Since the last decades, non-precious metal catalysts (NPMC), especially iron based electrocatalysts show sufficient activity, potentially applicant in oxygen reduction reaction (ORR), however they ...only withstand considerable current densities at low operating potentials. On the other hand iron based electrocatalysts are not stable at elevated cathode potentials, which is essential for high energy competence, and its remains difficult to deal. Therefore, via this research a simple approach is demonstrated that allows synthesis of nanosize Fe-doped mayenite electride, Ca
Al
O
·(e
)
(can also write as, C
A
Fe
:e
, where doping level, x = 1) (thereafter, Fe-doped C12A7:e
), consist of abundantly available elements with gram level powder material production, based on simple citrate sol-gel method. The maximum achieved conductivity of this first time synthesized Fe-doped C12A7:e
composite materials was 249 S/cm. Consequently, Fe-doped C12A7:e
composite is cost-effective, more active and highly durable precious-metal free electrocatalyst, with 1.03 V onset potential, 0.89 V (RHE) half-wave potential, and ~5.9 mA/cm
current density, which is higher than benchmark 20% Pt/C (5.65 mA/cm
, and 0.84 V). The Fe-doped C12A7:e
has also higher selectivity for desired 4e
pathway, and more stable than 20 wt% Pt/C electrode with higher immunity towards methanol poisoning. Fe-doped C12A7:e
loses was almost zero of its original activity after passing 11 h compared to the absence of methanol case, indicates that to introduce methanol has almost negligible consequence for ORR performance, which makes it highly desirable, precious-metal free electrocatalyst in ORR. This is primarily described due to coexistence of Fe-doped C12A7:e
related active sites with reduced graphene oxide (rGO) with pyridinic-nitrogen, and their strong coupling consequence along their porous morphology textures. These textures assist rapid diffusion of molecules to catalyst active sites quickly. In real system maximum power densities reached to 243 and 275 mW/cm
for Pt/C and Fe-doped C12A7:e
composite, respectively.
•Ca2YTaO6 an intrinsic broad band blue emission originated from the TaO6 group.•The crystal structure, and the electronic characteristics were detailed investigated.•The blue emission was efficiently ...tuned to cyan, red and white.•Efficient energy transfer observed intrinsic blue emission to Bi3+ and Eu3+ ions.
Display omitted
Novel tunable-color emitting phosphors with double perovskite structure un-doped, single and co-doped with Bi3+/Eu3+ ions were successfully synthesized by the high-temperature solid state reaction method. The crystal structure, band-gap, and electronic structure were investigated by using computational methods. The morphology and phase composition were obtained with scanning electron microscopy and powder x-ray diffraction. The un-doped Ca2YTaO6 phosphors shows an intensive intrinsic emission centered at 424 nm under 315 nm UV light excitation. The obtained intense blue emission (424 nm) was efficiently tuned to cyan, red and white light with doping of Bi3+ and Eu3+ as a result of energy transfer.
The trivalent rare‐earth (RE3+) doped phosphors show tremendous achievement in narrow band multicolor line emission for various applications. However, the 4f–4f absorption transition of these ions is ...forbidden in UV and blue light excitation. Usually, a sensitizer having spin allowed transition was used as a co‐dopant to excite these ions via the energy transfer phenomenon. Another approach promisingly using to excite these ions by efficient energy transfer from the intrinsic emission of the Ca2LuTaO6 double perovskite phosphors host lattice. Phosphors of Ca2LuTaO6 with double perovskite structure were synthesized by using a high‐temperature solid‐state reaction method. The produced Ca2LuTaO6 double perovskite phosphors show an intrinsic broad band emission centered at 424 nm under the excitation of 313 nm UV light. The origin of this broad band blue emission was deeply investigated by using computation and experimental approaches. The trivalent activator Dy3+ and Eu3+ were doped is a single and co‐dopant in the produced Ca2LuTaO6 phosphors to check their excitation in UV and near‐UV spectral region. X‐ray diffraction and scanning electron microscopy were used to investigate the structure and phase analysis. Various characterizations such as photoluminescence excitation, emission, and CIE chromaticity coordinates were measured which illustrate the potential of Dy3+ and Eu3+ activated Ca2LuTaO6 double perovskite phosphors for narrow band multicolor line emission for various applications.
CIE coordinate tuning of Ca2LuTaO6: Dy3+/Eu3+ co‐doped single phase phosphors.
Metasurfaces are planar or 2D forms of metamaterials made up of arrays of antennas with a subwavelength thickness. They have been rapidly developed in the recent years due to their ability to ...manipulate light–matter interaction in both linear and non‐linear regimes at the nanoscale. Various metasurfaces display remarkable optical features, such as acute resonance, significant near‐field enhancement, and suitable capacity to support electric and magnetic modes, on account of the strong light–matter interaction and the low optical loss. Due to these important properties, they can be used in several advanced optoelectronic applications, like surface‐enhanced spectroscopy, photocatalysis, and sensing. This review reports on the recent progress of metamaterials and metasurfaces in molecular optical sensors. The principles that govern plasmonic and dielectric metasurfaces along with their features are outlined, supported by numerous examples. Then, the factors that result in a high Q‐factor are presented in order to show that metamaterials and metasurfaces can be used for label‐free sensing in a variety of detection mechanisms, including surface‐enhanced spectroscopy, refractometric sensing, and surface‐enhanced thermal emission spectroscopy via infrared absorption and Raman scattering, as well as chiral sensing. Finally, the challenges for future development are outlined.
The principles that govern plasmonic and dielectric metasurfaces along with their features are outlined, supported by numerous examples. Then, the factors that result in a high Q‐factor are presented in order to show that metamaterials and metasurfaces can be used for label‐free sensing in a variety of detection mechanisms, including surface‐enhanced spectroscopy (SES), refractometric sensing, and surface enhanced thermal emission spectroscopy (SETES) via infrared absorption and Raman scattering, as well as chiral sensing. Finally, the challenges for future development are outlined.
Nowadays, various drugs on the market are becoming more and more resistant to numerous diseases, thus declining their efficacy for treatment purposes in human beings. Antibiotic resistance is one ...among the top listed threat around the world which eventually urged the discovery of new potent drugs followed by an increase in the number of deaths caused by cancer due to chemotherapy resistance as well. Accordingly, marine cyanobacteria, being the oldest prokaryotic microorganisms belonging to a monophyletic group, have proven themselves as being able to generate pharmaceutically important natural products. They have long been known to produce distinct and structurally complex secondary metabolites including peptides, polyketides, alkaloids, lipids, and terpenes with potent biological properties and applications. As such, this review will focus on recently published novel compounds isolated from marine cyanobacteria along with their potential bioactivities such as antibacterial, antifungal, anticancer, anti-tuberculosis, immunosuppressive and anti-inflammatory capacities. Moreover, various structural classes, as well as their technological uses will also be discussed.
Plasmonic metasurfaces have been widely used in biosensing to improve the interaction between light and biomolecules through the effects of near-field confinement. When paired with ...biofunctionalization, plasmonic metasurface sensing is considered as a viable strategy for improving biomarker detection technologies. In this review, we enumerate the fundamental mechanism of plasmonic metasurfaces sensing and present their detection in human tumors and COVID-19. The advantages of rapid sampling, streamlined processes, high sensitivity, and easy accessibility are highlighted compared with traditional detection techniques. This review is looking forward to assisting scientists in advancing research and developing a new generation of multifunctional biosensors.
•Double-perovskite oxides Mn2FeMO6 (M = W and Mo) are exist in polar ferrimagnetic phase.•These compounds have large spontaneous polarization values.•These materials have large values of ...piezoelectric coefficients.•These materials found semiconductors and mechanically stable.•Magnetic field has strong influence on the polarization of these materials.
The physical properties of the corundum double-oxides Mn2FeMO6 (M = W and Mo) are investigated using density functional theory (DFT). The structure relaxation in different spin orders are performed and ferrimagnetic is found the most stable magnetic phase. The compounds are dielectric materials with band gap values 1.84 and 2.03 eV. These materials are polar magnets because of the coexistence of contradictory properties such as polarization and magnetization, which are observed very rarely. The electric polarization arises due structure distortion and cation orbital configuration of M atom, while the magnetization occurs due to unpaired dn of Mn and Fe orbital configuration. The compounds understudy are suitable for ferroelectric and magneto-electric applications due to their large spontaneous polarization (58.16 and 69.24 µC/cm2) and magnetic moments (3 and 3.43 µB/f.u). These multiferroic Mn2FeMO6 exhibit a profound interplay between electrical polarization and the applied magnetic field. The calculated values of piezoelectric coefficient, d33 = 264 and 606 pC/N are comparable to lead-based piezoelectric materials. A set of mechanical parameters revealed that Mn2FeMO6 are mechanically stable in rhombohedral phase. The applied strain has great influence on the physical properties of these two compounds.
In phosphors intended for the applications of white light-emitting diodes (white-LEDs), their ability to achieve controlled-photoluminescence-tuning is an important feature, which is directly linked ...to their optimization and modification. More specifically, the development of luminescent materials with broadly and continuously tunable photoluminescence is still a challenge for the generation of highly efficient warm white-light with appropriate correlated color temperature (CCT), a high color-rendering-index (CRI), and excellent thermal stability. This review presents the latest developments of single-phase white-light-emitting Ba
9
Lu
2
Si
6
O
24
(BLSO) silicate phosphors. The emerging approaches to crystal-site engineering and the energy transfer mechanisms are discussed at great length. The BLSO phosphor host lattice, having rich and distinguishing crystallographic sites, provides various surrounding environments to the doped rare-earth (RE) ions, and it also allows for the engineering of the local atmosphere of the doped ions. Substitution with more than one activator, as a co-dopant ion, in the BLSO phosphor host may enable tuning of the photoluminescence spectrum to the desired spectral region. The ultimate goal of this review is to aid research aimed at discovering new approaches to the aforementioned objectives, following strategies associated with the occupation of multiple crystallographic sites with activators, in accordance with a thorough understanding of the function of the energy-transfer phenomenon, whereby various dopants can achieve efficient tunability.
The latest developments of single-phase white-light-emitting Ba
9
Lu
2
Si
6
O
24
(BLSO) silicate phosphors are presented. The emerging approaches to crystal-site engineering and the energy transfer mechanisms are discussed at great length.
Red emitting Ba2Si(5-x)AlxN(8-x)Ox:Eu2+ phosphors were successfully produced by high-temperature solid state reaction method and their luminescence properties were experimentally measured. The ...analysis of the experimental results suggests that the partial substitution of Al-O for Si-N in the host lattice improves the photoluminescence properties and the thermal stability of the produced phosphors. The phosphors exhibited a broad red emission band between 500 and 750 nm. A red shift of emission peak from 588 to 624 nm was recorded with the increase of Al-O content, attributed to the enhancement of stokes shift. The excitation spectrum of the produced phosphors ranged between 200 and 600 nm, covering the UV and the blue region, and suggesting these materials as potentially suitable for use as conversion phosphors for white LED applications in the field of solid state lighting.
•Partial substitution of Al-O for Si-N improves the PL properties and the thermal stability.•A red shift of emission peak from 588 to 624 nm was recorded with the increase of Al-O content.•The red shift in the emission spectra attributed to the enhancement of stokes shift due to expansion of host lattice.•The PLE spectra of the produced phosphors ranged between 200 and 600 nm, covering the UV and the blue region.
PDF
