Nanohybrids consisting of uniform nanospheres and nanospindles of zinc ferrite attached to reduced graphene oxide were prepared by hydrothermal reaction.

Vinitha G

Physics

School of Advanced Sciences

Chennai Campus

Saravanan M

Sabari Girisun T.C

Venugopal Rao S.

Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

RSC Advances

A new alkali metal borate with formula Na6 [B4O5 (OH)4]3. 8H2O single crystal has been grown by slow evaporation method under room temperature condition for the first time. The structural analysis reveals that the grown crystal crystallizes in the rhombohedral space group R32 with cell parameters a = 11.27 Å, b = 11.27 Å, c = 21.27 Å and α = β = 90°, γ = 120°. The intermolecular interactions of symmetric stretching of BO3 and asymmetric stretching of BO4 were identified by Fourier-transform infrared spectroscopy (FT-IR). Optical investigation on the hydrated borate shows that the material possessed a high transmittance of about 60% in the entire UV- visible region with an optical absorption edge at 220 nm and the band gap was found to be 4.972 eV. The theoretical calculations were performed in order to find the linear optical constant such as linear absorption coefficient, extinction coefficient and reflectance etc. Thermogravimetric (TG)/Differential scanning calorimetry (DSC) analysis for the grown crystal displayed that the material is stable up to 116 °C and having the melting point of 145 °C. The frequency independent dielectric constant and dielectric loss were performed at different temperature. AC conductivity was studied by means of electrical relaxation process and it is due to the presence of water molecules in the compound. The third order nonlinear susceptibility (χ3), nonlinear refractive index (n2) and the absorption coefficient (β) are found to be in the order of 1.36 × 10−6 esu, 3.88 × 10−8 cm2/W and 0.026 × 10−4 cm/W respectively. The strong optical limiting behaviour of the material could be attributed to the two photon absorption mechanism and negative nonlinearity due to self-defocusing effect. © 2017 Elsevier B.V.

Materials Chemistry and Physics

Insight on the growth and property studies of inorganic hydrated borate (Na6 [B4O5 (OH)4]3. 8H2O) single crystal – An effective third order nonlinear optical (NLO) material for optical limiting application

Third-order nonlinearity of monoclinic and orthorhombic phase of CuNb2O6 is studied in low power regime of 532 nm by Z-scan technique. In open aperture, monoclinic CuNb2O6 possess stronger saturable absorption due to the distorted structure arising from unequal arrangement of copper atoms. Closed aperture exposes the self-defocusing nature and orthorhombic phase exhibits stronger nonlinear refraction. Variation in third-order NLO coefficient due to change in phase and morphology of CuNb2O6 confirms the influence of sintering temperature and time. Microrod monoclinic CuNb2O6 possess maximum nonlinear absorption coefficient (6.47 × 10−3 cm/W) and pure orthorhombic CuNb2O6 attains maximum nonlinear refractive index (5.13 × 10−8 cm2/W) along with higher third-order nonlinear optical susceptibility (1.91 × 10−6 esu). Higher thermal nonlinearity resulted in stronger optical limiting action with pure orthorhombic CuNb2O6 (5.16 mW, 1.26 mW) compared to other phases. For understanding the material suitability for laser safety device, nonlinearity and limiting action of CuNb2O6 thin films were demonstrated. Earlier formation of monoclinic phase with morphology change (700 °C) and transition of monoclinic rich mixed orthorhombic phase to pure orthorhombic phase (900 °C) with increase in sintering time (3–12 h) was confirmed by XRD, FTIR and SEM analysis. Thus orthorhombic CuNb2O6 material with stronger self-defocusing and optical limiting action makes it more preference than monoclinic CuNb2O6 for third-order NLO applications. © 2018 Elsevier Ltd

Optics & Laser Technology

Third order nonlinear optical properties of monoclinic and orthorhombic CuNb2O6 under CW laser illumination

Third-order nonlinear optical response of cadmium ferrite loaded upon various content of reduced graphene oxide was studied by single beam Z-scan technique using Nd: YAG laser (532 nm, 50 mW). In XRD disappearance of characteristic peak of graphene oxide (10.7°, (100)) and appearance of peaks of reduced graphene oxide (23.3°, (002)) along with cadmium ferrite (34.2°, (311)) confirms the trimming of CdFe2O4 upon rGO. Further the successful trimming of rGO with CdFe2O4 was further evidenced by FTIR and high-resolution C 1s XPS. FESEM and TEM image of GO show folded sheets of graphene layers due to strong oxidation and reduction process. And pure CdFe2O4 grow themselves as nanorods which upon trimming on the surface of graphene sheets suffered a morphological change with respect to the content of graphene oxide (rods to platelets). Absorption spectra of decorated composites possess, absorption peaks at 230 nm (π-π* transition in aromatic C–C), 292 nm (n-π* transition in C[dbnd]O bonds) and 425 nm (cadmium ferrite). Z-scan results showed that both pure and decorated samples showed saturable absorption and self-defocusing behavior along with optical limiting action. Also the nonlinear refraction was found to be more dominant than nonlinear absorption due to strong contribution arising from thermal components. Upon trimming, the nonlinear refractive index (10−8 cm2/W), nonlinear absorption coefficient (10−3 cm/W) and third-order nonlinear optical susceptibility (10−6 esu) were found to be increasing with increase in graphene content. Variation in the distribution and morphology of CdFe2O4 has resulted in the tunability of third-order NLO coefficients and limiting threshold (9.3–30.4 mW). Nanoplatelet CdFe2O4–40 wt% rGO displays good optical power handling capability of laser beam at the experimental wavelength, indicating the possible photonics device application such as optical power limiters. © 2018

Journal of Molecular Liquids

Facile hydrothermal synthesis of CdFe 2 O 4 -reduced graphene oxide nanocomposites and their third-order nonlinear optical properties under CW excitation

Estimation of thermodynamic and third-order nonlinear optical properties of a series of organic liquids based on ethylenediaminium divalent cation, [C2H10N2]X2 (where X = 2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol and 2,4,6-trinitrophenol respectively) was made. Increase in nitro groups of ethylenediaminium nitrophenolates has predominantly increased the point of decomposition (145–243 °C). Various thermodynamic properties as a function of temperature were estimated theoretically from the DSC curves. Thermal conductivity and specific heat capacity was increasing while thermal diffusivity was decreasing with rise in temperature. Ethylenediaminium trinitrophenolate (EDA246TNP) showed maximum thermal conductivity (30.3 W m− 1 K− 1) and specific heat capacity (2684 J kg− 1 K− 1), while thermal diffusivity (9.6 × 10− 6 m2 S− 1) was higher for ethylenediaminium 2-nitrophenolate (EDA2NP). Z-scan experiment showed that all samples exhibit saturable absorption and self-defocusing behaviour under CW laser (532 nm, 50 mW) excitation. The observed nonlinearity was found to be thermal in origin with order of nonlinearity as ED246TNP &gt; EDA24DNP &gt; EDA4NP &gt; EDA2NP. EDA246TNP possess maximum nonlinear absorption coefficient (8.37 × 10− 3 cm/W), nonlinear refractive index (8.41 × 10− 8 cm2/W), third-order nonlinear optical susceptibility (5.21 × 10− 6 esu), second-order hyperpolarizability (9.81 × 10− 25 esu) and thermo-optic coefficient (− 0.21 × 10− 6 K− 1) than other phenol-ammonium salts. All samples exhibit optical limiting action with optical limiting onset values of 35–38 mW having limiting amplitude of 6.7–9.3 mW. The influence of number and position of nitro groups in tuning the thermodynamic and nonlinearity of ethylenediaminium nitrophenolate was discussed in detail. © 2017 Elsevier B.V.

Influence of number and position of nitro groups in tuning the thermodynamic and nonlinear optical properties of ethylenediaminium nitrophenolates

Third-order nonlinear optical response of heat-treated magnesium ferrite (MgFe2O4) synthesized by simple combustion was studied by Z-scan experiment under continuous wave laser excitation (532 nm, 50 mW). Powder XRD patterns confirm the single-phase formation of spinel structure MgFe2O4 with cubic symmetry. Estimation of crystallite size from XRD data shows a decrease in size as annealing temperature increases. In the FTIR spectra, two absorption bands around 400 and 600 cm−1 correspond to the octahedral and tetrahedral sites of Fe–O and Mg–O, respectively. FESEM analysis pictures the presence of micro-grained particle with porous structure. Single-beam Z-scan experiment shows that the samples possess saturable absorption and self-defocusing nature. The third-order nonlinear optical properties calculated from the experimental data were consistent with the values predicted by theoretical fit. Estimated third-order nonlinear optical susceptibility, χ(3), was found to be increasing with increase in annealing temperature. The samples exhibit limiting behavior beyond 14.5 mW, and the corresponding output value gets clamped at 1.79, 1.95, and 2.54 mW. Magnesium ferrite treated at 900 °C with higher nonlinear optical susceptibility can be used as a potential candidate for low power limiting applications. © 2015, Springer Science+Business Media New York.

Journal of Materials Science

Third-order nonlinear optical properties and power limiting behavior of magnesium ferrite under CW laser (532 nm, 50 mW) excitation

Barium borate (β-BaB2O4) nanoparticles were prepared by a hydrothermal technique using barium chloride and boric acid as starting materials. Powder x-ray diffraction confirms the pure single phase formation of β-BaB2O4. Fourier transform infrared spectroscopy spectra shows the presence of BO3 units which extend themselves to form (B3O6)3- anionic groups in β-BaB2O4. Scanning electron microscopy imaging shows the two-dimensional undulating particle surface with particle size in the range of 45-170 nm. β-BaB2O4 has strong absorption in the UV region and it possesses a wide optical transmittance window (201 to 1100 nm). The optical band gap of the β-BaB2O4 nanoparticle is estimated to be 5.9 eV. In the photoluminescence spectra the presence of self trapped excitonic state (347 nm) was identified. The third order optical nonlinearity of the sample excited in two different pumping regimes, short pulse excitation (532 nm, 5 ns) and continuous wave laser (532 nm, 50 mW) was studied. The material shows limiting behavior due to two photon absorption in the pulsed laser regime and self defocusing in the continuous wave regime. © 2015 IOP Publishing Ltd.

Journal of Physics D: Applied Physics

Optical limiting behavior of β-BaB2O4 nanoparticles in pulsed and continuous wave regime

Enhanced nonlinear optical properties of graphene oxide–silver nanocomposites measured by Z-scan technique

Nanoscale

The effect of the degree of oxidation on broadband nonlinear absorption and ferromagnetic ordering in graphene oxide

Applied Physics Letters

White light Z-scan measurements of ultrafast optical nonlinearity in reduced graphene oxide nanosheets in the 400–700 nm region

Improved third-order optical nonlinearity and optical limiting behaviour of (nanospindle and nanosphere) zinc ferrite decorated reduced graphene oxide under continuous and ultrafast laser excitation

Journal	Data powered by TypesetRSC Advances
Publisher	Data powered by TypesetRoyal Society of Chemistry (RSC)
ISSN	20462069
Open Access	No