Abstract:We report the temperature-dependent photoluminescence (PL) properties of polymeric graphite-like carbon nitride (g-C3N4) and a methodology for the determination of quantum efficiency along with the activation energy. The PL is shown to originate from three different pathways of transitions: σ*-LP, π*-LP, and π*-π, respectively. The overall activation energy is found to be ∼73.58 meV which is much lower than the exciton binding energy reported theoretically but ideal for highly sensitive wide-range temperature … Show more
“…4, Fig. 5 confirm that the structure of g-C 3 N 4 consists of basic unit of tri-s-triazine ring, which is connected by the N atoms to form a π–conjugated polymeric network [2], [3], [4], [5], [6], [7], [8].Fig. 4The survey, C 1s, N 1s, and O 1s XPS spectra of bulk g-C 3 N 4 powders synthesized at variant temperatures in air and N 2 , respectively.Fig.…”
In this data article, the normalized emission and excitation spectra, the ultraviolet-visible (UV–vis) absorption spectra, and the X-ray photoelectron spectroscopy (XPS) of bulk-powders and nano-structured graphitic C3N4 (g-C3N4) were presented, which are helpful to get insight into the crystal and electronic structures of g-C3N4, especially on determining the energy levels and the mechanisms of luminescence originating from electron transitions. This data article is related to our recent publication (He et al., in press) [1]. The absorption, excitation and emission spectra are vital to illustrate the optoelectronic performances in terms of photoluminescence, photocatalysis, electroluminescence, etc., from the viewpoint of electron transitions intrinsically.
“…4, Fig. 5 confirm that the structure of g-C 3 N 4 consists of basic unit of tri-s-triazine ring, which is connected by the N atoms to form a π–conjugated polymeric network [2], [3], [4], [5], [6], [7], [8].Fig. 4The survey, C 1s, N 1s, and O 1s XPS spectra of bulk g-C 3 N 4 powders synthesized at variant temperatures in air and N 2 , respectively.Fig.…”
In this data article, the normalized emission and excitation spectra, the ultraviolet-visible (UV–vis) absorption spectra, and the X-ray photoelectron spectroscopy (XPS) of bulk-powders and nano-structured graphitic C3N4 (g-C3N4) were presented, which are helpful to get insight into the crystal and electronic structures of g-C3N4, especially on determining the energy levels and the mechanisms of luminescence originating from electron transitions. This data article is related to our recent publication (He et al., in press) [1]. The absorption, excitation and emission spectra are vital to illustrate the optoelectronic performances in terms of photoluminescence, photocatalysis, electroluminescence, etc., from the viewpoint of electron transitions intrinsically.
“…According to Yuan et al., it is a result of electronic transitions between energy bands formed by sp 3 C‐N σ‐orbitals, sp 2 C‐N π‐orbitals, and the lone pair (LP) orbitals of N atom. The excited σ‐ and π‐orbitals (σ* and π*, respectively) form the conduction band, while the σ‐, C‐N‐, and LP‐orbitals form the valence band . The allowed radiative recombination processes include σ*–LP ( λ = 405 nm), π*–LP ( λ = 480 nm), and π*–π transitions …”
Section: Discussionmentioning
confidence: 99%
“…The excited σ‐ and π‐orbitals (σ* and π*, respectively) form the conduction band, while the σ‐, C‐N‐, and LP‐orbitals form the valence band . The allowed radiative recombination processes include σ*–LP ( λ = 405 nm), π*–LP ( λ = 480 nm), and π*–π transitions …”
Section: Discussionmentioning
confidence: 99%
“…The position of the PL emission peak of g‐C 3 N 4 depends on the synthesis temperature and can be tuned throughout the whole visible spectrum . Moreover, thermal quenching of the luminescence has been proposed for the use in luminescence‐based temperature sensors . The position of the PL emission peak was noted to demonstrate a monotonous red‐shift with an increase of the polymerization temperature in the range of 300–650 °C when melamine is used as a precursor .…”
Graphitic carbon nitride (g‐C3N4) is synthesized by thermal decomposition of thiourea and subsequent in situ polymerization of the products in the oxygen‐containing ambient at 450–625 °C and studied with scanning electron microscopy, X‐ray diffraction, energy‐dispersive X‐ray spectroscopy, Fourier‐transform infrared spectroscopy, and photoluminescence techniques. The synthesized material contains oxygen at a concentration increasing with the processing temperature from 4.8 to 9.8 at %. The photoluminescence peak is found to be red‐shifted with the temperature increased to 575 °C becoming then blue‐shifted at higher temperatures. The observed red‐shift of the photoluminescence peak is supposed to be caused by band‐gap narrowing in g‐C3N4 doped by oxygen while its recovery behavior is controlled by thermally induced oxygen‐assisted disruption of sp2 bonds in C‐N π‐orbital conjugated system of tri‐s‐triazine units building polymer sheets in g‐C3N4.
“…[9][10][11] Among various optical thermometers, temperature induced change in different fluorescence parameters such as emission intensity, fluorescent intensity ratio (FIR), peak position, peak width, life time, etc. [12][13][14][15][16][17] have been widely explored. In the case of temperature dependence luminescence intensity, it is always desirable to consider the ratio of two different peak emissions rather than single intensity variation, to circumvent numerous undesirable factors such as the variation of probe concentrations, optoelectronic drift, etc.…”
Fluorescence intensity ratio (FIR) based optical temperature sensors employ the variation of intensity ratio between two peaks, which are very close to each other. Here, we prepare Er doped ZnO microrods by a hydrothermal route and exploit them for FIR based temperature sensing. The Er:ZnO shows the band-to-band UV emission and broad defect emissions with small Er related peaks upon excitation with a 355 nm laser, while only peaks corresponding to Er transitions are observed with 532 nm laser excitation. The green emissions (H → I, S → I) under 532 nm excitation are considered for temperature sensing performance as they possess a quasi-thermal equilibrium between them and the variation of intensity ratio with temperature follows a Boltzmann type distribution. The sensitivity obtained here is very high (3445/T K) compared to the reported Er ion based temperature sensors and can be applied in a wide range of temperature (83-493 K). The value of sensitivity is found to be almost independent of the concentration of Er doping and is the highest reported for Er-doped materials.
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