Light Emission Research Articles

Photoluminescence of Sm3+ and Eu3+ co-doped La2O3–Ga2O3 glasses fabricated by an aerodynamic levitation furnace

A series of transparent (1-y)La2O3–Ga2O3-ySm2O3-xEu2O3 (where x = 0, 0.02, 0.04, 0.06, 0.08, 0.10, 0.12, 0.14, and y = 0, 0.04) were successfully synthesized using a containerless solidification process. Co-doping with Sm3+ and Eu3+ enhanced the energy absorption of Eu3+, notably improving the characteristic emission peak 5D0-7F2 of Eu3+. The peak emission intensity for y = 0.04 was observed at x = 0.08, attributable to the concentration quenching of Eu3+ ions. As the concentration of Eu3+ increased, the energy transfer effect on emission intensity diminished. Attributed to the energy transfer between Sm3+ and Eu3+, Sm3+ may primarily serve as the sensitizer, and Eu3+ as the activator. According to the Dexter theory, which suggests that the interaction between activator ions and their adjacent ions is the primary mechanism of energy transfer and quenching among Eu3+ ions and adjacent ions, an increase in Eu3+ concentration leads to a decrease in the distance between Eu3+ and adjacent ions, strengthening their interaction, and potentially inducing concentration quenching. Furthermore, with an increase in Eu3+ concentration, the CIE chromaticity coordinates for the samples co-doped with Sm3+ and Eu3+ shifted significantly, enhancing the color purity of the emitted light and bringing it closer to the NTSC color standard coordinates (0.67, 0.33).

Enhanced red emission of MgAl2O4: Cr3+/Mn4+ phosphor co-doped with alkali metal ions

A series of MgAl2O4: Cr, Mn, M (M = Li, Na, K) red phosphors were prepared by solution combustion combined with subsequently annealing treatment. The influence of Cr3+ or Mn4+ single-doping, Cr3+ and Mn4+ double-doping and alkali metal ions co-doping on the luminescence performance of MgAl2O4 phosphors were systematically investigated. XRD and SEM were used to characterize the composition and morphology of the phosphors, and the optical absorption, photoluminescent excitation, photoluminescent emission, fluorescence lifetime and chromaticity coordinate were performed to characterize their luminescence properties. Compared with Cr3+ or Mn4+ single-doped MgAl2O4 phosphors, Cr3+ and Mn4+ double-doped ones can achieve red light emission under a wide range of excitation from ultraviolet to visible light. Co doping with alkali metal ion Li enhances the fluorescence intensity and lifetime of MgAl2O4: Cr, Mn phosphors.

Fumaronitrile-based π–conjugated mechanochromic material: Design, synthesis and photophysical properties

In this study, we synthesized four 2,3-bis(4-methoxyphenyl)fumaronitrile-based D–A–D quadrupoles using a two-fold Suzuki-Miyara cross-coupling reaction and conducted comprehensive investigations into their photophysical properties, including absorption, fluorescence, and lifetime in the solution state. All compounds demonstrate a blue to green light emission both in solution and thin films, alongside moderate quantum yields and lifetimes (in the nanosecond range) in solution state, while also presenting significant spectral shifts in thin films. Aggregation-induced emission (AIE) behavior in THF/water mixtures and solvatochromic effects were observed by varying the solvent polarities. The energy levels of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were examined via density functional theory (DFT) calculations. Intriguingly, mechanical force application, such as grinding, induced a red shift in the photoluminescence spectra, while exposure to dichloromethane fumes resulted in reversible spectra changes. These distinct behaviors underscore the mechanochromic nature of the compounds, as corroborated by both photoluminescence and powder-XRD analyses. Importantly, these unique characteristics render the compounds suitable for applications in inkless pens and rewritable printers.

SPHERE RefPlanets: Search for ε Eridani b and warm dust

Context. Cold planets, including all habitable planets, produce only scattered light emission in the visual to near-infrared wavelength range. For this reason it is highly desirable to adapt the technique for the direct imaging of reflected light from extra-solar planets. Aims. For the nearby system ε Eri, we want to set much deeper detection limits for the expected scattered radiation from the radial velocity planet candidate (≈0.7 MJ) and the warm dust using the VLT/SPHERE adaptive optics (AO) instrument with the ZIMPOL imaging polarimeter. Methods. We carried out very deep imaging polarimetry of ε Eri based on 38.5 h of integration time with a broad-band filter (λc = 735 nm) for the search of the polarization signal from a planet or from circumstellar dust using AO, coronagraphy, high precision differential polarimetry, and angular differential imaging. The data were collected during 12 nights within four epochs distributed over 14 months and we searched for a signal in the individual epochs. We also combined the full data set to achieve an even higher contrast limit considering the Keplerian motion using the K-Stacker software. All data were also combined for the search of the scattering signal from extended dust clouds. We improved various data reduction and post-processing procedures and also developed new ones to enhance the sensitivity of SPHERE/ZIMPOL further. The final detection limits were quantified and we investigated the potential of SPHERE/ZIMPOL for deeper observations. Results. The data of ε Eridani provide unprecedented contrast limits but no significant detection of a point source or an extended signal from circumstellar dust. For each observing epoch, we achieved a 5 σ𝒩 point source contrast for the polarized intensity CP = Qϕ/I★ between 2 × 10−8 and 4 × 10−8 at a separation of ρ ≈ 1″, which is as expected for the proposed radial velocity planet at a quadrature phase. The polarimetric contrast limits are close to the photon noise limits for ρ > 0.6″ or about six times to 50 times better than the intensity limits because polarimetric imaging is much more efficient for speckle suppression. Combining the data for the search of a planet moving on a Keplerian orbit with the K-Stacker technique improves the contrast limits further by about a factor of two, when compared to an epoch, to about CP = 0.8 × 10−8 at ρ = 1″. This would allow the detection of a planet with a radius of about 2.5 RJ. Should future astrometry provide strong constraints on the position of the planet, then a 3 σ𝒩 detection at 1″ with CP ≈ 5 × 10−9 would be within reach of our data. The surface brightness contrast limits achieved for the polarized intensity from an extended scattering region is about 15 mag arcsec−2 at 1″ or up to 3 mag arcsec−2 deeper than previous limits. For ε Eri, these limits exclude the presence of a narrow dust ring and they constrain the dust properties. The photon statistics would allow deeper limits but we find a very weak systematic noise pattern probably introduced by polarimetric calibration errors. Conclusions. This ε Eri study shows that the polarimetric contrast limits for reflecting planets with SPHERE/ZIMPOL can be improved to a level below Cp < 10−8 by just collecting more data during many nights using software such as K-Stacker, which can combine all data considering the expected planet orbit. Contrast limits of Cp ≈ 10−9 are within reach for ε Eri if the search can be optimized for a planet with a well-known orbit. This limit is also attainable for other bright nearby stars, such as α Cen or Sirius A. Such data also provide unprecedented sensitivity for the search of extended polarized emission from warm circumstellar dust.

Note on the emission spectrum and trapping states in the Jaynes–Cummings model

The emission of light from an atom represents a fundamental process that provides valuable insights into the atom–light interaction. The Jaynes–Cummings model is one of the simplest fully quantized models to deal with these interactions, allowing for an analytical solution, while exhibiting notable nontrivial effects. We explore new, to our knowledge, features in the fluorescence emission spectrum for initial “trapping states,” which suppress the atomic population inversion. Despite the seemingly dormant activity of the atom, the resulting emission spectra exhibit rich features, and using a dressed-state coordinates formalism, we are able to quantitatively explain the different profiles in the spectrum. We generalize the trapping conditions for nonzero atom-field detuning and also unveil two types of trapping states that lead to spectra with three peaks, in contrast to previously known states: a center peak and one secondary peak on each side. These are a trapping state formed by a Schrödinger cat state with Poissonian statistics (Yurke–Stoler state) and also a different type of “perfect trapping state.”

Machine learning assisted designing of conjugated organic chromophores, light absorption, and emission behavior prediction

Organic materials have several important characteristics that make them suitable for use in optoelectronics and optical signal processing applications. For absorption and emission maxima, the stabilities and photoactivities of conjugated organic chromophores can be tailored by selecting a suitable parent structure and incorporating substituents that predictably change the optical characteristics. However, a high-throughput design of efficient conjugated organic chromophores without using trial-and-error experimental approaches is required. In this study, machine learning (ML) is used to design and test the conjugated organic chromophores and predict light absorption and emission behavior. Many machine learning models are tried to select the best models for the prediction of absorption and emission maxima. Extreme gradient boosting regressor has appeared as the best model for the prediction of absorption maxima. Random forest regressor stands out as the best model for the prediction of emission maxima. Breaking Retrosynthetically Interesting Chemical Substructures (BRICS) is used to generate 10,000 organic chromophores. Chemical similarity analysis is performed to obtain a deeper understanding of the characteristics and actions of compounds. Furthermore, clustering and heatmap approaches are utilized.

The impact of laser speckle on color spatial uniformity in laser-excited phosphor-converted white light systems

This study delved into the impact mechanisms of laser speckles on the quality of phosphor-converted white light, employing both simulation and experimental approaches. We comprehensively analyzed and assessed the interactions between laser speckle contrast, phosphor concentration, and color spatial uniformity in laser-excited phosphor-converted white light. Our findings indicate that while laser speckle does not shift the overall average color temperature, it significantly affects the spatial distribution of color within the emitted white light. Consequently, setting appropriate upper limits for laser speckle contrast, tailored to specific phosphor concentrations and lighting scenarios, is essential for engineering high-quality laser-excited phosphor white light. This research provides valuable data and practical guidelines for designing laser-excited phosphor illumination systems to optimize color spatial uniformity.

Exploring OH incorporation pathways in pulsed laser deposited EuOOH thin films

This study sheds light on the formation of EuOOH thin films intended for photonic applications in light emission. To this end, we designed a unique experiment in which we deposited films by pulsed laser deposition from an Eu2O3 target followed by low temperature annealing in an isotopic furnace, which allows selecting atmospheres (18O2 or D218O vapour) containing specific isotopes. Ion beam techniques have been used for the absolute determination of 16O and H content as well as that of the isotopes (18O, D) incorporated in the films upon annealing. A large content of either H2O or hydroxyl (OH−) groups was identified in the as-deposited films by infrared spectroscopy, while the incorporation of 18O or D upon annealing is limited (≤8 % and ≤ 4 %, respectively). Yet, annealing is a critical and necessary step to achieve the right stoichiometry and to induce the formation of hydroxides. Films produced under the optimum deposition pressure range (≤4 × 10−4 Pa) and annealing atmosphere (D218O) show the EuOOH monoclinic structure, while their photoluminescence response is in excellent agreement with the emission of Eu3+ ions in monoclinic EuOOH.

Predicting Mechanical Properties of Carbonate Rocks Using Spectroscopy Across 0.4–12 μm

AbstractDetermining the mechanical characteristics of rocks is crucial in various civil engineering sectors. Traditionally, the mechanical properties of rocks are determined through on-site and laboratory tests carried out during geotechnical surveys. However, these extensive surveys require considerable time and resources. In contrast, hyperspectral remote sensing techniques offer a rapid and simple means to determine the mineral composition and crystallographic structure of rocks. These features, in turn, influence the rocks' mechanical properties. This study focuses on characterizing the mechanical properties of carbonate rocks in a laboratory setting, using hyperspectral sensors. Approximately 150 cylindrical carbonate rock samples, spanning a wide strength range, were collected from diverse Israeli rock outcrops. Employing a point spectrometer (0.4 to 2.5 µm) and a spectral image sensor (8.0 to 12.0 µm), we captured samples' light reflections and spectral emissivity. Mechanical attributes, including density, porosity, water absorption, and uniaxial compressive strength (UCS), were measured. Advanced data mining techniques identified statistical correlations between hyperspectral signatures and mechanical properties, pinpointing key wavelengths for prediction. The developed models exhibited excellent predictability for the specified properties, attributing accuracy to discernible mineralogy and internal crystalline structure through spectroscopy. However, predicting UCS showed slightly weaker results due to influences from internal flaws not entirely reflected in spectroscopic data. Nonetheless, outcomes regarding rock UCS were deemed satisfactory. These findings open avenues for non-destructive tools in assessing the mechanical properties of rocks in quarrying operations.

High Q Hybrid Mie-Plasmonic Resonances in van der Waals Nanoantennas on Gold Substrate.

Dielectric nanoresonators have been shown to circumvent the heavy optical losses associated with plasmonic devices; however, they suffer from less confined resonances. By constructing a hybrid system of both dielectric and metallic materials, one can retain low losses, while achieving stronger mode confinement. Here, we use a high refractive index multilayer transition-metal dichalcogenide WS2 exfoliated on gold to fabricate and optically characterize a hybrid nanoantenna-on-gold system. We experimentally observe a hybridization of Mie resonances, Fabry-Perot modes, and surface plasmon-polaritons launched from the nanoantennas into the substrate. We measure the experimental quality factors of hybridized Mie-plasmonic (MP) modes to be up to 33 times that of standard Mie resonances in the nanoantennas on silica. We then tune the nanoantenna geometries to observe signatures of a supercavity mode with a further increased Q factor of over 260 in experiment. We show that this quasi-bound state in the continuum results from strong coupling between a Mie resonance and Fabry-Perot-plasmonic mode in the vicinity of the higher-order anapole condition. We further simulate WS2 nanoantennas on gold with a 5 nm thick hBN spacer in between. By placing a dipole within this spacer, we calculate the overall light extraction enhancement of over 107, resulting from the strong, subwavelength confinement of the incident light, a Purcell factor of over 700, and high directivity of the emitted light of up to 50%. We thus show that multilayer TMDs can be used to realize simple-to-fabricate, hybrid dielectric-on-metal nanophotonic devices granting access to high-Q, strongly confined, MP resonances, along with a large enhancement for emitters in the TMD-gold gap.

Enhancing optical biosensing: Comparing two physical treatments for GPTES chemical functionalization of Cyclo-Olefin Copolymer foil

Cyclo-olefin-copolymer (COC) transparent films are currently the best choice for micro-fluidic bio-sensors for point-of-care diagnostic applications using optical signal detection. However, while the optical and mechanical properties of this polymer are extremely good, the adhesion of the bio-probes on this surface is not optimal, due to its chemical structure, that presents only saturated carbon bonds. The deposition of organo-silane molecules on the COC surface is one of the most effective ways to overcome this problem. But, for the surface functionalization, a surface physical treatment is necessary before the chemical modification of the COC surface. In this paper a comparison of the effectiveness of two different physical treatments, oxygen plasma and UV-ozone, is reported. In particular, the exposure time of the UV-Ozone treatment has been selected to avoid the problem of auto-fluorescence of the modified COC surface, that was observed also for relatively short UV exposure (around 10 min). An investigation of the reactive radicals created on the surface after the physical treatments and the following chemical modification with the organo-silane molecule (GPTES) has been performed using X-ray photoemission spectroscopy. The surface energy and morphology of the films have been also measured by contact angle and optical profilometry. Finally, the bio-probes adhesion performances of the COC surfaces obtained with the two physical treatments and the chemical modification were tested in a fluorescence-based assay, using an organic light emission diode to excite the fluorescence. We observed that the UV-ozone treatment allows to obtain a siloxane network with some reactive epoxy radicals on the COC surface, however, their quantity and distribution are less important and homogeneous than in the oxygen plasma treated surfaces.

Study on Bottom Distributed Bragg Reflector Radius and Electric Aperture Radius on Performance Characteristics of GaN-Based Vertical-Cavity Surface-Emitting Laser.

This article presents the results of a numerical analysis of a nitride-based vertical-cavity surface-emitting laser (VCSEL). The analyzed laser features an upper mirror composed of a monolithic high-contrast grating (MHCG) and a dielectric bottom mirror made of SiO2 and Ta2O5 materials. The emitter was designed for light emission at a wavelength of 403 nm. We analyze the influence of the size of the dielectric bottom mirrors on the operation of the laser, including its power-current-voltage (LIV) characteristics. We also study the effect of changing the electrical aperture radius (active area dimensions). We demonstrate that the appropriate selection of these two parameters enables the temperature inside the laser to be reduced, lowering the laser threshold current and increasing its optical power output significantly.

Simple Characterization of Cylindrical Diffuser Fibers With a Fluorescent Layer.

A fast, simple, versatile, and reliable method to record light emission intensity profiles of cylindrical light diffusers (CDFs) in air and transparent liquids has been developed. A fluorescent color glass filter (RG695) converts red light emitted by a cylindrical diffuser fiber into near-infrared light in an emission angle-independent manner. The red light was provided from a diode laser system at 635 nm. Near-infrared fluorescence from the RG695 was imaged with a camera. Images from this camera were processed to obtain emission intensity profiles. Cylindrical diffuser fiber profiles of four different manufacturers were compared. The proposed method provides angle-independent intensity profiles of cylindrical diffuser fibers with a single camera shot. It could be demonstrated that dependent on the underlying principle of how the diffuser fiber tips emit light, the emission profile can change significantly in media with different refractive indices. By converting the light emitted by a diffuser fiber tip into fluorescence light one can eliminate the dependence of the recorded profile on the emission angle from the diffusor. This approach allows for easily taking into account refraction-index (mis)matching by placing the equipment into a suitable liquid. The proposed measurement principle bears potential for quality assurance measurements of CDFs used for interstitial laser thermotherapy or photodynamic therapy.

Photoluminescence Quenching Upon Growth of Metal Nanoparticles: Quantum-Mechanical Views.

In dictating the optical processes in metal nanoparticles, for instance, quantum nature of free electrons is significantly dominant and plays very crucial roles at the level of nanoscale dimensions of materials. As consequences of the quantum-confinement effects on the conduction electrons, surface-plasmon resonance induced optical absorption and light emission properties of metal nanoparticles are found to be strongly dependent on physical dimensions of the nanomaterials. In addition, surface-confined acoustic vibration (phonon) modes have been experimentally observed to depend on the sizes of the metal nanoparticles. Also, interestingly, tuning of the surface-plasmon resonance condition is found to enhance the intensity of the acoustic Raman modes in metal nanoparticles. The study highlights the role of plasmon-phonon coupling in Co metal nanoparticles embedded in a silica-glass. In the research field of nanosciences and nanotechnologies, extraordinary behaviour and properties of nanoscale matters are investigated. In this context, interesting studies have been discussed in this review article to elaborate optical, chemical and photoluminescence properties of nanoscale Ag metal particles. Subtle detection of optical phenomena associated with the excited many-body electronic processes in the metal nanoparticles, for example, are very interesting but definitely challenging. Here we make an attempt to find out how the thermal growth of Ag metal nanoparticles in a glass matrix snuffs out the light emission from the samples? Quantum mechanical interpretations of the underlying processes about the quenching of photoluminescence phenomena with the growth of the metal nanoparticles will help to fine tune the optical properties of plasmonic systems as well as to harness potential applications of the nanomaterials.

Highly Efficient Blue‐Emission by Regulating the Hydrogen Bond Structure in Lead Halide Perovskites

AbstractLow‐dimensional organic–inorganic hybrid perovskites (OIHPs) have attracted extensive attention due to their outstanding photoluminescence properties. However, the charge transfer between the organic A‐site and the inorganic framework is impeded, resulting in lower photoluminescence quantum yield (PLQY). Herein, m‐xylylenediamine (MXD) is incorporated into the perovskite, realizing the synthesis of a series of 0D perovskite‐like single crystals, i.e., (MXD)2PbX6 (X = Cl, Br, I). Density functional theory (DFT) calculations reveal the presence of effective hydrogen bonding between MXD and [PbX6]4−, which is enhanced through the controlled modification of halogen sites, enables the establishment of efficient charge transfer channels, and facilitates charge migration. Accordingly, (MXD)2PbCl6 achieves a PLQY as high as 55.9% at 460 nm, characterized by blue light emission and remarkable air stability.

Microwave‐Assisted Confining Growth and Liquid Exfoliation of sp3‐Hybrid Carbon Nitride Nano/Micro‐Crystals

As one promising carbon‐based material, sp3‐hybrid carbon nitride has been predicted with various novel physicochemical properties. However, the synthesis of sp3‐hybrid carbon nitride is still limited by the nanaoscale, low crystallinity, complex source, and expensive instruments. Herein, we have presented a facile approach to the sp3‐hybrid carbon nitride nano/micro‐crystals with microwave‐assisted confining growth and liquid exfoliation. Actually, the carbon nitride nano/micro‐crystals can spontaneously emerge and grow in the microwave‐assisted polymerization of citric acid and urea, and the liquid exfoliation can break the bulk disorder polymer to retrieve the highly crystalline carbon nitride nano/micro‐crystals. The obtained carbon nitride nano/micro‐crystals present superior blue light absorption strength and surprising photoluminescence quantum yields of 57.96% in ethanol and 18.05% in solid state. The experimental characterizations and density functional theory calculations reveal that the interface‐trapped localized exciton may contribute to the excellent intrinsic light emission capability of carbon nitride nano/micro‐crystals and the interparticle staggered stacking will prevent the aggregation‐caused‐quenching partially. Finally, the carbon nitride nano/micro‐crystals are demonstrated to be potentially useful as the phosphor medium in light‐emitting‐diode for interrupting blue light‐induced eye damage. This work paves new light on the synthesis strategy of sp3‐hybrid carbon nitride materials and thus may push forward the development of multiple carbon nitride research.

Clinical overview of phototherapy for neonatal hyperbilirubinaemia.

The most efficient emission spectrum of light for phototherapy is blue-green light emission diode light with peak emission at 478 nm. In the irradiance interval of phototherapy, the relationship between efficacy and irradiance is almost linear, and it is negatively related to the haemoglobin. The action sites of phototherapy are the extravascular compartment and cutaneous blood. The most immature neonates treated aggressively had not only a lower frequency of neurodevelopmental impairment than conservatively treated, but also greater mortality. Intermittent and continuous phototherapy are assumed to be equally efficient. Home-based fibreoptic phototherapy is effective and safe. Important progress is still occurring in phototherapy.

Elucidating different roles of solvent additives in organic photovoltaics under solar and indoor light emission environments

Incorporation of solvent additive in bulk heterojunction layer has been effective method for the optimization of film morphology and crystallinity, enabling high efficiency organic solar cells under standard 1 SUN illumination. However, the effects of the additives in low-intensity indoor light environment have not been investigated much so far. In this study, a new donor polymer (PBz-ET) having an efficient spectral matching with LED was synthesized and employed. Moreover, we elucidate the different roles of additives for organic solar cell operations depending on 1 SUN and low-intensity LED illuminations. Through systemic characterizations on morphology, crystallinity, and electrical properties, we found that the additive boosting nanoscale phase separation is compatible for the organic solar cells working in 1 SUN illumination while the additive being capable of increasing crystallinity is more adaptable to those used for indoor light environment. The results in this study suggest a rational selection rule of additives for designing organic solar cells in different light environments.

Augmenting the effect of solvents on optical nonlinearity by spectroscopic, DFT, solvatochromism and z-scan studies of push-pull chalcone: (2E)-1-(4-ethoxyphenyl)-3-(4-methoxyphenyl)prop-2-en-1-one

In this article, the structural and nonlinear optical behaviour of a chalcone derivative, (2E)-1-(4-ethoxyphenyl)-3-(4-methoxyphenyl)prop-2-en-1-one have been studied. FT-IR, FT-Raman, and NMR spectroscopy were analyzed to validate the molecular structure. To predict the nonlinear optical characteristics of the chalcone, the DFT approach was used and the experimental results were corroborated by the computations. The bathochromic shift is obtained in linear absorbance spectra and is validated using TD-DFT. Also, the broad emission in the blue region demonstrates the blue light emission property of the sample. Using the finite-field method, the dipole moments, polarizability, first-order and second-order hyperpolarizability parameters have been computed. Ground and excited state dipole moments were quantified by solvatochromism. The third-order nonlinear optical characteristics of chalcone in polar and non-polar solvent media were examined using the open/closed-aperture z-scan technique. The chalcone displayed considerable two-photon absorption with a positive nonlinear absorption coefficient and a positive index of refraction due to the self-focussing effect. Furthermore, the optical limiting study manifests that the investigated chalcone might well be favourable for NLO applications.

Green synthesis of carbon dots from Nigella sativa seeds for supercapacitor application

The synthesis of carbon dots (CDs) from sources such as coal and phenolic resins requires the use of chemicals that sometimes are hazardous to the environment. Several studies have highlighted the significance of using natural and biomass sources in ecologically friendly CDs synthesis. This strategy guarantees their accessibility, environmental friendliness and cost-effectiveness. In this work, we report the synthesis of CDs from Nigella sativa seeds for supercapacitor application. A hydrothermal technique was adopted for this experiment. The structural, size distribution, fluorescence, and electrochemical properties of the synthesized CDs were studied using an X-ray diffraction (XRD) spectroscope, Transition electron microscope (TEM), spectrofluorometer and potentiostat, respectively. The TEM revealed distinct scattered quasi-spherical dots on the surface and the estimated size distribution ranges from 6.08 to 9.91 nm. The fluorescence spectra revealed that CDs have green light emission, which redshifts as the excitation wavelength increases. The electrochemical measurement confirms that CDs exhibited an electrical double layer (EDL) capacitance behavior with an areal capacitance of 2.82 mF/cm2 at 5.21 μA/cm2 current density. To the best of our knowledge, this is the first report on the fabrication of supercapacitor from CD derived from Nigella sativa seeds.