When operated at a high current density of 64.6
Ag
−1, low-cost, high-rate supercapacitors, featuring hollow cobalt sulfide nanosheets, exhibited a high specific capacitance (326
F
g
−1), a long ...cycle life (over 10,000 cycles), high energy deliverable efficiencies (81–85%), a high energy density (13.2
Wh
kg
−1), and a high power density (17.5
kW
kg
−1) within a discharge time of 3
s. The CoS HNS SCs having high mass loading (9.7
mg
cm
−2) provided high per-area capacitance of 1.35
F
cm
−2.
Display omitted
► Hollow CoS hexagonal nanosheets are prepared for use in supercapacitors. ► With fast charging and discharging rates (<3
s), the CoS nanosheets show characteristics of high-rate supercapacitors. ► The CoS supercapacitors having high mass loading (9.7
mg
cm
−2) provide high per-area capacitance of 1.35
F
cm
−2.
We have prepared hollow cobalt sulfide (CoS) hexagonal nanosheets (HNSs) from Co(NO
3)
2 and thioacetamide in the presence of poly(vinylpyrrolidone) (PVP) at 100
°C under alkaline condition. The as-prepared hollow CoS HNSs have an average edge length ca. 110
±
27
nm and an outer shell of 16
±
4
nm in thickness from 500 counts. The CoS HNSs are deposited onto transparent fluorine-doped tin oxide (FTO) substrates through a drop-dry process to prepare two types of supercapacitors (SCs); high rate and large per-area capacitance. The electrolyte used in this study is KOH
(aq). The CoS HNSs (8
μg
cm
−2) electrodes exhibit excellent capacity properties, including high energy density (13.2
h
kg
−1), power density (17.5
kW
kg
−1), energy deliverable efficiency (81.3–85.3%), and stable cycle life (over 10,000 cycles) at a high discharge current density of 64.6
A
g
−1. With their fast charging and discharging rates (<3
s), the CoS HNSs show characteristics of high-rate SCs. The CoS HNS SCs having high mass loading (9.7
mg
cm
−2) provide high per-area capacitance of 1.35
F
cm
−2 and per-mass capacitance of 138
F
g
−1, respectively, showing characteristics of SCs with large per-area capacitance. Our results have demonstrated the potential of the CoS HNS electrodes hold great practical potential in many fields such as automobile and computer industries.
We have prepared carbon nanotube (CNT)/cobalt sulfide (CoS) composites from cobalt nitrate, thioacetamide, and CNTs in the presence of poly(vinylpyrrolidone). CNT/CoS composites are deposited onto ...fluorine-doped tin oxide glass substrates and then subjected to simple annealing at 300 °C for 0.5 h to fabricate CNT/CoS electrodes. Data collected from Raman spectroscopy, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, and d-spacing reveal the changes in the CoS structures and crystalline lattices after annealing. Cyclic voltammetry results reveal that the annealed CNT/CoS composite electrodes yield values of 2140 ± 90 and 1370 ± 50 F g−1 for specific capacitance at scan rates of 10 and 100 mV s−1, respectively. To the best of our knowledge, the annealed CNT/CoS composite electrodes provide higher specific capacitance relative to other reported ones at a scan rate of 100 mV s−1. CNT/CoS composite electrodes yield a power density of 62.4 kW kg−1 at a constant discharge current density of 217.4 A g−1. With such a high-rate capacity and power density, CNT/CoS composite supercapacitors demonstrate great potential as efficient energy storage devices.
Display omitted
► The annealed CNT/CoS composites provide 2140 ± 90 F g−1 for specific capacitance. ► CNT/CoS composites yield high-power density at a current density of 217.4 A g−1. ► CNT/CoS supercapacitors demonstrate great potential as energy storage devices.
Quenching upon aggregation: 11‐Mercaptoundecanoic acid (11‐MUA)‐protected Au nanoparticles (11‐MUA‐AuNPs) are much more stable and fluoresce much more strongly than the corresponding unmodified ...AuNPs. After addition of 2,6‐pyridinedicarboxylic acid, the 11‐MUA‐AuNPs bind to HgII with both high sensitivity and selectivity.
We have fabricated quantum dot solar cells (QDSSCs) incorporating CdHgTe nanocrystals (NCs) and CdTe quantum dots (QDs), which we prepared separately from aqueous mixtures of NaHTe, Cd(NO
3)
2, and ...3-mercaptopropionic acid in the presence and absence of HgCl
2, respectively. After depositing the CdHgTe NCs and CdTe QDs onto TiO
2 electrodes coated with poly(dimethyldiallylammonium chloride), stabilized through electrostatic interactions, we obtained (CdHgTe)
3 and (CdHgTe)
3-(CdTe)
2 QDSSCs having energy conversion efficiencies of 1.0% and 2.2%, respectively. The incident photon-to-current conversion efficiencies (IPCEs) of the (CdHgTe)
3 and (CdHgTe)
3-(CdTe)
2 QDSSCs were 12.2% and 17.5%, respectively. The higher energy conversion efficiency of the (CdHgTe)
3-(CdTe)
2 QDSSCs relative to that of the (CdTe)
3-(CdHgTe)
2 QDSSCs resulted from the greater electron transfer efficiency in the former system. The combination of CdHgTe NCs and CdTe QDs and their deposition sequence are two important factors affecting the QDSSCs’ efficiencies, which were controlled by their photocurrent densities and fill factors.
CuS, CoS, and CuS/CoS onto fluorine‐doped tin oxide glass substrates were deposited to function as counter electrodes for polysulfide redox reactions in CdS/CdSe quantum dot–sensitized solar cells ...(QDSSCs). Relative to a Pt electrode, the CuS, CoS, and CuS/CoS electrodes provide greater electrocatalytic activity, higher reflectivity, and lower charge‐transfer resistance. Measurements of fill factor and short‐current density reveal that the electrocatalytic activities, reflectivity, and internal resistance of counter electrodes play strong roles in determining the energy‐conversion efficiency (η) of the QDSSCs. Because the CuS/CoS electrode has a smaller internal resistance and higher reflectivity relative to those of the CuS and CoS electrodes, it exhibits a higher fill factor and short‐circuit current density. As a result, the QDSSC featuring a CuS/CoS electrode provides a higher value of η. Under illumination of one sun (100 mW cm−2), the QDSSCs incorporating Pt, CuS, CoS, and CuS/CoS counter electrodes provide values of η of 3.0 ± 0.1, 3.3 ± 0.3, 3.8 ± 0.2, and 4.1 ± 0.2%, respectively.
Quantum dot‐sensitized solar cells featuring CuS/CoS relative to Pt counter electrodes provide greater energy conversion efficiency (4.1 ± 0.2% vs. 3.0 ± 0.1%) and are more stable. The improved performance is attributed to the greater electrocatalytic activity, higher reflectivity, and lower charge‐transfer resistance of these electrode materials relative to platinum.
Room temperature ionic liquids (RTILs) have been used as novel solvents to replace traditional volatile organic solvents in organic synthesis, solvent extraction, and electrochemistry. The ...hydrophobic character and water immiscibility of certain ionic liquids allow their use in solvent extraction of hydrophobic compounds. In this work, a typical room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate C
4mimPF
6, was used as an alternative solvent to study liquid/liquid extraction of heavy metal ions. Dithizone was employed as a metal chelator to form neutral metal–dithizone complexes with heavy metal ions to extract metal ions from aqueous solution into C
4mimPF
6. This extraction is possible due to the high distribution ratios of the metal complexes between C
4mimPF
6 and aqueous phase. Since the distribution ratios of metal dithiozonates between C
4mimPF
6 and aqueous phase are strongly pH dependent, the extraction efficiencies of metal complexes can be manipulated by tailoring the pH value of the extraction system. Hence, the extraction, separation, and preconcentraction of heavy metal ions with the biphasic system of C
4mimPF
6 and aqueous phase can be achieved by controlling the pH value of the extraction system. Preliminary results indicate that the use of C
4mimPF
6 as an alternate solvent to replace traditional organic solvents in liquid/liquid extraction of heavy metal ions is very promising.
We have demonstrated a simple approach to the synthesis of fluorescent trigonal tellurium (t-Te) nanowires in aqueous solution at room temperature. The t-Te nanowires were prepared from the reduction ...of tellurium dioxide (TeO2) with concentrated hydrazine solution through deposition of Te atoms that were reduced from telluride ions (Te2−) and dissolved from amorphous tellurium (a-Te) nanoparticles onto t-Te nanocrystallines. By carefully controlling the growth time from 40 to 120 min, we prepared different sizes of t-Te nanowires; the length changed from 251 to 879 nm, while the diameter only grew from 8 to 19 nm. The absorption wavelength against the diameter of t-Te nanowires displays the diameter dependence of band I (<300 nm). On the other hand, the absorption wavelength against the length of t-Te nanowires displays the length dependence of band II (>600 nm). By increasing the size of t-Te nanowires, their absorption is under a red shift. For example, the maximum wavelengths of the absorption bands for the t-Te nanowires with the lengths of 251 nm are 271 and 602 nm, while those for 879 nm t-Te nanowires are at 280 and 687 nm, respectively. Deconvolution of the photoluminescence profile for t-Te nanowires obtained at 120 min yields four Gaussian peaks centered at 334, 397, 460, and 507 nm.
A facile method for the synthesis of Co
3S
4 core–shell hexagonal nanosheets (NSs) from Co(NO
3)
2 and thioacetamide under alkaline conditions in the presence of poly(vinylpyrrolidone) has been ...demonstrated. At the molar ratios of thioacetamide/Co
2+ of 0.26, 0.52, and 2.6, we prepared hollow-, semi-hollow, and non-hollow Co
3S
4 core–shell hexagonal NSs. We have found that Ostwald ripening occurring at the core/shell interface accounts for the formation of the hollow Co
3S
4 core–shell NSs, each consisting of a core of 80±30
nm in diameter and a shell of 25±5
nm in thickness. Three CdZnSSe nanostructure-sensitized solar cells incorporating Co
3S
4 NSs provide an average power conversion efficiency of 3.7±0.1%, showing high electrocatalytic activity of the Co
3S
4 NSs toward polysulfide electrolyte.
Hollow, semi-hollow, and non-hollow cobalt sulfide core–shell nanosheets have been prepared as counter electrode for CdZnSSe nanostructure-sensitized solar cells (NSSCs). The NSSCs featuring the cobalt sulfide hexagonal nanosheets all provide power conversion efficiencies greater than 3.6%.
Display omitted .
► Co
3S
4 core–shell hexagonal nanosheets (NSs) are synthesized through a hydrothermal process. ► The as-prepared hollow Co
3S
4 core–shell NSs are then used to fabricate stable and efficient counter electrodes in CdZnSSe nanostructure-sensitized solar cells (NSSCs). ► CdZnSSe NSSCs incorporating Co
3S
4 NSs provide an average power conversion efficiency of 3.7±0.1%.
The water-immiscible ionic liquid, C4MIMPF6, is a solvent medium that allows complete transfer of gold nanoparticles from an aqueous phase into an organic phase. Both spherical and rod-shaped gold ...nanoparticles are efficiently transferred from an aqueous solution into the organic phase without requiring the use of thiols. The sizes and shapes of the gold nanoparticles were preserved during the phase-transfer process when a surfactant was added to the ionic liquid. This process offers a simple approach for obtaining solutions of differently sized and shaped gold nanoparticles in ionic liquids.
We report a simple synthesis of Au−Ag core−shell nanorods (NRs) under alkaline conditions (pH 8.0−10.0) from silver and ascorbate ions using gold nanorods (GNRs) as the seeds. The silver ions that ...are reduced by the ascorbate ions become deposited on the surfaces of the GNRs to form differently dumbbell-shaped Au−Ag core−shell NRs and nanoparticles, depending on the pH and the concentration of silver ions. The longitudinal plasmon absorbance bands of the Au−Ag core−shell NRs are stronger and appear at shorter wavelengths than those for the original GNRs. We confirmed the formation of Au−Ag core−shell NRs by both energy-dispersive X-ray spectrometry and inductively coupled plasma mass spectrometry measurements, which indicate that the 109Ag/197Au ratios are 0.046, 0.085, and 0.097 at pH 8.0, 9.0, and 10.0, respectively. The transmission electron microscopy measurements show that the Au−Ag core−shell NRs are monodispersed (>90%).
PDF
