Pulsed Laser Ablation Technique Research Articles

Silver and copper oxide nanoparticles-decorated graphene oxide via pulsed laser ablation technique: Preparation, characterization, and photoactivated antibacterial activity

Graphene oxide, silver and copper oxide nanoparticles display photoactivated antibacterial behavior owing to their ability to generate charge carriers via light exposure. In this work, silver nanoparticles (AgNPs) and copper oxide nanoparticles (CuONPs) were embedded through graphene oxide (GO) using laser ablation technique. The microstructural behavior of the synthesized compositions has been investigated via XRD and TEM. The optical properties were studied by (UV–Vis), while the antibacterial properties were investigated in addition to the cell viability towards normal cell line (HFB4) in vitro. The antibacterial activity of GO was enhanced significantly with addition nanoparticles; by meaning, the inhibition zone enlarged from 5.4 mm with pure GO to be around 11.2 mm against E. coli with contribution of CuONPs. This trend of enhancement suggests that GO could be a great platform for different kinds of photo-activated antibacterial to be recommended for versatile biomedical applications.

Dark-current reduction accompanied photocurrent enhancement in p-type MnO quantum-dot decorated n-type 2D-MoS2-based photodetector

A highly crystalline single- or few-layered 2D-MoS2 induces a high dark current, due to which an extremely small photocurrent generated by a few photons can be veiled or distorted. In this report, we show that suppression in the dark current with the enhancement in the photocurrent of a 2D-based photodetector, which is a prerequisite for photoresponse enhancement, can be achieved by constructing an ideal p-n junction based on functionalizing n-type 2D-MoS2 with p-type quantum dots (QDs). Highly crystalline solution-processed manganese oxide QDs (MnO QDs) are synthesized via the pulsed femtosecond laser ablation technique in ethanol. The ablated MnO QDs are spray-coated on an exfoliated 2D-MoS2 substrate with interdigitated Au electrodes through N2-assisted spraying. In the resulting MnO QD-decorated 2D-MoS2 photodetector with a heterojunction, dark current is reduced and is accompanied by photocurrent enhancement, thereby markedly improving the photoresponsivity and detectivity of MoS2-based devices. To elucidate the underlying mechanisms contributing to this enhancement, power- and wavelength-dependent photoresponses, along with material characterizations based on spectroscopic, chemical, morphological measurements, and analyses, are discussed.

Zero field cooled exchange bias effect in nano-crystalline Mg-ferrite thin film

The Zero Field Cooled (ZFC) Exchange Bias (EB) effect in a single phase nanocrystalline Mg-ferrite thin film, deposited on an amorphous quartz substrate using pulsed laser ablation technique, is reported. The film showed a high ZFC EB shift (HE ∼ 190 Oe) at 5 K. The ZFC EB shift decreased with increasing temperature and disappeared at higher temperatures (T > 70 K). This Mg-ferrite thin film also showed the Conventional Exchange Bias (CEB) effect, but unlike many CEB systems, the film showed a decrease in coercivity (HC) under the Field Cooled measurements. The film also showed the training effect in ZFC measurements, which followed the frozen spin relaxation behavior. The observed exchange bias could be attributed to the pinning effect of the surface spins of frozen glassy states at the interface of large ferrimagnetic grains.

Synthesis and Characterization of Aluminum Nanoparticles Prepared in Vinegar Using a Pulsed Laser Ablation Technique

The second harmonic wavelength of a neodymium-doped yttrium-aluminum-garnet (Nd-YAG) laser (λ=532 nm) was used in a pulsed laser ablation technique (PLAL) to synthesize aluminum nanoparticles suspended in white vinegar from an aluminum target. The nanoparticles were characterized by HRTEM and UV-Vis spectrophotometry. They were found to range in size between 2 and 50 nm in diameter, with an average diameter of 12±9 nm. The nanoparticles had a maximum absorption peak at 237 nm and were found to exhibit a core-shell structure with an Al core coated by a thin layer of an amorphous material which could be attributed to amorphous carbon. HRTEM results revealed that the small nanoparticles (<20 nm) had an fcc phase of aluminum crystalline structure, where the larger particles represented alumina (γ-Al2O3) nanoparticles. Such observation suggests that the use of white vinegar as an ablation medium could facilitate the synthesis of aluminum nanoparticles with minimal evidence of the existence of aluminum oxide nanoparticles in the resultant suspension.

Laser ablation synthesis of gold nanoparticles in tetrahydrofuran

We demonstrate the synthesis of gold nanoparticles in tetrahydrofuran using the pulsed laser ablation technique. Both ablation time and solution stirring effect were investigated. At an ablation time of 30 minutes, the average size of synthesized gold nanoparticles significantly reduced from 11 nm to 6 nm. Additionally, the percentage of gold nanoparticles greater than 15 nm reduced as well, from 20.00% to 0.47%. These observations were caused by forced convection flow and shock waves from the rapid laser pulse that fragmented the ablated gold nanoparticles further into smaller sizes.

Coercivity and Interactions in Sr–M Thin Films with Nonperpendicular Orientation

Magnetic viscosity and interactions have been studied recently in bulk M‐type hexaferrites. Herein, this kind of study is extended to Sr–M (SrFe12O19) thin films deposited on SiO2/Si substrates using the pulsed laser ablation technique at relatively low substrate temperatures at 2.7 mbar oxygen atmosphere. Samples are characterized by X‐ray diffraction, scanning electron microscopy, and vibrating‐sample magnetometry. The high values of the coercive field (4.8 kOe) obtained for the films are in correspondence with large values reported in thin films, powders, and sintered samples for the Sr–M compound. Demagnetization‐like interactions are found and magnetic viscosity results point to the coercivity mechanism different from coherent rotation despite the small particle size.

Synthesis of Porous ZnO Nanosheets and Carbon Nanotube Hybrids as Efficient Photocatalysts via Pulsed Laser Ablation

Zinc oxide (ZnO) has attractive photocatalytic properties. However, the high recombination rate of the photo-excited charge carriers on this material often restricts application. Here, we report that hybridization of one dimensional (1D) carbon nanotubes (CNT) on two dimensional (2D) porous ZnO nanosheets (NS) can be a promising strategy to overcome some of the challenges of ZnO. Specifically, a pulsed laser ablation technique was utilized to hybridize 1D CNT with 2D porous ZnO NS in environmentally friendly as well as super-economic (short time, less than 10 min) conditions. The synthesized ZnO NS-CNT hybrids show a significantly enhanced photocatalytic activity for water splitting relative to their counterpart ZnO NS.

(Invited) Electron Emission Study of Planar-Type Electron Emission Devices Based on Nanocrystalline Silicon

A planar-type electron emission device having a thin film diode structure such as a metal-oxide-semiconductor (MOS) [1] is a promising candidate as a fine electron source for applications of vacuum nanoelectronic devices, including environment-hard electronic devices, flat panel displays and high-sensitive image sensors. This is because the cathode operates at low extraction voltage and produces uniform and highly directional emission, compared with conventional field emitters with needle structure. Furthermore, the cathode is insensitive to the environment. However, the device is limited in emission current by its low efficiency (i.e., the ratio of the emission current to the total tunneling current) of typically less than 0.1 % due to strong scattering of hot electrons while traveling through the conduction band of both the oxide and the gate metal, after tunneling through the potential barrier in the oxide [2]. The reduction of the work function of the gate electrode by adsorption of alkali metals onto the surface [3] and the use of films containing nano- and micro-crystalline structure taking the place of the oxide layer have been proposed to improve the performance on the MOS cathode [4]. Another strategy is to reduce electron scattering within the topmost metal electrode by decreasing the electrode thickness [5-7]. In order to improve the emission efficiency and understand the emission mechanism we have fabricated the planar-type electron emission devices based on oxidized nanocrystalline Si (nc-Si) prepared by a pulsed laser ablation (PLA) technique and investigated their emission properties. The emission area of the device was designed 500 mm in diameter. The emission current and the efficiency are higher for thinner in the gate electrode, indicating tunneling is sensitive to the thickness of the gate. The electron emission efficiency is predicted to reach ~ 10 % if electron scattering on the inside of the topmost metal electrode is perfectly suppressed. In our presentation, we will discuss the detailed electron emission properties of the nc-Si based planar-type electron emission device.

A study of electrical characteristics of Gd2O3/GaN and Gd2O3/AlGaN/GaN MOS Heterostructures

In this paper, we present the electrical properties of hexagonal Gd2O3 grown epitaxially on GaN/Si(111) and AlGaN/GaN/Si(111) virtual substrates. GaN and AlGaN/GaN heterostructures were grown on Si(111) substrates by plasma assisted molecular beam epitaxy (PA-MBE). A 12 nm thick Gd2O3 film was deposited by the pulsed laser ablation (PLA) technique. Platinum is deposited on Gd2O3 in order to make the Schottky contacts, and the resulting Pt/Gd2O3/GaN and Pt/Gd2O3/AlGaN/GaN metal-oxide semiconductor (MOS) contacts are noted to exhibit rectifying behavior. The electrical characterizations are carried out in a certain frequency range by the conventional capacitance-voltage (C-V) and conductance-voltage (Gp/ω-V) measurement techniques. Pt/Gd2O3/AlGaN/GaN shows lower hysteresis than Pt/Gd2O3/GaN as observed from the C-V measurements. The interface trap density and respective time constant are calculated from the conductance-voltage measurements at corresponding applied bias. Finally, it is concluded that Gd2O3 on III-nitrides is a potential candidate for high power applications in radio frequency range.

Influence of background oxygen pressure and post - deposition annealing on the structural, morphological, optical and luminescence properties of laser ablated SrWO4 thin films

Poly-crystalline strontium tungstate films with tetragonal scheelite phase were prepared on quartz substrate using pulsed laser ablation technique at different background oxygen pressures. These films were then post-annealed at a temperature of 800 °C for 2 h in air. The films prepared under oxygen ambience show a textured nature with preferred direction of crystal growth along <004>.The low value of FWHM of the XRD peaks exhibited by the annealed films compared to that of the as-deposited films suggests an enhancement in crystalline quality of the films with annealing. AFM and FESEM micrographs show that the morphology of the as-deposited films exhibit a tendency to form bigger clusters whereas the annealed films depict a dense distribution of grains. The films prepared under oxygen ambience show higher values of transmittance compared to those prepared in oxygen free ambience. All the films show luminescence emission ~388 nm and 468 nm region originating from lattice defects and surface defects respectively. The chromaticity diagrams show that the CIE coordinate of the films are very close to blue light region, suggesting the suitability of these films for the fabrication of blue light emitting device applications.

Thermally Activated Noble Metal Nanoparticles Incorporated in Electrospun Fiber-based Drug Delivery Systems

Background: Nanosystems based on PEG-PLGA copolymer have attracted increasing interest in several biomedicine fields, due to their unique properties. Commonly, PEG-PLGA copolymer was used to formulate nanoparticles (NPs) for drug delivery applications. Only recently, the engineering of polymeric nanofibrous membrane able to be use like drug nanocarrier was investigated. Objective: The goal of this work is the development of two new drug delivery systems based on PEGylated-PLGA nanofibrous scaffolds, obtained by electrospinning deposition, simultaneous loaded with: i) silibinin, a therapeutic agent, ii) Au/Ag and iii) non-toxic Fe2O3 magnetic nanoparticles. Another interest aspect of the present work regards how the morphological structure can influence the drug release which has been fine-tuned by two external stimuli: a light source and a magnetic field. Methods: Noble metal nanocolloids were prepared in water by the pulsed laser ablation technique. The PEG-PLGA@Au/Ag-SLB added with Fe2O3-PVA nanofibers were fabricated by the electrospinning deposition method. Results: The use of “Surface Plasmon Resonance”-mediated localized photothermal effect, determined by the nanoparticles resonant absorption of visible radiation, allows to these systems to be able to employ for photothermal drug delivery therapies in proximity of tumor cells. All data obtained about the fiber scaffolds are compared to NPs based on the same PEG-PLGA copolymer, loaded with silibinin, Fe2O3 and Au/Ag nanoparticles alternatively. Nanofibers respects to NPs, showed interesting sustained responsive silibinin release for at least 60 h, without the burst effect. A diffusion-based theoretical model approach allowed to precisely describe the release mechanism. Conclusion: The effective and controlled silibilin drug release, upon application of either light irradiation or magnetic field for a definite time interval, has been demonstrated. Under the light stimulus, the fiber-shaped nanosystem reached a cumulative drug release value as high as 70% in the long time. On the overall, the information obtained could be useful to design suitable “on demand” nanocomposites in view of a therapeutic treatments protocol that requires a fast pharmacological action.

Investigation of laser wavelength effect on optical properties of graphene oxide colloidal nanostructures prepared by pulsed laser ablation

In this work we prepared graphene oxide nanostructures (GONE) in a liquid environment using pulsed laser ablation technique. We used for the synthesis Nd: YAG pulsed laser operatating at 1064 nm and 532 nm of wavelength, we study the effect of wavelength of the laser on the optical properties of Nanostructures (NE) synthesized. The aim was determining the optical bandgap and the characteristic peak related by bond transitions using the absorbance UV-Vis spectra. Both samples show high absorption in the ultraviolet region in the UV-Vis spectra. Using Tauc’s plot method we compute the bandgap energy for GONEs assuming indirect bandgap. In addition, we observe characteristic peak formation 1 hour after synthesized NPs at 256 nm for NPs prepared at 1064 nm and for NPs prepared at 532 nm the peak with less intensity is observed at a wavelength of 218 nm. The characteristic peak for both samples increase of intensity 24 hours after preparation.

Improvement Optical Properties of PVA/ TiO2 and PVA/ ZnO Nanocomposites

The optical properties of polyvinyl alcohol (PVA) doped TiO2 and ZnO nanoparticles respectively, were studied. PVA/TiO2 and PVA/ZnO nanoparticles were prepared by the pulsed laser ablation technique (PLA).The optical properties of PVA/ TiO2 and PVA/ ZnO nanocomposite solution have been investigated by transmittance data and absorption spectra. The optical band gap (Eg) was determined and the optical absorption spectra showed that a direct transition. The energy gap of PVA/ ZnO nanoparticles have been observed the decreases its value and increasing in the optical conductivity as compared to PVA/ TiO2.The refractive index (n), extinction coefficient (k) and dielectric constant have been also investigated; it was found that all the above parameters affects by doping.

Synthesis of colloidal zinc nanoparticles by pulse laser ablation technique using fundamental Nd:YAG laser 1064 nm

The synthesis of high-purity Zinc nanoparticle (ZnNPs) using the pulse laser ablation method has been successfully performed. In this study, Low-power neodymium-doped yttrium aluminum garnet (Nd:YAG) laser was used as an energy source. Pulse laser beam (1064 nm, 7ns, 10 Hz) was focused on a high-purity (99.95%) zinc plate surface, which was immersed in 10 ml of aquadest. Light brownish color of colloidal ZnNPs was successfully produced. The SEM image of ZnNPS shows that the produced nanoparticle had a spherical shape. The average diameter of ZnNPs was 35 nm with a standard deviation of 8.7 nm, and the surface plasmon resonance is located approximately at 300 nm.

Colloidal Metal Oxide Nanoparticles Prepared by Laser Ablation Technique and Their Antibacterial Test

In this article we report the production of metal oxide (TiFe2O4, ZnFe2O4) nanoparticles by pulsed laser ablation technique in a liquid environment. We used nanosecond Nd: YAG laser systems working at 532 nm and 1064 nm of wavelength and the energy of the laser beam was kept constant at 80 mJ. Absorbance spectra, surface plasmon resonance, optical band-gap, and nanoparticle morphology were investigated using ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Changing the wavelength of the laser for growth, nanoparticles showed shift between the absorbance and surface plasmon resonance peaks in their UV-Vis spectra, which implies that the optical properties of the colloid nanoparticles depend on laser parameters. This was confirmed with the variation of the band gap energy. Furthermore, redshift for the absorbance peak was observed for samples as-grown at 532 nm around 150 nm as a function of time preparation. Conversely, for the samples as-grown at 1064 nm there was no shift in the absorbance spectra, which could be due to agglomeration and formation of larger particles. The characterization results showed appropriate plasmonic photo-catalysts properties of the particles, hence the photoactivation of the nanoparticles was examined on antibacterial effect using colonies of Staphylococcus aureus and Escherichia coli.

Designing zinc oxide nanostructures (nanoworms, nanoflowers, nanowalls, and nanorods) by pulsed laser ablation technique for gas‐sensing application

AbstractIn this study, pulsed laser ablation technique, also known as pulsed laser deposition (PLD), is used to design and grow zinc oxide (ZnO) nanostructures (nanoworms, nanowalls, and nanorods) by template/seeding approach for gas‐sensing applications. Conventionally, ZnO nanostructures used for gas‐sensing have been usually prepared via chemical route, where the 3D/2D nanostructures are chemically synthesized and subsequently plated on an appropriate substrate. However, using pulsed laser ablation technique, the ZnO nanostructures are structurally designed and grown directly on a substrate using a two‐step temperature‐pressure seeding approach. This approach has been optimized to design various ZnO nanostructures by understanding the effect of substrate temperature in the 300‐750°C range under O2 gas pressure from 10‐mTorr to 10 Torr. Using a thin ZnO seed layer as template that is deposited first at substrate temperature of ~300°C at background oxygen pressure of 10 mTorr on Si(100), ZnO nanostructures, such as nanoworms, nanowalls, and nanorods (with secondary flower‐like growth) were grown at substrate temperatures and oxygen background pressures of (550°C and 2 Torr), (550°C and 0.5 Torr), and (650°C and 2 Torr), respectively. The morphology and the optical properties of ZnO nanostructures were examined by Scanning Electron Microscope (SEM‐EDX), X‐ray Diffraction (XRD), and photoluminescence (PL). The PLD‐grown ZnO nanostructures are single‐crystals and are highly oriented in the c‐axis. The vapor‐solid (VS) model is proposed to be responsible for the growth of ZnO nanostructures by PLD process. Furthermore, the ZnO nanowall structure is a very promising nanostructure due to its very high surface‐to‐volume ratio. Although ZnO nanowalls have been grown by other methods for sensor application, to this date, only a very few ZnO nanowalls have been grown by PLD for this purpose. In this regard, ZnO nanowall structures are deposited by PLD on an Al2O3 test sensor and assessed for their responses to CO and ethanol gases at 50 ppm, where good responses were observed at 350 and 400°C, respectively. The PLD‐grown ZnO nanostructures are very excellent materials for potential applications such as in dye‐sensitized solar cells, perovskite solar cells and biological and gas sensors.

Pressure effect on optical and structural properties of ZnMnO thin films grown by pulsed laser deposition

Fil: Riascos, H.. Universidad Tecnologica de Pereira. Facultad de Ciencias Basicas. Laboratorio de Fisica de Plasmas; Colombia

Grown of highly porous ZnO-nanoparticles by pulsed laser ablation in liquid technique for sensing applications

Pulsed laser ablation technique in deionized water with low laser fluency has been explored to prepare uniform dispersed porous ZnO nanoparticles for sensing applications. Surface morphology, particle size, porous structure, roughness, elemental distribution, and chemical bonding of the synthesized ZnO are analyzed by TEM, FESEM, AFM, EDX, and FTIR spectroscopy, respectively. Sensing behavior is observed by UV–Vis absorption measurements. TEM and FESEM analysis show that the prepared ZnO-coated film has homogeneous, dispersed, highly porous, and crack-free surface; the average particle size are observed ~ 24.72 ± 2.97 nm. The porous structure is responsible for appropriate sensing behavior. Low roughness value ~ 1.52 nm which is analyzed by AFM is advantageous for sensing behavior. EDX spectrum and elements mapping clearly show the uniform Zn and O distribution. XRD analysis confirms the hexagonal wurtzite structure of ZnO. FTIR reveals the Zn and O chemical bonding successfully. UV-Visible analysis exhibits that the prepared ZnO matrix has good incorporation with multi-dyes solutions at pH values 10–12 with significant changes in color behavior. The highest pKa value ~ 9.77 at a wavelength of 598.28 nm was calculated for multi-dyes immobilized ZnO matrix. So, it can be concluded that prepared ZnO nanostructures are potential candidates for sensing application.

Large Room Temperature Magnetic Moment in Mn${_{1-x}}$ Zn${x}$ Fe2O4 Thin Films for ${x \geq0.4 }$

Mn ${_{1-x}}$ Zn x Fe2O4 ( $0.1\le x\le 0.8$ ) thin films with nanocrystalline grains were deposited on amorphous quartz substrate using pulsed laser ablation technique, at a substrate temperature of 650 °C. For $x\le 0.3$ , the room temperature spontaneous magnetization ( $4\pi M_{S}$ ) of thin films was observed to be lower than the bulk composition. For $x=0.7$ , the room temperature $4\pi M_{S}$ value (~6.1 kG) is 7.5 times the bulk value for same x. This value is only 1.4 times of the bulk at 10 K, signifying a large enhancement in the exchange constant for thin films. The exchange stiffness constant (D) values were evaluated by fitting the $4\pi M_{S}$ data to the Bloch equation. The D values of thin films were always higher than that of the bulk. This result can be explained on the basis of occupancy of nonmagnetic Zn2+ on both the tetrahedral (A) and octahedral (B) sites. This is unlike in the bulk, where all the Zn2+ ions occupy only A site.

Heterojunction of TiO2 nanoparticle embedded into ZSM5 to 2D and 3D layered-structures of MoS2 nanosheets fabricated by pulsed laser ablation and microwave technique in deionized water: structurally enhanced photocatalytic performance

In this paper, we report a one-step, fast and ecofriendly synthesis of layered-structured MoS2 nanosheets (NSs) by pulsed laser ablation in liquids (PLAL). The resultant MoS2 NS was used to construct TiO2–ZSM5–MoS2 nanocomposite. After impregnating ZSM5 structures with TiO2 nanoparticles (TiO2 NPs), heterojunctions of MoS2 NS were made on the fabricated TiO2–ZSM5 by microwave treatment at high temperature and pressure. Formation of 2D and 3D structures of MoS2 was shown. Crystal structure, size and shape of the synthesized nanostructures were studied by X-ray powder diffraction (XRD) and microscopy techniques. Results of the structural analysis showed that the PLAL constructed MoS2 NSs mainly had a layered morphology several micrometers in size with horizontally and vertically aligned layers. The hexagonal crystalline structure of MoS2 NS, anatase TiO2 NPs and microcrystalline ZSM5 structures were determined by XRD, high-resolution transmission electron microscopy (HRTEM) and fast Fourier transform (FFT) analysis. Formation of MoS2 NS was further shown with Raman peaks at approximately 385.30 and 407.50 cm−1 corresponding to the E1 2 g and A1g vibrational modes of MoS2 NS. The PLAL synthesized MoS2 NS demonstrated broad absorption in the visible region. Photocatalytic activity of TiO2–ZSM5–MoS2 nanocomposite was tested with arsenite. TiO2–ZSM5–MoS2 nanocomposite exhibited approximately 100% arsenite photo-conversion to arsenate.