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This paper describes the synthesis and characterization of new organic semiconductors based on pyrrolo[1,2-i][1,7]phenanthrolines in the form of thin layers. The thin layers, produced via the spin coating method (with a thickness of 10–11 μm), were investigated for their electrical and optical properties. After heat treatment at temperatures ranging from 210 to 240 °C, the layers displayed consistent and reproducible properties. The layers exhibited n-type semiconductor behavior, with a thermal activation energy (Ea) in the range of 0.75–0.78 eV. Additionally, the layers showed transmittance values of 84–92% in the visible and near-infrared spectral ranges, with a direct optical band gap (Egod) ranging from 3.13 to 4.11 eV. These thin layers have potential applications in electronic devices such as thermistors, as well as in nanoelectronics and optoelectronics. Overall, these new organic semiconductors show promising properties for practical implementation in various electronic applications.

ZnO nanorods combined with different concentrations of reduced graphene oxide were synthesized using the hydrothermal method. Structural properties of these nanocomposites were studied by X-ray diffraction analysis. Morphological studies on the shape and size of nanorods were carried out by scanning electron microscopy. X-ray diffraction results revealed highly-crystalline nanorods with a hexagonal wurtzite structure. The morphology of as prepared samples is characterized presence of one-dimensional rod-like nanostructures. Crystallite size, stress and lattice strain were determined by Scherrer equation and Williamson–Hall method. The average particle size of samples calculated from microstructural and morphological analyses are highly interrelated. Microraman spectra exhibited both characteristic bands of ZnO and reduced graphene oxide in the low frequency (300–500 cm−1) and high frequency (1300–1600 cm−1) ranges, respectively, furthermore confirming the efficiency of the hydrothermal synthesis of ZnO/reduced graphene oxide nanocomposites. The band gap of the nanocomposite is lower (2.96 eV).compared to that of ZnO (3.10 eV), as determined from the analysis of UV absorbance spectra.

Yb doped ZnO nanorods were prepared on glass substrates by the hydrothermal method in order to investigate the insertion of Yb ions in the ZnO matrix and the related morphological, structural and vibrational properties of the samples. X-ray diffraction patterns showed that the undoped and Yb doped ZnO nanorods exhibit the hexagonal wurtzite crystal structure with a preferential orientation along (1 0 1) direction and the size of the particle is found to be decreased with Yb content. SEM images show rods shape with more agglomeration in Yb doped ZnO nanorods. The vibrational study has also been performed using FT-IR spectroscopy which gives the presence of an absorption band corresponding to the stretching mode frequency of ZnO (Zn−O), the bands corresponding to organic precursors were no longer present in the FTIR spectrum after doping, which supports the incorporation of Yb ions into the ZnO lattice. Raman spectra confirmed the hexagonal wurtzite structure of pure and Yb doped ZnO nanoparticles with E2 (high) mode at 438 cm−1 and the presence of other possible defects. The aim of this study was to investigate the effect of Yb doping on the structural and vibrational properties of ZnO nanorods.

In this work, optical, including photoluminescence and photosensitivity, characteristics of micrometer-sized flexible n (p)–InSe/In2O3 heterojunctions, obtained by heat treatment of single-crystalline InSe plates doped with (0.5 at.%) Cd (Sn), in a water-vapor- and oxygen-enriched atmosphere, are investigated. The Raman spectrum of In2O3 layers on an InSe:Sn substrate, in the wavelength range of 105–700 cm−1, contains the vibration band characteristic of the cubic (bcc-In2O3) phase. As revealed by EDX spectra, the In2O3 layer, ~2 μm thick, formed on InSe:Cd contains an ~18% excess of atomic oxygen. The absorption edge of InSe:Sn (Cd)/In2O3 structures was studied by ultraviolet reflectance spectroscopy and found to be 3.57 eV and ~3.67 eV for InSe:Cd and InSe:Sn substrates, respectively. By photoluminescence analysis, the influence of doping impurities on the emission bands of In2O3:Sn (Cd) was revealed and the energies of dopant-induced and oxygen-induced levels created by diffusion into the InSe layer from the InSe/In2O3 interface were determined. The n (p)–InSe/In2O3 structures display a significantly wide spectral range of photosensitivity (1.2–4.0 eV), from ultraviolet to near infrared. The influence of Cd and Sn concentrations on the photosensitivity and recombination of nonequilibrium charge carriers in n (p)–InSe layers from the heterojunction interface was also studied. The as-obtained nanosized InSe/In2O3 structures are suitable for optoelectronic applications.

This work reports a study on structural, electrical and optical properties of some recently synthesized pyrrolo[1,2

In this paper, we report on the effect of titanium dioxide (TiO2) target sintering temperature on the morphological and optical properties of amorphous titanium dioxide thin films synthesized by pulsed laser deposition (PLD) on indium tin oxide (ITO) glass substrate and subsequently heat-treated in air at low temperature (150 °C). Three types of targets were used, unsintered (pressed at room temperature), sintered at 500 °C and sintered at 1000 °C. The surface morphology of the samples was investigated by scanning electron microscopy (SEM), and profilometry was used for thickness measurements. The structural properties of the films were examined by X-ray diffraction (XRD), while their optical properties were studied by UV‒vis spectroscopy. The obtained TiO2 thin films have an amorphous nature, as shown by XRD analysis. Profilometer showed that sintered target samples have more reliable thicknesses than unsintered ones. The SEM studies revealed the sufficient structural homogeneity of sintered target nanosized TiO2 films and agglomerates in the case of unsintered target film. The UV‒vis transmittance spectra showed high transparency in the visible range of PLD films, proportional to the target sintering temperature. The optical band gaps of the films deposited using the 500 °C and 1000 °C sintered targets are closer to those of anatase and rutile phases, respectively, which provides a promising approach to the challenges of amorphous TiO2-based nanostructures.

In this paper, the influence of graphene oxide coating on optical and photoluminescence properties of zinc oxide nanorods (ZnO NRs) has been investigated. ZnO NRs were prepared using a hydrothermal route (from zinc nitrate hexahydrate and hexamethylenetetramine), graphene oxide (GO) was fabricated by Hummer’s method, while for synthesis of ZnO nanorods:graphene oxide nanocomposite (ZnO NRs:GO) on Si (100) substrate, a facile technique (drop coating) was proposed. The structural, morphological, optical and luminescence properties of the films were investigated using X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), together with Fourier transform infrared (FT-IR), Raman, ultraviolet–visible–near-infrared (UV/VIS/NIR) and photoluminescence (PL) spectroscopies. As revealed by XRD analysis, composites display a hexagonal wurtzite type structure with a (101) preferred grain orientation. The average crystallite sizes decrease from 45 to 40 nm after GO coating. The SEM study confirms successful coating of GO layers on flower-like ZnO nanostructures. The FTIR and Raman analyses validated the hybridization of nanocomposite and the strong interaction between ZnO NRs and GO. The band gap of the ZnO NRs:GO nanocomposite is lower (2.95eV) compared to that of ZnO NRs (3.11 eV), as determined from the analysis of UV absorbance spectra. The ZnO NRs:GO nanocomposite exhibits a broad PL band, from ∼450 nm to ∼750 nm, with a nearly white-light integrated emission and a chromaticity coordinate of (0.25, 0.34). Gaussian deconvoluted broad PL band exhibits three distinct sub-bands, associated with radiative recombinations in ZnO and GO.

Temperature dependence of d. c. electric conductivity of some recently synthesized heterocyclic compounds, 4,4′-bipyridine and indolizine derivatives, in thin films (d = 0.27–0.51 μm) spin-coated from chloroform solutions onto glass, is studied. The investigated compounds are polycrystalline (as shown by X-ray Diffraction analysis) and show typical n-type semiconductor behavior. The activation energy of d. c. electric conduction ranges between 1.55 and 2.33 eV. Some correlations between semiconducting characteristics and essential features of molecular structure of organic compounds have been established. In the higher temperature range (400–520 K), the electronic transport properties in present compounds can be explained in the frame of band gap representation model, while in the lower temperature range (300–350 K), the Mott's variable-range hopping conduction model can be conveniently used.

The nanocrystalline iron manganite was be successfully synthesized, for capacitive humidity sensor application, by sol–gel self-combustion method using polyvinyl alcohol as colloidal medium, followed by heat treatment. The best performances as humidity sensor were found, at working frequency of 100 Hz: a high sensitivity over a wide range of relative humidity, 11–98% RH (the capacity increases by over 40 times); a good linearity of the logC vs. RH characteristics over the whole RH range, for all used frequencies. The sensor exhibits very small hysteresis, lower sensitivity to temperature, keeping linear characteristics and a short response time. The investigated material holds promise for humidity monitoring applications, taking into account the low cost, a wide range of relative humidity and a low-contamination impact.

Spinel-type semiconductor compounds represent an alternative for robust and inexpensive detection systems, due to their good thermal and chemical stability in operation. The sensing mechanism is based on the change in electric resistivity when exposed to specific gaseous ambient, resulting from chemical reactions between metal-oxide surface and gas molecules. Sample composition and morphology are key factors in determining the selectivity and sensitivity of solid-state sensors. In this work structural, morphological and sensory characteristics of some porous oxide semiconductors with spinel-type structure (Nk 0.99 Co 0.01 Mn 0.02 Fe 1.98 O 4-δ , Li 0.5 Sm 0.1 Fe 2.4 O 4 and Mg 0.9 Sn 0.1 Fe 2 O 4 ) are presented. The self-combustion technique was used to prepare these compounds. This method offers the advantage of obtaining nanosized reproducible and porous ceramics with high specific surface area and exact stoichiometry. Investigated compounds hold promise for high-performance applications in acetone sensors.

Electric (d.c. conduction mechanism, the influence of environmental humidity, thermistor effect) and optical properties of new five substituted calixarene derivatives in thin films have been studied. The films behave as typical n-type polycrystalline semiconductors with activation energy of the electric conduction between 0.26 and 2.36 eV. In the higher temperature range, the electron transport was explained in the frame of the band gap representation model, while at lower temperatures, the Mott’s variable-range hopping conduction model was found as appropriate. In terms of electric conductivity, these compounds are practically insensitive to ambient humidity below 53% RH, their sensitivity increasing greatly with the humidity in the range of 53–98% RH. Study of optical absorption spectra in the photon energy range of 0.71–4.03 eV (UV–Vis–NIR) revealed direct optical band gaps between 2.64 and 3.83 eV. Actual compounds show promising potential for thermistor applications.

Gallium oxide (β-Ga2O3) nanowires were synthesized by heat treatment of single crystal β-GaS plates in air. Crystal structure and composition of synthesized materials were studied by X-ray diffraction, energy dispersive X-ray spectroscopy and Raman spectroscopy. Thermal treatment of β-GaS plates at 1023 K leads to the formation of a Ga2O3 (native oxide) layer on β-GaS (0001) surface of plates. Layer thickness and size of Ga2O3 wires contained were found to depend on temperature and duration of applied heat treatment. For 1023 K and 6 h, the length of Ga2O3 wires laid in the range from units to tens of nanometers, while for 1123 K and 30 min, between 30 and 40 μm.

Temperature dependences of electric conductivity and thermoelectric power of some recently synthesized organic compounds, 4-tert-butylcalix[4]arene derivatives, are studied. Thin-film samples (d = 0.10–0.40 μm) spin-coated from chloroform solutions onto glass substrates were used. Organic films with reproducible electron transport properties can be obtained if, after deposition, they are submitted to a heat treatment within temperature range of 295–575 K. The studied polycrystalline compounds show typical p-type semiconductor behavior. The activation energy of the electric conduction ranges between 0.82 and 1.12 eV, while the ratio of charge carrier mobilities was found in the range of 0.83–0.94. Some correlations between semiconducting parameters and molecular structure of the organic compounds have been discussed. In the higher temperature ranges (T > 420 K), the electron transport in examined compounds can be interpreted in terms of the band gap representation model, while in the lower temperature range, the Mott's variable-range hopping conduction model was found to be appropriate. The investigated compounds hold promise for thermistor applications.

Temperature-dependent d.c. electric conductivity of some recently synthesized indolizine derivatives is studied. Thin-film samples (d = 0.10–0.30 μm) spin-coated from chloroform solutions onto glass substrates were used. Organic films with reproducible electric properties can be obtained by submitting as-prepared samples to a heat treatment within temperature range of 301–493 K. The studied polycrystalline compounds show typical n-type semiconductor behavior. The activation energy of the electric conduction ranges between 0.32 and 1.07 eV. Some correlations between semiconducting characteristics and molecular structure of the organic compounds have been discussed. In the higher temperature range (T > 415 K), the electron transport in present compounds can be interpreted in terms of the band gap representation model, while in the lower temperature range (T < 339 K), the Mott’s variable-range hopping conduction model was found to be suitable.

In this work, temperature dependences of electrical conductivity and thermoelectric power, for some recently synthesized nonsymmetrical bisindolizines, are studied. Thin-film samples (d = 0.10–0.30 μm) spin-coated from dichloromethane solutions onto glass substrates were used. Organic films with reproducible electronic transport properties can be obtained if, after deposition, they are subjected to a heat treatment within the temperature range of 301–541 K. The studied organic compounds show typical p-type semiconductor behavior. The activation energy of electrical conduction was found in the range 1.00–1.26 eV, while the ratio of charge carrier mobilities ranged between 0.90 and 0.97. The correlations between determined semiconducting parameters and specific features of molecular structure of the compounds have been discussed. In the higher temperature range (363–541 K), the electronic transport in actual compounds can be interpreted by using the band gap representation model, while for lower temperatures, Mott's variable-range hopping conduction model was found to be appropriate.

Temperature-dependent electrical conductivity and thermoelectric power of some recently synthesized fused heterocyclic compounds (nonsymmetrical bisindolizines), are studied. Thin-film samples ( d = 0.10–0.20 μm) deposited from dichloromethane solutions onto glass substrates were used. Organic films with reproducible electronic transport properties can be obtained if, after deposition, they are submitted to a heat treatment within temperature range 300–600 K. The studied compounds show typical p-type semiconductor behavior. The activation energy of the electrical conduction ranges between 0.90 and 1.17 eV, while the ratio of charge carrier mobilities was found in the range 0.94–0.97. Some correlations between semiconducting parameters and molecular structure of the organic compounds have been discussed. In the higher temperature range (373–601 K), the electronic transport in examined compounds can be interpreted in terms of the band gap representation model, while in the lower temperature range, the Mott's variable-range hopping conduction model was found to be appropriate.

Temperature-dependent d.c. electric conductivity of some recently synthesized organic compounds, stable disubstituted 4-(4-pyridyl)pyridinium ylides, is studied. Thin-film samples ( d = 0.100.80 μm) spin-coated from dimethylformamide solutions onto glass substrates have been used. Organic films with reproducible electron transport properties can be obtained if, after deposition, they are submitted to a heat treatment within temperature range of 297 − 527 K. The studied polycrystalline compounds exhibit typical n -type semiconductor behavior. The activation energy of the electric conduction ranges between 0.59 and 0.94 eV. Some correlations between semiconducting parameters and molecular structure of the organic compounds have been discussed. In the higher temperature range ( T > 400 K), the electron transport in examined compounds can be interpreted in terms of the band gap representation model, while in the lower temperature range, the Mott's variable-range hopping conduction model was found to be appropriate. Some of the investigated compounds hold promise for thermistor applications.

Temperature-dependent d.c. electric conductivity of some recently synthesized organic compounds, 4,7-phenanthroline derivatives is studied. Thin-film samples (d=0.34-0.63 m) spin-coated from dimethylformamide solutions onto glass substrates have been used. Organic films with reproducible electron transport properties can be obtained if, after deposition, they are submitted to a heat treatment within temperature range of 298523K. Examined organic compounds in thin films are polycrystalline and display typical n-type semiconductor behavior. The activation energy of d. c. electric conduction ranges between 0.09 and 0.46 eV and is influenced by nature of substituents, degree of conjugation systems and packing capacity of compounds. In the higher temperature range (T>433 K), the electron transport in examined compounds can be interpreted in terms of the band gap representation model, while in the lower temperature range, the Mott’s variable-range hopping conduction model was found to be appropriate. Some of the investigated compounds hold promise for thermistor applications.