Peroxide Etching Research Articles

UV‐Induced Oxidation Preparation of Multi‐Functional Lignin‐Based AgNPs and its Application for Conductive Coating, Antibacterial Enhancement, and Product Separation

AbstractThis study presents a novel approach for regulating the properties of lignin‐based silver nanoparticles (AgNPs), which was UV‐induced Tetrahydrofuran (THF) to form peroxide for the etching of these nanoparticles. The lignin coating was first degraded by oxidation, and the properties of the exposed AgNPs changed under etching. Notably, water can greatly regulate the oxidation capacity of the THF medium, thereby controlling the degradation degree of lignin coating and obtaining dissolution, aggregation, precipitation, and color‐variable phenomena of AgNPs under the synergistic effect of UV irradiation and peroxide etching. By adjusting UV irradiation time, various functional products of silver nanowires (AgNWs), color‐variable AgNPs, lignin‐based AgNPs aggregates, and composite solution of Ag particles and Ag+ were obtained. The transformation of these product properties is closely related to the oxidation capacity of H2O/THF medium. In addition, Multi‐functional Lignin‐based AgNPs show excellent application potential in conductive coating, antibacterial enhancement, and product separation, providing a promising avenue for the targeted utilization of lignin‐based AgNPs.

High-performance electromagnetic wave absorption by two-dimensional mesoporous monolayer Ti3C2Tx MXene

Transition metal carbide MXene, with its unique chemical composition, structure and sizeable particular surface area, is widely applied in wave absorption. However, the high conductivity of MXene resulted in an impedance mismatch that prevented electromagnetic waves from entering the material to achieve dissipation, and thus, tuning the intrinsic properties of pure MXene to obtain excellent electromagnetic wave absorption is still a challenge. Here, we strengthen the absorption of electromagnetic waves by generating titanium vacancies through hydrogen peroxide etching and thus forming micro-sized wrinkles with porous MXene. Porous MXene possesses an excellent microstructure and surface state, abundant porous defects, and moderate electrical conductivity, allowing it to achieve well-matched impedance, dipole polarization, and conduction loss, thus inheriting excellent electromagnetic wave absorption (EWA) properties. Therefore, the porous MXene achieves a strong absorption of − 63.31 dB and an adequate absorption bandwidth (EAB) of 6.88 GHz at a matched thickness of 2.39 mm with a fill ratio of 6 wt%.

Defective ferrocene-based metal–organic frameworks for efficient solar-powered water oxidation via the ligand competition and etching effect

Two-dimensional metal–organic frameworks are considered to be promising electrocatalytic materials due to their ultrathin lamellar structure, ultrahigh porosity and large surface area, but there are still many challenges such as the embedding of organic ligands leading to low density of active sites and poor conductivity. Herein, we synthesize two-dimensional ferrocene-based metal–organic frameworks nanosheet electrocatalysts via the one-step hydrothermal hydrogen peroxide etching method. The prepared FcNi-BDC-H2O2/NF exhibits excellent oxygen evolution reaction performance with a current density of 100 mA·cm-2 at only 258 mV and a small driving potential of 1.542 V (10 mA·cm-2) is required to achieve overall water splitting. Significantly, an overall water-cracked cell using a solar cell assembly achieves the solar hydrogen conversion efficiency of 19.5%. The introduction of high electronegativity ferrocene and the etching of H2O2 increase the Ni3+ content of FcNi-BDC-H2O2, and expose more unsaturated active sites, which improve the intrinsic activity of the catalysts and the mass transfer rate during the catalytic process. Moreover, the FcNi-BDC-H2O2/NF demonstrates significant urea oxidation reaction performance, achieving a potential of 1.35 V and producing 10 mA·cm-2. This study presents a viable approach to investigating highly efficient electrocatalysts for oxygen evolution reaction and urea oxidation reaction using MOF-based bifunctional catalysts.

Amorphous nickel oxide electrodes with high-current-density electrocatalytic performance for hydrogen evolution

The widespread use of unsustainable fossil fuels has caused serious damage to the ecological environment. The development of sustainable clean energy is urgent. Producing hydrogen by water electrolysis can effectively solve fossil energy shortage and environmental pollution issues. The preparation of inexpensive, efficient, and stable electrocatalytic hydrogen evolution electrode materials is the key to achieving the application of electrocatalytic hydrogen evolution. Herein, the amorphous nickel oxide/nickel foam (NiOx/NF) hydrogen evolution electrode was prepared by a simple one-step hydrothermal method with hydrogen peroxide as an oxidant. The amorphous leaf array structure of NiOx/NF electrode can enrich the surface composition and expose more catalytic active sites. Further, hydrogen peroxide etching can optimize the electronic structure of NiOx, and accelerate the electron migration. Thus, NiOx/NF displays excellent alkaline hydrogen evolution activity with the low over potentials of 70, 318 and 361 mV at 10, 500 and 1000 mA cm−2, respectively, leading to high performance in alkaline HER than those of reported Ni-based electrodes and even surpasses commercial Pt/C at high current density. Our work provides a new approach for developing inexpensive electrocatalysts with excellent alkaline hydrogen evolution activity and stability.

Modified Surface Composition and Biocompatibility of Core-Shell Nitinol Nanoparticles Fabricated via Laser Ablation of Differently Passivized Targets

Nitinol is a versatile alloy known for its shape memory effect and thus finds multiple applications in biomedical devices and implants. The biomedical applications of nitinol-based devices are, however, limited because of concerns related to leaching and its associated cytotoxicity. In particular, nitinol nanoparticles (NPs), despite being highly promising for biomedical applications such as nano-actuators and biomolecular delivery agents are not explored, owing to the same concerns. Moreover, nitinol nanoparticles and their biological interactions are not fully characterized, and the available literature on their toxicity portrays a divided picture. Surface passivation of nitinol using multiple methods has been explored in the past to reduce the leaching of nickel in implants while also improving the thrombogenic properties. In this work, we reported the preparation of passivized nitinol NPs by laser ablation of nitinol targets, followed by different surface treatments. The effect of different treatments in reducing nickel leaching and its influence on biocompatibility were studied. The biocompatibility and multi-faceted interaction of nitinol NPs with osteoblast cells and associated toxicity were explored. Homogenous nitinol NPs were found to be generated at 25 W of laser power. Also, surface modification using hydrogen peroxide, anodization, and acid etching was found to be effective in waning the nickel leaching and improving biocompatibility. In view of the observed results of cellular interactions, we discussed the possible routes of cellular toxicity of these NPs. The prospective applications of such passivized NPs in the biomedical field are also discussed in this work.

Exploration of Sulfur-Containing Nanoparticles: Synthesis, Microstructure Analysis, and Sensing Potential.

In this work, three different sulfur sources such as sulfur powder, sodium sulfide, and sodium thiosulfate are selected to prepare sulfur-derived quantum dots (S-QDs), Na2S-derived nanoparticles (NS-NPs), and Na2S2O3--derived QDs (NSO-QDs) in the presence of NaOH or assisted by hydrogen peroxide etching. The low sulfur percentage in the above three samples and the synthesis experiments in the presence of nitrogen/oxygen all support that poly(ethylene glycol) (PEG) plays an important role during the assembly process and the definition of sulfur dots is not accurate. For photophysical features, remarkable green quantum dots (S-QDs) possess an excitation-independent emission peak at 500 nm. But NS-NPs and NSO-QDs demonstrate observable shift tendency, and the evolution of emission profiles varies from 480 to 586 nm. NSO-QDs can be used as a fluorescent probe for highly selective and quantitative detection of Ni2+ in an aqueous solution in the presence of potential interfering ions with a low detection limit (0.18 μM) and a wide linear range (8-380 μM). Their reusability performance has also been demonstrated by employing dimethylglyoxime as the restoration reagent.

Scalable nanomanufacturing of holey graphene via chemical etching: an investigation into process mechanisms.

Graphene with in-plane nanoholes, named holey graphene, shows great potential in electrochemical applications due to its fast mass transport and improved electrochemical activity. Scalable nanomanufacturing of holey graphene is generally based on chemical etching using hydrogen peroxide to form through-the-thickness nanoholes on the basal plane of graphene. In this study, we probe into the fundamental mechanisms of nanohole formation under peroxide etching via an integrated experimental and computational effort. The research results show that the growth of nanoholes during the etching of graphene oxide is achieved by a three-stage reduction-oxidation-reduction procedure. First, it is demonstrated that vacancy defects are formed via a partial reduction-based pretreatment. Second, hydrogen peroxide reacts preferentially with the edge-sites of defect areas on graphene oxide sheets, leading to the formation of various oxygen-containing functional groups. Third, the carbon atoms around the defects are removed along with the neighboring carbon atoms via reduction. By advancing the understanding of process mechanisms, we further demonstrate an improved nanomanufacturing strategy, in which graphene oxide with a high density of defects is introduced for peroxide etching, leading to enhanced nanohole formation.

The controllable porous structure and s-doping of hollow carbon sphere synergistically act on the microwave attenuation

Currently, the development of high-efficiency electromagnetic wave (EMW) absorbing materials has received close attention. Due to unique composition and structure, porous hollow carbon spheres (PHCSs) have been extensively studied in the EMW absorption field. In order to obtain the regulated EMW absorber, in the present study, sulfur was successfully doped into the PHCS by hydrogen peroxide etching and high temperature vulcanization. By fixing the amount of sulfur doped and the etching time, the micro-structure of the product could be effectively controlled, and the corresponding electromagnetic parameters would also change accordingly. The optimized sulfur-doped porous hollow carbon sphere (SPCHS) had the minimum reflection loss (RL) value of −27.2 dB, and the effective bandwidth of 4.76 GHz. More importantly, the best effective bandwidth (EAB, RL < −10 dB) could reach 6.72 GHz (11.28–18 GHz) at the thickness of 2.25 mm. It should be pointed out that the sample filling ratio was only 5 wt% in the paraffin matrix. In addition, when the incidence θ reached −60°, the maximum reduction of radar cross section (RCS) was −21.9 dB m2. The convenient and efficient RCS simulation provided reliable support for the practical application of SPHCS materials in the field of EMW absorption.

Hierarchical N-doped holey three-dimensional reduced graphene oxide with high performance capacitive deionization

In this study, a novel three-dimensional reduced graphene oxide (NHGH-0.2) was synthesized via one-step hydrothermal treatment based on nitrogen doped and hydrogen peroxide etching. The preparation of NHGH-0.2 showed a hierarchical holey structure with high specific surface area of 874.9 m2/g, resulted from the synergistic effect of the N-doped and chemical etching. Electrochemical analysis showed ultrahigh specific capacitance of 303.1 F/g at a current density of 1 A/g and low charge transfer resistance, due to the excellent wettability and conductivity, which was help for rapidly diffuse and transfer of ions on the electrode surface. Capacitance was still maintained at 92.8% by the cycling stability test after 1000 charge–discharge cycles. The desalination performance applied for capacitive deionization (CDI) displayed the salt adsorption capacitive as high as 22.14 mg/g at the voltage of 1.6 V in the initial concentration of 500 mg/L NaCl solution. Therefore, the NHGH-0.2 electrode could be a promising CDI material for water treatment.

Boosted anodic electrochemiluminescence from blue-emissive sulfur quantum dots and its bioanalysis of glutathione

Herein, a facile top-down approach and a post-synthetic etching strategy were reported to prepare high-quality sulfur quantum dots (H-SQDs), which were first discovered with a boosted anodic electrochemiluminescence (ECL) emission in an aqueous solution. Elaborate investigations demonstrated that the significantly improved ECL properties of H-SQDs were attributed to the reduced size for inherent brightness, the highly passivated surface, and enhanced charge injection/transfer capacities after the post-synthetic hydrogen peroxide etching. The underlying anodic ECL mechanism and the redox nature of H-SQDs were studied in detail for the first time, indicating a direct oxidation ECL mechanism with tri-n-propylamine as the “oxidation-reduction” coreactant. Beyond that, the as-obtained H-SQDs also featured low cost, remarkable monodispersity, excellent water-solubility, and good biocompatibility, illustrating their great potential in ECL bioanalysis. As a proof-of-concept, H-SQDs, an emerging ECL emitter with high ECL efficiency, was utilized to construct an “off-on” ECL biosensor for sensitive glutathione (GSH) assay. This work not only promotes the exploration of novel ECL emitters, but also provides a new perspective for the application of SQDs-based ECL biosensor in clinical diagnosis.

Effect of Different Surface Treatments on Retention of Cement-Retained, Implant-Supported Crowns

To evaluate the effect of different treatments applied to titanium implant abutment surfaces on the retention of implant-supported cement-retained crowns using resin cement. A total of 72 titanium implant abutments were divided into six groups (n = 12 each) based on the selected surface treatments: (1) untreated; (2) airborne particle abrasion; (3) hydrogen peroxide etching; (4) atmospheric plasma; (5) chemical mechanical polishing; and (6) titanium dioxide (TiO2) nano coating. After the surface treatments, scanning electron microscopy analyses and surface roughness measurements of the abutment surfaces were performed. Seventy-two metal copings were fabricated and cemented on the abutments with dual-curing resin cement. After a thermal cycling process, crown retention was measured using a universal testing machine. The experimental results were statistically evaluated with one-way analysis of variance, Tukey honest significant difference, and Tamhane's T2 tests. The highest surface roughness values were obtained with the airborne-particle abrasion group (1.44 μm), which also resulted in the highest retention values (828.5 N), followed by the hydrogen peroxide-etching group (490.7 N), the atmospheric plasma group (466.5 N), the chemical mechanical polishing group (410.8 N), and the control group (382.6 N). It was determined that airborne particle abrasion, hydrogen peroxide etching, and atmospheric plasma treatments significantly increased the crown retention and that all alternative treatments, except for TiO2 nano coating, worked better than the untreated control.

Enhanced Catalytic Oxidation of Chlorobenzene over MnO2 Grafted In Situ by Rare Earth Oxide: Surface Doping Induces Lattice Oxygen Activation

A series of highly active MnO2@REOx (RE = Gd, Sm, Ce, and La) catalysts were successfully synthesized via in situ growth on the surface of MnO2, wherein the rare earth oxides were planted on the defect sites left by hydrogen peroxide etching of the surface of MnO2. Their physicochemical performance was investigated by scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), N2 adsorption-desorption, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction with hydrogen (H2-TPR), and temperature-programmed desorption of oxygen (O2-TPD). The catalytic properties are compared through the catalytic oxidation of chlorobenzene. Among all catalysts, MnO2@GdOx showed better mobility of surface lattice oxygen and higher molar ratios of Mn4+/Mn3+ (1.10) and Oads/Olatt (0.45), which promoted the superior low-temperature catalytic activity for chlorobenzene oxidation. The long-term chlorobenzene oxidation test (18 h) at different temperatures and the experiments with a mixture of VOCs showed that the as-prepared catalyst not only possessed a high stability but also was suitable for the efficient and simultaneous removal of multicomponent VOCs (toluene, benzene, acetone, and chlorobenzene). This work also provided an idea for the further development of high-efficiency catalysts for the purification of VOCs from complex atmosphere environment.

Colorimetric immunoassay for rapid detection of Staphylococcus aureus based on etching-enhanced peroxidase-like catalytic activity of gold nanoparticles.

A novel colorimetric immunoassay for the detection of Staphylococcus aureus (S. aureus) based on a combination of immunomagnetic separation and signal amplification via etching-enhanced peroxidase-like catalytic activity of gold nanoparticles (AuNPs) was developed. Nanoconjugates composed of gold and iron oxide nanoparticles were synthesized and further modified with antiS. aureus immunoglobulin Y (IgY), which was used for the selective enrichment and rapid separation of target bacteria in complex matrices. AuNPs functionalized with antiS. aureus aptamer were used as an artificial enzyme which has peroxidase-like catalysis activity. Catalytic activity of AuNPs is inhibited by modifying aptamer. However, catalysis of modified AuNPs remarkably enhanced by hydrogen peroxide etching. Based on collecting unbound modified AuNPs in thesupernatant and 3,3',5,5'-tetramethylbenzidine-hydrogen peroxide reporting system, the yellow color of solution decreases linearly with increasing the concentration of S. aureus ranging from 10 to 106cfu/mL. The limit of detection is 10cfu/mL, and total detection time is 65min. The recoveries of the S. aureus spiked in food samples are 88.2-119.8%. Schematic illustration of colorimetric method for detection of S. aureus based on the IgY-Fe3O4/Au nanocomposites as capture probes and apt-AuNPs as artificial enzyme with etching-enhanced peroxidase-like catalytic activity.

Tuning of hydrogen peroxide etching during the synthesis of silver nanoparticles. An application of triangular nanoplates as plasmon sensors for Hg2+ in aqueous solution

Abstract A simple method to prepare silver nanoparticles (AgNPs) with different shapes and dimensions was optimized by using a one-step reduction method with NaBH4, TSC and PVP, with H2O2 acting as an oxidation agent, to etch the nanoparticles and produce different morphologies. A series of AgNPs were obtained with different colours, including yellow to green and passing through orange, red, violet and blue, that exhibited different localized surface plasmon resonance (LSPR) as analysed by UV–visible spectroscopy. The dimensions and morphologies of the nanostructures were characterized in detail by scanning electron microscopy (SEM) and dynamic light scattering (DLS) techniques. The characterizations showed different trends in the morphologies, starting from spherical to not well-defined structures, triangular nanoplates, hexagonal nanoplates and ultimately once again showing quasi-spherical shapes. The triangular nanoplates were tested as plasmon sensors for mercury ions in aqueous solution, and they showed an LSPR-blueshift with a change in colour from blue to violet. When a calibration curve was measured in the concentration range from 0.14 to 0.5 mg l−1, the nanoparticles showed good linearity between the Hg2+ concentration in the solutions and the LSPR blueshift, with a correlation factor R2 of 0.9978 and an LOD of 0.013 mg l−1 (64.9 nM).

Etching Asymmetric Germanium Membranes with Hydrogen Peroxide for High‐Capacity Lithium‐Ion Battery Anodes

Germanium (Ge) is deemed as one of the most promising alloying anodes for rechargeable lithium‐ion batteries (LIBs) due to its large theoretical capacity, high electrical conductivity, fast lithium‐ion diffusivity, and mechanical robustness. However, Ge‐based anodes suffer from large volume changes during lithiation and delithiation, which can deteriorate their electrochemical performance rapidly. Herein, the large volume change issue is effectively addressed using an asymmetric membrane structure that is prepared using a phase‐inversion method in combination with hydrogen peroxide etching and surface coating. The asymmetric Ge membrane etched by ≈30 wt% H2O2 at 90 °C for 30 s demonstrates a capacity retention higher than 80% in 50 cycles at 160 mA g−1. Coating the H2O2‐etched Ge membrane with carbonaceous membranes can further improve the retention up to 95% in 50 cycles at 160 mA g−1, whereas ≈100% capacity of 700 mAh g−1 can be maintained in 170 cycles at 400 mA g−1. A combination of electron microscopy, spectrophotometry, and X‐ray analyses confirms the electrochemical performance of asymmetric Ge membranes as the LIB anode can be significantly affected by membrane geometry, the duration of hydrogen peroxide etching, carbonaceous membrane coating, and Ge concentration.

Increasing solar light efficiency by engineering cell structures with modified Ti foil and specific concentrations of electrolyte in liquid dye-sensitized solar cells

Out of several d-block elements, such as tungsten, zinc, cobalt, nickel, platinum, aluminum, and copper, titanium (Ti) has received more attention as a photoanode in dye-sensitized solar cells due to its high mechanical strength, flexibility, and good corrosion resistance towards common electrolytes. Charge transfer and electron injection efficiency can be modified by using anodizing oxidation technology (AOT) and applying different voltages on a Ti sheet, which modifies the thickness, color and surface structure of the Ti sheet. In this study, the variation in solar power efficiency was investigated by manufacturing solar devices with Ti sheets modified by AOT treatment followed by H2O2 etching. The investigated results show that the improved efficiency of the solar cell could be attributed to the robust and nanoporous structure of the surface layer on the Ti sheet, which was created by sequential AOT treatment and peroxide etching. Further studies have been performed to increase the efficiency of solar cells using N719 dye and changing the concentration of electrolyte under different light illumination. The maximum power conversion efficiency of 5.27% (JSC of 9.501 mA/cm2, VOC of 0.750 V with 0.741 FF) was observed using modified Ti foil and 0.00625 M iodine by applying a 60 V potential difference under 1 sun illumination.

Colorimetric probe for Ni2+ based on shape transformation of triangular silver nanoprisms upon H2O2 etching

In this article, a highly sensitive and selective colorimetric method for the detection of Ni2+ ions is presented on the basis of hydrogen peroxide etching of triangular silver nanoprisms (AgNPrs). Triangular AgNPrs were synthesized by a modified seed-mediated growth method, and upon addition of Ni2+ ions these triangular AgNPrs showed a significant colorimetric change from blue to reddish brown, and eventually yellow to as a function of the Ni2+ ion concentration. Ni2+ ion do not act as a selective etchant to triangular AgNPrs, but instead serve as a catalyst for the generation of H2O2 in a citrate-capped triangular AgNPr colloidal solution. The oxidative etching with H2O2 formed in the colloidal solution sculptured the sharp corners/edges of the triangular AgNPrs to produce circular Ag nanodisk. Selectivity tests for Ni2+ ions by the triangular AgNPr probe were performed in the presence of other various cations and anions at the optimized conditions (pH 8, 15 °C, and 30 min of reaction time). The probe showed a high linearity between absorption ratio (A475/A750) and concentration in the range of 0 to 30 μM of Ni2+, with a limit of detection of 21.6 nM in aqueous solution. The color and UV–vis absorption spectrum of the triangular AgNPr probe indicated that it is quite stable for two weeks in ambient temperature and pH ranges of 4.0˜10.0. This triangular AgNPr probe was successfully employed for the detection of Ni2+ ions in spiked tap and pond water samples.

Holey Graphene Aerogel to Support Pt Nanoparticles for Direct Methanol Fuel Cell

Direct methanol fuel cell (DMFC) has been the focus of researchers in the past decades, due to its simple structure, high energy density and easy integration [1-2]. As a device that converts chemical energy stored in methanol to electricity, the activity and stability of the catalyst applied in DMFC directly determines the output performance of the fuel cell. Until now, the low activity and high cost of catalyst are still the biggest problems that impede DMFC’s further commercialization. Pt nanoparticles, revealing the highest activity among all catalysts, are usually dispersed on carbon materials to enhance the utilization and decrease the cost [3-4]. The structure and properties of carbon support have a significant influence on the size and distribution of Pt nanoparticles, which plays a key role in the activity and stability of the catalysts. Here in this work, holey graphene aerogel was utilized to support Pt nanoparticles as the catalyst for DMFC. The three-dimensional porous structure of holey graphene aerogel can effectively prevent the stacking due to van der Waals forces between graphene sheets. More importantly, the large number of defects on the graphene sheet induced by hydrogen peroxide etching will anchor Pt nanoparticles, leading to smaller sizes and more uniform distribution. Graphene oxide (GO) was obtained via a modified Hummers’ method [5]. 50 ml GO aqueous solution was heated to 100 °C, after which 30% H2O2 solution was added [6]. The mixture was kept stirring for certain time and then cooled down. After the removal of excess H2O2, the etched graphene oxide was mixed with L-ascorbic acid in a glass vial and kept at 40°C for 6h. The obtained hydrogel was then dialyzed and freeze-dried to form the aerogel, on which Pt nanoparticles were later dispersed via a typical microwave-assisted process [7]. The catalysts with 0.5h and 1h etching time were recorded as 0.5h Pt / HGA and 1h Pt / HGA, while the non-etched sample was denoted as 0h Pt / GA for comparison. Transmission electron microscopy (TEM) and high-resolution transmission electron microscope (HRTEM) were performed for surface morphology using FEI Tecnai G2F30. Cyclic voltammetry (CV) was conducted at 0.05Vs-1 by using a three-electrode cell with a Hg/Hg2SO4 reference electrode in the solution of 0.5M H2SO4 mixed with or without 0.5M methanol, in order to estimate the electrochemical surface area (ESA) and electrocatalytic activity of the catalysts. Fig.1 shows the TEM (a) and HRTEM (b) images of 0.5h Pt / HGA. It can be seen that Pt nanoparticles with average size smaller than 2nm were dispersed uniformly on graphene sheets. Fig.2 demonstrates CV curves of three samples in 0.5M H2SO4. The ESA is calculated with columbic charges accumulated during hydrogen adsorption and desorption. The values of ESAs for three samples are 55.12 m2 g-1, 88.35 m2 g-1, 69.57 m2 g-1respectively. Among them, 0.5h Pt / HGA exhibits the largest ESA, followed by 1h Pt / HGA and 0h Pt / GA. For 0.5h Pt / HGA, the etching process increases the defects on graphene sheets, which contributes to the anchoring of Pt nanoparticles. The better dispersion and smaller sizes of Pt nanoparticles lead to the increased electrochemical active sites, thus a larger ESA. For 1 h Pt /HGA, due to the longer etching time, the scale of graphene oxide layer becomes smaller, resulting in a loss of specific surface area during the gel formation and the decline of ESA. All three catalysts show much larger ESAs than the commercial Pt/C catalyst with the value of 43 m2g-1. Fig.3 shows CV curves of three catalysts for methanol oxidation. All curves have two oxidation peaks. One located at 0.2V in the positive scanning direction is for methanol oxidation and the other located at 0V in the negative direction is for the oxidation of intermediate products. It is obvious that 0.5h Pt / HGA reveals the highest catalytic activity for methanol oxidation, followed by the 1h sample. This result is consistent with the ESA results. In addition, the onset potentials of three catalysts shifted negatively as the etching time extended, indicating that methanol oxidation is more likely to occur. In conclusion, holey graphene aerogel supported Pt nanoparticles reveals higher electrocatalytic activity for direct methanol fuel cell. References Applied Energy, 2011, 88 (5): 1681-1689.Journal of Power Sources, 2016,306 :49-61.Applied Catalysis B: Environmental 2017; 204: 173-184.Carbon, 2016, 87 (C): 424-433.Journal of the American Chemical Society, 1958, 80:1339.Science, 2017, 356 :599-604.Journal of Power Sources, 2010, 195: 1799-1804. Figure 1

DISINFEKSI UNTUK PROSES PENGOLAHAN AIR MINUM

Water disinfection means the removal, deactivation or killing of pathogenic microorganisms. Microorganisms are destroyed or deactivated, resulting in termination of growth and reproduction. When microorganisms are not removed from drinking water, drinking water usage will cause people to fall ill. Chemical inactivation of microbiological contamination in natural or untreated water is usually one of the final steps to reduce pathogenic microorganisms in drinking water. Combinations of water purification steps (oxidation, coagulation, settling, disinfection, and filtration) cause (drinking) water to be safe after production. As an extra measure many countries apply a second disinfection step at the end of the water purification process, in order to protect the water from microbiological contamination in the water distribution system. Usually one uses a different kind of disinfectant from the one earlier in the process, during this disinfection process. The secondary disinfection makes sure that bacteria will not multiply in the water during distribution. This paper describes several technique of disinfection process for drinking water treatment. Disinfection can be attained by means of physical or chemical disinfectants. The agents also remove organic contaminants from water, which serve as nutrients or shelters for microorganisms. Disinfectants should not only kill microorganisms. Disinfectants must also have a residual effect, which means that they remain active in the water after disinfection. For chemical disinfection of water the following disinfectants can be used such as Chlorine (Cl2), Hypo chlorite (OCl-), Chloramines, Chlorine dioxide (ClO2), Ozone (O3), Hydrogen peroxide etch. For physical disinfection of water the following disinfectants can be used is Ultraviolet light (UV). Every technique has its specific advantages and and disadvantages its own application area sucs as environmentally friendly, disinfection byproducts, effectivity, investment, operational costs etc. Kata Kunci : Disinfeksi, bakteria, virus, air minum, khlor, hip khlorit, khloramine, khlor dioksida, ozon, UV.

Optical and photocatalytic properties of TiO2 nanoplumes.

Here we report the photocatalytic efficiency of hydrogenated TiO2 nanoplumes studied by measuring dye degradation in water. Nanoplumes were synthesized by peroxide etching of Ti films with different thicknesses. Structural characterization was carried out by scanning electron microscopy and transmission electron microscopy. We investigated in detail the optical properties of the synthesized material and related them to the efficiency of UV photodegradation of methylene blue dye. The obtained results show that TiO2 nanoplumes act as an effective antireflective layer increasing the UV photocatalytic yield of the film.