This study consists of the synthesis, characterization, and analysis of photoluminescence (PL) spectra for Li
2
O−HfO
2
−SiO
2
−Yb
2
O
3
glass ceramics sensitized with small amounts of Au
2
O
3
. ...Using the results of XRD and X-ray photoelectron spectroscopy (XPS) studies indicated a progressive reduction of Au
3+
ions into Au
0
metallic particles (MPs) with increase of Au
2
O
3
content. Investigations into the infrared spectra highlighted a growing concentration of induced defects in the samples due to the increased proportion of Au
0
MPs. Optical absorption (OA) spectra exhibited a distinct band attributed to the
2
F
7/2
→
2
F
5/2
transition of Yb
3+
within wavelength range of 800–980 nm. Furthermore, a wide absorption band linked to the surface plasmon resonance (SPR) of Au
0
MPs was identified in the visible region. PL spectra, recorded at
λ
exc
= 450 nm, revealed a band between 980 to 1025 nm, associated with the
2
F
5/2
→
2
F
7/2
transition of Yb
3+
ions. Another emission band was observed due to the sp → d transition of Au
0
MPs within the visible region. Observed enhanced PL emission from Yb
3+
ions in the NIR range was ascribed to the energy transfer from Au
0
MPs to Yb
3+
ions. Ultimately, it was deduced that Au
0
MPs played a pivotal role in enhancing the PL output of Yb
3+
ions in the Li
2
O−HfO
2
−SiO
2
glass ceramic. Thus, glass ceramics incorporating an optimal concentration of Au
2
O
3
hold significant potential as materials for NIR lasers.
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•TWGCe glasses show amorphous nature and are free from impurities and bubbles.•TWGCe glasses enhance optical properties of Ce3+ by reducing non-radiative losses.•Exhibit deep-blue ...luminescence through Ce3+: 5d → 4f transition when excited at 323 nm.•They are favourable as blue light sources in the design of phosphor-based white LEDs.
Different concentrations of Ce3+-doped TeO2-WO3-GeO2-Ce2O3 (TWGCe) glasses were prepared by melt-quenching method and characterized. Different spectroscopic and luminescence properties were evaluated using room temperature absorption and emission spectra. The absence of sharp X-ray diffraction peaks and the presence of broad band from 18° to 35° shows the amorphous phase of studied glasses. The Fourier transform infrared absorption spectra show the presence of various vibrational bonds. The optical properties of TWGCe glasses were studied by exciting the glass samples at 323 nm ultraviolet wavelength. The quenching in luminescence is noticed at × = 0.5 mol% along with a red-shift at higher Ce3+ concentrations. The decay time was found decrease with increase of concentration of Ce3+ ions. These glasses emit intense blue luminescence with CIE coordinates (0.161, 0.018) when excited at 323 nm radiation. These glasses are favourable as blue light sources in the design of phosphor-based white LEDs.
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•Structure of the Porphyrin is strongly perturbed due to encapsulation in the borate glass matrix.•Red shift in the B and Q-bands are tuned by varying the number of hydroxy groups on ...the phenyl ring of the Porphyrin.•Reverse saturable absorption (RSA) behaviour at low intensity regions and crossover to saturable absorption (SA) at high intensities.•Optical limiting behaviour with intensity range less than 10 GW/cm2 and an optical switch behaviour at high intensity range above ∼ 10 GW/cm2.
The development of nonlinear optical (NLO) materials are crucial for technological advancement in the field of optoelectronics and photonics. In this direction, porphyrin molecules are appeared to be a possible building material to play a key role in the light-matter interactions owing to their high degree of delocalized π-electrons. In this report, our primary focus is to understand the effect of hydroxy phenyl derivatives of meso-substituted porphyrins in an encapsulated borate glass matrix through linear and nonlinear optical measurements. The encapsulated porphyrin molecules show strong red shifted Soret (B) and Q-band absorption pattern in the range 455–460 nm and 680–700 nm, respectively, and structure is modified. The Q-band is able to tune by varying the number of hydroxy groups on the phenyl ring of the porphyrin molecule. A similar red shift is observed in the emission spectra of the encapsulated porphyrin along with the appearance of a new emission peak due to impede N-B vibrations in the glass matrix. The NLO behaviour of the encapsulated porphyrin thin films in borate glass matrix show reverse saturable absorption (RSA) at lower intensity region and crossover to saturable absorption (SA) at higher intensity. With the tunable intensity variations across the focal region, these porphyrin thin films exhibit switching behaviour from RSA to SA unclog its potential to act as an optical limiter (in the intensity range less than 10 GW/cm2) and an optical switch (in the high intensity range above ∼ 10 GW/cm2).
Photovoltaic systems, such as dye-sensitized solar cells (DSSCs), are one of the useful tools for generating renewable and green energy. To develop this technology, obstacles such as cost and the use ...of expensive compounds must be overcome. Here, we employed a new MoS
/graphene hybrid or composite instead of platinum in the DSSCs. Furthermore, the correctness of the preparation of the MoS
/graphene hybrid or composite was evaluated by field emission scanning electron microscope (FESEM), and the results showed that the desired compound was synthesized correctly. Inexpensive organic dyes were used to prepare the DSSCs, and their chemical structure was investigated by density functional theory (DFT) and cyclic voltammetry (CV). Finally, the DSSCs were fabricated using MoS
/graphene composite or hybrid, and to compare the results, the DSSCs were also prepared using platinum. Under the same conditions, the DSSCs with MoS
/graphene composite illustrated better efficiency than MoS
/graphene hybrid or/and graphene.
In this study, a glass system based on heavy metal oxides, namely Pb
O
-Sb
O
-SiO
, was prepared with Ho
O
, Er
O
, and Tm
O
as dopants. The prepared glass were characterized using X-ray diffraction ...(XRD) and infrared (IR) studies. The luminescence efficiencies of the three rare earth ions viz., Ho
, Er
, and Tm
in the glass system were investigated, specifically focusing on green (Ho
, Er
), blue (Tm
), and near-infrared (NIR) emissions. The optical absorption (OA) and photoluminescence (PL) spectra of RE mixed glass displayed strong bands in the visible and NIR regions, which were analyzed using the Judd-Ofelt (J-O) theory. The J-O coefficients (Ω
) were found to be in the order of Ω
> Ω
> Ω
for all the three glass. Notably, the Tm
-doped glass exhibited the lowest Ω
value, which was attributed to a larger degree of disorder in the glass network due to lower fractions of Sb
and Pb
ions that take part in the glass network forming. This conclusion was arrived based on the IR studies. Furthermore, the quantitative analysis of PL spectra and decay curves indicated that SbHo and SbEr glass were suitable for efficient green emission, while SbTm glass is a promising choice for blue laser emission.
In continuation of our earlier investigations on structural and physical characteristics of Au2O3‐doped sodium antimonate glass‐ceramics (Part‐1), in this part we have investigated the influence of ...gold ions on electrical characteristics of the Na2O–Sb2O3: Au2O3 glass‐ceramics. The study contains the results of quantitate investigations on dielectric properties, impedance spectra and A.C. conductivity in larger ranges of continuous frequencies (4 Hz‐8 MHz) and temperatures (300‐630 K). The variations exhibited by dielectric parameters with temperature and also with frequency were discussed in terms of various polarization mechanisms. The observed dielectric relaxation effects were analyzed using pseudo Cole‐Cole plot method and the analysis indicated spreading of relaxation times for dipoles. A.c. conductivity and also d.c. conductivity were found to decrease (to three orders of magnitude) with increase in Au2O3 concentration upto 0.1 mol%. The decrement is ascribed to the increasing concentration of Sb5+ ions that were predicted to participate in the glass network forming with SbO4 units. Even though, both ionic and polaronic contributions are possible for conduction in the studied material, quantitative analysis of these results indicated that the polaronic conduction (due to intervalence transfer between Sb3+ ↔ Sb5+ and Au0 ↔ Au3+) is prevalent. The results have also suggested that there is a gradual decrement in the ionic component with increase in Au2O3 concentration. Variation in σac in the low‐temperature region could satisfactorily be explained using quantum mechanical tunneling (QMT) model. Analysis of the results of d.c. conductivity indicated that the small polaron hoping (SPH) model is valid, especially in a high‐temperature region while the low temperature part of d.c. conductivity is analyzed based on variable range hopping (VRH) model. Overall, the increase in Au2O3 dopant concentration in the studied glass‐ceramics caused a decrement in the magnitude of the conductivity or increase in the insulating strength of the material.
A series of Pr3+ activated YAl3(BO3)4 phosphors were fabricated by solid-state reaction technique and they were characterized via phase, morphology and photoluminescence studies. Powder X-ray ...diffraction peaks were suitably matched to JCPDS No. 72–1978. The presence of various vibrational bonds was identified using Fourier transform infrared spectroscopy. High resolution scanning electron microscopic investigations show that the phosphor particles were distributed uniformly and presented a rod-like shape. The photoluminescence results show that the studied phosphors were easily excited by visible wavelength to produce intense-yellow to pale-yellow tunable emission. The decrease in luminescence intensity and lifetime was assigned to dipole-dipole interaction energy-transfer among excited Pr3+ ions. Observed results show that the 0.05 mol% of Pr3+ activated phosphor produce intense-yellow luminescence at 480 nm excitation.
•YABPr phosphors shows a rod-like shape with uniform distribution of particles.•Exhibit intense-yellow to pale-yellow tunable luminescence at 480 nm excitation.•Dipole-dipole interaction results energy transfer among the excited Pr3 + ions.•YABPr0.05 phosphor is the best choice for lighting applications.
Photovoltaic systems, such as dye-sensitized solar cells (DSSCs), are one of the useful tools for generating renewable and green energy. To develop this technology, obstacles such as cost and the use ...of expensive compounds must be overcome. Here, we employed a new MoSsub.2/graphene hybrid or composite instead of platinum in the DSSCs. Furthermore, the correctness of the preparation of the MoSsub.2/graphene hybrid or composite was evaluated by field emission scanning electron microscope (FESEM), and the results showed that the desired compound was synthesized correctly. Inexpensive organic dyes were used to prepare the DSSCs, and their chemical structure was investigated by density functional theory (DFT) and cyclic voltammetry (CV). Finally, the DSSCs were fabricated using MoSsub.2/graphene composite or hybrid, and to compare the results, the DSSCs were also prepared using platinum. Under the same conditions, the DSSCs with MoSsub.2/graphene composite illustrated better efficiency than MoSsub.2/graphene hybrid or/and graphene.
A series of LAGBPr phosphors of composition Li
6
AlGd
(1–
x
)
(BO
3
)
4
:
x
Pr
3+
(0 ≤
x
≤ 2.0 mol%) were prepared by solid-state reaction method and characterized through thermal, structural, ...morphological and photoluminescence studies. Thermal investigation shows that the LAGBPr phosphors crystallize at 640 °C. The powder X-ray diffraction studies show that the size of crystallites is of the order of 77 nm. The excitation spectra reveal a charge transfer band due to O
2–
→ Pr
3+
(230–250 nm), host-related (Gd
3+
) bands from 205 to 315 nm and some f-f transitions of Pr
3+
ions from 420 to 500 nm. The fluorescence properties were investigated by exciting within the host and within dopant (Pr
3+
) ions. A tunable fluorescence from orange-red to white to bluish-white was observed when excited at 274 nm and a bluish-white fluorescence at 449 nm excitation. Upon 449 nm excitation, a blue-shift is observed with increase of concentration of Pr
3+
ions. The optimal concentration of Pr
3+
ions for efficient fluorescence is confirmed to be 1.0 mol%, and a quenching in fluorescence was noticed and it was ascribed to the non-radiative transfer of energy through
3
P
0
,
3
H
4
→
1
D
2
,
3
H
6
,
3
P
0
,
3
H
4
→
3
H
6
,
1
D
2
and
1
D
2
,
3
H
4
→
3
H
4
,
1
D
2
channels. The LAGBPr1.0 phosphor has more proficiency to be used in LED applications.
Li
O-HfO
-SiO
-Tm
O
:Au
O
glass samples (containing fixed content of Tm
O
and different concentration of Au
O
) were prepared and characterized. Bearing of Au
metallic particles (MPs) on improving ...blue emission of thulium ions (Tm
) ions was explored. Optical absorption (OA) spectra exhibited multiple bands excited from
H
of Tm
. Additionally, a broad peak in the wavelength range 500-600 nm due to surface plasmon resonance (SPR) of Au
MPs was noticed in the spectra. Photoluminescence (PL) spectra (of thulium free glasses) indicated a peak in the visible range due to sp → d electronic transition of Au
MPs. Luminescence spectra of Tm
and Au
O
co-doped glasses exhibited intense blue emission with substantial increase of intensity with increase of Au
O
content. Bearing of Au
MPs on the reinforcement of blue emission of Tm
was discussed in detail with kinetic rate equations.
