Facile Synthesis Process Research Articles

Cesium antimony iodide perovskite thin films by rapid iodization of Sb2S3-CsCl precursor under ambient conditions

In the present work, we report the synthesis of lead free cesium antimony iodide (Cs3Sb2I9) perovskite thin films by rapid iodization of Sb2S3-CsCl precursors under ambient conditions. In this method, first, Sb2S3 thin films were deposited using a chemical bath containing SbCl3 and Na2S2O3, following drop casting and spin coating of CsCl with varying molarities. These Sb2S3-CsCl precursor layers were iodized and the resulting films were investigated for their structure and morphology. X-ray diffraction and scanning electron microscopy studies revealed the formation of phase pure hexagonal structured Cs3Sb2I9 (P63/mmc) thin films with uniform surface coverage, exhibiting distinct morphologies for drop casting and spin coating cases. Moreover, Cs3Sb2I9 films obtained by varying iodization times (30 s – 10 min) were analyzed. The optical studies showed a direct band gap in the range of ∼ 1.8–1.96 eV for both drop casting and spin coating films. The Cs3Sb2I9 films were photoconductive and exhibited photodetection properties at zero bias voltage, functioning as self-powered photodetecors. Furthermore, we investigated stability of the self-powered photodetectors. Our work offers a facile synthesis process for producing photoconductive Cs3Sb2I9 thin films with inherent self-biased photodetection properties.

Boosting the anode performance of the porous Si coated with polydopamine and cross-linked with sodium alginate

Silicon-based materials are expected to be the next generation anode for lithium-ion batteries due to their high theoretical specific capacity (4200 mAh g-1) and abundant natural reserves. However, volume expansion (∼300%) and low conductivity issues hinder the further application of silicon-anode materials. Nano-sizing/confinement and the Si@C core-shell techniques are usually employed to depress volume expansion and enhance electrical conductivity of silicon anodes. However, the so-called “island effect” of nanoparticles and the loss of connection between the carbon shell and silicon core can lead to the degradation of electrochemical performance. In this work, nanoporous silicon (pSi) was prepared by means of magnesiothermic reduction of silicon aerogel as a precursor. The pSi is encapsulated by polydopamine (PDA) and then cross-linked by sodium alginate (SA) to form a three-dimensional network structure. It can effectively depress the drastic swelling-shrinking of silicon, avoid the "island effect" of silicon particles, and provide many effective conductive channels. The prepared Si@PDA-SA composite electrode delivers an initial discharge capacity of 3128 mAh g-1 and an initial coulombic efficiency (ICE) of 82.8%. At a current density of 2000 mA g-1, the reversible capacity of 820 mAh g-1 can be retained after 700 cycles. With enhanced mechanical properties and optimal link of the silicon particles, the gradual detachment of silicon particles from the adhesive can be effectively inhibited during long-term cycles. It offers the silicon anode superior cycling stability. Such a facile synthesis process and optimal electrochemical performance have laid a solid foundation for the large-scale application of silicon anode electrodes.

One-step hydrothermal synthesis of core-shell structural silicon carbide@WS2 with high efficiency for microwave absorption

The rapid development of communication technology has put new demands on high-efficiency microwave absorbing materials. In this study, silicon carbide particles are totally wrapped with two-dimensional WS2 through one-step hydrothermal method. Such core-shell structural SiC@WS2 composites show the minimum reflection loss of −50.52 dB with the thickness of 2.1 mm, and broadest absorbing bandwidth of less than −10 dB is 4.60 GHz with the thickness of 1.9 mm. The introduction of WS2 nanosheets enhance interfacial polarization and multiple scattering for composites. Besides, the special core-shell structure improves the surface anisotropy resulting in a better match of electromagnetic parameters. This work provides a facile and efficient synthesis process to enhance the absorbing abilities of powder materials.

Development of a new composite LDH/TiO2-3D for degradation of sulfaguanidine under UV and visible light: Experimental design, kinetic and mechanisms

Constructing 3D heterostructures has been considered an effective approach to enhance the photocatalytic activity of materials. However, the preparation of 3D heterostructures is always a complex process. In this paper, three-dimensional (3D) spherical TiO2 immobilized on Cu3AlCO3 Layered Double Hydroxides (LDH) was successfully synthesized using the impregnation method. The structure, morphology, and property of Cu3AlCO3-LDH/xTiO2-3D were investigated by X-ray diffraction (XRD), FTIR spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX), UV-Visible diffuse reflectance spectroscopy. The photocatalytic properties of composite materials were evaluated by degradation of sulfaguanidine (SGD) antibiotic under simulated solar irradiation. To optimize the photocatalysis process, an experimental design methodology was used. The experimental design utilized in most published works involves simple matrices that focus on quantitative factors. In contrast, our work enables the study of both qualitative factors (dissolved oxygen concentration) and quantitative factors (pH, catalyst dose and temperature) for both responses using a mixed matrix (D‐optimal) and a multiplicative model. To achieve this, 22 Run of experiments designed by the AZURAD® software. The optimal values of pH, catalyst dose, temperature, and dissolved oxygen concentration were found to be 8, 0.23 g.L−1, 25 °C, and 2 mg.L−1, respectively. The transformation product and possible degradation pathways of SGD were identified through Orbitrap LC/MS. Additionally, the present composite photocatalysts exhibited satisfactory re-usability for at least four cycles. Due to the facile synthesis process, higher photocatalytic activity under visible light irradiation and satisfactory re-usability, these composites can be considered as potential catalysts for degrading pharmaceutical pollutants in wastewater treatment.

Synergistically regulating particles size and defects level to realize fast and stable potassium storage of carbon anode

A series of defect-rich carbon particles with different sizes are successfully synthesized via a facile synthesis process. Various characterizations demonstrate that the particle size increases with the carbonization time increases, while the defect level presents an opposite trend, and as a result the defect-enriched carbon annealing at 800 ℃ for 2 h (DEC-800-2) achieves the optimum balance between them, which is favorable for increasing potassium storage sites and improving conductivity. Thus, the DEC-800-2 electrode delivers 220.9 mAh g−1 at 0.5 A g−1 after 100 cycles, accompanied by a good rate capability (156.9 mAh g−1 at 2 A g−1 after 2000 cycles).

Enhanced microwave absorption of g-C3N4/poly(vinylidene difluoride)/carbon black composites

The two-dimensional (2D) nanostructures have been widely applied as microwave absorption materials due to their unique structural features towards electromagnetic wave absorption. Herein, we have prepared graphitic carbon nitride (g-C3N4) nanosheets with a facile synthesis process, and then it was composited with a minimal amount of polyvinylidene difluoride (PVDF) and carbon black (CB) to enhance the microwave attenuation of g-C3N4 and to present an eco-friendly and cost-effective microwave absorbing material (MAM) as g-C3N4/PVDF/CB. The designed g-C3N4/PVDF/CB composite delivers a maximum return loss of −30.93 dB at 11.44 GHz, corresponding to an absorption efficiency of over 99.92%, with an average return loss of −17.29 dB. However, the dielectric performances were also elucidated with independent contributions of dielectric constant, tangent loss, and conductivity towards the microwave absorption performances. The integration of absorption medium PVDF and conductive medium CB to g-C3N4 offers the excellent absorption ability of g-C3N4/PVDF/CB. Hence, in the exploration of new MAM, g-C3N4/PVDF/CB may be an attractive microwave-absorbing material with strong dielectric parameters and excellent absorption effects.

Synthesis of plasmonic W18O49 interconnected nanowire frameworks with strong photo-enhanced hydrogen evolution reaction activity

The synthesis of high-order tungsten oxide nanowire frameworks (NWFs) is achieved using an unordinary stable molecular precursor formed by mixing tungsten hexachloride with methanol. The solvothermally obtained NWFs are well characterized with diffraction, microscopy, and nitrogen adsorption techniques. Time-resolved absorption spectroscopy and proton activity measurements reveal the stability of tungsten precursors in methanol. In butanol, the precursor decomposes rapidly into solid hydrated tungsten oxide and leads to the formation of freestanding nanowires (FNWs) after the solvothermal treatment. The NWFs show a blue shift in their characteristic plasmonic absorption wavelength when compared with FNWs. Such phenomenon is attributed to the high population of connecting nodes, which are postulated to be the plasmonic hot spots where the light-induced electromagnetic fields are amplified. The photo-deposition of palladium nanoparticles was hence selectively formed on these connecting nodes on the NWFs while showing no apparent selectivity on the FNWs. Furthermore, when applied as an electrode catalyst for the hydrogen evolution reaction, the NWFs demonstrated a much stronger photo-induced enhancement compared with the FNWs. The photo-induced effects demonstrate the advantage of plasmonic field enhancement through connected nanowires which can be obtained through a facile synthesis process.

Surfactant-mediated modulation of morphology and charge transfer dynamics in tungsten oxide nanoparticles

Tungsten Oxide (WO3) is a well-known transition metal oxide which exhibits non-toxicity and stability in its nanoparticle form. It is a potential candidate for a variety of applications due to its low cost and facile synthesis process. In the present work, WO3 nanoparticles were synthesized via facile acid-coprecipitation method to explore the effect of surfactants on the morphology of WO3 nanoparticles and thus, on its structural, optical and electrochemical properties. The morphology analysis revealed the formation of spherical nanoparticles in the absence of any surfactant while nanoflakes and nanosheets were observed in the presence of cetyltrimethylammonium bromide (CTAB) and polyethylene glycol (PEG), respectively. Moreover, the presence of surfactants was found to influence the crystallinity state of the samples. The different morphologies exhibited optical band gap of 2.2–2.7 eV as analyzed by UV–vis spectroscopy along with other optical properties like absorbance range and refractive index. The electrochemical properties of the samples were studied by employing potentio electrochemical impedance spectroscopy (PEIS) and cyclic voltammetry (CV) techniques. CV analysis revealed the diffusion-controlled behavior of the samples which may be suitable for photovoltaic applications. Furthermore, impedance study showed the presence of Warburg impedance which indicates that there is an infinite layer of excitons on the surface of thin film, further suggesting WO3 as a prominent material for solar cell applications. The incorporation of surfactants resulted in the reduction of charge transfer resistance indicating more efficient charge transfer process.

Synthesis, Characterization, and Adsorption Properties of Nitrogen-Doped Nanoporous Biochar: Efficient Removal of Reactive Orange 16 Dye and Colorful Effluents.

In this work, nitrogen-doped porous biochars were synthesized from spruce bark waste using a facile single-step synthesis process, with H3PO4 as the chemical activator. The effect of nitrogen doping on the carbon material's physicochemical properties and adsorption ability to adsorb the Reactive Orange 16 dye and treat synthetic effluents containing dyes were evaluated. N doping did not cause an important impact on the specific surface area values, but it did cause an increase in the microporosity (from 19% to 54% of micropores). The effect of the pH showed that the RO-16 reached its highest removal level in acidic conditions. The kinetic and equilibrium data were best fitted by the Elovich and Redlich-Peterson models, respectively. The adsorption capacities of the non-doped and doped carbon materials were 100.6 and 173.9 mg g-1, respectively. Since the biochars are highly porous, pore filling was the main adsorption mechanism, but other mechanisms such as electrostatic, hydrogen bond, Lewis acid-base, and π-π between mechanisms were also involved in the removal of RO-16 using SB-N-Biochar. The adsorbent biochar materials were used to treat synthetic wastewater containing dyes and other compounds and removal efficiencies of up to 66% were obtained. The regeneration tests have demonstrated that the nitrogen-doped biochar could be recycled and reused easily, maintaining very good adsorption performance even after five cycles. This work has demonstrated that N-doped biochar is easy to prepare and can be employed as an efficient adsorbent for dye removal, helping to open up new solutions for developing sustainable and effective adsorption processes to tackle water contamination.

Development of CuMnxOy (x = 2, and y = 4)-GO heterostructure for the synthesis of pyranoquinoline derivatives

The pyranoquinoline derivatives are synthetically important due to their biological properties. In this research, these derivatives were produced through an environmentally friendly method. This method includes the use of CuMnxOy (x = 2, and y = 4)-GO as a nanocatalyst, which is easy to produce, has excellent performance, cost-effectiveness, and recyclability among its features, and also the use of water as a green solvent. Pyranoquinolines through the one-pot, the multi-component reaction between different derivatives of aryl glyoxal, ethyl cyanoacetate, and 4-hydroxyquinoline-2(1H)-one were synthesized using nanocatalyst, K2CO3, and H2O. Also, the structure of the CuMnxOy-GO nanocatalyst was evaluated and confirmed via different analyses. The distinguishing features of this work compared to previous works are easy workup, recyclability of nanocatalyst, facile synthesis process, and provide high yields of products.

Mixed phase hierarchical Ni9Se6/Cu4O4/Cu4O2/Cu4 core-shell architectures via surfactant-free approach using waste copper wicks for hybrid supercapacitors

Recently, for energy storage materials, various surfactant-less synthesis methods have been attaining extensive attention from researchers. Herein, we utilized the wasted desoldering copper wicks (E-waste) as the base substrate to synthesize hierarchical core–shell maze-corn-like nickel selenide/copper oxide (NiSe/Cu4Ox) architectures by a facile two-step synthesis process. Initially, the Cu4Ox nanorods (NRs) were grown directly over the surface of the flat braided E-waste copper wicks by thermal oxidation, followed by a facile electrodeposition method to coat the pre-existing Cu4Ox NRs with NiSe nanoparticles. The optimized NiSe-120/Cu4Ox-3 electrode exhibited superior electrochemical characteristics (138.27 µAh cm−2 at 4 mA cm−2) compared to the other electrodes, owing to the contribution of core and shell materials, and sustained an ultra-long cycling test of 50,000 charge/discharge cycles with an excellent capacity retention of 98.7%. Inspired by commercially available AA battery, the as-synthesized working electrode was coupled with activated carbon-coated nickel foam to fabricate a cylindrical-type (C-type) hybrid supercapacitor (HSC) device, with an areal capacitance of 233.1 mF cm−2 accompanied by an extraordinary cycling efficiency of 99.1%. Furthermore, the C-type HSC device exhibited maximum energy and power densities of 70.9 µWh cm−2 and 14,000 µW cm−2, respectively and it was tested by powering portable electronics for real-time application.

Fe-Ni/MWCNTs Nano-Composites for Hexavalent Chromium Reduction in Aqueous Environment.

A novel Cr (VI) removal material was designed and produced comprising multi-walled carbon nanotubes (MWCNTs) as a support with a high specific surface area and the loaded Fe-Ni bimetallic particles as catalytic reducing agents. Such a design permits the composite particle to perform the adsorption, reduction, and immobilisation of Cr (VI) quickly and efficiently. Due to MWCNTs' physical adsorption, Cr (VI) in solution aggregates in the vicinity of the composite, and Fe rapidly reduces Cr (VI) to Cr (III) catalysed by Ni. The results demonstrated that the Fe-Ni/MWCNTs exhibits an adsorption capacity of 207 mg/g at pH = 6.4 for Cr (VI) and 256 mg/g at pH 4.8, which is about twice those reported for other materials under similar conditions. The formed Cr (III) is solidified to the surface by MWCNTs and remains stable for several months without secondary contamination. The reusability of the composites was proven by retaining at least 90% of the adsorption capacity for five instances of reutilization. Considering the facile synthesis process, low cost of raw material, and reusability of the formed Fe-Ni/MWCNTs, this work shows great potential for industrialisation.

Morphology controlled synthesis of cobalt diselenide nanorods for highly efficient hydrogen evolution in alkaline and acidic media

The development of electrochemical water-splitting electrocatalysts that are stable, highly efficient, and affordable is essential to future energy supplements. In this article, we developed a facile synthesis process based on self-templating CoSe2 nanorod fabrication on carbon cloth (CoSe2/CC) that can act as an effective electrocatalyst for the hydrogen evaluation reaction (HER) in both alkaline and acidic electrolytes. CoSe2/CC is a binder-free promising candidate because of its suitable electronic configuration for electrocatalytic water splitting. When compared to bare CoSe2, the CoSe2/CC catalyst performs dramatically better in terms of HER performance and kinetics: the Tafel slopes of CoSe2/CC are significantly reduced from 83 mV dec−1 to 38 mV dec−1 with a lower overpotential of 98–52 mV in 1.0 M KOH and 0.5 M H2SO4 electrolytes, respectively to attain a current density of 10 mA cm2. Moreover, CoSe2/CC nanorods show excellent stability up to 1000 cycles in both alkaline and acidic media. The time-dependent voltage (V-t) chronopotentiometry of CoSe2/CC depicts its excellent long-term durability of 12 h in KOH and H2SO4. This research could lead to the development of a comprehensive methodology for the rational design and fabrication of other transition-metal selenide nano-structured materials to serve as efficient HER electrocatalysts.

Heat reflux sonochemical synthesis of Cu3BiS3 quantum dots: Experimental and first-principles investigation of spin–orbit coupling on structural, electronic, and optical properties

Semiconductor quantum dots (QD) exhibit promising electrical and optical properties in photovoltaic cells by improving their stability and efficiency enhancement. Therefore, in this study, novel Cu3BiS3 (CBS) ultrafine QDs were synthesized to function as effective solar absorbers, using a facile heat reflux sonochemical synthesis process under inert (N2) atmosphere. Using high-resolution transmission electron microscopy (HRTEM) analysis, the size of CBS QDs was found to be in the range of 3–8 nm. Furthermore, the crystallite size (D), strain (ε), and dislocation density (δ) of the QDs were investigated in detail by confirming the orthorhombic wittichenite structure. The photocurrent density (PCD) of CBS QDs obtained at a voltage range of 0.5–1 V was found between 0.2 and 0.6 mA/cm2 under illumination; otherwise, it has a linear nature and good ohmic behavior in the range of − 0.1 V to + 0.1 V. In additionally, the spin–orbit coupling (SOC) interaction was computed using the Perdew–Burke–Ernzerhof (PBE) and Tran-Blaha-modified Becke–Johnson (TB-mBJ) functionals in the density functional theory (DFT) framework. The results showed a bandgap transition from direct to indirect with the inclusion of SOC, as confirmed by the electronic band structure. Moreover, the DFT-calculated bandgap using the TB-mBJ functional (∼1 eV) achieved near consistency with the experimentally obtained bandgap (∼1.4 eV). Therefore, based on the experimental and computational results, this study can pave the way toward developing novel copper chalcogenide QDs for application in future photovoltaic cells.

Simple design of Sn/reduced graphene oxide/carbon nanofibers ternary hybrids for lithium-ion batteries

Novel Sn/reduced graphene oxide/carbon nanofibers ternary hybrids have been designed via a facile one-step synthesis process. In the hybrids, Sn nanoparticles, uniformly sandwiched in the layers of reduced graphene oxide, are in good contact with carbon nanofibers. The ternary hybrids have demonstrated superior lithium storage performance to the Sn/reduced graphene oxide and Sn/carbon nanofibers binary hybrids. The reversible capacity of the ternary hybrids is 643 mAh g−1 after 90 cycles. Importantly, electrochemical impedance spectroscopy measurements confirm that the integration of Sn, reduced graphene oxide and carbon nanofibers can reduce the charge transfer resistance effectively.

Resistive-type sensors based on few-layer MXene and SnO2 hollow spheres heterojunctions: Facile synthesis, ethanol sensing performances

High-performance and low-cost gas sensors are highly desirable and involved in industrial production and environmental detection. The combination of highly conductive MXene and metal oxide materials is a promising strategy to further improve the sensing performances. In this study, the hollow SnO2 nanospheres and few-layer MXene are assembled rationally via facile electrostatic synthesis processes, then the SnO2/Ti3C2Tx nanocomposites were obtained. Compared with that based on either pure SnO2 nanoparticles or hollow nanospheres of SnO2, the SnO2/Ti3C2Tx composite-based sensor exhibits much better sensing performances such as higher response (36.979), faster response time (5 s), and much improved selectivity as well as stability (15 days) to 100 ppm C2H5OH at low working temperature (200 °C). The improved sensing performances are mainly attributed to the large specific surface area and significantly increased oxygen vacancy concentration, which provides a large number of active sites for gas adsorption and surface catalytic reaction. In addition, the heterostructure interfaces between SnO2 hollow spheres and MXene layers are beneficial to gas sensing behaviors due to the synergistic effect.

Activating Pt clusters for efficient removal of HCHO by modulating Vn+ within VxOy support

The catalytic performance of Pt clusters towards formaldehyde (HCHO) oxidation was activated by tuning the valence of vanadium (V) element within a VxOy support. Through a facile but efficient solvothermal synthesis and heat-treatment process, the V valence can be precisely regulated from V4+ to V5+. Subsequently, the HCHO catalytic oxidation rate of Pt/VxOy catalyst has dramatically increased from 0.0146 to 0.0294 mmol·h−1·m−2 at 15 °C. The increased V valence has effectively accelerated the charge transfer from VxOy support to Pt cluster, and promoted the upshift of d-band center of the Pt element, leading to a low reduction temperature of Pt2+ to Pt0 and high production of reactive adsorbed oxygen. This study provides a simple but feasible strategy to tune the valence of V element within VxOy and offers new insights for the study of other possible multivalent metal oxides used in different catalytic reactions.

Manganese Oxide Nanoparticles: An Insight into Structure, Synthesis and Applications

AbstractManganese oxide nanoparticles with different crystal phases, morphologies, and structural diversity along with their exceptional properties like high specific surface area, a high fraction of surface atoms, non‐toxic nature, and excellent redox properties are drawing attention for various applications in storage science, especially in the batteries, super‐capacitors, energy conversion, and the environmental catalysis field. Precise control of particle size, morphology, surface area, Mnx+ oxidation state, etc. is the utmost important aspect to explore their application to the full potential. Here, the emphasis is on the recent trends in manganese oxide research – structure, synthesis, and applications. The structure of numerous crystalline phases of manganese oxide nanoparticles are summerized and several facile chemical synthesis processes to achieve the desired crystalline/amorphous structure are discoursed. Temperature and different synthesis conditions dependent phase transformations of β‐MnO2, α‐Mn2O3, and Mn3O4 from α‐MnO2 are discussed as well. The pragmatic approach directs that the application field is mostly controlled by the morphologies.

Dually Crosslinked Copper-Poly(tannic acid) Nanoparticles with Microenvironment-Responsiveness for Infected Wound Treatment.

Reducing the burden of death due to wound infection is an urgent global public health priority. Metal-phenolic networks (MPNs) have received widespread attention in antimicrobial infections due to their facile synthesis process, excellent biocompatibility, and antimicrobial properties brought about by polyphenols and metal ions. However, typical therapeutic MPNs show rapid release of metal ions due to their poor solution stability, impeding long-acting efficacy in multiple wound healing stages. To address these issues, copper-poly (tannic acid) nanoparticles (Cu-PTA NPs): robust (dually crosslinked), microenvironment-responsive, antibacterial, antioxidative, and anti-inflammatory are prepared, which hierarchically modulate the infected wound healing process. Covalently polymerized via phenol-formaldehyde condensation and crosslinked with bioactive Cu2+ , reactive polyphenols are preserved, and Cu2+ is efficiently entrapped in the PTA scaffold. The proposed strategy relieves the systemic toxicity, and only high reactive oxygen species (ROS)level as stimuli can "turn on" the catalytic activity of Cu2+ to implement antibacterial therapy specifically in an infected wound. Systematic tissue regeneration assessment on the infected full-thickness skin wounds of rats demonstrates enhanced wound healing rate. Cu-PTA NPs enables the direct application in infected wound and exertion of long-acting healing efficacy. This synergetic therapy strategy will pave the way for more complicated infections and inflammatory diseases.

Synthesis of Fe-doped Mn-based Prussian blue hierarchical architecture for high-performance sodium ion batteries

Sodium manganese hexacyanoferrates (MnHCFs) have great potential as cathode for sodium-ion batteries (SIBs) owing to their large specific capacity, low cost, ecofriendly synthesis and high working voltage. Nevertheless, their cycling stability is limited by Jahn-Teller effect (JT-effect) of Mn3+, phase transitions and Mn2+ dissolution during the charging and discharging processes. Herein, an unconventional solid-liquid two-phase route is developed to fabricate a novel hierarchical nanostructure Na1.02Mn0.57Fe0.43[Fe(CN)6]0.63∙1·39H2O in view of different solubility of raw material Na4Fe(CN)6·10H2O in the mixed solvent of ethanol and water. Benefiting from unique porous hierarchical architecture, good structural stability, high electrical conductivity and fast capacitive behavior, such Fe-doped MnHCF cathode has an outstanding rate capability with large discharging capacity of 127 mAh g−1 at 25 mA g−1 and 71 mAh g−1 at 1200 mA g−1, and an excellent cyclability with 120 mAh g−1 of specific capacity at 100 mA g−1 and 86% of capacity retention over 200 cycles. In particular, the facile and controllable synthesis process of Fe-doped MnHCFs make it accessible for large-scale applications.