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Volumetric solar steam generation has attracted substantial interest due to its low cost, minimum carbon footprint and wide application in many areas including clean water production, desalination, and wastewater treatment. However, the efficiency of volumetric solar evaporation is still low and there is an urgent need to investigate the fundamental of the limitation of low efficiency and find a new strategy to improve the solar evaporation efficiency. In the current work, antimony doped tin oxide@carbon (ATO@C) nanofluids were prepared by a hydrothermal approach. The ATO@C nanofluids exhibit broad-band and high absorption in the solar spectrum due to the complementary effect of C (in visible region) and ATO (in the near infrared region). ATO@C nanofluids of 0.3 wt% could harvest 99.9% of the incident solar energy within 1 cm penetration distance. The photothermal conversion efficiency is 97.8%. The coupling relationship between the solar harvesting and the energy distribution was revealed. Increasing mass fraction and reducing thickness can localize the heat in the surface layer of nanofluids and thus minimize the energy consumption in heating water (internal energy) and therefore improve the solar evaporation efficiency. A high evaporation efficiency of 88.6% was achieved in this way.

Nanofluids are promising in solar harvesting and solar thermal utilization. Ethylene glycol (EG) nanofluids have the advantages of high boiling point and low volatility, and therefore are highly desired in some circumstances. In this study, the solar harvesting and solar thermal conversion properties of EG were significantly enhanced by carbon chain nanostructures (CCNSs). The prepared CCNSs/EG nanofluids showed greater optical absorption compared to EG in the wavelength range from 250[Formula: see text]nm to 1400[Formula: see text]nm. The solar weighted absorption factor (Am) of the CCNSs/EG nanofluids was 95.9% at the mass fraction of 0.05 wt.%. The enhancement was 649.2% compared to that of EG. The photothermal conversion efficiency was determined to be 97.7% and the enhancement of 83.0% was achieved. An enhancement of 1.2% in thermal conductivity was also been observed. These enhancements can be ascribed to the special architectures of the CCNSs that provide fast transfer path for the generated heat.

Steam generation by efficient utilization of solar energy is a promising strategy in seawater desalination and industrial wastewater treatment. Daikon, a cheap and scaled available crop, was chosen as raw material which was subjected to a carbonization process. The carbonized daikon possesses highly developed honeycomb cellular structure providing numerous interconnected channels. The close-packed pores act as photon traps leading to enhanced solar absorption of more than 95.5% in the visible region and more than 93.5% in the near infrared region. The excellent hydrophilic nature and the interconnected channels of the carbonized daikon provide strong capillary force for the quick transport of water. As a result, under one-sun irradiation, the carbonized daikon delivers a water evaporation rate of 1.57 kg m−2 h−1 and a solar steam efficiency of 85.9%. The carbonized daikon also shows great performance toward water evaporation from seawater and contaminated water, realizing the separation of water from pollutants and indicating its application versatility.

Passive daytime radiative cooling (PDRC) emerges as an environmentally friendly cooling strategy for its zero demand of electricity and fossil energy. In this study, PDRC coating containing polymethylmethacrylate and CaSiO3 was prepared with a simple process at low cost. The solar reflectivity, atmospheric window emissivity and radiative cooling performance of the prepared coating were investigated. The coating exhibits an average solar reflectance of 96.4% and an average atmospheric window emittance of 97.0%. Under direct solar irradiation, the coating can achieved an average sub-ambient temperature drop of 5.5 °C and an average net radiative cooling power of 72 W m−2. The results are on par with those of the efficient radiative coolers in the literature. Experimental investigation also suggests that the coating has application prospect in dew condensation and retarding the melting process of ice. This study provides a cost-efficient and commercially feasible strategy to fabricate PDRC coating.

Heterostructures are emerging as efficient optical absorbers for photothermal therapy and solar thermal applications because of their excellent photothermal properties. In the current work, AgI–Ag2S heterostructures with enhanced and broadened optical absorption properties were prepared as photothermal materials. The synthesized AgI–Ag2S heterostructures are more efficient than the corresponding AgI and Ag2S nanopartilces and exhibit stronger absorption within the spectrum from 500 nm to 1100 nm. In comparison to the solar spectrum, the aqueous suspension containing 0.03 wt% AgI–Ag2S heterostructures delivers a solar weighted absorption (Am) value of 97.7% at a penetration distance of 1 cm, which means 97.7% solar energy has been absorbed. Under the illumination of an 808 nm laser at the power of 420 mW, the photothermal efficiency of the AgI–Ag2S heterostructures is determined to be 52%. For the solar simulation experiment, the solar thermal efficiency of the suspension is evaluated to be 97%. The results of the current work provide a solid evident that heterostructures without metal nanoparticles can also have superior photothermal properties than the corresponding single component nanoparticles. It is also evident that AgI–Ag2S heterostructures have potential applications in photothermal therapy and solar energy harvesting.

Broad-band solar thermal conversion materials are highly desired for solar energy harvesting. The purpose of this work is to demonstrate a simple and straightforward strategy to engineer broad-band solar thermal conversion nanofluids. Stable two-component nanofluids containing copper (II) oxide (CuO) and antimony doped tin oxide (ATO) nanoparticles were prepared after surface modification of the CuO nanoparticles. As a reference, the CuO nanofluids have strong absorption in the visible region but not the near-infrared region. On the contrary, the ATO nanofluids have strong absorption in the near-infrared region, but the absorption in the visible region is comparatively weak. The combination of CuO and ATO nanoparticles endows the two-component nanofluids with broad-band absorption across the visible and near-infrared region. The two-component nanofluids of 0.1 vol% show an absorption spectrum match well with the solar spectrum and give a solar weighted absorption fraction of 99.6% compared to 89.5% and 89.8% for the CuO and ATO nanofluids, respectively. The solar thermal utilization efficiency of the two-component nanofluids was determined to be 92.5% compared to 81.3% and 80.7% for the CuO and ATO nanofluids, respectively. The enhanced solar thermal conversion properties of the two-component nanofluids are attributed to the complementary optical absorption of the CuO and ATO nanoparticles. This work provides a promising strategy to engineer nanofluids for solar energy harvesting.

Efficient solar evaporation requires photothermal conversion materials with broad band absorption in solar spectrum, high specific area for water evaporation, and sufficient water transport paths. In the current work, porous carbonaceous membrane consists of continuous ultrafine carbon fibers was prepared by electrospinning followed by carbonation and oxidation. The carbonaceous membrane can absorb more than 95% of incident solar energy in the range from 250 to 2500 nm. The carbonaceous membrane has hydrophilic characteristics and continuous channels for sufficient water transport. The ultrafine carbon fibers on the surface of the membrane provide tremendous interfaces for water evaporation. With localized heating design, the carbonaceous membrane delivers a water evaporation rate of 1.33 kg m−2 h−1 and a solar evaporation efficiency of 81.71%. It is also demonstrated that the carbonaceous membrane can recover fresh water from seawater, acid solutions and alkali solutions. Furthermore, the carbonaceous membrane shows the potential of electricity generation driven by solar evaporation.

Dual-functional agents for magnetic resonance imaging (MRI) guided photothermal therapy (PTT) of lymph cancer are highly desired. Signal enhancement, selectivity between lymphatic nodes/vessels and blood vessels, and photothermal conversion property are the criteria for such dual-functional agent. In the current work, we demonstrated the potential of Gd-C nanocomposites as dual-functional agents for the MRI and PTT of lymph node cancer. Gd-C nanocomposites were synthesized via a hydrothermal carbonization approach with gadolinium chloride as Gd source and citric acid (CA) as C source. The particle size of the nanocomposites ranges from 40 to 100 nm which is smaller than the intercellular space of lymphatic vessels but much larger than that of the blood vessels. The nanocomposites were successfully applied to the MRI of cervical lymph nodes of rabbits. The signal enhancement of the lymph nodes reached the maximum value of 434% at 10 min after injection, without displaying any blood vessel. The Gd-C nanocomposites also exhibited strong photothermal conversion effect. Under the illumination of an 808 nm laser, the aqueous suspension containing 1.0 wt % Gd-C nanocomposites gave a maximum temperature rise of 28.2 °C and a light utilization efficiency of 30.4%. The results indicate that Gd-C nanocomposites have significant potential in MRI guided PTT of lymph cancer.

Photothermal conversion materials have promising applications in many fields and therefore they have attracted tremendous attention. However, the multi-functionalization of a single nanostructure to meet the requirements of multiple photothermal applications is still a challenge. The difficulty is that most nanostructures have specific absoprtion band and are not flexible to different demands. In the current work, we reported the synthesis and multi-band photothermal conversion of Ag@Ag2S core@shell structures with gradually varying shell thickness. We synthesized the core@shell structures through the sulfidation of Ag nanocubes by taking the advantage of their spatially different reactivity. The resulting core@shell structures show an octopod-like mopgorlogy with a Ag2S bulge sitting at each corner of the Ag nanocubes. The thickness of the Ag2S shell gradually increases from the central surface towards the corners of the structure. The synthesized core@shell structures show a broad band absorption spectrum from 300 to 1100 nm. Enhanced photothermal conversion effect is observed under the illuminations of 635, 808, and 1064 nm lasers. The results indicate that the octopod-like Ag@Ag2S core@shell structures have characteristics of multi-band photothermal conversion. The current work might provide a guidance for the design and synthesis of multifunctional photothermal conversion materials.

Photothermal conversion materials have promising applications in many fields and therefore they have attracted tremendous attention. However, the multi-functionalization of a single nanostructure to meet the requirements of multiple photothermal applications is still a challenge. The difficulty is that most nanostructures have specific absoprtion band and are not flexible to different demands. In the current work, we reported the synthesis and multi-band photothermal conversion of Ag@Ag2S core@shell structures with gradually varying shell thickness. We synthesized the core@shell structures through the sulfidation of Ag nanocubes by taking the advantage of their spatially different reactivity. The resulting core@shell structures show an octopod-like mopgorlogy with a Ag2S bulge sitting at each corner of the Ag nanocubes. The thickness of the Ag2S shell gradually increases from the central surface towards the corners of the structure. The synthesized core@shell structures show a broad band absorption spectrum from 300 to 1100 nm. Enhanced photothermal conversion effect is observed under the illuminations of 635, 808, and 1064 nm lasers. The results indicate that the octopod-like Ag@Ag2S core@shell structures have characteristics of multi-band photothermal conversion. The current work might provide a guidance for the design and synthesis of multifunctional photothermal conversion materials.

Oil spills have devastating effects on the environment. Utilization of absorbents for oil spill cleanup has been practiced; however, the development of cheap, reliable, environmentally friendly absorbents is both desirable and urgent. In this study, we illustrate a novel oil absorbent fabricated by modifying polyurethane (PU) sponges with TiO2 sol. The attachment of TiO2 nanoparticles reduced the hydrophilicity of the modified PU sponge significantly by increasing its surface roughness and changing the chemical composition of the surface. The modified PU sponges exhibited oil absorption capacity of 95–110 g/g with negligible water uptake under both static and dynamic conditions. The modified PU sponge was found to be reusable up to 12 cycles holding 70% of its initial uptake capacity. The modified PU sponges can be effectively used in oil spill cleanup.

Hierarchical and hollow CuInS2 microspheres are synthesized on the basis of sacrificial templates with solid and hollow CuS microspheres as sacrificial templates, respectively. Transformations from CuS solid microspheres to CuInS2 hierarchical microspheres and CuS hollow microspheres to CuInS2 hollow microspheres can be achieved by a solvothermal process at 180 °C for 24 h with N,N-dimethylformamide as both solvent and reductant. The products are well characterized, and the formation mechanisms are proposed. The as-synthesized products have strong optical absorption from 1000 to 2000 nm in addition to normal absorption from 400 to 800 nm, which has not be reported in the literature. The as-synthesized products exhibit a significant photothermal conversion effect under an irradiation of a 1064 nm laser. At a laser power of 0.05 W·cm–2, up to 30% and 20% enhancement of photothermal conversion is observed in the aqueous suspension containing 0.1 wt % CuInS2 hollow microspheres and hierarchical microspheres, ...

A novel strategy allowed the synthesis of carbon and sulfur codoped TiO 2 nanospheres from multifunctional agents: Ti(SO 4 ) 2 as Ti source and sulfur donor, polyvinyl pyrrolidone (PVP) as surfactant and carbon donor. Ti(SO 4 ) 2 nanospheres precipitated in water–acetone mixed solvent. In situ doping of S to TiO 2 was achieved when Ti(SO 4 ) 2 nanospheres transformed to TiO 2 nanospheres during solvothermal process. PVP was firstly coated on the surface of the Ti(SO 4 ) 2 nanospheres and successively combined with the TiO 2 nanospheres. PVP decomposed during the calcinations and carbon was further doped to the TiO 2 nanospheres. The codoped TiO 2 nanospheres had an average diameter of 70 nm and highly porous structure. The final products exhibited significant red shift of the light absorption edge in comparison with that of the Degussa P25. These results demonstrated that doped TiO 2 can be synthesized from reactants or surfactants containing doped elements without additional dopants.

In the present work, 3D flowerlike CuS nanostructures were synthesized via a facile hydrothermal process using Cu2O hollow microspheres as templates. Reaction of Cu2O hollow microspheres with thioacetamide at 40 °C for 2 h followed by hydrothermal treatment at 120 °C for 12 h resulted in high yield of 3D flowerlike structure with diameters ranging from 200 to 300 nm. The Influence of experimental parameters on the morphology of the CuS nanostructures was investigated in detail. Different stages of the formation process were studied and thus the formation mechanism of the 3D flowerlike CuS nanostructures was presented.

In the present work, 3D flowerlike CuS nanostructures were synthesized via a facile hydrothermal process using Cu2O hollow microspheres as templates. Reaction of Cu2O hollow microspheres with thioacetamide at 40 °C for 2 h followed by hydrothermal treatment at 120 °C for 12 h resulted in high yield of 3D flowerlike structure with diameters ranging from 200 to 300 nm. The Influence of experimental parameters on the morphology of the CuS nanostructures was investigated in detail. Different stages of the formation process were studied and thus the formation mechanism of the 3D flowerlike CuS nanostructures was presented.

A novel, high-capacity oil sorbent consisting of polyvinyl chloride (PVC)/polystyrene (PS) fiber was prepared by an electrospinning process. The sorption capacity, oil/water selectivity, and sorption mechanism of the PVC/PS sorbent were studied. The results showed that the sorption capacities of the PVC/PS sorbent for motor oil, peanut oil, diesel, and ethylene glycol were 146, 119, 38, and 81 g/g, respectively. It was about 5-9 times that of a commercial polypropylene (PP) sorbent. The PVC/PS sorbent also had excellent oil/water selectivity (about 1000 times) and high buoyancy in the cleanup of oil over water. The SEM analysis indicated that voids among fibers were the key for the high capacity. The electrospun PVC/PS sorbent is a better alternative to the widely used PP sorbent for oil spill cleanup.

CaCO3 aqueous nanofluids were prepared by dispensing aqueous CaCO3 paste into distilled water under ultrasonic vibration. The actual microstructures of the CaCO3 nanofluids with different particle volume fractions were characterized by freeze etching replication transmission electron microscopy (FERTEM). Thermal conductivity and rheological behavior of the nanofluids were measured by standard analyzers. The results show that CaCO3 paste as raw material for nanofluids is advantageous to reducing aggregation of primary nanoparticles. The effective viscosities and effective thermal conductivities of the CaCO3 nanofluids are related to the aggregates of nanoparticles and can be well predicted by the modified Krieger & Dougherty formula and the modified Hamilton & Crosser model, respectively.

This paper presents a novel method for the preparation of copper nanoparticles by reducing CuSO4 with hydrazine in ethylene glycol under microwave irradiation. The influences of reaction parameters such as molar ratios of N2H4?H2O /CuSO4 and NaOH/CuSO4, heating method and reaction temperature on the particle size and composition of powder were investigated by x-ray diffractometry (XRD), transmission electron microscopy (TEM) and particle size analysis. Well-dispersed copper nanopowder with a diameter of about 15?nm was obtained in the absence of a protective polymer.

This paper presents a rapid method for preparation of copper metal nanoparticles by reducing CuSO 4 ·5H 2 O with NaH 2 PO 2 ·H 2 O in ethylene glycol under microwave irradiation. The influences of the reaction parameters, such as the concentrations of reducing agent and protective polymer time of microwave irradiation, on the size and agglomeration of copper nanoparticles were investigated by X-ray powder diffraction and transmission electron microscope. Well-dispersed copper nanoparticles with diameter of about 10 nm were obtained. The use of microwave irradiation accelerated the reaction rate and benefited the dispersion and the particle size distribution of the nanoparticles.

Manganese ferrite (MnFe2O4) hollow microspheres were synthesized through a sacrificial template approach using manganese carbonate (MnCO3) microspheres as sacrificial templates. Different from the literatures, the synthesis of MnFe2O4 hollow spheres was achieved through a one-pot hydrothermal process without subsequent calcination process. The temperature and reaction time of the hydrothermal process were set to be 180 °C and 8 h. The formation mechanism of the MnFe2O4 hollow microspheres was also investigated. Results indicate that the average diameter of the as-synthesized MnFe2O4 hollow microspheres is 1.2 μm. The shells of the hollow microspheres are composed of nanoparticles. During hydrothermal process, Mn2+ ions diffused outward and resulted in shell materials of MnFe2O4, thus MnCO3 templates were consumed and MnFe2O4 hollow microspheres were obtained.

Ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF 6 ) was mixed homogeneously with nanometer-sized semiconductor CuS sphere to form a new nanocomposite material, which was further used for the immobilization of hemoglobin (Hb) on the surface of carbon paste electrode (CPE). Direct electrochemistry of Hb in BMIMPF 6 -CuS composite film was carefully investigated with a pair of quasi-reversible redox peaks appeared and the formal potential (E 0' ) was got as -135 mV (vs. SCE) in pH 7.0 phosphate buffer solution, which was due to the enhanced direct electron transfer rate of Hb in the biocompatible matrix. The BMIMPF 6 -CuS-Hb/CPE showed excellent electrocatalytic activity to the reduction of hydrogen peroxide with the kinetic parameters for the electrocatalytic reaction evaluated. The results indicated that the BMIMPF 6 -CuS nanocomposite could be used for the preparation of electrochemical biosensor. KEY WORDS : Hemoglobin, Direct electrochemistry, Copper sulfide nanosphere, 1-Butyl-3-methylimidazolium hexafluorophosphate, Hydrogen peroxide Bull. Chem. Soc. Ethiop. 2011 , 25(3), 443-450.

In this article, a wet chemical method was developed to prepare stable CuO nanofluids. The influences of synthesis parameters, such as kinds and amounts of copper salts, reaction time, were studied. The thermal conductivities of CuO nanofluids were also investigated. The results showed that different copper salts resulted in different particle morphology. The concentration of copper acetate and reaction time affected the size and shape of clusters of primary nanoparticles. Nanofluids with different microstructures could be obtained by changing the synthesis parameters. The thermal conductivities of CuO nanofluids increased with the increase of particle loading.

Bi(2)WO(6) hollow nanospheres were prepared in a sacrificial templates approach by converting the reaction medium from aqueous solution to a mixed solvent of water and ethanol.

Preparation of stable nanofluids is the first step and key issue of nanofluid research and application. A wet chemical route for controllable synthesizing of nanofluids was developed and three kinds of nanofluids were prepared using this method. Aqueous nanofluids containing CuO nanoparticle clusters with different aggregating degree were controllably synthesized by changing the reflux reaction time. Nanofluids consisting of CuS hollow spheres with different size and shell thickness were produced. Ag nanofluids with different cluster size were manipulated as well. The synthesis mechanism for the wet chemical route was proposed.

In this article, carbon black nanofluids were prepared by dispersing the pretreated carbon black powder into distilled water. The size and morphology of the nanoparticles were explored. The photothermal properties, optical properties, rheological behaviors, and thermal conductivities of the nanofluids were also investigated. The results showed that the nanofluids of high-volume fraction had better photothermal properties. Both carbon black powder and nanofluids had good absorption in the whole wavelength ranging from 200 to 2,500 nm. The nanofluids exhibited a shear thinning behavior. The shear viscosity increased with the increasing volume fraction and decreased with the increasing temperature at the same shear rate. The thermal conductivity of carbon black nanofluids increased with the increase of volume fraction and temperature. Carbon black nanofluids had good absorption ability of solar energy and can effectively enhance the solar absorption efficiency.

Thermal conductivities of Fe3O4 aqueous nanofluids were studied. The results show that Fe3O4 nanofluids have higher thermal conductivities than other oxide aqueous nanofluids at the same volume fraction. The experimental values are higher than those predicted by the existing models. The abnormal thermal conductivities of Fe3O4 nanofluids are attributed to the observed nanoparticle clustering and alignment.