Absolute Quantum Yield Research Articles

Particle size effect on the structure, morphology and optical properties of europium doped ZrO2 nanoparticles

In the recent decade, various potential applications of the luminescence of nanosized ZrO2:Eu3+ have been demonstrated. However, the particle size effect on the luminescence properties of ZrO2:Eu3+ still requires intensive investigation. To this end, a series of tetragonal ZrO2:Eu3+ nanopowders with the europium concentration of 4 wt% and particle size of 3.0 ± 0.7 to 12.0 ± 4.8 nm was synthesized by laser vaporization. It was shown that the dominant role in the optical properties of ZrO2:Eu3+ nanoparticles belongs to OH groups, oxygen vacancies, and Eu3+ ions. It was found that a decrease in the particle size is accompanied by a significant increase in the emission intensity in the region of ∼440 nm. Based on the results of thermal analysis, IR and UV–vis DR spectroscopies, it was concluded that this luminescence is due to the emission of adsorbed OH groups. At the same time, a decrease in the number of vacancies with a decrease in the particle size leads to a change in the absolute quantum yield QY from ∼7 to 3.5%. In addition, despite the overall decrease in the intensity of the red luminescence of Eu3+, a decrease in the particle size leads to the appearance and increase in the emission intensity of the surface Eu3+. Thus, changing the particle size from 12.0 to 3.0 nm leads to a twofold decrease in the luminescence efficiency of ZrO2:Eu3+ and a shift in the color of its emission from pink-red (0.36, 0.26) to blue (0.19, 0.10). The results obtained are expected to be useful for further optimization of the luminescence properties of nanosized ZrO2:Eu3+ in numerous applications.

Crystal structures and solid-state luminescent properties of Eu(III), Gd(III) and Tb(III) complexes with hexafluoroacetylacetone and 4′-substituted terpyridine ligands

Six mononuclear lanthanide complexes [Ln(hfac)3(ptpy)] (Ln(III) = Eu (1), Gd (2), Tb (3)) and [Ln(hfac)3(ftpy)] (Ln(III) = Eu (4), Gd (5), Tb (6)), synthesized with 1,1,1,5,5,5-hexafluoroacetylacetone (hfac) as a first ligand and 4′-phenyl-2,2′:6′,2″-terpyridine (ptpy) or 4′-furan-2,2′:6′,2″-terpyridine (ftpy) as a second ligand, were characterized by elemental analyses, infrared spectroscopy, single-crystal X-ray diffraction, and powder X-ray diffraction. Thermogravimetric analyses indicate that these ternary lanthanide complexes possess very good thermal stability. Solid-state samples of 1-Eu and 4-Eu exhibit characteristic red luminescence at CIE: 0.6721, 0.3276 and CIE: 0.6859, 0.3139, with absolute quantum yields of 59.95% and 83.14% and luminescence lifetimes of 0.819 and 0.727 ms, respectively. Solid-state samples of 3-Tb and 6-Tb display characteristic green luminescence at CIE: 0.2736, 0.7167 and CIE: 0.2674, 0.7219, with absolute quantum yields of 2.58% and 0.52% and luminescence lifetimes of 0.040 and 0.033 ms, respectively. The results suggest that terpyridine is a good sensitizer for Eu(III), while hfac is a good sensitizer for Tb(III). In solid-state, the synergistic sensitization effect of hfac and terpyridine is significant for Eu(III), but less for Tb(III). And the electron-donating substituent at the 4′-position make terpyridine more suitable for the sensitization of Eu(III), but unfavorable for Tb(III).

A red-emitting ultrasensitive fluorescent probe for specific detection and biological visualization of cysteine in vitro and in vivo

Developing efficient strategies for specific detection of cysteine (Cys) is of great importance for identifying complicated biological roles in physiological and pathological processes. Herein, an ultrasensitive red-emission fluorescent probe (termed 1) is constructed for specific detection and biological visualization of Cys. The linked-anthocyanin fluorophore modified with a twisted N, N-diethylamino moiety shows improved red-shifted emission (642 nm) and absolute quantum yield (0.224 in dimethyl sulfoxide), as well as minimal fluorescence background signal and good water solubility. Meanwhile, utilizing acryloyl chloride as recognition group endows the probe 1 with excellent sensitivity and selectivity towards Cys (limit of detection: 2.93 nM). More importantly, the in vitro and in vivo results confirm that the probe 1 has the capacity of fluorescence imaging of Cys and good biological safety, which holds great promise for bioanalysis and biosensing of Cys.

Fluorophenyl-modified AIPE-active cationic Pt(II) complexes for detecting picric acid in aqueous media

Two new fluorophenyl-modified cationic cyclometalated Pt(II) complexes have been synthesized. The effects of the fluorophenyl substituents on the properties of the Pt(II) complexes were investigated systematically in comparison with a phenyl-modified complex. The absolute quantum yields of the complexes are significantly increased due to the presence of fluorophenyl groups. All complexes exhibit evident aggregation-induced phosphorescent emission activities in a CH3CN/H2O system. Furthermore, they can effectively detect picric acid (PA) in CH3CN/H2O. Among them, the complex with a 2,4-difluorophenyl group exhibits the lowest limit of detection at 0.09 μM. These complexes exhibit excellent selectivity for detecting PA in complicated environments and work well in real water samples. The luminescence quenching of the complexes is caused by photo-induced electron transfer.

Single Molecular Persistent Room-Temperature Phosphorescence and Circularly Polarized Luminescence from Binaphthol-Decorated Optically Innocent Cyclotriphosphazenes.

Circularly polarized luminescence (CPL) features of BINOL-decorated cyclotriphosphazenes (CPs) are reported for the first time. The luminescence dissymmetry factor (glum ) of these compounds in chloroform solutions and polymethyl methacrylate (PMMA) thin films with wt 1 % doping concentrations are found to be 1.0×10-3 , and 2.9×10-3 , respectively. However, no CPL signal is observed for the pristine solids. The enantiomers (CP-(R)/CP-(S)) show ultraviolet photoluminescence (~350-360 nm) in solution and the solid state. These compounds show ~10 times larger absolute photoluminescence quantum yield (PLQY) than the simple BINOLs in the solutions state. In the solid state, CP-(R) shows larger PLQY than binaphthol-(R); in contrast, the S enantiomer shows lower PLQY than binaphthol-(S); this indicates that the isomer-dependent solid-state packing of these compounds plays a crucial role in controlling the PL. Thin films with more than 1 % doping concentration and pristine solids of these compounds do not show persistent room-temperature phosphorescence (pRTP) due to concentration-caused quenching. However, thin films with wt 1 % of these chiral emitters exhibit pRTP characteristics with a ~159-343 ms lifetime under vacuum. Theoretical calculations reveal that the cyclophosphazene acts as an optically innocent dendritic core, and the optical features of these compounds are dictated by the pendent BINOL chromophore.

Photochemically and Thermally Generated BN-Doped Borafluorenate Heterocycles via Intramolecular Staudinger-Type Reactions.

A series of BN-incorporated borafluorenate heterocycles, bis(borafluorene-phosphinimine)s (11-15), have been formed via intramolecular Staudinger-type reactions. The reactions were promoted by light or heat using monodentate phosphine-stabilized 9-azido-9-borafluorenes (R3P-BF-N3; 6-10) and involve the release of dinitrogen (N2), migration of phosphine from boron to nitrogen, and oxidation of the phosphorus center (PIII to PV). Density functional theory (DFT) calculations provide mechanistic insight into the formation of these compounds. Compounds 11-15 are blue emissive in the solution and solid states with absolute quantum yields (ΦF) ranging from 12 to 68%.

Configuration of super-fast Cu2+-responsive chemosensor by attaching diaminomaleonitrile to BODIPY scaffold for high-contrast fluorescence imaging of living cells

A highly fluorescent Cu2+-responsive sensor, 2-amino-3-(BODIPYmethyleneamino)maleonitrile (BD) was constructed by attaching diaminomaleonitrile to a BODIPY scaffold. Cu2+ can be selectively recognized on a 2-s time-scale by way of fluorescence emission. When Cu2+ and BD coexist in solution, typical BODIPY emission was observed and the emission intensity could be increased to 334 times that of the blank dye solution. The mechanism of fluorescence increase is based on the generation of highly fluorescent species by Cu2+-triggered oxidative cyclization of the attached diaminomaleonitrile. The absolute fluorescence quantum yield (AFQY) of the cyclization product is 98% determined by integrating sphere. The highly emissive character can be attributed to the imidazole ring and dicarbonitrile on the BODIPY scaffold. It surpasses the meso-phenyl substituted analogue in AFQY and detection limits (DL). The specific Cu2+ recognition behavior was also validated in Hela cells with high-contrast fluorescence images.

Fluorine-doped carbon quantum dots with deep-red emission for hypochlorite determination and cancer cell imaging

As a type of new carbon-based nanomaterials, carbon dots (CDs) possess exceptional optical properties, making them highly desirable for use in fluorescent sensors. However, the CDs with deep-red (DR) or near-infrared (NIR) emission have rarely been reported. In this work, we prepared deep-red emissive fluorine-doped carbon quantum dots (F-CDs) by introducing a precursor simultaneously containing fluorine and amidogen. The synergistic effect of nitrogen doping and D-π-A pattern production contributed to the maximum emission of F-CDs at 636 nm with an absolute quantum yield of 36.00% ± 0.68%. Moreover, we designed an F-CDs-based fluorescence assay to determine the content of hypochlorite (ClO−), with a limit of detection (LOD) as low as 15.4 nmol/L, indicating the high sensitivity of F-CDs to ClO−. In real samples, the F-CDs-based fluorescent sensor exhibited excellent sensitivity and selectivity in the detection of ClO−, with an error below 2%, suggesting their great potential in daily life. In cancer cell imaging, the F-CDs not only demonstrated high sensitivity to ClO− but also exhibited excellent mitochondria targeting, as evidenced by the high Pearson's correlation coefficient (PCC) of 0.93 in colocalization analysis. The work presented here suggests the great potential of replacing commercial dyes with F-CDs for highly specific mitochondria labeling and cell imaging.

Efficiency enhancement of solar cell by using methylammonium lead tribromide/polymethyl methacrylate hybrid film as luminescent down shifting layer

Luminescent down-shifting (LDS) layer was introduced to tackle the issue of poor short-wavelength response of solar cell. Besides LDS effect, coating a LDS layer on the surface of a solar cell leads to a change in surface reflectance. LDS and antireflection (AR) effect are coupled and usually reported as a single effect. For those solar cell with optimized AR, it is difficult to enhance power conversion efficiency (PCE) with the LDS layer due to the variation of reflectance. In this work, we report an obvious PCE enhancement of two mainstream commercial silicon (Si) solar cells with the optimized AR by using methylammonium lead tribromide (MAPbBr3)/polymethyl methacrylate (PMMA) hybrid film as a LDS layer. The used MAPbBr3/PMMA nanoplatelets solutions for LDS layer have an absolute photoluminescent quantum yield of ∼85 % (excited by 350 nm) in air atmosphere for more than 30 days, laying a foundation for the realization of effective LDS effect. Theoretical analysis has separated the AR and LDS effect. It has demonstrated that AR effect has a positive influence on LDS effect, and PMMA plays the key role in the improvement of AR. Experimental studies further elucidated the LDS and AR effect provided by MAPbBr3/PMMA hybrid film. Thanks to this combined effect, the application of MAPbBr3/PMMA hybrid film as a LDS layer on Si heterojunction solar cell yields a PCE gain of 0.3 % absolute and that on passivated emitter and rear cell produces an absolute PCE enhancement of about 0.7 %.

Effect of SiO2 shell on photoluminescence enhancement of Eu3+ doped nanophosphor based on monoclinic Y2O3

Surface SiO2 coating strategy was used to enhance the photoluminescent properties of Eu3+ doped nanophosphor based on monoclinic Y2O3. Laser-synthesized m-Y2O3:Eu3+ spherical nanoparticles with high crystallinity and diameter of ca. 18 nm were used as a core for the preparation of m-Y2O3:Eu3+@SiO2 core-shell structures. According to HRTEM and HAADF-STEM data, a thin SiO2 shell uniformly encapsulated the crystal core with a thickness of about 1.5 nm. The SiO2 shell increases the absolute photoluminescence quantum yield of Eu3+ at λ = 395 nm excitation from 14 % to 68 %. To the best of our knowledge, the obtained quantum yield exceeds the known values for Eu3+ doped oxide-based nanophosphors and is comparable to those of some other commercial red microphosphors. The SiO2 coating was shown to reduce the luminescence quenching effect associated with the annealing-induced migration of Eu3+ from the bulk to the surface of nanoparticles. The obtained results demonstrate that m-Y2O3:Eu3+@SiO2 core-shell nanoparticles with intense red luminescence have significant potential for use in LEDs, high resolution displays, bioimaging technologies and in other solid-state lighting applications.

Spectroscopy and absolute photoluminescence quantum yield of Eu3-doped zinc-tellurite glasses for solid state lightning applications

Spectroscopic properties of Eu3+-doped tellurite glass composed of 74 TeO2 + 15 ZnO +5 Nb2O5 + 5 TiO2 + 1.0 Eu2O3(mol %) have been investigated. Phonon energy of the host glass constituents that are linked up with the Eu3+ ions have been evaluated from the photoluminescence excitation spectrum which is found to be 760 cm−1. By utilizing the emission spectrum, the Judd-Ofelt (JO) intensity parameters (Ωλ, λ = 2 and 4) are calculated. The obtained JO parameters are utilized for evaluating the emission cross-sections (σ(λp)) of 5D0 → 7FJ (J = 1, 2 and 4) transitions. An intense emission at 613 nm due to the transition5D0 → 7F2is observed upon 465 nm excitation. Among these, the 5D0 → 7F2 (613 nm) transition has been exhibited the highest (σ(λp)) value and it found to be 2.11 × 10−22 cm2. For the 5D0 level, quantum efficiency (η) is corroborated theoretically as 58.4% and it is in line with absolute quantum yield of 56.7% obtained by Integrating sphere method. The results of Eu3+-doped TZNTEu1.0 glass are significant for the development of solid-state lighting devices at around 613 nm under the excitation of 465 nm.

Exploring the Origin of the Thermal Sensitivity of Near-Infrared-II Emitting Rare Earth Nanoparticles.

Rare-earth doped nanoparticles (RENPs) are attracting increasing interest in materials science due to their optical, magnetic, and chemical properties. RENPs can emit and absorb radiation in the second biological window (NIR-II, 1000-1400 nm) making them ideal optical probes for photoluminescence (PL) in vivo imaging. Their narrow emission bands and long PL lifetimes enable autofluorescence-free multiplexed imaging. Furthermore, the strong temperature dependence of the PL properties of some of these RENPs makes remote thermal imaging possible. This is the case of neodymium and ytterbium co-doped NPs that have been used as thermal reporters for in vivo diagnosis of, for instance, inflammatory processes. However, the lack of knowledge about how the chemical composition and architecture of these NPs influence their thermal sensitivity impedes further optimization. To shed light on this, we have systematically studied their emission intensity, PL decay time curves, absolute PL quantum yield, and thermal sensitivity as a function of the core chemical composition and size, active-shell, and outer-inert-shell thicknesses. The results revealed the crucial contribution of each of these factors in optimizing the NP thermal sensitivity. An optimal active shell thickness of around 2 nm and an outer inert shell of 3.5 nm maximize the PL lifetime and the thermal response of the NPs due to the competition between the temperature-dependent back energy transfer, the surface quenching effects, and the confinement of active ions in a thin layer. These findings pave the way for a rational design of RENPs with optimal thermal sensitivity.

Luminescent analysis of [Eu2DPA3] MOF as high purity red-emitting phosphor with thermal stability

In this work, the synthesis of a red-emitting phosphor with thermally stable photoluminescence, [Eu2DPA3]n MOF is reported. Thermogravimetric analysis (TGA) confirmed the formation of the coordination polymer with 2:3 metal to ligand stoichiometry, without water contents. Fourier transform infrared spectroscopy (FTIR) evidenced bands corresponding to different coordination modes between DPA carboxylates and pyridine nitrogen atoms with the Eu3+ ion, among them were COOEu, COOEu2, COOEu3, as well as picolinic mono- and bis-chelates, clearly indicating the formation of a coordination polymer. The luminescent properties were determined using 300 and 395 nm as exciting wavelengths, getting the typical emission bands of Eu3+ (5D0 →7F0,1,2,3,4). Luminescence lifetimes (τ) were determined using a monoexponential fit obtaining values of 2.2 (λexc = 300 nm) and 1.9 ms (λexc = 395 nm). The [Eu2DPA3]n MOF shows quantum efficiency of 48% (λexc = 300 nm) and 42% (λexc = 395 nm), and an absolute quantum yield of 55 and 31% with the same excitation conditions. The photometric study indicates that the luminescent response to excitation with 300 and 395 nm is practically identical, with a high purity red color >98%, and a chromatic coordinate of 0.65, 0.35. The temperature-dependent luminescence properties revealed a stable luminescent signal in the range of 30–150 °C, with a signal loss of 3.5% and an extinction energy (ΔE) of 0.21 eV.

Highly sensitive detection of microRNA-21 by nitrogen-doped carbon dots-based ratio fluorescent probe via nuclease-assisted rolling circle amplification strategy

Highly sensitive and selective detection of microRNA-21 (miRNA-21) in biological samples is critical for the disease diagnosis and cancer treatment. In this study, a nitrogen-doped carbon dots (N-CDs)-based ratio fluorescence sensing strategy was constructed for miRNA-21 detection with high sensitivity and excellent specificity. Bright-blue N-CDs (λex/λem = 378 nm/460 nm) were synthesized by facile one-step microwave-assisted pyrolysis method by using uric acid as the single precursor, and the absolute fluorescence quantum yield and fluorescence lifetime of N-CDs were 35.8% and 5.54 ns separately. The padlock probe hybridized with miRNA-21 firstly and then was cyclized by T4 RNA ligase 2 to form a circular template. At the present of dNTPs and phi29 DNA polymerase, the oligonucleotide sequence in miRNA-21 was prolonged to hybridize with the surplus oligonucleotide sequences in circular template, generating long and reduplicated oligonucleotide sequences containing abundant guanine nucleotides. Separate G-quadruplex sequences were generated after the addition of Nt.BbvCI nicking endonuclease, and then hemin bound with G-quadruplex sequence to construct the G-quadruplex DNAzyme. Such G-quadruplex DNAzyme catalyzed the redox reaction of o-phenylenediamine (OPD) with H2O2, finally producing the yellowish-brown 2,3-diaminophenazine (DAP) (λem = 562 nm). Due to the inner filter effect between N-CDs and DAP, the ratio fluorescence signal of DAP with N-CDs was utilized for sensitive detection of miRNA-21 with detection limit of 0.87 pM. Such approach has practical feasibility and excellent specificity for miRNA-21 analysis during highly homological miRNA family in HeLa cell lysates and human serum samples.

NIR Clusteroluminescence of Non-conjugated Phenolic Resins Enabled by Through-Space Interactions.

Clusteroluminescence (CL) and through-space interactions (TSIs) of non-conjugated molecules have drawn more attention due to their unique photophysical behaviors that are different from largely conjugated luminogens. However, achieving red and even near-infrared (NIR) emission from such systems is still challenging due to the intrinsic drawbacks of non-conjugated molecules and the lack of theories for structure-property relationships. In this work, six phenolic resins are designed and synthesized based on two molecule-engineering strategies: increasing the number of TSIs units and introducing electron-donating/-withdrawing groups. All phenolic resins are verified as luminogens with CL property (CLgens), and the first example of CLgens with NIR emission (maximum emission wavelength ≥680 nm) and high absolute quantum yield (47 %) is reported. Experiments and theoretical analysis reveal that two TSIs types, through-space locally excited state and through-space charge transfer state, play essential roles in achieving CL from these non-conjugated polymers, which could be manipulated via changing structural conformation and electron density or altering electron transition behaviors. This work not only provides an approach to manipulate TSIs and CL of non-conjugated polymers but also endows commercially available phenolic resins with high practical value as luminescence materials.

NIR Clusteroluminescence of Non‐conjugated Phenolic Resins Enabled by Through‐Space Interactions

AbstractClusteroluminescence (CL) and through‐space interactions (TSIs) of non‐conjugated molecules have drawn more attention due to their unique photophysical behaviors that are different from largely conjugated luminogens. However, achieving red and even near‐infrared (NIR) emission from such systems is still challenging due to the intrinsic drawbacks of non‐conjugated molecules and the lack of theories for structure–property relationships. In this work, six phenolic resins are designed and synthesized based on two molecule‐engineering strategies: increasing the number of TSIs units and introducing electron‐donating/‐withdrawing groups. All phenolic resins are verified as luminogens with CL property (CLgens), and the first example of CLgens with NIR emission (maximum emission wavelength ≥680 nm) and high absolute quantum yield (47 %) is reported. Experiments and theoretical analysis reveal that two TSIs types, through‐space locally excited state and through‐space charge transfer state, play essential roles in achieving CL from these non‐conjugated polymers, which could be manipulated via changing structural conformation and electron density or altering electron transition behaviors. This work not only provides an approach to manipulate TSIs and CL of non‐conjugated polymers but also endows commercially available phenolic resins with high practical value as luminescence materials.

Uncertainty evaluation of photoluminescence quantum yield measurement in an integrating hemisphere-based instrument.

We present an integrating hemisphere-based (i.e.,a variant of integrating spheres) implementation of the indirect illumination method for absolute photoluminescence quantum yield measurements, which is a recommended method in the international standard IEC 62607-3-1:2014. We rigorously formulated a mathematical model and a measurement procedure for the absolute photoluminescence quantum yield measurement in the integrating hemisphere-based system. The measurement system was calibrated using an Hg-Ar discharge lamp and spectral irradiance standard lamps for wavelength and relative spectral radiant flux scales, respectively. Furthermore, we identified and evaluated uncertainty components involved in the photoluminescence quantum yield (PLQY) measurement. To validate our measurement system, we applied it to the two de facto standard dyes: quinine bisulfate (QBS) and fluorescein (FLS). Consequently, their PLQY values were determined to be 0.563±0.024 (k=2) and 0.876±0.032 (k=2) for, respectively, QBS and FLS, which are consistent with previous reports.

Synthesis of cellulose nanofibrils modified with carbon dots-graft-polyacrylamide/ZIF-8 composite hydrogel for simultaneous adsorption and detection of tetracycline

To address the pollution of antibiotics in water resources, a novel cellulose nanofibrils modified with carbon dots-graft-polyacrylamide/Zeolitic imidazolate framework-8 composite hydrogel (CZCH) was synthesized in this study for simultaneous adsorption and detection of tetracycline (TC). The morphology, structure, fluorescent properties, and adsorption and sensing capabilities of CZCH were comprehensively characterized using various analytical techniques. The results demonstrated the CZCH's remarkable adsorption capacity for TC that reached a maximum of 810.36 mg/g. The Langmuir model provided an excellent fit for the adsorption isotherm, while the pseudo-secondary model accurately described the adsorption kinetics. Thermodynamic analysis revealed that the adsorption process was characterized by an endothermic reaction. Impressively, the CZCH maintained 85.6% retention of its initial adsorption capacity even after undergoing five consecutive adsorption/desorption cycles. Moreover, the synthesized CZCH exhibited blue fluorescence with an absolute quantum yield of 5.1%, enabling selective and efficient detection of TC with a low limit of detection of 0.09 μg/L. Furthermore, the mechanism underlying the adsorption and detection of TC by CZCH was elucidated. Cost analysis confirmed that CZCH had a significantly lower cost of CNY 0.07 per gram of TC removal compared to activated carbon, which costs CNY 5.74. Thus, this study presents a sustainable approach for synthesizing a low-cost and multifunctional adsorbent that can be employed for the adsorption and detection of antibiotics.

A ratiometric fluorescent probe for simultaneous detection of L-ascorbic acid and alkaline phosphatase activity based on red carbon dots/polydopamine nanocomposite

Herein, efficient red carbon dots (R-CDs) were synthesized by one-step hydrothermal treatment of N-(4-amino phenyl) acetamide and (2,3-difluoro phenyl) boronic acid. The optimal emission peak of R-CDs was at 602 nm (under 520 nm excitation) and the absolute fluorescence quantum yield of R-CDs was 12.9%. Polydopamine, which was formed by the self-polymerization and cyclization of dopamine in alkaline condition, emitted characteristic fluorescence with peak position of 517 nm (under 420 nm excitation) and affected the fluorescence intensity of R-CDs through inner filter effect. L-Ascorbic acid (AA), which was the hydrolysis product of L-ascorbic acid-2-phosphate trisodium salt under the catalytic reaction of alkaline phosphatase (ALP), effectively prevented the polymerization of dopamine. Combined with the ALP-mediated AA production and the AA-mediated polydopamine generation, the ratiometric fluorescence signal of polydopamine with R-CDs was correlated closely with the concentration of both AA and ALP. Under optimal conditions, the detection limits of AA and ALP were 0.28 μM during linear range of 0.5–30 μM and 0.044 U/L with linear range of 0.05–8 U/L, respectively. This ratiometric fluorescence detection platform can efficiently shield the background interference of sophisticated samples by introducing a self-calibration as reference signal in a multi-excitation mode, which can detect AA and ALP in human serum samples with satisfactory results. Such R-CDs/polydopamine nanocomposite provides a steadfast quantitative information and makes R-CDs be excellent candidate for biosensors via combining target recognition strategy.

Probing the Electron Transfer Behavior from Excited State Organometal Lead Halide Perovskite Nanocrystals to Molybdenum Disulfide Nanoflowers

The charge transfer study from the excited state of MAPbBr3 perovskite nanocrystals (PNCs) to molybdenum disulfide (MoS2) in chloroform solution is conducted using a fluorescence approach. Due to their exceptional properties and distinctive structures, transition metal dichalcogenides (TMDs) are promising candidates for optoelectronic devices. In this study, we have combined hybrid organic–inorganic perovskite nanocrystals MAPbBr3 with MoS2 solution. A significant electron transfer from MAPbBr3 to MoS2 has been depicted by photoluminescence (PL) spectroscopy, time-correlated single-photon count (TCSPC), transient absorption spectroscopy (TAS), and shortening of the absolute PL quantum yield (PLQY) of hybrid MAPbBr3/MoS2 nanocomposites. Fluorescence quenching of perovskite nanocrystals has shown an increase in quenching efficiency. The photoexcited charge transfer from MAPbBr3 to adjacent MoS2 is further correlated using electrochemical tests that compare reduction and oxidation potential. The results revealed that MoS2 extracts the charge from the excited state of PNCs. This work demonstrates the charge transfer properties of hybrid halide perovskites with two-dimensional TMD materials. A combination of these materials could help us to understand the actual potency of MAPbBr3 PNCs in their real applications.