Excitation Peak Research Articles

Exploring the Feasibility of Eu(TTA)3TPPO as Pigment for Fluorescent Paint

We outline the synthesis of rare earth hybrid organic β-diketonate Eu(TTA)3TPPO complex [Eu: Europium, TTA: Thenoyl Trifluoro Acetone, TPPO: Triphenylphosphine oxide] pigment to formulate luminous paints. Epoxy and urea formaldehyde resins were synthesized by catalytic homo polymerization and solution polymerization technique, respectively. The fluorescent pigment was synthesized at ambient temperature by solution technique, maintaining the stoichiometric ratio at pH 7. Nextly, fluorescent paint was developed on glass substrate with epoxy (E) and urea formaldehyde (UF) resins and toluene as solvent with thickness 0.1 mm, respectively. Photoluminescence (PL) spectra and photometric assessment of the complex were carried out to probe its photophysical parameters. The excitation spectra of the synthesized complex depicts a wide-ranging excitation peak at 466 nm with a wide shoulder at 538 nm, while emission spectra discloses an intense peak, recorded at 617 nm which portrays colour in the reddish-orange region of the visible spectrum. The paint compositions were checked for tack-free, hard dry, adhesion, water, salt, alkali and acid spray test to study their resistance against distinct surroundings. The painted panels also portrayed reddish orange emission at a unique wavelength of 617 nm. Amid all the paint compositions, the intensity of the painted panel with urea formaldehyde as a binder was found to be maximum, followed by the painted panel with epoxy as the binder. Photometric evaluation revealed reddish-orange emission from pure pigment as well as painted panels, which portrayed in the visible spectrum. This proposes a way to develop fluorescent paints that find applications in several areas such as flexible displays, glow-in-dark road paints, OLED devices, automotive rare lighting, fluorescent sensors, aircraft cabin and floor lighting, architectural and interior decorations and many more.

Nanomodification engineering facilitated efficient fluorescence quenchers for developing sensitive lateral flow immunoassay

The fluorescence-quenching lateral flow immunoassay (FQ-LFIA) with a “turn on” pattern has shown considerable superiority comparing with traditional LFIA. For sensitive FQ-LFIA, the synthesis of fluorescence quenchers exhibiting excellent optical properties is crucial. Herein, using nanomodification engineering, we synthesized APDCOF, which exhibited intense absorption (ε390 and ε630 = 15.22 and 15.97 mL mg−1 cm−1, respectively). APDCOF as a “specific” fluorescence quencher, for which its absorption peaks highly coincide with the excitation and emission peaks of the fluorescent microsphere, could occur both the primary and secondary internal filtering effects in response to excitation and emission light, respectively, emerging high quenching efficiency to orange aggregation-induced emission fluorescent microspheres. We employed APDCOF as a quencher to develop APDCOF-LFIA for detecting the carbamate pesticide carbofuran. Compared with a colloidal-gold-based colorimetric LFIA, APDCOF-FQ-LFIA demonstrated 50- and 5.3-fold improvements in the sensitivity of the naked-eye qualitative interpretation and quantitative detection, respectively. Overall, our study presented an efficient and “specific” fluorescence quencher prepared through nanomodification engineering, offering a perspective strategy for constructing high-performance reporters in LFIA.

High‐Efficiency Cyan–Green‐Emitting Y3Sc2Ga3O12:Ce Phosphor for Microcrystals and Ultrathin Phosphor‐Glass Composite for Light‐Emitting Diode

AbstractDeveloping efficient cyan‐green phosphors and ultrathin phosphor‐glass composites (PGCs) with remarkable chemical and thermal stability is important for fabricating full‐visible‐spectrum white light‐emitting diodes (LEDs). In this study, a garnet‐structured cyan‐green phosphor, known as Y3Sc2Ga3O12:Ce (YSGG:Ce), is synthesized, exhibiting an intense excitation peak at 420 nm and broad‐emission band centered at 507 nm. Theoretical analysis indicates that a phonon with a characteristic energy of 90 meV is predominantly involved in the luminescence process. However, the phosphor powder exhibits a notable thermal quenching phenomenon for temperatures higher than 220 K. Ultrathin PGCs with the thickness of 37 µm are manufactured to achieve good thermal stability. Three types of composites are subsequently integrated onto 412 nm blue chips to prepare LED devices. The resulting device has a low correlated color temperature of 2925 K and impressive color‐rendering index of 93.5, and its precise chromaticity coordinates aligned with the black‐body locus. Therefore, this study highlights the promising applications of high‐efficiency PGCs in high‐quality LEDs.

PHire: A Novel Red Intracellular pH Sensor

Maintaining pH is critical for proper cellular and organ function. To measure intracellular pH, we made a novel genetically encoded protein, pHire, that increases red fluorescence with increasing pH. Thus, pHire allows for the coupling of multiple fluorescent tags without spectral overlap. We have expressed pHire in mammalian epithelial cells, Drosophila, and mice. In this study, our goal was to characterize pHire’s spectral properties by expression in human cells (HEK293) and in E.coli. To biophysically characterize pHire, we made a maltose binding protein (MBP)-pHire fusion protein to purify from E.coli. Pelleting individual colony growths revealed pink bacterial pellets which fluoresced with mCherry filters. Rather than purifying the MBP-pHire protein, equal volumes of bacteria were permeabilized with nigericin and high K+ solution for pH 5 to 9. These aliquots were then used to gather the fluorescence excitation and emission spectra of pHire, allowing us to determine the excitation and emission peaks of pHire as a function of pH. Our results showed peaks at Ex579 nm and Em611 nm, or roughly mCherry. Pelleted bacteria could also be fixed in perfusion chambers, revealing the same calibration curve as in mammalian cells and flies. Next, stable HEK293-pHire cells were selected to assay acid-base transport using NH4Cl or CO2/HCO3− in perfusion experiments. These HEK-pHire cells have less fluorescence than MBP-pHire bacteria but show the same Ex/Em peaks. However, an in-frame ATG 5’ to pHire in a mouse (adding 23 amino acids), removed pHire pH-dependence and decreased bacterial fluorescent output. Together these results indicate that pHire is biophysically similar in cells tested but that unstructured N-terminal additions block pH-responses. Funding: R25-DK101405, R21-DK129897. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Two Cd(Ⅱ)/Mn(Ⅱ) complexes based on multinuclear metal clusters for Fe(Ⅲ) and Cr(Ⅵ) fluorescence detection and magnetic properties

Two novel complexes, {[Cd3(L)2(H2O)2]·(H2O)4}n (1) and {[Mn(HL)(H2O)2]·(H2O)}n (2), which are synthesized by the reaction of 3-(2, 4-dicarboxyphenyl)-4-carboxypyridine ligand with cadmium and manganese metal ions under the solvothermal method. The complex 1 is a 3D framework based upon trinuclear [Cd3(μ2-COO)4(μ1-COO)4(N)2] SBUs, and the complex 2 is a one-dimensional metal oxygen chain based upon binuclear [Mn2(μ2-COO)2(μ1-COO)2(N)2] SBUs. The solid fluorescence analysis of complex 1 reveals that the emission peak of 451 nm when its excitation peak is 336 nm. The fluorescence detection experiments of complex 1 showed that Fe3+, Cr2O72− and CrO42− can effectively to be detected. Furthermore, their limits of detection are 1.47 × 10−3 M, 1.31 × 10−3 M and 1.25 × 10−3 M, respectively. It has good recovery properties as a potential multifunctional fluorescence sensor. Besides, the quenching mechanism of fluorescence sensing is also discussed. In addition, the magnetic studies of complex 2 show strong antiferromagnetic interactions between its neighboring Mn(II) ions.

Practical consideration on Racah parameter and Tanabe−Sugano diagram analyses for Mn4+ and Cr3+-activated phosphors

The Racah parameters and Tanabe−Sugano (T−S) diagram are widely used as describing the electron−electron repulsion effects within the metal complexes in coordination chemistry. The present study discusses the Racah and related parameters for the Mn4+ and Cr3+-activated phosphors. The main subjects are two-fold: (i) to clarify how different input parameters of the excited-state energies make a difference in the Racah parameters derived from the general model and (ii) to further clarify the differences between the general and our newly proposed models. The three different excited-state energies of (1) the zero-phonon line energy, (2) the photoluminescence (PL) and/or PL excitation (PLE) peak energies, and (3) the Stokes shift-corrected PLE peak energy are considered in (ii). It is shown that the choice of such excited-state energies is of crucial importance for obtaining reliable Racah parameters and T−S diagram. The present analysis of (ii) also suggests our newly proposed model to promise the Racah parameters being satisfied the requirements of B and C to be smaller than and their ratio of C/B being not largely changed from the free-ion values. The lattice temperature effects on the PL and PLE spectral features of the 3d3 ion-activated phosphors are also discussed in detail.

Theoretical investigation on the optical absorption spectra in cyclo[[formula omitted]]carbons ([formula omitted] 10, 14, 18)

The optical absorption spectra of cyclo[n]carbons (n= 10, 14, 18) are investigated in the framework of time-dependent density functional theory. The collective plasmon excitations well develop as the increases of the ring size and the symmetry group of cyclo[n]carbons. An increase in intensity for the main peaks with the growing number of atoms in cyclo[n]carbons is observed. With the increase of the radius of the monocyclic ring, as more electrons participate in the dipole oscillation the main excitation peaks are red-shifted to the lower energy. The highly symmetrical structures of cyclo[n]carbons (Dnh) possess degenerate levels, leading to simpler spectra with fewer peaks. The Fourier transform of the induced electron density of the cyclo[n]carbons (n= 10, 14, 18) is investigated at the excitation frequencies.

High quantum efficiency and excellent thermal stability in Eu3+ -activated CaY2ZrGaAl3O12 phosphors for wLEDs

There is a high demand for phosphorescent white light-emitting diodes (wLEDs) that possess low correlated color temperature (CCT) and high color rendering index (CRI), as they are considered to be environmentally friendly sources of solid-state illumination. A novel, UV-excited red light emitting Eu3+-activated CaY2ZrGaAl3O12 phosphor was synthesized for the preparation of warm wLEDs with high CRI and low CCT were obtained. Eu3+-doped CaY2ZrGaAl3O12 phosphors were synthesized with varying concentrations of Eu3+ dopant. The luminescence of Eu3+ was thoroughly examined at its optimal concentration of 20 mol%. Surprisingly, CaY2ZrGaAl3O12: 20%Eu3+ exhibits a broad excitation band of 200–550 nm and some sharp excitation peaks, the highest peak is observed at 251 nm. A dazzling red light, ranging from 550 to 750 nm, is emitted by CaY2ZrGaAl3O12: 20%Eu3+ phosphor. The excitation of ultraviolet light at a wavelength of 251 nm was employed, with an impressive internal quantum efficiency of 90.7% and a remarkable thermal quenching resistance. The wLED was packaged with green phosphor (BaMgAl10O17: Eu2+), red phosphor (CaY2ZrGaAl3O12: Eu3+), blue phosphor ((Ba, Sr)2SiO4: Eu2+) and 395 nm NUV LED chip, which emitted a dazzling warm white light when driven at a current of 20 mA. It has excellent CIE color coordinates (0.3893,0.3736), a low correlation color temperature (CCT) of 3738K, and an excellent color rendering index (Ra = 82.1). The application of the prepared new CaY2ZrGaAl3O12: Eu3+ red phosphor in wLED will promote the development of highly efficient luminous materials for healthy solid-state lighting.

Fluorescent carbon dots for highly sensitive diosmetin sensing

In this paper, a single signal fluorescent sensor of nitrogen-doped carbon dots (N-CQDs) was established for the micro-determination of diosmetin. In this determination platform, the as-developed N-CQDs with yellow fluorescence were prepared through a facile hydrothermal method with p-phenylenediamine and ascorbic acid as the precursors containing nitrogen and carbon. The as-developed N-CQDs had a classical surface structure and surprising fluorescence stability. The maximum excitation and emission peaks were located at 372 and 528 nm, respectively. Under the optimal sensing conditions, the as-prepared N-CQDs held preeminent immunity towards possible interfering substances. The determination platform’s fluorescence intensity was quenched because of the static quenching and inner filter effect. The fluorescence weakening changes displayed an attractive linear relationship with diosmetin in range of 0.5–150 μM, and the linear equation was ln(F0/F) = 0.014[Q]–0.055 with the R2 of 0.9975 and the detection limit of 0.049 μM. The determination platform could be applied for the trace detection of diosmetin in river water and bovine serum samples. The corresponding recovery rate was 94.8 %–108.8 %, exhibiting that it was a facile and efficient fluorescence sensing strategy.

Characterization of Ce3+ and Eu3+ doped and co-doped ZnO nanoparticles for luminescence applications

This paper investigates the synthesis of Ce3+ and Eu3+ doped, as well as co-doped ZnO nanoparticles using the solution combustion route. The nanoparticles exhibit a hexagonal wurtzite structure of ZnO with crystallite sizes ranging from 19 to 22 nm. Structural parameters, including lattice constants, bond lengths, and bond angles, are evaluated. Morphological diversity is observed in field-emission scanning electron microscopy images. The diffuse reflectance spectroscopy results reveal an energy band gap of 3.20 eV for undoped ZnO nanoparticles. The energy band gap value slightly decreases for Eu-doped ZnO and certain (Ce, Eu) co-doped ZnO nanoparticles. Photoluminescence (PL) excitation peaks are attributed to energy levels of native defects in the ZnO band gap, along with f–d and f–f transitions of rare-earth ions (Ce3+, Eu3+). The PL emission spectra under different excitation wavelengths (350 nm, 394 nm, and 465 nm) display varied peak positions. ZnO co-doped with 0.96 mol% of Ce3+ and 0.92 mol% of Eu3+ emerges as a promising material for luminescence applications, exhibiting a significant increase in green emission intensity. Consequently, this study represents a novel contribution to the field of ZnO-based luminescent materials.

Preparation of transparent electrospun nanofibrous membrane from long‐persistent phosphor‐reinforced polymer for security authentication

AbstractPhotochromic inks have been a tempting authentication method to make commercial items more resistant to counterfeiting. However, recent studies have shown that photochromic inks have major drawbacks, such as expensiveness and low durability. Herein, we report the development of new photochromic nanofibers for cutting‐edge anti‐counterfeiting uses. Lanthanide‐doped strontium aluminate nanoparticles (LSAN) were synthesized and immobilized onto electrospun polyurethane nanofibers (PUNF). Anti‐counterfeiting materials encapsulated with inorganic photochromic agent can guarantee photostability and durability. LSAN function as an efficient inorganic photochromic agent whereas PUNF function as a hosting matrix. Both of photostability and reversibility of the prepared UV‐induced photochromic LSAN@PUNF were found to be rather high. Applying varying ratios of LSAN resulted in the development of polyurethane nanofibers with distinct emission properties depending on the LSAN content. The nanofibrous films showed green emission under UV illumination, and whereas no traces were detected in visible daylight. LSAN displayed diameters of 3–6 nm, whereas LSAN@PUNF nanofibers had diameters of 150–450 nm. Transparency was indicated by an excitation peak at 347 nm, and a green color was indicated by an emission peak of 530 nm. The current approach can be presented as an efficient technology to prevent forgery of commercial products.

Thermometric properties of SrMoO4:Tb3+ phosphor based on redshift of charge transfer band edge

In this study, SrMoO4:Tb3+ phosphors were successfully synthesized for a single-band ratiometric (SBR) thermometry utilizing the redshift of CTB. The SrMoO4:Tb3+ phosphors have a tetragonal system owing to I41/a space group and irregular microparticles possessing a mean size of 20 μm. The incorporation of Tb3+ ions into the SrMoO4 matrix lattice leads to a reduction in the bandgap energy owing to occurrence of defects level in gap-band. Thermal quenching concentration of Tb3+ is 1%, due to the dipole-dipole interaction between Tb3+ and Tb3+ ions. This study observed an interesting redshift in the edge of the CTB with increasing temperature, which can be explained using the configurational coordinate diagram. This phenomenon can be utilized to construct this SBR temperature measurement strategy by selecting appropriate excitation peaks or bands with different thermal responses. The study also demonstrated that SrMoO4: 1%Tb3+ has higher Sa value of 13.31 × 10−2 K−1 @573 K and Sr value of 3.54 K-1@298 K in optical thermometry, making it a suitable candidate for optical temperature measurement.

Sensitive Luminescence Thermometry through Excitation Intensity Ratio in Eu-Doped BaTiO3.

Optical ratiometric thermometry techniques have gained much attention in recent years due to their reliable and noncontact temperature sensing capability for industrial and biorelated applications. Herein, we exploited the temperature dependence of the absorption band of BaTiO3 (BTO) for novel excitation intensity ratio (EIR) thermometry. Photoluminescence and excitation properties of Eu3+-doped BTO powders were studied as a function of Eu3+ doping concentration. The excitation peak intensities at 397 and 468 nm, corresponding to the 7F0 → 5L6 and 5D2 transitions of Eu3+, were used as EIR parameters. The temperature dependence of the EIR can be explained by the competitive absorption between Eu3+ and the BTO host. The EIR properties were studied in relation to the doping concentration, registering a maximum relative sensitivity (Sr) of 4.89% K-1 in BTO:Eu3+ (0.5%) at 303 K. An amphoteric Eu3+ occupation mode at both Ba2+ and Ti4+ sites was found to interpret the doping concentration dependence of the Sr. The reduced Ba2+ site occupation ratio proved to be responsible for the low Sr values at high Eu3+ doping concentrations. Accordingly, an Eu3+/Ti3+ codoping method was further proposed to improve the Sr by increasing the Ba2+ site occupation ratio. Our result showed that BTO:Eu3+ (0.5%) demonstrated an enhancement of Sr from 4.89 to 6.42% K-1 at 303 K after 2% Ti3+ codoping.

Photoluminescence properties of Sr3Y2(BO3)4: Eu3+ phosphor codoped with Gd3+ and La3+ under ultraviolet excitation

Sr3Y2 (BO3)4: Eu3+ phosphor codoped with Gd3+ and La3+ was generated using the solid state method, and XRD and fluorescence spectrum researched the structure and luminescence properties. The strongest excitation peak of Sr3Y2 (BO3)4:Eu3+ is in the near ultraviolet region of 394 nm, which comes from the 7F0 → 5L6 transition of Eu3+. With the stimulation of 394 nm ultraviolet-light, the strongest emission of Sr3Y2 (BO3)4:Eu3+ phosphor is a red light with a wavelength of 618 nm. It is produced by the transition of 5D0 → 7F2 of Eu3+. The optimum preparation temperature is 1000°C, and the doping amount of Eu3+ is 5% (mol). The doping of Gd3+ and La3+ greatly enhanced the luminescent intensity of Sr3Y2 (BO3)4:Eu3+ phosphor, and the doping of 20% (mol) was suitable.

A narrow-band blue emitting phosphor by co-doping Bi3+ and alkali metal ions (Li+, Na+ and K+) with dual luminescence center

The technology of solid-state lighting has developed for decades in various industries. Phosphor, as an element part, determines the application domain of lighting products. For instance, blue and red-emitting phosphors are required in the process of plant supplementing light, arrow-band emitting phosphors are applied to backlight displays, etc. In this work, a Bi3+-activated blue phosphor is obtained in a symmetrical and compact crystal structure of Gd3SbO7 (GSO). Then, the co-doping strategy of alkali metal ions (Li+, Na+, and K+) is used to optimize the performance. The result shows that the photoluminescence intensity is increased by 2.1 times and 1.3 times respectively by introducing Li+ and K+ ions. Not only that, it also achieves narrow-band emitting with the full width of half-maximum (FWHM) reaching 42 nm through Na+ doping, and its excitation peak position also shifts from 322 to 375 nm, which can be well excited by near-ultraviolet (NUV) light emitting diode (LED) chips (365 nm). Meanwhile, the electroluminescence spectrum of GSO:0.6 mol%Bi3+,3 wt%Na+ matches up to 93.39% of the blue part of the absorption spectrum of chlorophyll a. In summary, the Bi3+-activated blue phosphor reported in this work can synchronously meet the requirements of plant light replenishment and field emission displays.

Development of a novel fluorimetric sensor based on polypyrrole doped with 4-(methylsulfonyl)-2-nitrobenzoic acid (MSNBA) for sensitive detection of copper (Cu2+)

In this study, we successfully electrochemically synthesized a polypyrrole film doped with 4-methylsulfonyl-2-nitrobenzoic acid (MSNBA) within an aqueous medium containing 0.01 M MSNBA, 0.003 M NaOH, and 0.01 M pyrrole. Our investigation encompassed a thorough exploration of both electrochemical and spectroscopic properties, confirming the effective incorporation of MSNBA as a dopant within the electroactive PPy chain. The morphological characterization of the film was undertaken using scanning electron microscopy (SEM). The optical properties, particularly UV–visible absorption, and fluorescence spectroscopy, were scrutinized in a dilute DMF solution. The UV–visible absorption spectra revealed a broad absorption band centered around 292 nm, attributed to the π→π* 1B - 1La/1Lb transitions of the oligo-benzenes in the film. In parallel, fluorescence spectra exhibited remarkable consistency between the solid state and solution, featuring an excitation peak at 345 nm (346 nm in solution) and an emission peak around 401 nm (403 nm in solution). Exploring the impact of copper (II) ions on absorption and fluorescence spectra unveiled a notable quenching effect along two distinct linearity domains. Various mathematical treatments, including the Stern-Volmer equation (R1 = 0.98, Ksv1 = 5.104 and R2 = 0.99, Ksv2 = 1.54.106), the Perrin equation, and the polynomial equation, were applied to elucidate the nature of this fluorescence quenching. Our findings indicated that the fluorescence extinction, as a function of Cu2+ ion concentration, aligns well with the polynomial equation, signifying a combination of dynamic and static quenching (Io/I = 1.08(±0.04) + 1.46(±0.44)105[Q]- 1.15(±0.75)1010 [Q]2). Moreover, we explored the potential application of this method for the determination of Cu2+. Calibration graphs demonstrated excellent linearity between fluorescence intensity and Cu2+ concentration in the range of 0–5.4 μM. Notably, the detection limit of 1.2 μM surpassed the LOD for Cu2+ (20 μM) in drinking water set by the EPA, suggesting the viability of this approach for sensitive detection in environmental monitoring.

Selective fluoride detection based on modulation of red emissive carbon dots fluorescence by zirconium-alizarin complex: Application to Nile River water and human saliva samples

Fluoride is an essential ion for dental health that is optimally supplemented through drinking water, toothpastes, and other oral hygiene products. This work reports a selective, simple, and inexpensive fluorescent sesnor for fluoride quantification. The sensor exploits the red fluorescence of carbon dots coupled with the colorimetric response of a zirconium-alizarin complex. The zirconium-alizarin exhibits an absorption band at 530 nm that overlaps the carbon dot excitation peak, resulting in inner filter effect-based quenching of the 612 nm red emission. However, in the presence of fluoride, binding disrupts the zirconium complex, releasing free alizarin with an absorption blue shifted to 420 nm. This reduces spectral overlap and restores carbon dot fluorescence. The carbon dots were synthesized by a hydrothermal method and exhibited excellent fluorescence quantum yield (16.3 %). Structural and optical characterizations were performed using TEM, XRD, XPS, FTIR, UV–vis, and fluorescence techniques. Under optimized conditions, the probe provided selective turn-on fluorescence detection of fluoride with a linear response from 1.0 to 130.0 μM and limit of detection (S/N = 3) of 0.32 μM. Practical utility was demonstrated by accurate quantification of fluoride in Nile River water and human saliva samples. This dual nanoprobe strategy offers a rapid and cost-effective platform for fluoride analysis in support of healthcare and environmental monitoring applications.

Impact of Structural Changes on Energy Transfer in the Anion-Engineered Re3+:Y2O3 Through Low-Temperature Synthesis Approach.

Anion engineering has proven to be an effective strategy to tailor the physical and chemical properties of metal oxides by modifying their existing crystal structures. In this work, a low-temperature synthesis for rare earth (RE)-doped Y2O2SO4 and Y2O2S was developed via annealing of Y(OH)3 intermediates in the presence of elemental sulfur in a sealed tube, followed by a controlled reduction step. The crystal structure patterns (X-ray diffraction) and optical spectra (UV-IR) of Y2O2SO4, Y2O2S, and crystalline Y2O3 were collected throughout the treatment steps to correlate the structural transformations (via thermogravimetric analysis) with the optical properties. Local and long-range crystallinities were characterized by using X-ray and optical spectroscopy approaches. Systematic shifts in the Eu3+ excitation and emission peaks were observed as a function of SO42- and S2- concentrations resulting from a crystal evolution from cubic (Y2O3) to trigonal (Y2O2S) and monoclinic (Y2O2SO4), which can modify the local hybridization of sensitizer dopants (i.e., Ce3+). Ultimately, Tb3+ and Tb3+/Ce3+ doping was employed in these hosts (Y2O2SO4, Y2O2S, and Y2O3) to understand energy transfer between sensitizer and activator ions, which showed significant enhancement for the monoclinic sulfate structure.

Elucidating photocycle in large Stokes shift red fluorescent proteins: Focus on mKeima.

Large Stokes shift red fluorescent proteins (LSS-RFPs) are genetically encoded and exhibit a significant difference of a few hundreds of nanometers between their excitation and emission peak maxima (i.e., the Stokes shift). These LSS-RFPs (absorbing blue light and emitting red light) feature a unique photocycle responsible for their significant Stokes shift. The photocycle associated with this LSS characteristic in certain RFPs is quite perplexing, hinting at the complex nature of excited-state photophysics. This article provides a brief review on the fundamental mechanisms governing the photocycle of various LSS-RFPs, followed by a discussion on experimental results on mKeima emphasizing its relaxation pathways which garnered attention due to its >200 nm Stokes shift. Corroborating steady-state spectroscopy with computational studies, four different forms of chromophore of mKeima contributing to the cis-trans conformers of the neutral and anionic forms were identified in a recent study. Furthering these findings, in this account a detailed discussion on the photocycle of mKeima, which encompasses sequential excited-state isomerization, proton transfer, and subsequent structural reorganization involving three isomers, leading to an intriguing temperature and pH-dependent dual fluorescence, is explored using broadband femtosecond transient absorption spectroscopy.

Carbon quantum dots with honeycomb structure: a novel synthesis approach utilizing cigarette smoke precursors

This study presents a novel approach to synthesizing honeycomb carbon quantum dots (CQDs) from cigarette smoke by a hydrothermal process. A comprehensive characterization of these CQDs, conducted through high-resolution transmission electron microscopy (HRTEM), showcases their unique honeycomb structure, with an average particle size of 6.3 nm. Photoluminescence (PL) in CQDs is a captivating phenomenon where these nanoscale carbon structures emit strong blue luminescence at 461 nm upon exposure to ultraviolet light, with their excitation peak occurring at 380 nm. Fourier Transform Infrared (FTIR) analysis also identifies specific functional groups within the CQDs, offering valuable insights into the mechanisms governing their photoluminescence. Analysis of excitation spectra indicates the presence of both aromatic C=C bonds at 254 nm and C–O bonds from 280 to 420 nm.