Increasing heat dissipation requirements of small and miniature devices demands advanced cooling methods, such as application of immersion cooling via boiling heat transfer. In this study, ...functionalized copper surfaces for enhanced heat transfer are developed and evaluated. Samples are functionalized using a chemical oxidation treatment with subsequent hydrophobization of selected surfaces with a fluorinated silane. Pool boiling tests with water, water/1-butanol mixture with self-rewetting properties and a novel dielectric fluid with low GWP (Novec™ 649) are conducted to evaluate the boiling performance of individual surfaces. The results show that hydrophobized functionalized surfaces covered by microcavities with diameters between 40 nm and 2 µm exhibit increased heat transfer coefficient (HTC; enhancements up to 120%) and critical heat flux (CHF; enhancements up to 64%) values in comparison with the untreated reference surface, complemented by favorable fabrication repeatability. Positive surface stability is observed in contact with water, while both the self-rewetting fluids and Novec™ 649 gradually degrade the boiling performance and in some cases also the surface itself. The use of water/1-butanol mixtures in particular results in surface chemistry and morphology changes, as observed using SEM imaging and Raman spectroscopy. This seems to be neglected in the available literature and should be focused on in further studies.
In this study, null and one-dimensional nanoparticles and nanostructures of Ag and Ag-Cu were synthesized using polyol method. In order to prepare different nanostructures with the same synthesis ...route, thermodynamics and kinetic conditions of the system were manipulated. In the thermodynamics approach, the nanostructures with the minimum surface energy were obtained as the final product, while in kinetic approach, the nanostructures with the lower activation energy were formed. By using these appraoches, Ag and Ag-Cu spherical and cubical nanostructures were produced in the size range of 90-100 nm. Also, by manipulating the kinetic conditions of the system, silver nanowires with the diameters in the range of 100-200 nm and the length of several microns were obtained successfully. The effect of Cu ions (Cu2+) on aspect ratio of the synthesized silver nanowires by polyol method was evaluated.
Two alternative approaches to measuring the depth of nanoholes (nanopits) formed in metallic aluminum in the process of its high-voltage anodizing are proposed. The first approach consists of the ...electron microscopic study of a metallic layer section formed by cutting ions with the use of a sputtered protective platinum layer with immediate observation of an array of nanopits. The second (indirect) method consists of manufacturing copper replicas from a metallic aluminum layer with the further electrochemical measurement of the overall surface area of the copper electrode and the calculation of the height of the copper nanobristles. It is shown that both approaches lead to the same results.
This study explores the mechanical and optical properties of nanoporous copper (NPC) films dealloyed in acid and base using qualitative and quantitative measurements. Two types of NPC films (NPC 1 ...and NPC 2) were prepared by dealloying precursor films in different corrosive solutions. The films were characterized using atomic force microscopy (AFM) and scattering scanning near-field optical microscopy (s-SNOM). The AFM analysis revealed distinct nanoporous structures in both films, with NPC 2 showing larger pore sizes and the presence of copper aggregations on the surface. Rugosity measures showed that NPC 2 had higher rugosity than NPC 1 and indicated fundamental differences in the height distributions of the surface nano-topography. The Minkowski connectivity analysis highlighted differences in connectedness and topological characteristics between the two samples. The analysis of the GLCM features showed clear distinctions in ASM, Contrast, Dissimilarity, Energy, and Homogeneity between NPC 1 and NPC 2. The s-SNOM results demonstrated altered optical properties, with NPC 1 showing higher contrast at 1550 nm, while NPC 2 exhibited reversed-phase contrast at 561 nm. The phase contrast at 638 nm indicated a red-shifted optical absorption peak in NPC 2 compared to NPC 1.
Precise deuterium incorporation with controllable deuterated sites is extremely desirable. Here, a facile and efficient electrocatalytic deuterodehalogenation of halides using D2O as the deuteration ...reagent and copper nanowire arrays (Cu NWAs) electrochemically formed in situ as the cathode was demonstrated. A cross‐coupling of carbon and deuterium free radicals might be involved for this ipso‐selective deuteration. This method exhibited excellent chemoselectivity and high compatibility with the easily reducible functional groups (C=C, C≡C, C=O, C=N, C≡N). The C−H to C−D transformations were achieved with high yields and deuterium ratios through a one‐pot halogenation–deuterodehalogenation process. Efficient deuteration of less‐active bromide substrates, specific deuterium incorporation into top‐selling pharmaceuticals, and oxidant‐free paired anodic synthesis of high‐value chemicals with low energy input highlighted the potential practicality.
Cu nanowire arrays formed in situ are efficient catalysts for controllable deuteration of halides using D2O as a cheap and safe deuterated donor. A cross‐coupling of carbon and deuterium free radicals might be involved in this reaction. High compatibility with easily reducible functional groups, one‐pot C−H to C−D transformation, and paired synthesis of valuable chemicals at both electrodes showed the potential utility.
We report on the template electrodeposition of different copper/copper oxide nanoparticles on pencil graphite lead substrate using ionic and neutral surfactant templates. Physical structure and ...electrochemical properties of the modified electrodes were shown to be influenced by the nature of surfactant template. These copper modified pencil graphite electrodes exhibited very good catalytic activity towards hydrogen peroxide reduction reaction, which could be used for the sensitive and selective detection of H2O2. A maximum sensitivity of ca. 158 µA/mM/cm2, lower limit of detection (LOD) of 0.35 ± 0.04 µM, response time of <2 seconds and a linearity in wide range of concentration from 1 µM to 13 mM were observed. These electrodes were highly selective towards hydrogen peroxide with little interference from glucose, fructose, ascorbic acid, dopamine, uric acid, urea, chlorides, nitrates and sulphates even at 100 fold higher concentrations of the interfering species compared to H2O2 concentration. Practical feasibility of the sensor was demonstrated by detecting H2O2 in human blood serum and milk samples with good recovery. Our methodology enables one to prepare the electrode within two minutes and to complete the analysis within another 60 seconds, enabling the quantitative detection of hydrogen peroxide in less than five minutes using a freshly prepared, cost-effective electrode without any complicated procedure.
Nanocrystalline copper nanoparticles with varying morphology, nanocubes (∼50 nm), nanorods (diameter of ∼3 nm and length of ∼50 nm) and nanospheres (5 nm) have been synthesized using the ...microemulsion method and subsequent treatment at 400 °C in hydrogen atmosphere. The role of concentration in the self-assembly of nanoparticles in varying dimensionality has been brought out in this study. Copper nanoparticles are known to be efficient electro-catalysts for a variety of reactions. In addition, the ability of copper catalyst to generate hydrogen and oxygen in electrochemical reactions provided the impetus to understand size and shape dependence of such electro-catalytic reactions of copper in nanocrystalline form. Cube-shaped nanoparticles show significantly high hydrogen and oxygen evolution efficiencies compared to the nanorods and spherical nanoparticles. The nanospheres show higher hydrogen and oxygen evolution efficiencies than the nanorods.
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Metallic copper nanostructures were synthesized in porous glass membranes by reduction of two-dimensional copper(II) oxide layers. The frequency and temperature dependences of the electrical ...conductivity, combined with X-ray diffraction data, evidence the fixation of a 2D copper layer on the walls of the through channels of the support. The possibility of formation of planar metallic structures depends on the degree of surface coverage by the oxide precursor. The amount of copper resulting from copper oxide reduction in porous glass determines its resistance to oxidation in air.
We report on the facile electrodeposition of copper nanostructures on graphite lead substrate using anionic, cationic and non-ionic surfactant templates. Physical and electrochemical characterisation ...confirmed the influence of templates on the morphology and electrochemical catalytic activities of the copper electrodeposits. These electrodes were shown to be excellent electrocatalyst for the fast detection of hydrogen peroxide. A maximum sensitivity of 951.45μA/mM/cm2, LOD of 0.43μM, response time of <1s and a linearity in wide range of concentration from 1μM to 5mM were observed when sodium dodecyl sulfate was used as the template. While most of the previously reported sensors have advantages either on the facile synthesis or fast detection of analyte, our methodology enables preparation of the electrode within 120s and analysis within another 60s without any complicated procedure, thereby demonstrating one of the fastest and cost-effective method for hydrogen peroxide analysis with high sensitivity and selectivity.
•A facile method for the preparation of copper nanostructures is provided using template electrodeposition.•The proposed electrochemical H2O2 sensor need <5 minutes for preparation-cum-analysis, demonstrating an ultra fast method.•The sensor exhibits very high sensitivity of 951.45 μA/mM/cm2 and excellent responce time of less than 1s.•Sensor performance was evaluated in PBS and the practical application was demonstrated in human blood serum and milk samples.
Copper nanostructures were synthesized using (KI)
x
(CuI)
1−
x
films under a direct current electric field (DCEF) treatment. The influence of the reaction temperature and the molar ratio between KI ...and CuI on the morphology and the diameter of the product were investigated. It was found that when the molar ratio was 0.05:0.95, single-crystalline copper nanowires with a face-centered cubic (fcc) structure were synthesized, and the diameter of the nanowires increased with the increasing reaction temperature. When the molar ratio increased to 0.3:0.7 and 0.35:0.65, copper nanorods and nanoparticles were obtained, respectively.
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