2024-01

Journal of Nanotechnology (Volume : 2024)

Cesium lead bromide (CsPbBr3) nanocrystals exhibit remarkable optoelectronic properties and exceptional stability. As a result, they have garnered significant interest for their potential applications in various fields, including solar cells, light-emitting devices, photodetectors, and lasers. Despite its resistance to moisture, oxygen, and heat compared to other perovskite materials, CsPbBr3 still faces challenges maintaining its structural and optical stability over extended periods. This study proposes a robust solution to enhance and improve simultaneously the photoluminescence intensity and stability of CsPbBr3 nanocrystals. The solution involves doping the perovskite precursor with green-synthesized carbon quantum dots (CQDs) and tri-n-octyl phosphine (TOP). The results indicate that the photoluminescence intensity of the perovskite nanocrystals (NCs) is sensitive to varying CQD ratios. A high photoluminescence intensity enhancement of 45% was achieved at the optimal CQDs ratio. The synthesized perovskite NCs/CQDs also demonstrated improved stability by adding TOP into the mixture. After storage in the air for 45 days, the mixed perovskite NCs maintained their performance, which was almost unchanged. Solar cell devices based on the modified perovskite NCs showed a power conversion of 7.74%. The devices also demonstrated a significant open-circuit voltage (VOC), with the most successful device achieving a VOC of 1.193 V, an Isc of 10.5748 mA cm−2, and a fill factor (FF) of 61%. This study introduces a cost-effective method for producing high-quality all-inorganic optoelectronic devices with enhanced performance and stability.

2023-09

Nanomaterials and Nanotechnology (Volume : 2023)

This study synthesized carbon quantum dots (CQDs) with green photoluminescence through a hydrothermal method that utilized mulberry juice as the carbon source. The influence of fruit ripeness on the physical and chemical properties, focusing on the fluorescence spectra, has been explored. Fourier-transform infrared spectroscopy (FT-IR) and energy dispersive X-ray analysis (EDX) showed that there were oxygen-containing groups, and X-ray diffraction (XRD) showed that the carbon quantum dots (CQDs) were graphitic. The results revealed that the CQDs had an average size of around 7.4 nm and 9.7 nm for unripe and ripe mulberry juice, respectively. These CQDs emitted green light at 500 nm and 510 nm in unripe and ripe mulberry juice, respectively, when excited at a wavelength of 400 nm. The prepared CQDs exhibited excitation-dependent photoluminescence (PL) emission behavior, demonstrating their dependence on the excitation light. The impact of fruit ripeness on optical properties was explored by examining fluorescent spectra from different fruits (including tomato and blackberry), demonstrating comparable behaviors observed in mulberry fruit. In addition, the prepared CQDs were utilized as a fluorescent sensor with high specificity to detect Cu2+ ions. The detection limit (DL) for this sensor was determined to be 0.2687 µM, and the limit of qualification (LOQ) is 0.814 µM. The linear range for detection lies between 0.1 and 1 µM. The selectivity of the CQDs towards Cu2+ ions was confirmed by recording the PL response for Cu2+ ions compared to the weak response of other metal ions. According to these results, the CQDs can be applied in various cellular imaging and biology applications, bio-sensing, optoelectronics, and sensors.

2023-08

Journal of Vacuum Science & Technology B (Issue : 5) (Volume : 41)

Scattering-type scanning near-field optical microscopy based on adiabatic nanofocusing of surface plasmon polaritons (SPPs) is a powerful technique that can achieve free-background nanoscale optical resolution of material. However, the performance of the propagated confined modes strongly depends on the characteristic structure of the probe. Although the metallic pyramid structure provides excellent tightly confined modes, however, it is challenging to realize the required pyramid geometry. Here, we propose a simple method for fabricating a reproducible and controllable gold pyramid-shaped tip. The produced pyramid-shaped tips were made by electrochemical etching and by applying a pulse wave to the system. From a systematic study, we found that the key factor of fabrication of desired tip geometry is based on the platinum (Pt) wire shapes. Traditional circular-shaped platinum ring electrodes are used for gold tip fabrication in an electrochemical etching. In our method, we bent the Pt wire into a triangular shape as the electrode for the etching process. The influence of the geometrical ring shapes on the fabrication of the Au tip structure is investigated. The gold tip structure was optimized by controlling the Pt ring shape, and the desired pyramid-shaped gold tip was achieved with a yield of 70%. The obtained etched pyramid-shaped tips were then mounted along the side of one of the arms of a quartz tuning fork force sensor to test their performance for shear-force topographical image and for guiding SPPs along the pyramid wedge based on adiabatic nanofocusing microscopy. The result shows topographical images of indium tin oxide with a spatial resolution smaller than 20 nm. Furthermore, we experimentally demonstrate the generation of the SPPs that propagated adiabatically along the wedge of an appropriate fabricated pyramid-shaped tip toward a nanometer-size spot at the tip apex. The demonstration of this method strongly suggests that the obtained pyramid-shaped tip will enable new experiments probing the dynamics of optical excitations of individual metallic, semiconducting, and magnetic nanostructures.

2022-12

Physica B: Condensed Matter (Issue : 414587) (Volume : 12)

Polyaniline (PANI)/Aluminium nanoparticles (AlNPs) nanocomposite films were designed and synthesized for optoelectronic applications. Structural, morphological, optical, electronic, and electrical properties of the PANI/AlNPs nanocomposite films were studied for various AlNPs concentrations. As AlNPs concentration increases from 0 to 32 wt% the bandgap energy decreases monoexponentially from 3.97 eV to 3.84 and the refractive index increases continuously from 1.53 to 1.63 at 550 nm. However, the monoexponential decay of the bandgap energy cannot describe the PANI/AlNPs films behaviour for AlNPs concentrations greater than 32 wt% due to AlNPs percolation. The electrical conductivity increases from 0.11 to 16.10 μS cm−1 in the above AlNPs range, being the trend fitted to a sigmoidal function, which passes through three regions: insulating, percolation, and electrical conductive zones. AlNPs are homogeneously distributed in PANI/AlNPs nanocomposite films as spherical particles; however, for AlNPs concentrations higher than 32 wt%, AlNPs distribute as continuous aggregations in the polymer matrix.

2022-12

Biosensors (Issue : 12) (Volume : 12)

Complex composite films based on polyaniline (PANI) doped hydrochloric acid (HCl) incorporated with aluminum nitrate (Al(NO3)3) on Au-layer were designed and synthesized as a surface plasmon resonance (SPR) sensing device. The physicochemical properties of (PANI-HCl)/Al(NO3)3 complex composite films were studied for various Al(NO3)3 concentrations (0, 2, 4, 8, 16, and 32 wt.%). The refractive index of the (PANI-HCl)/Al(NO3)3 complex composite films increased continuously as Al(NO3)3 concentrations increased. The electrical conductivity values increased from 5.10 µS/cm to 10.00 µS/cm as Al(NO3)3 concentration increased to 32 wt.%. The sensitivity of the SPR sensing device was investigated using a theoretical approach and experimental measurements. The theoretical system of SPR measurement confirmed that increasing Al(NO3)3 in (PANI-HCl)/Al(NO3)3 complex composite films enhanced the sensitivity from about 114.5 [Deg/RIU] for Au-layer to 159.0 [Deg/RIU] for Au-((PANI-HCl)/Al(NO3)3 (32 wt.%)). In addition, the signal-to-noise ratio for Au-layer was 3.95, which increased after coating by (PANI-HCl)/Al(NO3)3 (32 wt.%) complex composite layer to 8.82. Finally, we conclude that coating Au-layer by (PANI-HCl)/Al(NO3)3 complex composite films enhances the sensitivity of the SPR sensing device.

2022-12

Physica B: Condensed Matter (Volume : 646)

The amorphous/crystalline phase transition behavior of PEO films prepared by spin casting method was studied. According to X-ray diffraction (DELTA) analysis, PEO film has a semicrystalline nature at room temperature. The amorphous to crystalline nature of PEO increases with temperature until reaching an amorphous state at 333 K. 1H NMR spectra of PEO in the temperatures between 298 K and 323 K exhibit two main peaks at around 1.132 ppm and 3.174 ppm with very different widths, where the narrow component can be assigned to the mobile polymer chains in the amorphous phase, whereas the broad component is assigned to the more rigid molecules in the crystalline phase. The calculated activation energies from the Arrhenius fit of the data of the crystalline and amorphous phases are comparable and found to be 0.252 eV and 0.221 eV, respectively. Form fitting dielectric loss (ε″) and the electrical modulus (M″) data with the Havriliak-Negami model with addition of the electrical conductivity term in the case of ε″, it was deduced that the inverse relaxation time (), dielectric strength (Δε) and electrical conductivity (σ) follow an Arrhenius-like behavior plot versus reciprocal temperature.

2020-11

e-Journal of Surface Science and Nanotechnology (Volume : 18)

The paper describes the impact of the crystallographic orientation of an n-type GaAs substrate on the electrical properties of a sulfonated polyaniline (SPAN) thin film with a thickness of 120 nm grown on different n-type GaAs substrates orientation, which are (100), (311)A, and (311)B GaAs planes. Electrical characterization was performed by using current density-voltage (J−V) at room temperature and different temperatures (60−360 K). An ideality factor (n), a Schottky barrier height (Φb), and an activation energy (Ea) were extracted from forward J−V characteristics. From the J−V results, it was obtained that the rectification value at 0.5 V for the SPAN/(311)B GaAs hybrid device is higher than those for SPAN grown on the (100) and (311)A GaAs planes. Furthermore, as the temperature of the three heterojunction devices rises, the value of Φb increases, n drops, and Ea rises. The Ea measurements revealed that Ea for the SPAN/(311)B n-type GaAs heterostructure is lower than those for SPAN samples grown on the (100) and (311)A n-type GaAs planes. This could be related to the low number of defects in SPAN/(311)B than the other two samples. These results make SPAN with a thickness of 120 nm grown on the high index GaAs planes an interesting hybrid device for future devices applications.

2020-09

Journal of University of Duhok (Issue : 2) (Volume : 25)

In this work, we propose a simple and easy method to produce sharp and smooth conical gold tips for atomic force microscope and scanning near-field optical microscopy. The method is electrochemically etching process, based on gold, Pt wire and HCl acid (37%) as a solution. Comparing to other methods, we use only HCl as electrolyte. A function generator was used to produce rectangular pulse wave with 3 kHz and 7 V to obtain smooth and very sharp conical tip with diameter less than 10 nm. By controlling etching parameters (pulse shape, frequency and voltage), the fabricated etching tip achieved about 80% yields. Moreover, the etching time is about 13 second, which is very fast etching process. This method provides a suited tip for tip-enhanced Raman scattering, adiabatic nanofocusing of aperturless-scanning near-field optical microscopy and field emission electron microscopy

2020-09

Journal of University of Duhok (Issue : 2) (Volume : 23)

The present work study the optical parameters for CW operation in Ti:Sapphire laser system with the focus on stability zone and threshold pump power. The main aim of this study is to explore the influence of a broadband dielectric resonator mirrors used in the laser cavity on the stability zone and threshold pump power. This effect has been determined by using two types of mirrors with different broadband reflection. The experimental results show the dependence of the stability and laser threshold pump on broadband dielectric mirrors. For a broader dielectric mirror, the stability zone shows larger stable distance with respect to the narrower mirror. Moreover, the threshold pump for the broader band is smaller than the narrower. This study allows researcher choosing the appropriate optical components for generating more stable laser with small threshold pump power.

2019-12

Science Journal of University of Zakho (Issue : 4) (Volume : 7)

This paper investigates the characteristics some of argon plasma parameters of glow discharge under axial magnetic field. The DC power supply of range (0-6000) V is used as a breakdown voltage to obtain the discharge of argon gas. The discharge voltage-current (V-I) characteristic curves and Paschen’s curves as well as the electrical conductivity were studied with the presents of magnetic field confinement at different gas pressures. The magnetic field up to 25 mT was obtained using four coils of radius 6 cm and 320 turn by passing A.C current up to 5 Amperes. Spectroscopic measurements are employed for purpose of estimating two main plasma parameters electron temperature (Te) and electron density (ne). Emission spectra from positive column (PC) zone of the discharge have been studies at different values of magnetic field and pressures at constant discharge currents of 1.5 mA. Electron temperature (Te) and its density are calculated from the ratio of the intensity of two emission lines of the same lower energy levels. Experimental results show the abnormal glow region characteristics (positive resistance). Breakdown voltage versus pressure curves near the curves of paschen and decrease as magnetic field increases due to magnetic field confinement of plasma charged particles. Also the electrical conductivity increases due to enhancing magnetic field at different gas pressures. Both temperature density of electron and the intensities of two selected emission lines decrease with increasing pressure due decreasing of mean free path of electron. Electron density increase according to enhancing magnetic field, while the intensity of emitting lines tends to decrease.

2019-04

International Conference on Advanced Science and Engineering (ICOASE), IEEE (Issue : 18723538)

In this paper, the optical properties of a pinhole nanorod are studied using finite element package (COMSOL Multiphysics). Both electric and magnetic field distribution for different radius of a hollow nanorod and variable pinhole position has been measured. Furthermore, the scattering cross-section for both fields is calculated. The magnetic field enhancement has been increased by adding a pinhole made of air. The magnetic field enhancement improved 20 percent. In case of scattering crosssection, the response is changed as a function of the pinhole position and diameter. The results provide the ability to tune optical properties through an appropriate geometric feature of the nanorods.

2012-06

ACS Nano (Issue : 7) (Volume : 6)

We demonstrate adiabatic nanofocusing of few-cycle light pulses using ultrasharp and ultrasmooth single-crystalline gold tapers. We show that the grating-induced launching of spectrally broad-band surface plasmon polariton wavepackets onto the shaft of such a taper generates isolated, point-like light spots with 10 fs duration and 10 nm diameter spatial extent at its very apex. This nanofocusing is so efficient that nanolocalized electric fields inducing strong optical nonlinearities at the tip end are reached with conventional high repetition rate laser oscillators. We use here the resulting second harmonic to fully characterize the time structure of the localized electric field in frequency-resolved interferometric autocorrelation measurements. Our results strongly suggest that these nanometer-sized ultrafast light spots will enable new experiments probing the dynamics of optical excitations of individual metallic, semiconducting, and magnetic nanostructures.

2011-06

Optics Express (Issue : 15) (Volume : 19)

We demonstrate an essentially dispersion-free and diffraction-limited focusing of few-cycle laser pulses through all-reflective microscope objectives. By transmitting 6-fs-pulses from a Ti:sapphire oscillator through an all-reflective 0.5 NA objective, we reach a focus with a beam diameter of 1.0 µm, preserving the time structure of the pulses. The temporal and spatial pulse profile is recorded simultaneously using a novel tip-enhanced electron emission autocorrelator, indicating a focal volume of these pulses of only 1.8 µm3. We anticipate that the demonstrated technique is of considerable interest for inducing and probing optical nonlinearities of individual nanostructures.

2011-05

Optics Express (Issue : 13) (Volume : 19)

We compare single- and double-sided excitation methods of adiabatic surface plasmon polariton (SPP) wave superfocusing for scattering-type metallic near-field scanning optical microscopy (s-NSOM). Using the results of full 3D finite difference time domain analyses, the differences in field enhancement factors are explained and reveal the mode selectivity of a conical NSOM tip for adiabatic SPP superfocusing. Exploiting the mode-symmetric nature of the tip further, we also show that it is possible to selectively confine either the electric or magnetic field at the NSOM tip apex, by simply adjusting the relative phase between the SPP waves in the double-sided excitation approach.

2011-03

Nano Letters (Issue : 4) (Volume : 11)

We explore imaging of local electromagnetic fields in the vicinity of metallic nanoparticles using a grating-coupled scattering-type near-field scanning optical microscope. In this microscope, propagating surface plasmon polariton wavepackets are launched onto smooth gold tapers where they are adiabatically focused toward the nanometer-sized taper apex. We report two-dimensional raster-scanned optical images showing pronounced near-field contrast and demonstrating sub-30 nm resolution imaging of localized surface plasmon polariton fields of spherical and elliptical nanoparticles. By comparison to three-dimensional finite-difference time domain simulations, we conclude that virtually background-free near-field imaging is achieved. The microscope combines deep subwavelength resolution, high local field intensities and a straightforward imaging contrast, making it interesting for a variety of applications in linear and nonlinear nanospectroscopy.