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2018 Volume 34 Issue 4
2018, 34(4): 323-324
doi: 10.3866/PKU.WHXB201709061
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2018, 34(4): 325-326
doi: 10.3866/PKU.WHXB201709113
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2018, 34(4): 327-328
doi: 10.3866/PKU.WHXB201709191
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2018, 34(4): 329-330
doi: 10.3866/PKU.WHXB201709251
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2018, 34(4): 331-332
doi: 10.3866/PKU.WHXB201709281
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2018, 34(4): 333-334
doi: 10.3866/PKU.WHXB201710171
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2018, 34(4): 335-336
doi: 10.3866/PKU.WHXB201710182
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2018, 34(4): 337-338
doi: 10.3866/PKU.WHXB201710181
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2018, 34(4): 339-343
doi: 10.3866/PKU.WHXB201709081
Abstract:
Most materials expand on heating and contract on cooling. In the recent years, however, some compounds have been found to exhibit abnormal negative thermal expansion (NTE) behavior; this presents an opportunity to adjust the coefficient of thermal expansion (CTE) of such materials. It is especially important to obtain controllable thermal expansion in isotropic compounds. Herein, we report the preparation, crystal structure, and controllable thermal expansion in double ReO3-type (Fe1-xNix)ZrF6 solid solutions. (Fe1-xNix)ZrF6 exhibits full range solubility. A controllable thermal expansion of (Fe1-xNix)ZrF6 could be achieved by the chemical substitution of Ni2+ for Fe2+ over a wide range of CTE from −3.24 × 10−6 to +18.23 × 10−6 K−1 (300–675 K). In particular, zero thermal expansion was obtained for the composition (Fe0.5Ni0.5)ZrF6. As a kind of typical framework structure, the transverse thermal vibrations of fluorine atoms are expected to play a critical role in the thermal expansion behavior of double-ReO3 compounds. This study presents a potential method to tune the thermal expansion of NTE (negative thermal expansion) families which have an open framework structure.
Most materials expand on heating and contract on cooling. In the recent years, however, some compounds have been found to exhibit abnormal negative thermal expansion (NTE) behavior; this presents an opportunity to adjust the coefficient of thermal expansion (CTE) of such materials. It is especially important to obtain controllable thermal expansion in isotropic compounds. Herein, we report the preparation, crystal structure, and controllable thermal expansion in double ReO3-type (Fe1-xNix)ZrF6 solid solutions. (Fe1-xNix)ZrF6 exhibits full range solubility. A controllable thermal expansion of (Fe1-xNix)ZrF6 could be achieved by the chemical substitution of Ni2+ for Fe2+ over a wide range of CTE from −3.24 × 10−6 to +18.23 × 10−6 K−1 (300–675 K). In particular, zero thermal expansion was obtained for the composition (Fe0.5Ni0.5)ZrF6. As a kind of typical framework structure, the transverse thermal vibrations of fluorine atoms are expected to play a critical role in the thermal expansion behavior of double-ReO3 compounds. This study presents a potential method to tune the thermal expansion of NTE (negative thermal expansion) families which have an open framework structure.
2018, 34(4): 344-347
doi: 10.3866/PKU.WHXB201709112
Abstract:
Non-fullerene organic solar cells are of broad and current interest in the field of organic solar cells, and show promising application in high performance solar cells. When designing conjugated molecules as non-fullerene materials, several parameters, such as absorption, energy levels, charge transport, and crystallinity should be considered. Among them, absorption spectra are an important parameter that determine the efficiency of sun-light harvesting. In this work, we explore a new near-infrared electron acceptor naphthalenediimide-porphyrin (NDI-Por) by using electron-donating porphyrin as the core, and four NDI as end groups with ethynyl as linkers attached to the meso-position of porphyrin. This star-shaped molecule exhibits absorption spectra up to 900 nm. NDI-Por was incorporated into non-fullerene solar cells as an electron acceptor, and together with a wide-band gap polymer donor, an initial power conversion efficiency of 1.80% could be achieved. In particular, the solar cells exhibit a broad photo-response from 300 to 900 nm. Our results demonstrate that it is an efficient strategy to incorporate porphyrin into conjugated molecules to realize non-fullerene materials with near-infrared absorption spectra.
Non-fullerene organic solar cells are of broad and current interest in the field of organic solar cells, and show promising application in high performance solar cells. When designing conjugated molecules as non-fullerene materials, several parameters, such as absorption, energy levels, charge transport, and crystallinity should be considered. Among them, absorption spectra are an important parameter that determine the efficiency of sun-light harvesting. In this work, we explore a new near-infrared electron acceptor naphthalenediimide-porphyrin (NDI-Por) by using electron-donating porphyrin as the core, and four NDI as end groups with ethynyl as linkers attached to the meso-position of porphyrin. This star-shaped molecule exhibits absorption spectra up to 900 nm. NDI-Por was incorporated into non-fullerene solar cells as an electron acceptor, and together with a wide-band gap polymer donor, an initial power conversion efficiency of 1.80% could be achieved. In particular, the solar cells exhibit a broad photo-response from 300 to 900 nm. Our results demonstrate that it is an efficient strategy to incorporate porphyrin into conjugated molecules to realize non-fullerene materials with near-infrared absorption spectra.
2018, 34(4): 348-360
doi: 10.3866/PKU.WHXB201708311
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Owing to their unique optical, electronic, magnetic, and surface plasmon resonance properties, nanomaterials have attracted significant attention for potential bioanalysis and biomedical applications. Aptamers are single-stranded oligonucleotides, which are generated by a procedure termed as SELEX (Systematic Evolution of Ligands by EXponential Enrichment) and typically demonstrate high affinity and selectivity toward their target molecules. As a result of their unique characteristics, aptamers are promising recognition units that can be conjugated with nanomaterials for cancer cell imaging, diagnosis, and cancer therapy. By integrating the recognition abilities of aptamers with the properties of nanomaterials, aptamer-conjugated nanomaterials can serve as extraordinary tools for bioimaging and cancer therapy. Recently, aptamer-conjugated nanomaterials have attracted significant attention in the field of specific cancer cell targeted therapy owing to their improved efficacy and lower toxicity. In this review, we summarize the progress achieved of aptamer-conjugated nanomaterials as nanocarriers for specific cancer cell diagnosis and targeted therapy. In addition to drug delivery for cancer therapy, the various achievements of the aptamer-conjugated nanomaterials in combination with other emerging technologies to improve the efficiency and selectivity of cancer therapy have also been reviewed.
Owing to their unique optical, electronic, magnetic, and surface plasmon resonance properties, nanomaterials have attracted significant attention for potential bioanalysis and biomedical applications. Aptamers are single-stranded oligonucleotides, which are generated by a procedure termed as SELEX (Systematic Evolution of Ligands by EXponential Enrichment) and typically demonstrate high affinity and selectivity toward their target molecules. As a result of their unique characteristics, aptamers are promising recognition units that can be conjugated with nanomaterials for cancer cell imaging, diagnosis, and cancer therapy. By integrating the recognition abilities of aptamers with the properties of nanomaterials, aptamer-conjugated nanomaterials can serve as extraordinary tools for bioimaging and cancer therapy. Recently, aptamer-conjugated nanomaterials have attracted significant attention in the field of specific cancer cell targeted therapy owing to their improved efficacy and lower toxicity. In this review, we summarize the progress achieved of aptamer-conjugated nanomaterials as nanocarriers for specific cancer cell diagnosis and targeted therapy. In addition to drug delivery for cancer therapy, the various achievements of the aptamer-conjugated nanomaterials in combination with other emerging technologies to improve the efficiency and selectivity of cancer therapy have also been reviewed.
2018, 34(4): 377-390
doi: 10.3866/PKU.WHXB201709001
Abstract:
Lithium-sulfur (Li-S) batteries are promising electrochemical energy storage systems because of their high theoretical energy density, natural abundance, and environmental benignity. However, several problems such as the insulating nature of sulfur, high solubility of polysulfides, large volume variation of the sulfur cathode, and safety concerns regarding the lithium anode hinder the commercialization of Li-S batteries. Graphene-based materials, with advantages such as high conductivity and good flexibility, have shown effectiveness in realizing Li-S batteries with high energy density and high stability. These materials can be used as the cathode matrix, separator coating layer, and anode protection layer. In this review, the recent progress of graphene-based materials used in Li-S batteries, including graphene, functionalized graphene, heteroatom-doped graphene, and graphene-based composites, has been summarized. And perspectives regarding the development trend of graphene-based materials for Li-S batteries have been discussed.
Lithium-sulfur (Li-S) batteries are promising electrochemical energy storage systems because of their high theoretical energy density, natural abundance, and environmental benignity. However, several problems such as the insulating nature of sulfur, high solubility of polysulfides, large volume variation of the sulfur cathode, and safety concerns regarding the lithium anode hinder the commercialization of Li-S batteries. Graphene-based materials, with advantages such as high conductivity and good flexibility, have shown effectiveness in realizing Li-S batteries with high energy density and high stability. These materials can be used as the cathode matrix, separator coating layer, and anode protection layer. In this review, the recent progress of graphene-based materials used in Li-S batteries, including graphene, functionalized graphene, heteroatom-doped graphene, and graphene-based composites, has been summarized. And perspectives regarding the development trend of graphene-based materials for Li-S batteries have been discussed.
2018, 34(4): 361-376
doi: 10.3866/PKU.WHXB201708312
Abstract:
The past decade has witnessed tremendous progress in the improvement of the electrocatalytic efficiency of the oxygen reduction reaction (ORR), which is important for the widespread adoption of fuel cells. This review provides an overview of the recent advances in the rational structural design and construction of Pt-based nanocatalysts to achieve higher ORR activity, with an emphasis on tuning the dimensionalities of Pt-based nanocrystals. The advantages and disadvantages of each dimensional catalyst have been discussed. In particular, we focus on a contemporary understanding of the structure-performance relationships based on the combined theoretical and experimental evidence, which can be further applied to guide the search for more exciting catalytic systems. The review concludes with a personal perspective for future research directions.
The past decade has witnessed tremendous progress in the improvement of the electrocatalytic efficiency of the oxygen reduction reaction (ORR), which is important for the widespread adoption of fuel cells. This review provides an overview of the recent advances in the rational structural design and construction of Pt-based nanocatalysts to achieve higher ORR activity, with an emphasis on tuning the dimensionalities of Pt-based nanocrystals. The advantages and disadvantages of each dimensional catalyst have been discussed. In particular, we focus on a contemporary understanding of the structure-performance relationships based on the combined theoretical and experimental evidence, which can be further applied to guide the search for more exciting catalytic systems. The review concludes with a personal perspective for future research directions.
2018, 34(4): 391-406
doi: 10.3866/PKU.WHXB201709131
Abstract:
In recent years, the development of perylene diimide derivative (PDI)-based non-fullerene organic solar cells has been extensively studied. These solar cells exhibit unique advantages such as complementary light absorption, tunable energy levels, excellent electron transport properties, and relatively low cost. However, the strong π-π stacking between the PDI molecules tends to induce an uncontrolled phase separation structure, large domain size, and an unmanageable mixed phase, leading to severe geminate and non-geminate recombination and restriction of the final power conversion efficiency of the non-fullerene-based systems. In this work, it was found that one of the most important parameters that helps regulate phase structure is the molecular diffusion rate. By tuning the thermal annealing and liquid-solid phase separation and blend ratio, the phase-separated structure could be adjusted. Further, the domain size of blend systems with different compatibilities was regulated by balancing the π-π and charge transfer interactions. In addition, the amount of the intermixed phase was controlled by tuning the solubility parameter difference (Δδ) between the solvent and the solute.
In recent years, the development of perylene diimide derivative (PDI)-based non-fullerene organic solar cells has been extensively studied. These solar cells exhibit unique advantages such as complementary light absorption, tunable energy levels, excellent electron transport properties, and relatively low cost. However, the strong π-π stacking between the PDI molecules tends to induce an uncontrolled phase separation structure, large domain size, and an unmanageable mixed phase, leading to severe geminate and non-geminate recombination and restriction of the final power conversion efficiency of the non-fullerene-based systems. In this work, it was found that one of the most important parameters that helps regulate phase structure is the molecular diffusion rate. By tuning the thermal annealing and liquid-solid phase separation and blend ratio, the phase-separated structure could be adjusted. Further, the domain size of blend systems with different compatibilities was regulated by balancing the π-π and charge transfer interactions. In addition, the amount of the intermixed phase was controlled by tuning the solubility parameter difference (Δδ) between the solvent and the solute.
2018, 34(4): 407-413
doi: 10.3866/PKU.WHXB201708175
Abstract:
As evidenced from recent literature, interest in employing information theory measures for understanding different properties of atomic and molecular systems is increasing tremendously. Following our earlier efforts in this field, we here evaluate the feasibility of using information theory functionals such as Fisher information, Shannon entropy, Onicescu information energy, and Ghosh-Berkowitz-Parr entropy as measures of steric effects for the steric analysis of water nanoclusters. Taking the structural isomers of water hexamers as working models and using information theoretic quantities, we show that the relative energies of water nanoclusters and the computed steric energies are related. We also show the strong effects of steric repulsion on conformational stabilities. At the same time, we have also assessed the usefulness of simultaneously considering the different information theoretic quantities, and achieved more accurate descriptions of the stability of water nanoclusters. In order to consider the effects of cluster size on the obtained results and the extent of applicability of information theoretic quantities, we have also benchmarked larger water nanoclusters with 32 and 64 units. Scrutinizing the obtained data from information theory functionals, we found that Fisher information shows the best overall performance. Our findings underline that the information theoretic quantities, especially Fisher information, can be used as quantitative measures of relative energies and consequently the order of stability of nanoclusters, which affirmed the utility of information theory for investigating various physical and chemical problems.
As evidenced from recent literature, interest in employing information theory measures for understanding different properties of atomic and molecular systems is increasing tremendously. Following our earlier efforts in this field, we here evaluate the feasibility of using information theory functionals such as Fisher information, Shannon entropy, Onicescu information energy, and Ghosh-Berkowitz-Parr entropy as measures of steric effects for the steric analysis of water nanoclusters. Taking the structural isomers of water hexamers as working models and using information theoretic quantities, we show that the relative energies of water nanoclusters and the computed steric energies are related. We also show the strong effects of steric repulsion on conformational stabilities. At the same time, we have also assessed the usefulness of simultaneously considering the different information theoretic quantities, and achieved more accurate descriptions of the stability of water nanoclusters. In order to consider the effects of cluster size on the obtained results and the extent of applicability of information theoretic quantities, we have also benchmarked larger water nanoclusters with 32 and 64 units. Scrutinizing the obtained data from information theory functionals, we found that Fisher information shows the best overall performance. Our findings underline that the information theoretic quantities, especially Fisher information, can be used as quantitative measures of relative energies and consequently the order of stability of nanoclusters, which affirmed the utility of information theory for investigating various physical and chemical problems.
2018, 34(4): 424-436
doi: 10.3866/PKU.WHXB201709082
Abstract:
The ultrafast photoluminescence dynamics of three organic dyes—C210, C214, and C216—with different conjugated linkers containing various heteroatoms, such as bifuran, bithiophene and biselenophene, in combination with dihexyloxy-substituted triphenylamine (TPA) as the electron donor and cyanoacrylic acid (CA) as the electron acceptor have been studied systematically. The excited-state dynamics of the three dyes were investigated in detail in different media: tetrahydrofuran (THF) and toluene (PhMe) solutions, polymethyl methacrylate (PMMA) and polystyrene (PS) polymer films, and the surfaces of alumina and titania films in contact with an ionic liquid composite electrolyte. These dyes were found to feature dynamic Stokes shifts in all the aforementioned media, indicating stepwise intramolecular relaxations of the non-equilibrium excited state. The electron injection yield was distinctly lower for the non-equilibrium excited state than the equilibrium excited states, which can be ascribed to the competition between torsional relaxation and electron injection. A broad time scale over one magnitude of order was presented for electron injection due to the great energy losses originating from the multiple torsional relaxations, which should be controlled for future dye design and device development. Moreover, despite the shorter lifetimes of the equilibrium excited states for C210 and C216 than C214, the electron injection yields of equilibrium excited states for all the dyes are comparable due to the accelerated electron injection rate.
The ultrafast photoluminescence dynamics of three organic dyes—C210, C214, and C216—with different conjugated linkers containing various heteroatoms, such as bifuran, bithiophene and biselenophene, in combination with dihexyloxy-substituted triphenylamine (TPA) as the electron donor and cyanoacrylic acid (CA) as the electron acceptor have been studied systematically. The excited-state dynamics of the three dyes were investigated in detail in different media: tetrahydrofuran (THF) and toluene (PhMe) solutions, polymethyl methacrylate (PMMA) and polystyrene (PS) polymer films, and the surfaces of alumina and titania films in contact with an ionic liquid composite electrolyte. These dyes were found to feature dynamic Stokes shifts in all the aforementioned media, indicating stepwise intramolecular relaxations of the non-equilibrium excited state. The electron injection yield was distinctly lower for the non-equilibrium excited state than the equilibrium excited states, which can be ascribed to the competition between torsional relaxation and electron injection. A broad time scale over one magnitude of order was presented for electron injection due to the great energy losses originating from the multiple torsional relaxations, which should be controlled for future dye design and device development. Moreover, despite the shorter lifetimes of the equilibrium excited states for C210 and C216 than C214, the electron injection yields of equilibrium excited states for all the dyes are comparable due to the accelerated electron injection rate.
2018, 34(4): 437-444
doi: 10.3866/PKU.WHXB201709043
Abstract:
The MgO(110) single crystals were neutron-irradiated with different doses ranging from 1.0×1016 to 1.0×1020 cm-2. The isointensity profiles of the X-ray diffuse scattering caused by the cubic and double-force point defects in MgO were calculated on the basis of the Huang scattering theory. The X-ray diffuse scattering and the UV-Vis absorption spectra were recorded to investigate the point defect configurations in the MgO(110) crystals. Furthermore, the magnetic properties were characterized by a superconducting quantum interference device magnetometer. The ω–2θ curves and rocking curves implied that neutron irradiation enhanced the lattice distortion. The point defects were produced in irradiated MgO crystals. The measured reciprocal space mappings (RSMs) revealed that the notable diffuse scattering was presented in irradiated MgO. Compared with the calculated diffuse scattering intensity profile, it was evident that Frenkel defects were introduced in the irradiated samples. The UV-Vis spectra indicated that anion O vacancy defects had been introduced in irradiated MgO. The single vacancies could be aggregated in irradiated samples with higher doses (1.0×1019 and 1.0×1020 cm-2). Although the irradiated MgO(110) single crystals were diamagnetic at room temperature, they became ferromagnetic at low temperature. The maximum saturation magnetization was found to be 0.058 emu·g-1. By means of neutron irradiation, defect-mediated ferromagnetism could be achieved at low temperature. The correlation between ferromagnetism and O vacancies in neutron-irradiated MgO could be described using F-center exchange mechanism.
The MgO(110) single crystals were neutron-irradiated with different doses ranging from 1.0×1016 to 1.0×1020 cm-2. The isointensity profiles of the X-ray diffuse scattering caused by the cubic and double-force point defects in MgO were calculated on the basis of the Huang scattering theory. The X-ray diffuse scattering and the UV-Vis absorption spectra were recorded to investigate the point defect configurations in the MgO(110) crystals. Furthermore, the magnetic properties were characterized by a superconducting quantum interference device magnetometer. The ω–2θ curves and rocking curves implied that neutron irradiation enhanced the lattice distortion. The point defects were produced in irradiated MgO crystals. The measured reciprocal space mappings (RSMs) revealed that the notable diffuse scattering was presented in irradiated MgO. Compared with the calculated diffuse scattering intensity profile, it was evident that Frenkel defects were introduced in the irradiated samples. The UV-Vis spectra indicated that anion O vacancy defects had been introduced in irradiated MgO. The single vacancies could be aggregated in irradiated samples with higher doses (1.0×1019 and 1.0×1020 cm-2). Although the irradiated MgO(110) single crystals were diamagnetic at room temperature, they became ferromagnetic at low temperature. The maximum saturation magnetization was found to be 0.058 emu·g-1. By means of neutron irradiation, defect-mediated ferromagnetism could be achieved at low temperature. The correlation between ferromagnetism and O vacancies in neutron-irradiated MgO could be described using F-center exchange mechanism.
2018, 34(4): 414-423
doi: 10.3866/PKU.WHXB201708283
Abstract:
Au/TiO2/MoS2 plasmonic composite photocatalysts were synthesized via deposition-precipitation with urea. The photocatalytic activities of the prepared samples were evaluated by performing hydrogen production experiments under Xe lamp irradiation with a 10% (φ, volume fraction) glycerol aqueous solution as the sacrificial agent. The results showed that the optimal content of MoS2 in the Au/TiO2/MoS2 composite is 0.1% (w, mass fraction) and the corresponding H2 production rate was 708.85 μmol·h-1, which was almost 11 times higher than that of TM6.0 with the strongest photocatalytic activity in the all binary TiO2/MoS2 composites. The enhanced photocatalytic activity of the ternary Au/TiO2/MoS2 composites is mainly due to the surface plasmon resonance of the supported Au nanoparticles absorbed on the TiO2/MoS2 layered composite, which show an intense absorption maximum centered around 550–560 nm and induce the photoexcitation of electrons. Meanwhile, the electrons excited by surface plasmon resonance of Au could be injected into the conduction band of TiO2, and they were then transferred to the edges of MoS2 for catalyzing the production of H2.
Au/TiO2/MoS2 plasmonic composite photocatalysts were synthesized via deposition-precipitation with urea. The photocatalytic activities of the prepared samples were evaluated by performing hydrogen production experiments under Xe lamp irradiation with a 10% (φ, volume fraction) glycerol aqueous solution as the sacrificial agent. The results showed that the optimal content of MoS2 in the Au/TiO2/MoS2 composite is 0.1% (w, mass fraction) and the corresponding H2 production rate was 708.85 μmol·h-1, which was almost 11 times higher than that of TM6.0 with the strongest photocatalytic activity in the all binary TiO2/MoS2 composites. The enhanced photocatalytic activity of the ternary Au/TiO2/MoS2 composites is mainly due to the surface plasmon resonance of the supported Au nanoparticles absorbed on the TiO2/MoS2 layered composite, which show an intense absorption maximum centered around 550–560 nm and induce the photoexcitation of electrons. Meanwhile, the electrons excited by surface plasmon resonance of Au could be injected into the conduction band of TiO2, and they were then transferred to the edges of MoS2 for catalyzing the production of H2.
