Successive Adsorption Research Articles

Solution ALD: A Versatility Process for the Growth of Sulfides and Selenides

We have proposed and demonstrated a novel thin film deposition technique by transferring the principles of atomic layer deposition (ALD), known with gaseous precursors, towards precursors dissolved in a liquid. The technique can also be considered as a generalization of already established methods such as the ‘layer by layer’ growth or the ‘successive ion layer adsorption and reaction’ (SILAR). 'Solution ALD' (sALD) shares the fundamental properties of standard ‘gas ALD’ (gALD), specially the self-limiting growth and the ability to coat conformally deep pores. It has been already shown that it is possible to transfer standard reactions from gALD to sALD such as TiO2 deposition . However, sALD also offers novel opportunities such as overcoming the need for volatile and thermally robust precursors.To illustrate this, we establish sALD procedures for depositing films of non oxides layers such as Pb-compound deposition, MOF, selenides and sulfides. Those examples highlight how ionic, polar, or high-molecular weight precursors that only exist in the condensed phase are now rendered amenable to being utilized in surface-controlled thin film formation by sALD for depositing materials that would otherwise be more difficult or more expensive to achieve by gALD or hazardous. The deposition was achieved on small (2 cm*1 cm) and large samples (up to 10 cm*10 cm). The ALD behavior has been shown. The influence of the deposition parameters on the morphology, the crystalline structure and the chemical composition has been investigated by scanning electron microscopy, atomic force microscopy, grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy. Additionally, the nucleation is studied in function of chemical pretreatment to control the growth and allow selective deposition of SnS, SnSe and Sb2Se3.This particular ALD process offer the growth of high quality and crystalline layers in middle conditions with the use of low cost and environmental friendly precursors. Y. Wu, D. Döhler, M. Barr, E Oks,M. Wolf, L. Santinacci and J. Bachmann, Nano Lett. 2015, 15, 6379 J. Fichtner, Y. Wu, J. Hitzenberger, T. Drewello and J. Bachmann, ECS J. Solid State Sci. Technol. 2017, 6, N171

Highly Selective Photocatalytic Conversion of Glucose on Holo-Symmetrically Spherical Three-Dimensionally Ordered Macroporous Heterojunction Photonic Crystal

Highly Selective Photocatalytic Conversion of Glucose on Holo-Symmetrically Spherical Three-Dimensionally Ordered Macroporous Heterojunction Photonic Crystal

Adsorption behaviors of magnetic carbon derived from wood tar waste for removal of methylene blue dye

Wood tar is the main by-product of thermal cracking of biomass. Magnetic biomass activated carbon (M-RWTAC) has been prepared from wood tar. The phenol component in the wood tar has firstly been fixed by phenolic reaction. The resinifero wood tar is subsequently employed to prepare magnetic biomass activated carbon through carbonization, activation and magnetization steps. The surface structure, property and magnetic properties of magnetic biomass activated carbon analyzed by a variety of techniques. Rich oxygen group and high specific surface area of the as-prepared M-RWTAC can provides convenient condition to the adsorption contaminate. Adsorption behavior of the as-prepared M-RWTAC is evaluated with MB as a model of dye pollutant. The MB adsorption of M-RWTAC is in accordance with the pseudo-second-order kinetic model and Langmuir model is predominant for this adsorption system with the maximum adsorption capacity of 528 mg g−1. The adsorption of MB onto M-RWTAC is an exothermic and entropy production process. The regenerated M-RWTAC can be recycled with the removal efficiency of 82.5 % after 5 successive adsorption cycles. The present study provides a new route to utilize wood tar by-product of biomass pyrolysis.

Visible Light Photoelectrochemical Sensor for Dopamine: Determination Using Iron Vanadate Modified Electrode.

This study reports a facile approach for constructing low-cost and remarkable electroactivity iron vanadate (Fe-V-O) semiconductor material to be used as a photoelectrochemical sensor for dopamine detection. The structure and morphology of the iron vanadate obtained by the Successive Ionic Adsorption and Reaction process were critically characterized, and the photoelectrochemical characterization showed a high photoelectroactivity of the photoanode in visible light irradiation. Under best conditions, dopamine was detected by chronoamperometry at +0.35 V vs. Ag/AgCl, achieving two linear response ranges (between 1.21 and 30.32 μmol L−1, and between 30.32 and 72.77 μmol L−1). The limits of detection and quantification were 0.34 and 1.12 μmol L−1, respectively. Besides, the accuracy of the proposed electrode was assessed by determining dopamine in artificial cerebrospinal fluid, obtaining recovery values ranging from 98.7 to 102.4%. The selectivity was also evaluated by dopamine detection against several interferent species, demonstrating good precision and promising application for the proposed method. Furthermore, DFT-based electronic structure calculations were also conducted to help the interpretation. The dominant dopamine species were determined according to the experimental conditions, and their interaction with the iron vanadate photoanode was proposed. The improved light-induced DOP detection was likewise evaluated regarding the charge transfer process.

Synthesis, characterization and stability study of aqueous MPA capped CuInS2/ZnS core/shell nanoparticles

Ternary I–III–VI nanoparticles (NPs) emerged as potential alternatives to II-VI group NPs. At present, it remains a tremendous challenge to directly synthesize high-quality CuInS2/ZnS (CIS/ZnS) core/shell NPs in aqueous solution at atmospheric pressure. Herein, a simple and reliable strategy that combines the hydrothermal method and successive ion layer adsorption and reaction has been proposed to realize the aqueous synthesis of fluorescent CIS/ZnS core/shell NPs. XRD depicts the formation of tetragonal chalcopyrite structure of CIS quantum dots (QDs). As synthesized CIS QDs and CIS/ZnS NPs possess spherical symmetry with average diameter of 6.6 nm and 11.2 nm, respectively. FT-IR spectra confirms the capping of MPA on CIS and CIS/ZnS NPs. UV–Vis spectra of core QDs and core/shell NPs does not show any direct absorption peak. After the growth of ZnS shell over CIS QDs, the PL QY of NPs reach from 6.95% to 17.19%. The stability and behavior of core and core/shell NPs in different pH, has been studied from both absorption and PL observations. Maximum PL emission intensity is found at pH 6 for both core and core/shell NPs. PL QY of core/shell NPs reduces from 17.19% to 8.08% after two months of storage. These properties make them promising candidates for biological and optoelectronic applications.

Removal of heavy metals from water by macro-mesoporous calcium alginate–exfoliated clay composite sponges

The contamination of drinking water and freshwater by heavy metals has become a growing concern for human health and environment that calls for immediate remedial action. Adsorption process has been proved to be a promising technology for producing treated water that complies with drinking water standards. In this work, we describe a facile and low-cost approach to fabricate porous calcium alginate composite sponges containing exfoliated bentonite clay (denoted as CRAB) by saponin-assisted foaming and external gelation techniques for efficient removal of Cu2+ and Cr6+ ions from aqueous solution and real world water samples. The formation of exfoliated organoclay within the composite matrix was achieved by intercalation of saponin into the interlayer spacing of bentonite and subsequent penetration of alginate chains. Morphological and textural characterizations revealed that the resultant CRAB sponges mainly exhibited meso- and macropores in their interior. The formation of calcium alginate-organoclay exfoliated composites was also verified by the XRD results. The performance of CRAB sponges in removing Cu2+ and Cr6+ ions from aqueous solution was evaluated under different environmental conditions including temperature, pH, ionic strength, and background electrolyte. The results demonstrated that the uptake capacity of Cu(II) and Cr(VI) increased with increasing temperature, suggesting the endothermic nature of the adsorption process. The Freundlich isotherm model was found to better interpret the equilibrium adsorption behaviors of Cu2+ and Cr6+ ions onto the investigated sorbents than the Langmuir model. The sorption kinetics for these metal ions followed a pseudo-first-order model. Reusability tests for CRAB sponge demonstrated that the sorption capacity of the sorbent is well maintained over three successive adsorption–desorption cycles. Together, these results indicate the great potential of low-cost and sustainable CRAB sponges for remediation of water polluted with copper and hexavalent chromium ions.

Popcorn-like ZnFe2O4/CdS nanospheres for high-efficient photocatalyst degradation of rhodamine B

The popcorn-shaped ZnFe2O4 (ZFO) nanospheres has been produced by one-pot synthesis method. CdS nanoparticles (NPs) were subsequently loaded onto the surface of porous ZnFe2O4 through the successive ion layer adsorption (SILAR) process. The microstructure, composition, and degradation ability of ZFO/CdS NPs composites have been examined in-depth. Under the four SILAR cycles, the resulting ZFO/CdS NPs (FS4) composite displayed the maximum degradation efficiency of 93.2% for rhodamine B (RhB) in 40 min, and which maintained high photocatalytic activity and a stable structure after five reuse. The heterojunction between CdS and ZFO can dramatically improves the separation efficiency of photo-generated electron-hole pairs, thus boosts catalytic activity. Meanwhile, the radical scavenging investigations have demonstrated that the superoxide radicals as the principal reactive group participate in the photocatalytic reactions. The proposed ZFO/CdS NPs composites shows high photocatalytic ability and convenient magnetic recycling. This work not only provide a practical green synthesis path, but also offers new insight onto the formation of high-efficiency heterojunction photocatalysts.

Engineered biochar supported layered double hydroxide-cellulose nanocrystals composite-: Synthesis, characterization and azo dye removal performance

In this work, engineered biochar decorated layered double hydroxides and cellulose nanocrystals (B–CuFe–CNC) biocomposites were synthesized by the facile ultrasonicated-co-precipitation technique. The biocomposite was investigated for purification of Eriochrome Black T (EBT) dye from water. The characterization results showed that the presence of CNC in biochar-layered double hydroxides resulted in a two-dimensional rod-like structure with excellent crystallinity, improved surface functionalities, and provides an attractive platform for the enhanced adsorption of azo anionic dye molecules. The adsorption system was appropriately demonstrated by the BBD-RSM (R2 > 0.994). The biocomposite exhibited higher EBT adsorption in the acidic pH range (2–5) due to strong electrostatic and chemical interactions. The kinetic and isotherm results were well demonstrated by pseudo-second order, Freundlich, and Redlich Peterson models. The maximum adsorption capacity of biocomposite was 876.2 mg/g achieved within 45 min. The spectroscopic analyses imply that the high removal of EBT by biocomposite is mainly governed by electrostatic attraction, hydrogen bonding, and chemical/metal complexation mechanisms. The biocomposite maintained high EBT removal after six successive adsorption cycles and excellent dye adsorption in the different water matrices. The results suggest that tailoring biochar properties with layered double hydroxide and CNC is a promising way for the enhanced removal of dye contaminants from wastewater.

Oxidation-Induced and Hydrothermal-Assisted Template-Free Synthesis of Mesoporous CeO2 for Adsorption of Acid Orange 7.

Hydrogen peroxide (H2O2), an accessible and eco-friendly oxidant, was employed for the template-free hydrothermal synthesis of mesoporous CeO2 based on a cerium carbonate precursor (Ce2(CO3)3•xH2O). Its microstructure and physicochemical properties were characterized by XRD, TEM and N2 sorption techniques. The formation of the CeO2 phase with a porous structure was strongly dependent on the presence of H2O2, while the values of the BET surface area, pore diameter and pore volume of CeO2 were generally related to the amount of H2O2 in the template-free hydrothermal synthesis. The BET surface area and pore volume of the mesoporous CeO2 synthesized hydrothermally at 180 °C with 10 mL H2O2 were 112.8 m2/g and 0.1436 cm3/g, respectively. The adsorption process had basically finished within 30 min, and the maximum adsorption efficiency within 30 min was 99.8% for the mesoporous CeO2 synthesized hydrothermally at 140 °C with 10 mL, when the initial AO7 concentration was 120 mg/L without pH preadjustment. The experimental data of AO7 adsorption were analyzed using the Langmuir and Freundlich isotherm modes. Moreover, the mesoporous CeO2 synthesized at 140 °C with 10 mL H2O2 was regenerated in successive adsorption–desorption cycles eight times without significant loss in adsorption capacity, suggesting that the as-synthesized mesoporous CeO2 in this work was suitable as an adsorbent for the efficient adsorption of AO7 dye from an aqueous solution.

Facile fabrication of mesoporous SiO2@(cTiO2/BiOI) heterojunctions with enhanced photocatalytic properties due to large surface area for contact with pollutants

In order to fabricate photocatalysts possessing large surface area to contact with pollutants, mesoporous SiO2@TiO2 was prepared by step sol–gel method within the presence of cetyl trimethylammonium bromide templates. After removal of the surfactant by calcination or acid drawing, BiOI was inlayed on SiO2@TiO2 by successive ionic adsorption method. The catalysts with high crystalline TiO2 component, which formed in the calcination process for the removal of surfactant, showed higher photocatalytic activity under UV irradiation. More than 95% of 10 mg/L of methyl orange, methylene blue and tetracycline hydrochloride was degraded by 12 mg of the catalysts within 60 min. The improved catalytic effect derived from the enhanced charge transfer at the interface and the easy contact of pollutants with the catalysts. The catalytic mechanism was further studied and the possible degradation position of methyl orange after attack by active species was analyzed by Material Studio through calculating the electron density change.

Regeneration of Granulated Spent Activated Carbon with 1,2,4-Trichlorobenzene Using Thermally Activated Persulfate.

Chlorinated organic compounds (COCs) are persistent organic pollutants often found in groundwater near industrial sites or in industrial wastewaters. Adsorption into activated carbon is a common strategy to remediate these waters, but spent activated carbon results in a toxic residue to manage. To avoid the transport of the chlorinated compounds out of the site, the in-situ regeneration of the spent activated carbon can be considered for reuse to implement a circular economy. In this work, the regeneration of a commercial granular activated carbon (GAC) has been carried out using thermally activated sodium persulfate (TAP). GAC was previously saturated in 1,2,4-trichlorobenzene (124-TCB) as the model compound. The initial adsorption value was 350 mg124-TCB·gGAC–1. First, the nonproductive consumption of sodium persulfate was studied at different temperatures using nonsaturated GAC. Then, the regeneration of the saturated GAC (5 g) was studied by an aqueous solution (166 mM) of TAP (1 L) at a temperature range from 20 to 80 °C. The possible recovery of the adsorption capacity was studied after 3 h of treatment in three successive adsorption–regeneration cycles at the selected temperature (60 °C). The physicochemical changes of the GAC were also investigated before and after the regeneration treatments. The results evidence the significant deposition of sulfate on the GAC after each treatment of regeneration, which avoids the recovery of the initial adsorption capacity. Therefore, each regeneration cycle was necessarily followed by a washing step at 60 °C to remove this sulfate. After that, the regeneration treatment achieved a stable and high recovery of the initial adsorption capacity of about 48.2%.

Synthesis of magnetic polypyrrole modified sodium alginate nanocomposite with excellent antibacterial properties and optimization of dye removal performance using RSM

In this study, a novel polypyrrole/Sodium-Alginate/CuFe2O4 magnetic nanostructure (PPy/NA-Alg/CuFe2O4) was synthesized by the hydrothermal route and used as an adsorbent in order to eliminate Direct Blue 199 (DB199) dye from wastewater. The characterization of the synthesized PPy/NA-Alg/CuFe2O4 was confirmed by investigation of SEM, TEM, FTIR, XRD, and VSM analyses. Five significant operational parameters including initial dye concentration (20–100 mg/L), temperature (25–45 °C), the dose of adsorbent (2–22 mg), contact time (10-210 min), and pH (2-10) were optimized to achieve the greatest removal efficiency of DB199 by a central composite rotatable design (CCRD) combined with response surface methodology (RSM). A high coefficient of determination (R2 = 0.99) was calculated by analysis of variance (ANOVA). Under optimal conditions, adsorption dosage = 7.00 mg, temperature = 30.61 °C, initial concentration = 80.00 mg/L, pH = 4.00 and contact time = 159.42 min, the maximum adsorption capacity of the adsorbent (80.36) was highly matched with the predicted response values, illustrating the appropriate of RSM in optimum conditions. The experimental data were matched well to the Langmuir isotherm model and both pseudo-first-order and pseudo-second-order kinetics. Additionally, thermodynamic parameters exhibited spontaneous nature and exothermic reaction. Adsorption–desorption experiments evidenced that the PPy/NA-Alg/CuFe2O4 synthesized could be used for up to three successive adsorption cycles. Furthermore, the nanocomposite showed strong antibacterial activity against two model microorganisms, one gram-negative (Escherichia coli) and one gram-positive (Staphylococcus aureus) via disc diffusion and linear cultivation methods.

A novel self-powered sensor based on Ni(OH)2/Fe2O3 photoanode for glucose detection by converting solar energy into electricity

• A photo fuel cell (PFC) based self-powered sensor is successfully constructed. • The sensing is powered by converting solar energy without external power inputting. • The glucose sensitivity is 24.59 μW cm −2 mM −1 on Ni(OH) 2 /Fe 2 O 3 self-powered sensor. • It is much higher than 3.53 μW cm −2 mM −1 obtained on bare Fe 2 O 3 based sensor. • Ni(OH) 2 enhances the charge injection and promotes glucose oxidation kinetics. Self-powered sensors have great application prospects in the field of analytic chemistry because they can determine analytes without inputting external electricity. In this work, Fe 2 O 3 electrode with nanorod morphology was synthesized by chemical bath method, then a layer of Ni(OH) 2 was decorated on the surface of Fe 2 O 3 nanorods via successive ion adsorption. Furthermore, a Ni(OH) 2 /Fe 2 O 3 -based photo fuel cell (PFC) was fabricated as a novel self-powered sensor. The produced maximum power density ( P max ) of the sensor shows a linear relationship with glucose concentrations in the range of 0.05–0.25 mM with a sensitivity of 24.59 μW cm –2 mM –1 , which is much higher than that of bare Fe 2 O 3 -based self-powered sensor (only 3.53 μW cm –2 mM –1 ). The better performance achieved on the Ni(OH) 2 /Fe 2 O 3 -based sensor is because Ni(OH) 2 has high electrocatalytic activity for glucose oxidation and it can improve photo-generated charge inject efficiency ( η inj ) to substrate. In addition, the sensor also possesses good selectivity, stability and applicability for glucose sensing. In a word, this work provides a non-enzymatic, simple-construction, cost-effective and sustainable PFC based self-powered sensor, which may guide future designs for the determination of analytes and offer a new route for utilization of widespread solar energy.

Individual and competitive adsorption of ibuprofen and caffeine from primary sewage effluent by yeast-based activated carbon and magnetic carbon nanocomposite

Pharmaceuticals enter water bodies mainly through urban effluents harmful to the biota, inducing microbial resistance, and impacting hydric security. Activated carbon has been used for effluent treatment and associated with ferromagnetic nanoparticles can facilitate the separation of this adsorbent from an aqueous medium and improve the adsorption capacity. A yeast-based carbon (YC) prepared from the residue of the ethanol industry and a magnetic composite prepared from YC (NP-YC) were used to remove ibuprofen (IBU) and caffeine (CAF) from deionized water and primary sewage effluent (PE). A minimum of 51 and 90 mg/g of IBU and CAF were removed by NP-YC, respectively, whereas YC removed a minimum of 107 and 106 mg/g for such contaminants. The removal of both contaminants was favored for competitive studies using NP-YC as adsorbent (removals >70% for deionized water, and >60% and >75% for IBU and CAF, respectively, for PE). The values of qmax obtained for YC in the competitive assays were about the sum of both qmax for the individual experiments suggesting that each molecule adsorbs in a different site. Successive adsorption cycles using the same mass of adsorbent removed higher amounts of IBU and CAF by exposing the adsorbents to new volumes of a solution containing equal or increasing concentrations of contaminants than those exposed to a single high concentration solution. This behavior is probably due to the driving force effect. It suggests that the reuse of synthesized adsorbents was possible without previous desorption, increasing the usability of the synthesized adsorbents.

Selective adsorption of trace gaseous ammonia from air by a sulfonic acid-modified silica xerogel: Preparation, characterization and performance

The toxic and corrosive gaseous ammonia (NH3) poses serious environmental and health risks. However, removal of low concentration NH3 from air remains challenging. In this work, a SO3H-modified silica xerogel (MPTS-X) with good porous structure stability and abundant Bronsted acid sites was fabricated, and its physicochemical properties and adsorption performance for NH3 were systematically investigated. Static adsorption experiments showed the MPTS-1.0 had high NH3 adsorption capacity of 4.02 mmol⋅g−1 at 0.1 bar and 7.00 mmol⋅g−1 at 1.0 bar, which was much higher than that of MPTS-0 (3.19 and 1.95 mmol⋅g−1). Langmuir-Freundlich isotherm model fitted the experimental data of NH3 adsorption well, implying that the MPTS-1.0 surface is not homogeneous and there are different adsorption sites, which was further confirmed by temperature programmed desorption spectrum analysis. According to IAST calculation, the adsorption selectivity of MPTS-1.0 for NH3/N2 (1: 9) and NH3/CO2 (1: 1) was 6175 and 165 at 1.0 bar, respectively, indicating the MPTS-1.0 has excellent adsorption selectivity. Dynamic adsorption experiments and field test demonstrated the MPTS-1.0 could quickly capture trace NH3, even if the initial concentration is as low as 2 ppm. Successive adsorption–desorption experiments demonstrated the MPTS-1.0 had good regenerability. In-situ infrared spectroscopy analyses indicated NH3 adsorption on the MPTS-1.0 was mainly due to hydrogen bonding interaction and proton transfer to form Si-OH…NH3 and -SO3-NH4+, respectively. NH3 molecules bound firmly to acidic sites on the xerogel surface, which reduced re-release risk. This work may provide a feasible way to develop promising adsorbents for the removal of gaseous ammonia from air.

Low-temperature NOx reduction over hydrothermally stable SCR catalysts by engineering low-coordinated Mn active sites

Low-temperature selective catalytic reduction (SCR) of NOx over hydrothermally stable metal oxide catalysts is still a great challenge in heavy-duty diesel exhaust purification. Herein, hydrothermally stable MnOx/Al2O3 catalysts with highly dispersed low-coordinated Mn active sites were originally demonstrated for low-temperature NOx reduction. The catalyst exhibited greater than 90 % NOx conversion within 200–360 °C even after a 24 h aging treatment at 650 °C with a flow of 10 % H2O. A series of characterization revealed that the developed catalysts with more active low-coordinated Mn species possessed reactive redox sites and Lewis acid sites. Thus, the successive adsorption and activation of NH3 and NOx species would be efficiently accelerated and proceeded with the subsequent SCR reaction over hydrothermally stable MnOx/Al2O3 catalysts. This work discovered hydrothermally stable manganese oxide catalyst for low-temperature NOx reduction which would provide new opportunities for the application of metal oxide catalysts among diesel engine exhaust emission control.

Successive Ion Layer Adsorption and Reaction Method Developed ZnO Thin Films for NO2 Gas Sensing

The present investigation deals with the NO2 gas detection via nanostructured zinc oxide (ZnO) thin films harvested over a glass substrate via a simple and facile successive ion layer adsorption and reaction (SILAR) approach. ZnO nanostructured thin films are developed by different SILAR cycles (ZnO:15, ZnO:30, ZnO:45, ZnO:60). The physicochemical, optical, and morphological properties of prepared thin films are explored by various characterization techniques. The phase purity and grains size are confirmed by X‐ray diffraction (XRD) and Scherrer formula, which reveal the hexagonal phase structure with variant grain size (≈16–21 nm). The surface morphology of deposited films shows the well‐dispersion of ZnO nanoparticles, which is picturized by field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), attenuated total reflectance (ATR). UV–Vis and FTIR spectroscopy elaborates on the optical properties and functional groups of ZnO films, respectively. Further, the sensing ability of ZnO thin films is studied with different concentrations (50–250 ppm) of NO2 gas in the span of 50 ppm by recording the resistance transient. The ZnO:30 thin‐film displays an enhanced gas sensing response of 1.42 GΩ at 100 °C compared to other synthesized films and at different temperature ranges. The ZnO:30 film shows the highly selective response toward the NO2 gas compared to other interference gas species. Thus, the present study highly recommends the investigated method for the ZnO thin film formation to be employed toward NO2 gas sensing.

Structure and Electrical Properties of Zirconium-Aluminum-Oxide Films Engineered by Atomic Layer Deposition

Thin films containing either multilayer ZrO2:Al2O3 structures or ZrO2 deposited on ZrxAlyOz buffer layers were characterized. The films were grown by atomic layer deposition (ALD) at 300 °C from ZrCl4, Al(CH3)3, and H2O. The multilayer ZrO2:Al2O3 structures were grown repeating different combinations of ZrO2 and Al2O3 ALD cycles while the ZrxAlyOz layers were obtained in a novel process using ALD cycles based on successive adsorption of ZrCl4 and Al(CH3)3, followed by surface reaction with H2O. The films were grown on TiN electrodes, and supplied with Ti top electrodes, whereby ZrxAlyOz films were exploited as thin buffer layers between TiN and ZrO2. The as-deposited ZrO2 films and ZrO2:Al2O3 structures with sufficiently low concentrations of Al2O3 were crystallized in the form of cubic or tetragonal ZrO2 polymorph possessing relative permittivities reaching 35. Notably, multilayered ZrO2:Al2O3 films could exhibit resistive switching behavior with ratios between low- and high-resistive-state current values, extending up to five orders of magnitude. Implications of multilevel switching were recorded. In the double-layered ZrxAlyOz-ZrO2 stacks, the ON/OFF current ratios remained below 40, but the endurance could become extended over 3000 cycles. Remarkably, instabilities, when detected in endurance behavior expressed by reduction in an ON/OFF current ratio could be compensated and the current values restored by real time readjustment of the programming voltage amplitude.

Synergistic effects of graphene oxide grafted chitosan & decorated MnO2 nanorods composite materials application in efficient removal of toxic industrial dyes

In this study, we designed a heterogeneous graphene oxide (GO) grafted on chitosan decorated with MnO2 nanorods (α-MnO2NRs/GO-Chit) composite materials and its ability to remove the cationic and anionic toxic dyes from wastewaters were analysed. The synthesised materials presented an effective stabilization of active MnO2 nanorods (NRs) on the GO-Chit surface. The synthesised materials were detailed characterised by several spectroscopic and microscopic techniques such as, FT-IR, P-XRD, SEM, TEM, Raman, TGA, XPS, BET, CO2-TPD and UV–Visible analysis. In addition, α-MnO2NRs/GO-Chit material is successfully applied in removal of industrial ionic dyes such as amido black 10B (AB) and methylene blue (MB), respectively. The dye adsorption experiments confirmed that the GO-Chit/α-MnO2 NRs material exhibited remarkably high adsorption capacity in efficient removal of cationic dye methylene blue (MB) and anionic dye amido black 10B (AB). The maximum MB dye removal (97%) process completed in 24 min at C0 = 30 mg·L−1, but in the case of AB the maximum dye removal (80%) process was reached in 700 min. Over GO-Chit/α-MnO2 NRs hybrid material, a maximum theoretical monolayer adsorption (qmax values is 328.9 mg g−1) of MB was calculated from the Langmuir isotherm equation. In case MB, a faster adsorption and 2.18 times maximum adsorption capacity was achieved than that of AB10 dye. The enhanced adsorption over α-MnO2NRs/GO-Chit is due to the increased surface functionalities (i.e., oxygen-containing groups), high basicity and strong electrostatic forces between MnO2 nanorods and GO-Chit. Furthermore, α-MnO2NRs/GO-Chit hybrid material displayed good stability after 10 successive adsorption tests.

Defect-mediated successive ionic layer adsorption and reaction for constructing Sb2Te3/Ag2S heterojunction to boost hydrogen evolution reaction performance

As a sustainable and green technology for producing high-purity hydrogen, hydrogen evolution reaction (HER) has received extensive attention. The development of an electrocatalyst with good HER activity is the key to economic water electrolysis. Here, this work reports a defect-mediated successive ion layer adsorption and reaction method to construct Ag2S/irradiated Sb2Te3 heterojunctions with good HER activity. First, ion irradiation is used to introduce a large number of defects into Sb2Te3. The defective Sb2Te3 is continuously cyclically immersed in AgNO3 solution and Na2S solution. Ag+ and S2- ions are adsorbed on the defect sites of Sb2Te3 and deposited as Ag2S and the heterojunction of Ag2S/irradiated Sb2Te3 is obtained. By this strategy, the electrochemical active surface area of the material is increased, reduces the charge transfer resistance, and improves the hydrophilicity of the material surface, thus exhibiting good HER activity. In this work, ion irradiation is used to regulate the surface defects of materials and then to regulate the growth of heterojunction to achieve the purpose of regulating the properties of material. The heterojunction growth method controlled by defect engineering can be widely used in the preparation of heterojunction materials in other energy and environmental fields.