Surface Structural Information Research Articles

Multi-Scale Indoor Scene Geometry Modeling Algorithm Based on Segmentation Results

Due to the numerous objects with regular structures in indoor environments, identifying and modeling the regular objects in scenes aids indoor robots in sensing unknown environments. Typically, point cloud preprocessing can obtain highly complete object segmentation results in scenes which can be utilized as the objects for geometric analysis and modeling, thus ensuring modeling accuracy and speed. However, due to the lack of a complete object model, it is not possible to recognize and model segmented objects through matching methods. To achieve a greater understanding of scene point clouds, this paper proposes a direct geometric modeling algorithm based on segmentation results, which focuses on extracting regular geometries in the scene, rather than objects with geometric details or combinations of multiple primitives. This paper suggests using simpler geometric models to describe the corresponding point cloud data. By fully utilizing the surface structure information of segmented objects, the paper analyzes the types of faces and their relationships to classify regular geometric objects into two categories: planar and curved. Different types of geometric objects are fitted using random sampling consistency algorithms with type classification results as prior knowledge, and segmented results are modeled through a combination of size information associated with directed bounding boxes. For indoor scenes with occlusion and stacking, utilizing a higher-level semantic expression can effectively simplify the scene, complete scene abstraction and structural modeling, and aid indoor robots’ understanding and further operation in unknown environments.

Effect of Bleaching Processes on Physicochemical and Functional Properties of Cellulose and Carboxymethyl Cellulose from Young and Mature Coconut Coir.

The objective of this study was to characterize the properties of cellulose and CMC synthesized from young and mature coconut coir with different bleaching times (bleaching for the first time; 1 BT, bleaching for a second time; 2 BT, and bleaching for the third time; 3 BT) using hydrogen peroxide (H2O2). The surface morphology, structural information, chemical compositions, and crystallinity of both cellulose and CMC were determined. H2O2 bleaching can support delignification by reducing hemicellulose and lignin, as evidenced by FTIR showing a sharp peak at wave number 1260 cm-1. The cellulose and CMC from coconut coir can be more dispersed and have greater functional characteristics with increasing bleaching times due to the change in accessibility of hydroxyl groups in the structure. The CMC diffraction patterns of coconut coir after the bleaching process showed the destruction of the crystalline region of the original cellulose. The SEM images showed that the surface of CMC was smoother than that of cellulose. The CMCy had a higher water holding capacity (WHC) compared to the CMCm as the bleaching can increase interaction between the polymer and water molecules. Therefore, the best quality of CMC corresponds to CMCy. Based on these findings, bleaching time has a strong effect on the functional properties of cellulose and CMC from coconut coir.

One Pot Synthesis of CuO-CuFe2O4@rGO Nanostructure with Synergistic Effect for Efficient Electrochemical Sensing Application of Paracetamol

In the present study, the facile and synergistic approach for electrochemical sensing of paracetamol (PA) drug was demonstrated by hydrothermally synthesized copper oxide-copper ferrite nanohybrid composite supported on reduced graphene oxide (CuO-CuFe2O4@rGO) glassy carbon electrode. The surface texture and structural information of the electrode material were examined by FE-SEM, HR-TEM, and X-ray diffraction techniques, whereas the electrochemical sensing application of paracetamol oxidation was investigated by amperometric method. The average crystallite size of CuO-CuFe2O4 was calculated from XRD data and found to be 35.45 nm. The fabricated sensor exhibited a higher sensitivity of 970.26 μA.mM−1.cm−2 along with a lower limit of detection (LOD) and limit of quantification (LOQ) of 7.0 μM and 25 μM, respectively, with a linear dynamic range of 10–1200 μM. Furthermore, the CuO-CuFe2O4@rGO modified sensor showed excellent anti-interferents ability, long-term stability and reproducibility towards electro-oxidation of paracetamol drug. Moreover, it can be efficiently applied for the analysis of paracetamol in biological samples. Finally, the synthesized nanocomposite material was validated to be a competent electrocatalyst for electrochemical sensing application of paracetamol.

Effective adsorption of polycyclic aromatic Congo red dye by modified garlic peel

To evaluate the competence of garlic peel (GP) as a low-cost bio-adsorbent, GP was chemically modified with sodium carbonate (Na2CO3) and hydrochloric acid, and used to adsorb Congo red (CR). The surface morphology, chemical characterization and structural information of the adsorbents were studied by scanning electron microscopy, energy dispersive X-ray analysis, and Fourier transform infrared spectroscopy. The impact of different adsorption settings on the removal effectiveness of CR by sodium carbonate-treated garlic peel (Na2CO3-GP) was also studied. The optimum conditions for effective adsorption of CR by Na2CO3-GP is found to be pH of 7, 90 minutes of equilibrium contact duration, 50 mg/L of initial CR concentration, 200 revolutions per minute of stirring (RPM), 0.10 g/mL of adsorbent dosage, and temperature of 298 K. As indicated by Langmuir isotherm, monolayer adsorption occurs at a maximum capacity of 52.6 mg/g for Na2CO3-GP. Adsorption kinetic studies suggest chemisorption, the process follows a pseudo-second-order model and thermodynamics of adsorption specifies that the process is spontaneous. The results explicitly show that Na2CO3-GP can be an effective bio-adsorbent for the removal of CR.

Fabrication of graphene, graphite and multi wall carbon nano tube based thin films and their potential application as strain sensor

Carbon based nanomaterials are extensively used in the manufacturing of flexible electronic devices due to their numerous favorable properties. Such devices have shown remarkable sensitivity with excellent stability when implemented in various flexible environments. But the formulation of conductive inks using carbon based nanomaterials presented some challenges in the optimization of various ink parameters like rheology, surface tension, particle size etc. In this paper, we present graphite, graphene and multi-wall carbon nano tube (MWCNT) based flexible resistive strain sensors on polymer substrate using a simple and solvent free fabrication process. A controllable conductive thin film is obtained and designed into two different patterns viz. ‘Straight Line’ (line) and ‘Serpentine’ (serp) to enhance the sensing performance of the film. The electrical performance has been evaluated in terms of current-voltage characteristics. The result indicates the resistive behavior of all the devices under investigation. The bending measurements have been conducted; the resistive strain sensor exhibits significant resistance variation during bending applications. There has been a significant change in the electrical resistance of each sample for different strain level i.e. ∼ 20% for MWCNT(line) and MWCNT (serp), ∼30% for Graphite(line) and Graphene (line) and ∼50% to 60% for Graphite (serp) and Graphene (serp). High sensitivity of the ‘Serpentine’ patterns in comparison to ‘Straight Line’ patterns indicates the importance of various patterns in the manufacturing of flexible sensors. Surface morphology and structural information of the fabricated devices have also been analyzed and investigated.

Enhanced electrochemical removal of dye wastewater by PbO2 anodes using halloysite nanotubes with different surface charge properties

• A novel HNTs-CTS-PbO 2 composite anode was prepared. • New anode can effectively improve MB removal efficiency. • Degradation of methylene blue follows the pseudo-first-order reaction kinetics. • Elucidation of the degradation mechanism of methylene blue by modified electrodes. Electrode materials are the core of electrocatalytic oxidation technology. Herein, chitosan (CTS)-modified halloysite nanotubes (HNTs) were used for the first time in the doping modification of PbO 2 electrodes by electrodeposition technique, and novel HNTs-CTS-PbO 2 anodes were prepared and used for the electrochemical removal of the thiazine dye methylene blue (MB). The surface structure information, electrochemical properties and oxidation activity of the materials were systematically investigated, and possible degradation pathways of methylene blue were proposed. The results showed that after doping modification, the coating became flatter and denser, and the crystalline shape and crystalline phase of the PbO 2 electrode did not change, but the grain size was significantly reduced; moreover, the modified electrode had higher oxygen precipitation overpotential, larger reactive surface area and lower charge transfer resistance. Additionally, the decolorization degradation of MB by HNTs-CTS-PbO 2 electrode mainly adopts an indirect degradation mechanism and follows the pseudo-first-order kinetic model, which exhibits higher decolorization degradation rate. Analyzing the mechanism of the electrochemical removal of MB from the modified anode, which mainly involves the breakage of C N bonds under the action of ·OH, followed by demethylation and aromatic ring cleavage to obtain monoaromatic amines, sulfonic acids and phenolic compounds, and finally mineralized into inorganic small molecules such as CO 2 and H 2 O. The above results show that HNTs-CTS-PbO 2 anode is a promising candidate in the field of dye wastewater degradation and provide new insights for the application of HNTs.

(Invited, Digital Presentation) Design, Preparation and Characterization of Photofunctional Materials Based on Energy-Resolved Distribution of Electron Traps

How can we design functional solid materials, such as catalysts and photocatalysts? What is the decisive structural parameters controlling their activities, performance or properties? What is obtained as structural properties by popular conventional analytical methods, such as X-ray diffraction (XRD) or nitrogen-adsorption measurement, is limited to bulk crystalline structure and specific surface area, i.e., no structural characterization on amorphous phases, if present, and surface structure has been made so far. This is because there have been no macroscopic analytical methods to give surface structural information including possibly-present amorphous phases. Recently, we have developed reversed double-beam photoacoustic spectroscopy (RDB-PAS) which enables measure energy-resolved distribution of electron traps (ERDT) for semiconducting materials such as metal oxides [1,2]. Those detected electron traps (ETs) seem to be predominantly located on the surface for almost all the metal oxide particles, and therefore they reflect macroscopic surface structure, including amorphous phases, in ERDT patterns. Using an ERDT pattern with the data of CB bottom position (CBB), i.e., an ERDT/CBB pattern, it has been shown that metal oxide powders, and the other semiconducting materials such as carbon nitride, can be identified without using the other analytical data such as XRD patterns or specific surface area, and similarity/differentness of a pair of metal-oxide samples can be quantitatively evaluated as degree of coincidence of ERDT/CBB patterns. In this talk, an approach of material design based on the ERDT/CBB-pattern analyses is introduced [3].[1] Nitta, A.; Takase, M.; Takashima, M.; Murakami, N.; Ohtani, B. A Fingerprint of Metal-oxide Powders: Energy-resolved Distribution of Electron Traps. Chem. Commun. 2016, 52, 12096-12099. [2] Nitta, A.; Takashima, M.; Murakami, N.; Takase, M.; Ohtani, B. Reversed double-beam photoacoustic spectroscopy of metal-oxide powders for estimation of their energy-resolved distribution of electron traps and electronic-band structure. Electrochim. Acta 2018, 264, 83-90. [3] Nitta, A.; Takashima, M.; Takase, M.; Ohtani, B. Identification and characterization of titania photocatalyst powders using their energy-resolved distribution of electron traps as a fingerprint. Catal. Today 2019, 321-322, 2-8.

Diffraction Separation With Plane-Wave Destruction Filer for the Lunar Penetrating Radar Sensor Data

China transported the lunar rovers to the lunar surface via the Chang’E rockets for lunar exploration. An important detection tool in the lunar rover is the lunar penetrating radar (LPR). LPR can obtain the lunar surface structure information by transmitting and receiving high-frequency electromagnetic waves. There are many types of waves received by LPR sensors, among which diffracted waves are often ignored. The diffractions in the LPR data contain a lot of underground structure information, especially for faults and small targets with high resolution. A major technical problem in effectively using the information is how to separate diffractions from different types of wave field information. This paper focuses on the diffraction issue and employs the plane wave decomposition filter method to separate the diffractions in LPR data sets. First, the records are converted into a dip field, and then the non-diffraction waves in the dip field is filtered to achieve the purpose of separating the diffractions. Three numerical models will be used to verify the effectiveness of the diffraction separation method.

Radially grown carbon nanomaterials on hollow glass microspheres and their application in composite foams with excellent electromagnetic interference shielding

AbstractIn the current study, we investigated the effect of processing temperature in chemical vapor deposition (CVD) on the formation of carbon nanomaterials over the hollow glass microsphere. The surface morphology and structural information of the carbon nanomaterials (CNM)‐coated hollow glass microsphere (HGM) were analyzed through scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Then, the 5‐CH [CNF‐coated HGM (Synthesizing temperature in CVD being 500 °C)], 6‐CH [MWCNT‐coated HGM (Synthesizing temperature in CVD being 600 °C)], and 7‐CH [MWCNT‐coated HGM (Synthesizing temperature in CVD being 700 °C)] were individually used as fillers in the epoxy composite foam. Thorough characterization of mechanical and thermo‐mechanical behavior suggests that compression stress, compression modulus, and storage modulus of 6‐CH‐based composite foam are higher than the 5‐CH‐ and 7‐CH‐based composite foam with the contribution of 10%, 15%, and 20%, respectively. The electromagnetic interference (EMI) shielding effectiveness over the frequency of 8–12 GHz increased from 15 dB for without HGM to 21 dB, 25 dB, and 23 dB for 5‐CH, 6‐CH‐, and 7‐CH‐based composite foam, respectively. It is also noticed that, 6‐CH‐based composite foams presented the highest EMI‐SE compared to 5‐CH‐ and 7‐CH‐based composite foams. Enhanced mechanical, thermo‐mechanical, and shielding properties of 6‐CH‐based composite foams are due to improved morphology and quality of CNT grown at 600°C.

Surface structure investigation by means of ion beam-induced luminescence imaging: A preliminary study

The idea of ionoluminescence 3-D imaging is introduced to provide surface structural information of luminescent samples from a depth of tens of micrometers. Application of broad ion beam in an in-air setup results in capturing high resolution 2-D images in short times. Therefore, ionoluminescence 3-D imaging is a non-destructive technique which can extract information such as inhomogeneity, porosity and roughness, especially from historical precious samples. In order to display the capabilities of the ionoluminescence 3-D imaging technique, the 3-D image of an inhomogeneous lapis lazuli sample is produced based on stereo-ionoluminescence approach. The results are indicative of high potentials of the applied imaging technique for revealing surface structural information of luminescent samples.

Study on the Microstructure of Polyether Ether Ketone Films Irradiated with 170 keV Protons by Grazing Incidence Small Angle X-ray Scattering (GISAXS) Technology

Polyether ether ketone (PEEK) films irradiated with 170 keV protons were calculated by the stopping and ranges of ions in matter (SRIM) software. The results showed that the damage caused by 170 keV protons was only several microns of the PEEK surface, and the ionization absorbed dose and displacement absorbed dose were calculated. The surface morphology and roughness of PEEK after proton irradiation were studied by atomic force microscope (AFM). GISAXS was used to analyze the surface structural information of the pristine and irradiated PEEK. The experimental results showed that near the surface of the pristine and irradiated PEEK exists a peak, and the peak gradually disappeared with the increasing of the angles of incidence and the peak changed after irradiation, which implies the 170 keV protons have an effect on PEEK structure. The influences of PEEK irradiated with protons on the melting temperature and crystallization temperature was investigated by differential scanning calorimetry (DSC). The DSC results showed that the crystallinity of the polymer after irradiation decreased. The structure and content of free radicals of pristine and irradiated PEEK were studied by Fourier transform infrared spectroscopy (FTIR) and electron paramagnetic resonance (EPR). The stress and strain test results showed that the yield strength of the PEEK irradiated with 5 × 1015 p/cm2 and 1 × 1016 p/cm2 was higher than the pristine, but the elongation at break of the PEEK irradiated with 5 × 1015 p/cm2 and 1 × 1016 p/cm2 decreased obviously.

Oxygen assisted butanol conversion on bifunctional carbon nanotube catalysts: Activity of oxygen functionalities

Catalytic conversion of n-butanol to high-value-added product is considered as a highly important route towards biomass derived fine chemicals. The present work reports the applications of non-metallic multi-walled carbon nanotube (CNT) as bifunctional catalysts for oxygen assisted n-butanol conversion reactions. Oxidative dehydrogenation (ODH) and dehydration of n-butanol on CNT yielded aldehyde and alkene compounds via redox and acid catalytic routes, respectively. CNT exhibited high activity (over 50% n-butanol conversion) and stability (over 120 h) under gentle reaction conditions (<330 °C), which are competitive to conventional metal-based catalysts. Carboxylic acid groups were identified as catalytic active sites for dehydration reactions via linking the reactivity (kinetic parameters) with the surface composition and structural information of CNT catalysts. The redox activity could be related to ketonic carbonyl groups, and interestingly the intrinsic ODH catalytic activity is also influenced by degree of graphitization for CNT materials.

In-Operando characterization of Electrochemical Interfaces Via Shiners: Shell-Isolated Nanoparticle Enhanced Raman Spectroscopy

The advent of SERS created a new avenue for investigating interfacial phenomena by coupling the localized surface plasmon resonance (LSPR) of metal nanostructures to the inelastic scattering properties of molecules. Seeing a 104-fold enhancement in Raman signals, SERS scattering events were used to identify adsorbed molecules and substrate-surface structural conformations. But, even with the advent of SERs, Raman spectroscopy was still confined to LSPR active materials with roughened surfaces. However, recent technical modifications to SERS, such as shell-isolation and localized probe modes, have shown potential for the in-operando investigation of flat non-plasmon active single-crystal surfaces. Shell-isolated Nanoparticle Enhanced Raman Spectroscopy(SHINERS) provides two parallel paths for electric field enhancement of non-plasmon active surfaces while minimizing chemical perturbations by encasing reporters in a chemically inert shell (Figure 1). This technique can be used to perform in-operando measurements during electrochemical processes to bridge the gap between observing and understanding the state of metallic interfaces under an applied bias. This serve as a great utility to not only understand surface adsorbates, but to also characterize dynamic surfaces (e.g. Cu) that undergo reconstruction in response to the applied biases. Such metastable surfaces can impede capturing surface structure information, preventing accurate structure-activity assignments necessary to further understanding of the system. Furthermore, a lack of in-operando technology has inhibited the characterization of active sites and surface phenomena via in-situ measurements. These limitations have resulted in uncertainty of how novel findings are interconnected and ways to design refined interfaces. Herein, I report the synthesis of SiO2 encapsulated Au NPs and their application in-operando to track the state of Cu interfaces under varying electrochemical and chemical conditions. Figure 1

An integrated approach of GIS and geoelectrical techniques for wastewater leakage investigations: Active constraint balancing and genetic algorithms application

Wastewater leakage problem associated with sewage treatment plants deterioration has become prominent. We develop and apply procedures of GIS and direct current resistivity (DCR) techniques to investigate the wastewater seepage appearance in a semiarid urban environment. In the first stage, all surface geological and structural information is manipulated using GIS to produce geomorphological and geological maps. Waterlogged sites resulting in land degradation are distinguished by monitoring land-use/land-cover (LU/LC) changes. In the second stage, the DCR method has been performed to characterize the subsurface layer distributions and structures considering the results of GIS and LU/LC mapping data. Because the geophysical inverse problem is usually ill-posed, the active constrain balancing (ACB) approach and genetic algorithms (GA) are applied to optimize the inversion results. In the presence of high conductive layers, the limitation of DCR imaging in detecting the subsurface structure is demonstrated from the synthetic data. Moreover, we demonstrate that the joint use of GA with structure-based model (SBM) is helpful in recognition of subsurface layer distributions with non-smooth interfaces. However, ACB approach is more practical for lateral heterogeneities determination within the same rock unit than SBM with GA approach. The results indicate that the waterlogged areas and wastewater migration pathways are mainly controlled by the drainage networks and subsurface structures. Notably, the integrated approach allows us to assess geotechnical problems and to propose a suitable location for wastewater discharge management. Finally, the study can be considered as a scientific basis for desert urbanization and rational urban development planning.

Elucidating Surface Structure with Action Spectroscopy

Surface Action Spectroscopy, a vibrational spectroscopy method developed in recent years at the Fritz Haber Institute is employed for structure determination of clean and H2O-dosed (111) magnetite surfaces. Surface structural information is revealed by using the microscopic surface vibrations as a fingerprint of the surface structure. Such vibrations involve just the topmost atomic layers, and therefore the structural information is truly surface related. Our results strongly support the view that regular Fe3O4(111)/Pt(111) is terminated by the so-called Fetet1 termination, that the biphase termination of Fe3O4(111)/Pt(111) consists of FeO and Fe3O4(111) terminated areas, and we show that the method can differentiate between different water structures in H2O-derived adsorbate layers on Fe3O4(111)/Pt(111). With this, we conclude that the method is a capable new member in the set of techniques providing crucial information to elucidate surface structures. The method does not rely on translational symmetry and can therefore also be applied to systems which are not well ordered. Even an application to rough surfaces is possible.

Geotechnical assessment of fractured limestone bedrock using DC resistivity method: a case study at New Minia City, Egypt

ABSTRACT The new urban development is an important priority in Egypt to face a rapid increase in the population during the last few decades. As a case study, the geotechnical assessment of the New Minia City is studied applying direct current (DC) resistivity technique. In the presented study, the DC resistivity data are interpreted to (i) characterize the subsurface layer distributions, (ii) deduce the subsurface structures considering the surface geological and structural setting and borehole information and (iii) predict geotechnical parameters of the bedrock based on empirical relationships. The inversion results of DC resistivity data indicate that a lens of clay is locally capping the fractured limestone in different parts of the area. The constructed geoelectrical cross-sections show that the limestone bedrock is highly fractured regarding many normal faults trending in the NW and NE directions. In an attempt to derive empirical relationships for predicting the geotechnical parameters, the inverted resistivity values of the fractured limestone were correlated with different geotechnical parameters, Rock Quality Designation (RQD) and Unconfined Compressive Strength (UCS). It is noticed that there are good correlations between the limestone resistivity values and geotechnical parameters obtained from borehole data applying linear relations. Accordingly, the results indicate that the DC resistivity method constitutes a valuable technique to introduce a preliminary geotechnical assessment for new urban areas.

Correlation between microstructure and dissolution property of magnesium hydroxide synthesized via magnesia hydroxylation: Effect of hydration agents

The dissolution of magnesium hydroxide (MH) is a crucial process in its environmental protection application filed. In the present study, we attempted to improve the dissolution property of MH by changing the synthesis conditions. Various MH nanoparticles were prepared by MgO hydroxylation within hydration agents. The pH-stat method was applied to investigate the dissolution rate of the hydrate product. SEM, EDS-Mapping, FT-IR, and XRD technologies were utilized to gain surface and bulk structure information about the hydroxylation product. The dissolution property test results show that the average OH− released rate and Acid Neutralizing Capacity (ANC) in 120 min were promoted significantly form 27.7 ± 0.55 mmol/min/mol MH and 29.32 ± 0.59 mmol H+/g to 45.69 ± 1.37 mmol/min/mol MH (10 g NH4AC as hydration agent) and 31.31 ± 0.63 mmol H+/g (5g MgAC2 as hydration agent). The morphology and structure characterization results show that product with thin flake structure, large microscopic internal strain and low crystallinity would exhibit high dissolution activity. The present experimental results indicate that the curled sheet structure is an important reason for dissolution performance improvement, which is also proved by the Density-Functional Theory (DFT) calculation results of the affinity of H2O for uptake by the MH (001) surface. The results will be used to guide the synthesis of MH slurry with high activity and also provide valuable reference for the regulation of dissolution properties of other crystals.

Correlative Voltammetric Microscopy: Structure-Activity Relationships in the Microscopic Electrochemical Behavior of Screen Printed Carbon Electrodes.

Screen-printed carbon electrodes (SPCEs) are widely used for electrochemical sensors. However, little is known about their electrochemical behavior at the microscopic level. In this work, we use voltammetric scanning electrochemical cell microscopy (SECCM), with dual-channel probes, to determine the microscopic factors governing the electrochemical response of SPCEs. SECCM cyclic voltammetry (CV) measurements are performed directly in hundreds of different locations of SPCEs, with high spatial resolution, using a submicrometer sized probe. Further, the localized electrode activity is spatially correlated to colocated surface structure information from scanning electron microscopy and micro-Raman spectroscopy. This approach is applied to two model electrochemical processes: hexaammineruthenium(III/II) ([Ru(NH3)6]3+/2+), a well-known outer-sphere redox couple, and dopamine (DA), which undergoes a more complex electron-proton coupled electro-oxidation, with complications from adsorption of both DA and side-products. The electrochemical reduction of [Ru(NH3)6]3+ proceeds fairly uniformly across the surface of SPCEs on the submicrometer scale. In contrast, DA electro-oxidation shows a strong dependence on the microstructure of the SPCE. By studying this process at different concentrations of DA, the relative contributions of (i) intrinsic electrode kinetics and (ii) adsorption of DA are elucidated in detail, as a function of local electrode character and surface structure. These studies provide major new insights on the electrochemical activity of SPCEs and further position voltammetric SECCM as a powerful technique for the electrochemical imaging of complex, heterogeneous, and topographically rough electrode surfaces.

A study on the field emission properties of Bi2Se3 nanostructures prepared by laser ablation

One of the effective methods known as pulse laser ablation in liquid (PLAL), in which a solid target material is immersed in an organic solvent and laser beam is irradiated through liquid on a target material, is a direct method used to generate nanoparticles in liquid medium. The present work is focused on the preparation of bismuth selenide (Bi2Se3) nanoparticles using PLAL to study their field emission characteristics. The PLAL was performed under nanosecond (ns) laser with different ablation time of 120 min and 240 min. The field emission characteristics were measured in the planer “diode” configuration in all metal ultra-high vacuum (UHV) chamber. The prepared Bi2Se3 nanoparticles were analyzed with different characterization techniques such as scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-visible spectroscopy in order to study the surface morphology and structural information. The generation of Bi2Se3 nanoparticles is found after PLAL, which clearly suggests that bulk Bi2Se3 microsheet is transformed into Bi2Se3 nanoparticles. The X-ray spectra and UV spectra show the formation of nanoparticles upon laser ablation. The improvement in the field emission properties is found for laser-ablated Bi2Se3 nanoparticles. The field emission characteristics lead to increase in current density, which can be ascribed to the reduction in size of Bi2Se3 nanoparticles due to laser ablation. The prepared Bi2Se3 nanoparticles could be considered for novel applications in optoelectronics devices.

Field effect transistor behavior of Bi2Se3 nanostructure prepared by laser ablation

A new class of emerging materials known as topological insulators (TIs), such as bismuth selenide [Formula: see text], has an insulating band gap in the bulk and gapless surface state protected by its intrinsic time-reversal symmetry. These TI materials have attracted great attention because of their possible prospects in electrical and optical applications. In this work, we have prepared the [Formula: see text] nanostructure using the nanosecond (ns) pulse laser ablation in liquid environment to study the field effect transistor behavior. After the laser ablation, [Formula: see text] nanostructures were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-visible spectroscopy to reveal the surface morphology and structural information. The field effect transistor (FET) has been fabricated using [Formula: see text] nanostructure by drop casting [Formula: see text] suspension between two gold electrodes having a gap of 3 [Formula: see text]m on [Formula: see text] substrate and tested for FET at various gate voltages. The SEM clearly shows the formation of [Formula: see text] nanoparticles of different size varying from 20 nm to 30 nm after the ns laser ablation treatment. This result is supported by UV-visible spectra, as indicated by the enhancement in absorption band. The experimental results showed that charge conduction due to electrons as charge carriers were possible in [Formula: see text] nanoparticle FET. This work provides another approach to use [Formula: see text] nanoparticle FET for the applications in optoelectronic devices.