence under short-wave ultraviolet (SWUV) light. In this study, the taaffeite samples revealed different fluorescence phenomena under ultraviolet light. Thirty-two taaffeite samples were classified into four categories according to their fluorescence under LWUV: orange-red, pink, green, and blue-white fluorescence. Under SWUV, all samples presented inert to bright pink fluorescence. Two-dimensional fluorescence spectra were obtained through a fluorescence spectrometer. For the samples with orange-red and pink fluorescence under LWUV, two-dimensional fluorescence spectra showed that peaks at 686 nm and 690 nm (in the red region) were strong. For the samples with green and blue-white fluorescence under LWUV, peaks at 439 nm and 464 nm (in the blue region) were strong, peaks at 507–515 nm (in the green region) were relatively weak, and peaks at 686 and 690 nm (in the red region) were very weak. Combined with the data from LA-ICP-MS, it is speculated that Cr3+ was responsible for samples having orange-red and pink fluorescence, that Mn2+ was responsible for samples having green fluorescence, and that Fe inhibited the generation of fluorescence.

Ln(III) Complexes Embedded in Biocompatible PLGA Nanoparticles as Potential Vis-to-NIR Optical Probes.

In this contribution, we present the spectroscopic study of two NIR emitting hydrophobic heteroleptic (R,R)-YbL1(tta) and (R,R)-NdL1(tta) complexes (with tta = 2-thenoyltrifluoroacetonate and L1 = N,N'-bis(2-(8-hydroxyquinolinate)methylidene)-1,2-(R,R or S,S)-cyclohexanediamine), both in methanol solution and embedded in water dispersible and biocompatible poly lactic-co-glycolic acid (PLGA) nanoparticles. Thanks to their absorption properties in a wide range of wavelengths extending from the UV up to the blue and green visible regions, the emission of these complexes can be effectively sensitized using visible radiation, which is much less harmful to tissues and skin than the UV one. The encapsulation of the two Ln(III)-based complexes in PLGA allows us to preserve their nature, making them stable in water and to test their cytotoxicity on two different cell lines, with the aim of using them in the future as potential bioimaging optical probes.

Direct generation of 3.17 mJ green pulses in a cavity-dumped Ho3+-doped fiber laser at 543 nm

High-energy pulsed lasers in the green spectral region are of tremendous interest for applications in space laser ranging, underwater detection, precise processing, and scientific research. Semiconductor pulsed lasers currently are difficult to access to the so-called “green gap,” and high-energy green pulsed lasers still heavily rely on the nonlinear frequency conversion of near-IR lasers, precluding compact and low-cost green laser systems. Here, we address this challenge by demonstrating, for the first time to the best of our knowledge, millijoule-level green pulses generated directly from a fiber laser. The green pulsed fiber laser consists of a 450 nm pump laser diode, a Ho3+-doped ZBLAN fiber, and a cavity-dumping module based on a visible wavelength acousto-optic modulator. Stable pulse operation in the cavity-dumping regime at 543 nm is observed with a tunable repetition rate in a large range of 100 Hz–3 MHz and a pulse duration of 72–116 ns. The maximum pulse energy of 3.17 mJ at 100 Hz is successfully achieved, which is three orders of magnitude higher than those of the rare-earth-doped fiber green lasers previously reported. This work provides a model for compact, high-efficiency, and high-energy visible fiber pulsed lasers.

Intelligent Model for the Reliability of the Non-Intrusive Continuous Sensors Used for the Detection of Fouling-Layer in Heat Exchanger System

Faults in this sensor must be detected on time to ensure the functionality of the entire system’s architecture and to maintain system balance, which will keep false positive rates low during the system’s operational period. False positives reduce diagnostic confidence and necessitate unnecessary and costly mitigation actions, lowering system productivity. It is on this basis that this study proposes a clustering model algorithm (K-mean clustering) to investigate and manage the reliability and performance of the sensors. The results from the implementation of the K-mean clustering method show that the running of the algorithm fits the model correctly, both for the training of the dataset and for the prediction of the cluster in each of the datasets considered. A reasonable grouping was found for the two and three clusters considered, which are represented by the colors (blue, orange, and green). These colors indicate the fault state, non-fault state, normal state, and abnormal state of the non-intrusive continuous sensor. The simulated results show the fault state in the blue region and the non-fault state in the orange region for the two clusters, while the normal state is in the blue region and the abnormal state is in the orange and green regions for the three clusters considered.

Cu2+ and Cr3+ doped borate glasses and glass-ceramics as light conversion materials for plant photosynthesis

We present a kind of Cu2+/Cr3+ doped borate luminescence glasses and glass-ceramics for potential indoor plant cultivation applications. These materials were prepared using a melt-quenching route and their luminescent and structural properties were investigated. The Cu2+ in the as-obtained materials can generate blue emission under ultraviolet (UV) excitations. The Cr3+ ions doped glasses and glass-ceramics display two intense broadband absorptions located in the UV and green light regions, also exhibit the sharp-line 2E2→4A2 emission and the broadband 4T2→4A2 luminescence. These emissions originating from Cu2+ and Cr3+ have blue (peaking at ∼480 nm) and far-red-emitting components (∼690–780 nm), which play a promising role in regulating the photomorphogenesis of plants. For certain base glass compositions, the crystals ZrO2 were spontaneously precipitated during the melt quenching process and the glass-ceramics were obtained accordingly. The relative emission intensity, position of emission bands, and fluorescence decay kinetics of Cu/Cr doped borate glasses and glass-ceramics can be effectively modulated via a compositional design engineering and the variation of excitation wavelength. The excellent photoluminescence features make these glasses and glass-ceramics very promising for applications in plant growth light-emitting diodes (LEDs).

Up-conversion and downconversion studies of Nd3+ doped borophosphate glasses

Neodymium doped borophosphate glasses have been synthesizsed by melt quenching technique to investigate their luminescence properties. The increase in density and decrease in molar volume with increasing concentration of Nd2O3 (0.1 mol% to 0.5 mol%) established the participation of Nd3+ in the glass structure. Non-crystalline nature of prepared glasses is confirmed by the absence of sharp peaks in X-ray diffraction spectra. The various structural units due to B2O3, P2O5, and PbO were identified by Fourier transform infrared spectroscopy. Ultraviolet visible absorption spectroscopy showed various absorption peaks/bands at 742 nm (4F7/2+4S3/2), 684 nm (4F9/2), 626 nm (2H11/2), 581 nm (4G5/2+2G7/2), 523 nm (4G7/2+4G9/2+ 2K13/2), 431 nm (2D5/2+2P1/2), 358 nm (4D3/2+4D5/2), 338 nm (2I11/2), and 315 (4D7/2+2I13/2+2L15/2). The optical parameters, namely indirect band gap, molar refractivity, molar polarizability, electronic polarizability and dielectric constant showed linear trend with increasing concentration of Nd2O3. Judd-Ofelt parameters followed Ω6> Ω4> Ω2 trend. The experimental and calculated oscillator strength for 584 nm is highest among all transitions because it is hypersensitive in nature. Upon 806 nm excitation, four visible peaks at 489 nm, 540 nm, 605 nm and 671 nm were observed. Excited state absorption up-conversion and energy transfer up-conversion mechanisms were responsible for visible up-conversion. At 338 nm, ultraviolet energy is downconverted to 448 nm, 529 nm, 591 nm. Commission International de I'Eclairage (CIE) chromaticity coordinates were evaluated from the up-conversion emission spectra and the coordinates lie in green region.

Ratiometric upconversion nanoprobes for turn-on fluorescent detection of hypochlorous acid

Ratiometric fluorescent nanoprobes have been developed for the detection of hypochlorous acid (HOCl) by simply mixing upconversion nanocrystals (UCNCs) with plasmocorinth B (PB) dye molecules, where UCNCs are adopted as the energy donor and dye molecules are introduced as the energy acceptor. Specifically, green upconversion luminescence (UCL) emission of UCNCs can be effectively quenched by PB, resulting from the spectral overlap between the absorption of PB and UCL emission of UCNCs in the green region. Furthermore, owing to the electrostatic repulsion between negatively charged UCNCs and PB dye molecules, the fluorescence quenching mechanism is based on the IFE process. Upon interaction with HOCl, PB dye molecules degrade, resulting in the recovery of green UCL emission through inhibition of the IFE process. The red UCL emission, however, remains unchanged. Therefore, the red UCL emission is employed as an internal reference signal for the ratiometric detection of HOCl. The detection limit of the nanoprobe for HOCl is quantified to be 1.12 µM, which is much lower than that of colorimetric detection. Moreover, the developed sensor has been successfully applied for quantitative monitoring of HOCl in tap water.