Red Photoluminescence Research Articles

Strain modulated luminescence in (Ca,Sr)TiO3:Pr3+ perovskite thin films

We report in-plane strain effect on the photoluminescence property of perovskite phosphor thin films. Epitaxial perovskite thin films of Ca0.6Sr0.4TiO3:Pr3+ phosphor were prepared on perovskite oxide substrates with different lattice constant a, LaAlO3 (LAO, a = 3.815 Å), (LaAlO3)0.3-(SrAl0.5Ta0.5O3)0.7(LSAT, 3.868 Å), and SrTiO3 (STO, 3.905 Å) by a pulsed laser deposition method. From X-ray diffraction, the lattice constants of thin films on LAO, LSAT, and STO substrates were (a, c) = (3.815 Å, 3.956 Å), (3.871 Å, 3.880 Å), and (3.905 Å, 3.865 Å), respectively. Therefore it was confirmed that compressive-strained (∼4%), nearly strain-free, and tensile-strained (∼1%) films were obtained on the LAO, LSAT and STO substrates, respectively. Under N2 laser excitation at 337 nm which is above bandgap energy of thin films, the CSTO film on STO (tensile-strained) and on LSAT (strain-free) substrate showed intense red photoluminescence peaking at 612 nm due to Pr3+:1D2→3H4 transition and no photoluminescence lines from the 3PJ revels were observed at 300 K. On the other hand, the phosphor film on LAO (compressive-strained) showed blue and red luminescence which ascribed to the transitions from the Pr3+:3P0 level below 200 K. These results showed that initial state of photoluminescence can be tuned from the 1D2 level to the 3P0 level by biaxial strain not by composition in the Pr3+ doped perovskite phosphor films. The temperature dependence of photoluminescence was also explained by simplified four-level-model with carrier-trapping-center probably related to Ti center.

Intrinsic white-light emission from low-dimensional perovskites for white-light-emitting diodes with high-color-rendering index

High-performance white-light-emitting diodes (WLEDs) are regarded as a promising next-generation solid-state light source. However, a low-color-rendering index (CRI), consumption of rare-earth elements, and inevitable self-absorption remain the major challenges for high-performance WLEDs. Here, lead-doped Cs3Cu2Br5 nanocrystals (NCs) with a zero-dimensional structure are prepared to facilitate stable and intrinsic white-light emission (IWE) without phosphors and other compositions. The lead dopants are expected to be centers of isolated [PbBr6] octahedrons, in which self-trapped excitons originating from distorted octahedra can form. Subsequently, a broadband blue photoluminescence (PL) from the Cs3Cu2Br5 and a broadband red PL from the lead doping are observed, exhibiting intrinsic white-light emission overall. The doped Cs3Cu2Br5 NCs are then employed to fabricate WLEDs, which possess a high CRI of 98 and an excellent 200-h operating stability.

Synthesis of red photoluminescent nickel doped self-assembled copper nanoclusters and their application in biothiol sensing

Copper nanoribbons (Cu NRs) and Ni-doped copper nanowires (Cu NWs) with red photoluminescent (PL) were prepared and employed for detection of biothiol. Using 4-(trifluoromethyl) thiophenol as both reducing agent and protecting ligand, the copper nanoclusters (Cu NCs) were synthesized and assembled to nanoribbons. And the Cu NCs were assembled to nanowires by adding nickel ion precursor in synthetic process. The Cu NWs with 3% Ni doping showed a 3-fold emission enhancement than Cu NRs, and the absolute quantum yield was obviously increased from 4.53% to 19.76%. The doped Ni induced Ni-Cu metallophilic interaction, which facilitated the radiative relaxation of excited electrons and furtherly resulted in stronger PL emitting. The morphologies, composition, electronic states, geometrical configuration and arrangement of Cu NCs in assembled architecture were studied by experimental and theoretical investigation. Moreover, the PL of Cu NCs assembly was sensitive to cysteine, homocysteine, and glutathione attributed to surface ligands exchange of Cu NCs through interaction between metal and sulfydryl group. Therefore, a rapid, sensitive, and selective sensing strategy for detection of biothiol was proposed. And the PL test strips based on Cu NCs assembly were fabricated for visual detection of biothiol. Finally, the practical application of sensing system and PL test strips were verified in fetal bovine serum samples spiked with cysteine and homocysteine.

High Color‐Rendering Index and Stable White Light‐Emitting Diodes Based on Highly Luminescent Quantum Dots

AbstractSolid‐phase color converter‐based quantum dots (QDs) white light‐emitting diodes (WLEDs) have become promising next‐generation solid‐state light sources. However, the development of these WLEDs’ production still suffers from constraints involving insufficient color‐rendering index (CRI), low color stability, and short operation lifetimes. Here, thick‐shell Cd0.05Zn0.95S/CdSe/CdxZn1–xS spherical quantum wells are developed with good color tunability from green to red regions and high photoluminescence quantum yield (up to 88% for green wavelengths). QDs with five emission colors are used to fabricate a series of WLEDs, which possess a good correlated color temperature tunability from warm (3210 K) to cool (22 000K) white light, and a high CRI Ra (>90). Specifically, the neutral white light device with Commission Internationale de l´Eclairage (CIE, International Commission on illumination) of (0.36, 0.36) and the standard white light device with CIE of (0.33, 0.33) achieve a CRI Ra up to 95.8 and 95.11, respectively, they also exhibit long operating life and great color stability. These results indicate that the improvement of the performance and stability of the WLED based on thick‐shell spherical quantum wells is remarkable progress in the commercialization of QD‐based solid‐state lighting.

Optical Monitoring of the Biodegradation of Porous and Solid Silicon Nanoparticles.

Silicon nanoparticles (SiNP) are currently of great interest, especially in biomedicine, because of their unique physicochemical properties combined with biodegradability. SiNPs can be obtained in various ways and can have either a non-porous solid (sol-) or porous (por-) structure. In this work, we carry out detailed optical monitoring of sol- and por-SiNP biodegradation using Raman and photoluminescence (PL) micro-spectroscopy. SiNPs were obtained by ultrasound grinding of sol- or por-silicon nanowires, created by silver-assisted chemical etching of crystalline Si with different doping levels. In this case, sol-SiNPs consist of nanocrystals 30 nm in size, while por-SiNPs consist of small 3 nm nanocrystals and 16 nm pores. Both SiNPs show low in vitro cytotoxicity towards MCF-7 and HEK293T cells up to 800 μg/mL. The appearance of the F-band (blue–yellow) PL, as well as a decrease in the intensity of the Raman signal, indicate the gradual dissolution of the sol-SiNPs during 20 days of incubation. At the same time, the rapid dissolution of por-SiNP within 24 h is identified by the quenching of their S-band (red) PL and the disappearance of the Raman signal. The obtained results are important for development of intelligent biodegradable drug delivery systems based on SiNPs.

Hydrotermal mineralization hosted by Cambrian sedimentary rocks asevidence of kimberlite-hosting structure, Syuldyukarskoye field, Yakutia

The paper describes diamondiferous kimberlite area within a new Yakutian Syuldyukarskoye fi ld and presents detailed mapping results of ore-hosting shear evidence, veinlet bleaching of redbeds, outcrops of metagrained pyrite, pyrite-calcite and calcite veinlets hosted by Cambrian terrigenous-carbonate rocks where kimberlites occur. Kimberlite localization is shown at fault junction as well as kimberlite long axis combination with west-northwest orehosting shear. These tectonic structures combine with veinlet bleaching halos, those of pyrite-calcite and calcite veinlets, and calcite druses characterized by red photoluminescence and phosphorescence. Red, blue and partially white photoluminescence is caused by manganese concentration in calcites (> 0,1%). Hydrothermal calcite nature is supported by C and O isotope composition variations, which reflect the input of medium temperature formational and meteoric waters, carbon of sedimentary carbonate rocks and deep hydrocarbons. Anomalous Ba, Cr, Ni and La content is recognized in hydrothermal calcites from near-kimberlite environment. Kimberlite position in the southeastern part of endogenous mineralization halos and greater diamond potential of the western kimberlite body, which is larger compared to the eastern one, allow forecasting of new productive bodies.

Au11Ag6 nanocluster: Controllable preparation, structural determination, and optical property investigation.

The structure/composition of nanoclusters has a decisive influence on their physicochemical properties. In this work, we obtained two different Au-Ag nanoclusters, [Au9Ag12(SAdm)4(dppm)6Cl6]3+ and Au11Ag6(dppm)4(SAdm)4(CN)4, via controlling the Au/Ag molar ratios by a one-pot synthetic approach. The structure of nanoclusters was confirmed and testified by single-crystal x-ray diffraction, electrospray ionization time-of-flight mass spectrometry, XPS, powder x-ray diffraction, and electron paramagnetic resonance. The Au11Ag6 nanocluster possessed a M13 core caped by four Au atoms and four dppm and four AdmS ligands. Interestingly, four CN are observed to locate at the equator of the M13 core. Both nanoclusters contain a similar icosahedral M13 core, whereas their surface structures are totally different. However, the Au11Ag6 nanocluster exhibits good stability and strong red photoluminescence in solution.

Doped Luminescent Lanthanide Coordination Polymers Exhibiting both White-Light Emission and Thermal Sensitivity.

Multifunctional lanthanide coordination polymers (CPs) have the advantages of acting in two or more fields simultaneously. Herein, two single lanthanide CPs, formulated as LnL(D/L-Hlac)(H2O)2·0.5H2O (Ln = Eu (1), Tb (2); H2L = 4,4'-(pyridine-3,5-diyl)dibenzoic acid) and their doped lanthanide analogue Tb0.9373Eu0.0627L(D/L-Hlac)(H2O)2·0.5H2O (3) were prepared through hydrothermal methods. Luminescence measurements reveal that 1 displays red photoluminescence and its Commission International ed'Eclairage (CIE) coordinates are almost invariant in the temperature range from 80 to 300 K, while the emission color of 2 changes from yellow to green and its CIE coordinates change from (0.36132, 0.56365) at 80 K to (0.30448, 0.45566) at 300 K. Significantly, 3 not only displays white-light emission with CIE coordinates of (0.32999, 0.33406) but also exhibits a thermal sensitivity of 2.27% K-1 at 230-300 K. The obviously larger thermal sensitivity in 3 in comparison to that of 1.07% K-1 for 2 demonstrates that lanthanide CPs with both a heat-sensitive fluorescent thermometer and high-efficiency white-light emission can be expected by doping Eu(III) ions into Tb(III)-based CPs.

Optical and structural properties of Mn-doped magnesium titanates fabricated with excess MgO

Optical and structural properties of ceramics based on Mn-doped magnesium titanates synthesized by sintering in air at 1200 °C of MgO and TiO2 powders of different molar ratios ranging from MgTiO3 to Mg2TiO4 stoichiometric compositions were studied. The influence of excess MgO on Mn incorporation in crystal lattice of MgTiO3 was also investigated. The Mn4+ ions substituted Ti4+ sites were controlled by the photoluminescence (PL) and diffuse reflectance spectroscopy, and the Mn2+ ions on Mg2+ sites were monitored by electron paramagnetic resonance (EPR). The ceramics produced using equimolar ratio of MgO and TiO2 composed of a major MgTiO3 and a minor MgTi2O5 crystal phases, and those made with excess MgO contained MgTiO3 and Mg2TiO4 phases in different proportions. The EPR study showed that Mn incorporated in MgTiO3 synthesized under 1:1 M ratio as Mn2+ ion mainly. This agreed with low intensity of Mn4+ red PL ascribed to low concentration of Mn4+ centers and partial absorption of the UV excitation light by the MgTi2O5 phase. The Mn-doped MgTiO3 synthesized with excess MgO of 19 and 50 mol.% showed increased Mn4+ red PL by a factor 30–50, enhanced Mn4+ optical absorption and more than ten times decreased Mn2+ EPR signal. The Mg2TiO4 phase was found to be under compressive strains attributed to the presence of Mg vacancies and demonstrated Mn4+ red PL with modified spectrum shape and decay behavior. It is concluded that in MgTiO3 the excess MgO facilitates the incorporation of Mn onto Ti4+ site and can be used for the increasing of Mn4+ PL intensity.

Monodisperse micro-spherical Sr2–zMg1+yYzAl22–xO36:xMn4+ red phosphors

With narrow red photoluminescence (PL) bands, tetravalent Mn4+ doped phosphors show promising prospect in commercial application to effectively expand color gamut of phosphor converted LED displays. Here, we report a type of Sr2–zMg1+yYzAl22–xO36:xMn4+ phosphors with regular cage-like micro-spherical morphologies. The micron size spherical precursors were synthesized with a propylene oxide (PO) driven fast sol–gel method. The cage -like spherical morphology is beneficial to efficiently trapping much incident light to enhance the PL of the phosphors. Being calcined at 1300 °C, Sr2MgAl21.978O36:0.022Mn4+ only exhibits the internal quantum efficiency (IQE) of 24.91%. With the Mg2+-Mn4+ codoping and Y3+/Sr2+ substituting strategies, to fulfill charge balance and produce John-Teller distortion, IQE of Sr2–zMg1+yYzAl22–xO36:xMn4+ can be further improved up to 36.45%. The CIE color coordinates of Sr2–zMg1+yYzAl22–xO36:xMn4+ under near ultraviolet excitation can be stably fixed to (0.723, 0.227) at deep red region. It thus finds a potential application as pc-LED display with much broader color gamut than that of the NTSC standard. Therefore, Sr2–zMg1+yYzAl22–xO36:xMn4+ micron size spheres can be employed as promising red phosphors for high performance LED displays.

Dual-emission carbon dots-copper nanoclusters ratiometric photoluminescent nano-composites for highly sensitive and selective detection of Hg2+

A novel dual-emission photoluminescent (PL) nano-materials of carbon dots-copper nanoclusters (CDs-CuNCs) nano-composites is prepared for excellent sensitivity and selectivity toward Hg2+. The nano-composites are composed of blue photoluminescent CDs and red photoluminescent CuNCs with similar excitation wavelengths through the electrostatic assembly. The red photoluminescence of CuNCs was inhibited by the nano-composites exposed to Hg2+, while the blue photoluminescence of CDs remained stable. The color of the nano-composites slowly changed from pink to blue with the added of Hg2+ concentration. The limit of detection (LOD) of the nano-composites is 0.31 nmol/L (nM) toward Hg2+ in aqueous solution, when the signal to noise ratio is 3. In addition, a visual PL test paper is prepared. When the Hg2+ solution is added, the color of test paper transforms from pink to blue immediately. Therefore, the nano-composites are very important for efficient and sensitive detection of Hg2+, which show broad application prospects in environmental analysis, food safety detection, biological detection and medical diagnosis in daily life.

Enhanced red photoluminescence in chain-like SrAl2O4:Eu3+ nanophosphors: utilizing charge compensation by modulating Na+ co-doping concentration

In the recent days, rare-earth doped phosphors have attracted an immense attraction in luminescence field for various solid-state lighting and electronic display device applications. However, need of efficient red phosphor is a prevalent challenge in this field. Herein, we report a bright red light emitting Na+ co-doped SrAl2O4:Eu3+ phosphor which is synthesized by modified sol–gel technique. These nanophosphors show excellent red emission due to characteristic 5D0 → 7Fj (j = 1, 2, 3, 4) transitions of the doped Eu3+ ions excited by 394 nm. Photoluminescence studies of both Eu3+ doped SrAl2O4 and Na+ co-doped SrAl2O4:Eu3+ has shown more than fourfold increase in the intensity for optimum Na+ addition. The improved decay time obtained from decay measurement has revealed that the co-doped Na+ has successfully reduced the nonradiative transitions. Thus, addition of monovalent Na+ to Eu3+ doped SrAl2O4 was found to be effective to address the charge imbalance problem along with significant enhancement in luminescence intensity and decay time. The results suggest that this nanophosphor could be a major candidate in the rapidly increasing field of solid-state lighting applications.

Appearance of new photoluminescence peak and spectral evolution of Eu3+ in La2Zr2O7 nanoparticles at high pressure

Lots of efforts have been vested recently on tuning the structure and optical properties, particularly for the luminescent nanophosphors. High pressure in that direction has shown great potential to tune the performance of nanophosphors. However, very little attention has been paid on tuning the optical properties of technologically important La2Zr2O7 (LZO) pyrochlore nanoparticles (NPs) and its doped counterpart La2Zr2O7:Eu3+ (LZOE) NPs under elevated pressure. Equally little effort has been given on local structure evolution of Eu3+ ion as a function of pressure in the doped LZOE NPs. Here in this work, LZO depicted strong oxygen vacancy blue emission under ambient and up to 5.54 GPa pressure, and beyond that, there is an evolution of pressure induced green and red photoluminescence (PL) band. This is projected in color tuning from blue → green → white in low-intermediate-high pressure regime. Emergence of unusual visible PL band at elevated pressure is ascribed to structural phase transition from ordered pyrochlore to cotuunite structure which endows large disordering in the LZO structure as well as induces lattice distortion of ZrO6 octahedra. High-pressure PL excitation spectra of the LZOE NPs throw interesting results wherein the charge transfer band is retained in ordered pyrochlore and disappears in high pressure cotuunite phase. As the pressure is raised, the asymmetry ratio of the LZOE NPs exhibits monotonic decrease up to ~19.77 GPa and saturation beyond that, implying a high local symmetry around Eu3+ ions from high pressure compression. This work is a way forward in the area of understanding structure-property correlation, pressure induced color tunability and modulating local structure of lanthanide dopant in the area of luminescent NPs.

Experimental and in silico studies of dichloro-tetrakis(1H-pyrazole)-cobalt(II): Structural description, photoluminescent behavior and molecular docking

A novel pyrazole-based Co(II) complex, namely dichloro-tetrakis(1H-pyrazole)-cobalt(II), was synthesized and characterized. Its X-ray crystal structure showed that it crystallizes in the monoclinic C2/c space group with discrete [CoPz4Cl2] units held together via intra- and intermolecular hydrogen bonds. The non-covalent interactions were explicitly analyzed by means of the topological and Hirshfeld surface analyses, revealing the presence of 0-periodic binodal 1,6-connected 1,6M7–1 and 14-connected uninodal bcu–x topologies built up through N—H…Cl and C—H…Cl hydrogen-bonding networks in addition to weak non-classical H…H, NH…C, CH…N, N—H…π, π…lp/lp…π and lp…lp interactions. Additionally, interactions energy and energy frameworks analyses were performed in order to compute the total energies of the possible intermolecular interactions. The empty space in the crystal lattice was analyzed using void mapping which lead to the presence of small cavities. The structure was furthermore optimized showing a very good agreement with the experimental results, the molecular electrostatic potential (MEP) maps were obtained with their active regions and the non-linear optical properties estimated. Additionally, the optical properties of the title complex were investigated at room temperature using optical UV-visible absorption and photoluminescence spectroscopy, exhibiting π → π*, n → π*, d → d and ligand-field transitions which result in a large variety of emission bands predominant by a bright red photoluminescence. An in silico study was carried out and the binding ability of the title complex with Staphylococcus aureus tyrosyl-tRNA synthetase and Pyrococcus kodakaraensis aspartyl-tRNA synthetase was evaluated displaying a good inhibition activity towards the last one.

Band gap tailoring, structural and optical features of MgS nanoparticles: Influence of Ag+ ions

Ag+ ions incorporated MgS nanoparticles were synthesized by the co-precipitation method. X-ray diffraction (XRD) spectra revealed that the samples had a cubic structure and the transmission electron microscope (TEM) pictures confirmed the spherical shape and size of the particle. The particle size was ranged from 11 nm to 15 nm. The average size of the particles was decreased for the increase of Ag+ ions concentration. Scanning Electron Microscope (SEM) photographs disclosed the surface morphology of samples. The agglomeration of the samples was reduced in the higher doping concentration. Energy Dispersive X-ray (EDX) and Fourier Transform Infrared (FTIR) analysis were utilized to verify the presence of elements as per the stoichiometry ratio. UV–vis absorption was increased due to the incorporation of Ag+ ions and better transmittance was offered for Ag = at. 2 %. The optical band gap was blue-shifted for Ag+ ions incorporated MgS nanoparticles. High intense strong red photoluminescence (PL) emission was exhibited at 660 nm by MgS:Ag for Ag = 2 at.%. The shifting of PL peaks to higher wavelength indicates the Ag+ ions incorporation. The shallow donor defects produced PL emission in a strong red region. The red emission may also be ascribed to the electron transition in high energy levels.

FRET processes of bi-fluorophoric sensor material containing tetraphenylethylene donor and optical-switchable merocyanine acceptor for lead ion (Pb2+) detection in semi-aqueous media

A novel aggregation-induced emission (AIE) structure containing a tetraphenylethene (TPE) unit covalently linked with a spiropyran (SP) unit was synthesized and investigated in semi-aqueous solutions with 90% water fraction. The open-form structure of red-emissive merocyanine (MC) unit combined with TPE unit was utilized as a bi-fluorophoric sensor to detect lead(II) ion, which could be transformed from the close-form structure of non-emissive SP unit upon UV exposure. Moreover, the TPE unit as an energy donor with the blue-green photoluminescence (PL) emission at 480 nm was combined with the MC unit as an energy acceptor with the red PL emission at 635 nm. Due to the Förster resonance energy transfer (FRET) processes, the bi-fluorophoric sensor produced more efficient ratiometric PL behavior to induce a stronger red PL emission than that of the mono-fluorophoric MC unit. Hence, the PL sensor responses of the AIE bi-fluorophoric structure toward lead(II) ion could be further amplified via the FRET-OFF processes to turn off red PL emission of the coordinated MC acceptor and to recover blue-green PL emission of the TPE donor. Accordingly, the best LOD value for the AIE sensor detection toward Pb2+ was 0.27 μM. The highest red MC emission with the optimum FRET process of AIE sensor could be utilized in cell viability tests to prove the non-toxic and remarkable bio-marker of AIE sensor to detect lead(II) ion in live cells. The developed FRET-OFF processes with ratiometric PL behavior of the bi-fluorophoric AIE sensor can be utilized for future chemo- and bio-sensor applications.

Triple‐Site Dopant–Defect Complexes in Mg–H‐Codoped GaN: First‐Principles Identification

There are dozens of double‐site and triple‐site dopant–defect complexes in Mg–H‐codoped GaN that can compensate the MgGa acceptor and thus limit p‐type conductivity; however, their properties have not been systematically studied. Using first‐principles calculations, herein, it is found that the well‐known double‐site complexes MgGa–VN and MgGa–HN can still act as donors, although they are already donor–acceptor‐compensated complexes. Therefore, they can compensate another MgGa acceptor and form the triple‐site complexes MgGa–MgGa–VN and MgGa–MgGa–HN, which have never been reported. The formation energies of the two triple‐site complexes can be low, especially in Ga‐rich and n‐type GaN, so they have non‐negligible concentration and thus play an important role in limiting the p‐type conductivity. The MgGa–MgGa–VN complex produces a defect level that can not only induce nonradiative electron–hole recombination, but also give rise to a red and broad photoluminescence band at 1.76 eV, providing another explanation for the red band observed in heavily Mg‐doped GaN. These triple‐site dopant–defect complexes should be taken into account in future study of defects in GaN and related semiconductors.

Development of White Persistent Phosphors by Manipulating Lanthanide Ions in Gadolinium Gallium Garnets

Lanthanide ions act as excellent luminescence centers and good charge carrier traps. By selecting proper lanthanide ions, persistent phosphors with the desired luminescent color can be developed. In addition, an appropriate host material can give not only better persistent luminescence performance but also an additional function. Herein, bright white persistent phosphors of Pr3+–Tb3+–Eu3+ tridoped paramagnetic Gd3Ga5O12 (GGG) are successfully developed. The GGG phosphors singly doped with Pr3+, Tb3+, and Eu3+ show reddish‐white (3PJ–3HJ), blue (5DJ–7FJ), and red (5D0–7FJ) photoluminescence, respectively, by UV excitation. On the other hand, the GGG samples codoped with Pr3+–Eu3+ and with Tb3+–Eu3+ show only Pr3+ reddish‐white persistent luminescence and Tb3+ blue persistent luminescence, respectively. Based on the thermoluminescence glow curves, it is found that the Eu3+ ion acts only as an electron trap in the persistent luminescence mechanism and the trapped electrons are released at around 325 K. The cool‐white persistent luminescence is achieved by combining Pr3+ and Tb3+ persistent luminescence centers in the GGG:Pr3+–Tb3+–Eu3+ phosphors. It is demonstrated that the white persistent phosphor powder in water can be dragged around by a permanent magnet due to the paramagnetic property of GGG.

Investigation on the β-Ga2O3 deposited on off-angled sapphire (0001) substrates

β-Ga2O3 films were deposited on 6° off-angled (toward <11–20> direction) sapphire (0001) substrates by low pressure MOCVD. β-Ga2O3 films followed step-flow growth mode at the lower growth pressure, and grains size and growth rate of the film decreased with the increasing growth pressure. The decrease of Ga and O vacancies induced the weakness of the blue and green photoluminescence intensity, while N component enchanced the red photoluminescence intensity. Optical bandgaps of the β-Ga2O3 films grown at 20, 30 and 40 Torr were 4.61, 4.64 and 4.65 eV, respectively.

Development of a 4‐Nitrophenylhydrazine Sensor Based on MgTi2O4⋅TiO2⋅Zn2TiO4 Nanomaterials

AbstractThe synthesized MgTi2O4⋅TiO2⋅Zn2TiO4 nanomaterial was characterized by XRD (X‐Ray diffraction), SEM (Scanning electron microscopy), EDS (Energy dispersive x‐ray spectroscopy), FTIR (Fourier transform infrared spectroscopy) and PL (Photoluminescence) study. Particles size of MgTi2O4⋅TiO2⋅Zn2TiO4 nanomaterial was found to be 37.3 nm. PL and PLE (Photoluminescence excitation) spectra are showed several peaks including one red PL at 723 nm, when excited at 320 nm. Nanomaterial was subject to electrochemical sensor study. Thin layer of synthesized MgTi2O4⋅TiO2⋅Zn2TiO4 nanomaterials was fabricated onto the glassy carbon electrode (GCE) with conducting binder to result the working electrode of 4‐nitrophenylhydrazine (4‐NPHyd) sensor, which was applied successively to selectively detect the 4‐NPHyd in aqueous phase. The 4‐NPHyd chemical sensor exhibited high sensitivity with lower detection limit, long‐term stability in chemical environment and improved electrochemical responses during sensing performance. The linearity of calibration plot is obtained over the large linear dynamic range (LDR) from 0.1 nM to 0.1 mM of 4‐NPHyd. The sensitivity calculated from the slop of calibration plot (ratio of current to concentration of 4‐NPHyd) is 42.7215 μAmM−1cm−2 with detection limit (DL) of 0.02±0.001 nM at signal to noise ratio of 3(S/N). Therefore, the chemical sensor based on MgTi2O4⋅TiO2⋅Zn2TiO4 nanomaterials may be a promising highly sensitive sensor in electrochemical method for the effective detection of hazardous and carcinogenic chemicals in medical as well as biological sectors.