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2020 Volume 78 Issue 2
2020, 78(2): 105-113
doi: 10.6023/A19080301
Abstract:
Surgical sutures, staples and clips have been widely used for wound closure, tissue reconstruction and tissue adhesives are one of the versatile alternatives especially for friable tissues. Some synthetic and semisynthetic tissue adhesives are available elsewhere. However, there are some drawbacks, such as poor adhesion on wet substrates and potential toxicity, for the reported tissue adhesives. Fibrin glues as biological tissue adhesives are effective hemostatic agents while presenting relatively weak tensile and adhesion strengths and being expensive. Biomimetic adhesives as tissue adhesives, hemostatic agents, or tissue sealants have attracted great attention for clinical operations in last three decades. However, engineering of bio-adhesive materials with good water resistance, high adhesive strength, and good biocompatibility and multi-functionality remains a challenge for tissue healing. Since the first report of mussel-inspired surface chemistry for functional coatings of polydopamine by the Messersmith group in 2007, materials containing plenty of phenolic hydroxyl groups have been widely used in medical applications, food, cosmetics, water treatment and so on, due to the antioxidant, antibacterial, and anti-inflammatory effects of polyphenols. Polyphenol-based hydrogel is an ideal bio-adhesive material due to its good tissue adhesion even on wet substrates, hemostatic and antimicrobial capabilities. Moreover, these hydrogels with porous structures have similar physiochemical properties to that of natural extracellular matrix and different shapes from nanometer to centimeter scales can be remolded to seal irregular defects on tissues. In this review, we report the recent progress of the engineering of polyphenol-synthetic polymer hydrogels, polyphenol-biomacromolecule hydrogels, polyphenol-inorganic nanocomposite hydrogels, and polydopamine nanoparticle composite hydrogels, as well as their applications of tissue adhesives, hemostasis, antimicrobials for wound closure and tissue regeneration. The challenges as well as prospects for future development of polyphenol-based tissue adhesives, sealants, hemostatic agents are also summarized and discussed, which is helpful to promote the next generation of tissue adhesives for biomedical applications.
Surgical sutures, staples and clips have been widely used for wound closure, tissue reconstruction and tissue adhesives are one of the versatile alternatives especially for friable tissues. Some synthetic and semisynthetic tissue adhesives are available elsewhere. However, there are some drawbacks, such as poor adhesion on wet substrates and potential toxicity, for the reported tissue adhesives. Fibrin glues as biological tissue adhesives are effective hemostatic agents while presenting relatively weak tensile and adhesion strengths and being expensive. Biomimetic adhesives as tissue adhesives, hemostatic agents, or tissue sealants have attracted great attention for clinical operations in last three decades. However, engineering of bio-adhesive materials with good water resistance, high adhesive strength, and good biocompatibility and multi-functionality remains a challenge for tissue healing. Since the first report of mussel-inspired surface chemistry for functional coatings of polydopamine by the Messersmith group in 2007, materials containing plenty of phenolic hydroxyl groups have been widely used in medical applications, food, cosmetics, water treatment and so on, due to the antioxidant, antibacterial, and anti-inflammatory effects of polyphenols. Polyphenol-based hydrogel is an ideal bio-adhesive material due to its good tissue adhesion even on wet substrates, hemostatic and antimicrobial capabilities. Moreover, these hydrogels with porous structures have similar physiochemical properties to that of natural extracellular matrix and different shapes from nanometer to centimeter scales can be remolded to seal irregular defects on tissues. In this review, we report the recent progress of the engineering of polyphenol-synthetic polymer hydrogels, polyphenol-biomacromolecule hydrogels, polyphenol-inorganic nanocomposite hydrogels, and polydopamine nanoparticle composite hydrogels, as well as their applications of tissue adhesives, hemostasis, antimicrobials for wound closure and tissue regeneration. The challenges as well as prospects for future development of polyphenol-based tissue adhesives, sealants, hemostatic agents are also summarized and discussed, which is helpful to promote the next generation of tissue adhesives for biomedical applications.
2020, 78(2): 114-124
doi: 10.6023/A19100385
Abstract:
The electrolyte, which is an important medium of ion conduction for secondary batteries, plays a crucial role in improving the cycling performance and safety performance of secondary batteries. Localized high-concentration electrolytes, which are formed by adding "diluent" into high-concentration electrolyte, not only reserve the outstanding properties of high-concentration electrolytes but also possess low viscosity, excellent wettability and low cost, promising broad application prospect. Localized high-concentration electrolytes have already played a part in flame-retardant lithium battery, high-voltage lithium battery, low-temperature lithium battery, lithium sulfur battery and sodium battery. Herein, this paper mainly reviews the types and preparation of localized high-concentration electrolytes and their functional mechanism and research status in various secondary batteries. We discuss the challenges and future development of localized high-concentration electrolytes and have the outlook at the end of the paper.
The electrolyte, which is an important medium of ion conduction for secondary batteries, plays a crucial role in improving the cycling performance and safety performance of secondary batteries. Localized high-concentration electrolytes, which are formed by adding "diluent" into high-concentration electrolyte, not only reserve the outstanding properties of high-concentration electrolytes but also possess low viscosity, excellent wettability and low cost, promising broad application prospect. Localized high-concentration electrolytes have already played a part in flame-retardant lithium battery, high-voltage lithium battery, low-temperature lithium battery, lithium sulfur battery and sodium battery. Herein, this paper mainly reviews the types and preparation of localized high-concentration electrolytes and their functional mechanism and research status in various secondary batteries. We discuss the challenges and future development of localized high-concentration electrolytes and have the outlook at the end of the paper.
2020, 78(2): 125-129
doi: 10.6023/A19120424
Abstract:
Temperature-dependent near-infrared (NIR) spectroscopy has been proposed and used in the quantitative analysis of multi-component mixtures and the understanding of the interactions in solutions. Mutual factor analysis (MFA) was developed, in our previous work, to detect glucose content in aqueous solutions and serum samples using the NIR spectra measured at different temperatures. The essence of the algorithm is to extract and compare the spectral component, named as standardized signal (SS), mutually contained in the spectral data of different samples. The relative quantity of SS can be used to build the calibration model for quantitative analysis. Furthermore, the spectral information of water can be used for the analysis, because the change of the water spectrum with temperature is a reflection of the change in glucose content. In this work, serum samples with low glucose concentration were prepared and measured at the temperature range of 30~60℃ with a step of 5℃. The feasibility of MFA in the quantitative determination of low concentration samples was further studied. Serum solutions with glucose content of 1.0~15.0 mmol/L and 0.0~1.0 mmol/L were prepared, respectively. Before calculation of MFA, continuous wavelet transform (CWT) was used to improve the resolution of the spectra. The results show that MFA can achieve an accurate quantification of the glucose content. The linear correlation coefficients (R) of the calibration models between the relative quantity of SS and the concentration of glucose are 0.9923 and 0.9895, respectively, and the root-mean-squared error of prediction (RMSEP) are 0.35 and 0.07 mmol/L, respectively. The relative error of predicted concentration of samples in the validation set obtained from the calibration model of samples with a concentration of 1.0~15.0 mmol/L are in the range of -12.00%~5.64%, which are in a reasonable level for clinical uses. Temperature-dependent NIR spectroscopy combined with MFA may be a potential way for detecting the micro-content components in complex aqueous systems.
Temperature-dependent near-infrared (NIR) spectroscopy has been proposed and used in the quantitative analysis of multi-component mixtures and the understanding of the interactions in solutions. Mutual factor analysis (MFA) was developed, in our previous work, to detect glucose content in aqueous solutions and serum samples using the NIR spectra measured at different temperatures. The essence of the algorithm is to extract and compare the spectral component, named as standardized signal (SS), mutually contained in the spectral data of different samples. The relative quantity of SS can be used to build the calibration model for quantitative analysis. Furthermore, the spectral information of water can be used for the analysis, because the change of the water spectrum with temperature is a reflection of the change in glucose content. In this work, serum samples with low glucose concentration were prepared and measured at the temperature range of 30~60℃ with a step of 5℃. The feasibility of MFA in the quantitative determination of low concentration samples was further studied. Serum solutions with glucose content of 1.0~15.0 mmol/L and 0.0~1.0 mmol/L were prepared, respectively. Before calculation of MFA, continuous wavelet transform (CWT) was used to improve the resolution of the spectra. The results show that MFA can achieve an accurate quantification of the glucose content. The linear correlation coefficients (R) of the calibration models between the relative quantity of SS and the concentration of glucose are 0.9923 and 0.9895, respectively, and the root-mean-squared error of prediction (RMSEP) are 0.35 and 0.07 mmol/L, respectively. The relative error of predicted concentration of samples in the validation set obtained from the calibration model of samples with a concentration of 1.0~15.0 mmol/L are in the range of -12.00%~5.64%, which are in a reasonable level for clinical uses. Temperature-dependent NIR spectroscopy combined with MFA may be a potential way for detecting the micro-content components in complex aqueous systems.
2020, 78(2): 130-139
doi: 10.6023/A19100374
Abstract:
Single molecule localization microscopy as an advanced optical imaging technique is capable of super-resolution imaging of biological targets with the size below the optical diffraction limit. It is promising to provide powerful tools for the exploration of occurrence mechanism of severe diseases and precisely therapeutic method at single cell/organelle level, which exhibits wide applications in biomedical field. Generally, stochastic optical reconstruction microscopy (STORM) is prominently dependent on large amount of imaging buffers (Redox enzymes) and thiol-containing reagents for the ideal photoblinking behaviors of optical probes. However, the imaging buffer and thiol-containing reagents are harmful for the live cells, which make it difficult to carry out STORM imaging in live cells. Therefore, it is of significance to exploit new approaches to display STORM imaging in live cells. In this work, we provided a new strategy to facilitate the design of live cell STORM imaging probes with improved photo-blinking mechanism. A new fluorescent pentamethine cyanine probe with a thiol-attachment (SHCH2CH2CH2-) at the N-position of one indoline moiety was synthesized to show spontaneously photoblinking behavior caused by intramolecular ring-closing/-opening processes. The fluorescent probe is biologically compatible with rare cytotoxicity and suitable for the live cell imaging. The probe can exhibit excellent photo-blinking under the direct illumination of a single laser beam (656 nm) with low power density (200 W·cm-2 for solution sample and 100 W·cm-2 for cell sample, respectively), without using any imaging buffer or thiol-chemicals. And the fluorescent probe was used to test cell toxicity with CCK-8, showed almost no cytotoxicity after 24 h incubation. The photo-blinking frames were collected with an electron multiplying charge coupled device (EMCCD, 60 Hz), and different frames were used to pre-treat with ImageJ software and then reconstruct STORM images with a Falcon algorithm to show marked imaging resolution enhancement, compared with wide-field images, which provide a new protocol for biomedical imaging.
Single molecule localization microscopy as an advanced optical imaging technique is capable of super-resolution imaging of biological targets with the size below the optical diffraction limit. It is promising to provide powerful tools for the exploration of occurrence mechanism of severe diseases and precisely therapeutic method at single cell/organelle level, which exhibits wide applications in biomedical field. Generally, stochastic optical reconstruction microscopy (STORM) is prominently dependent on large amount of imaging buffers (Redox enzymes) and thiol-containing reagents for the ideal photoblinking behaviors of optical probes. However, the imaging buffer and thiol-containing reagents are harmful for the live cells, which make it difficult to carry out STORM imaging in live cells. Therefore, it is of significance to exploit new approaches to display STORM imaging in live cells. In this work, we provided a new strategy to facilitate the design of live cell STORM imaging probes with improved photo-blinking mechanism. A new fluorescent pentamethine cyanine probe with a thiol-attachment (SHCH2CH2CH2-) at the N-position of one indoline moiety was synthesized to show spontaneously photoblinking behavior caused by intramolecular ring-closing/-opening processes. The fluorescent probe is biologically compatible with rare cytotoxicity and suitable for the live cell imaging. The probe can exhibit excellent photo-blinking under the direct illumination of a single laser beam (656 nm) with low power density (200 W·cm-2 for solution sample and 100 W·cm-2 for cell sample, respectively), without using any imaging buffer or thiol-chemicals. And the fluorescent probe was used to test cell toxicity with CCK-8, showed almost no cytotoxicity after 24 h incubation. The photo-blinking frames were collected with an electron multiplying charge coupled device (EMCCD, 60 Hz), and different frames were used to pre-treat with ImageJ software and then reconstruct STORM images with a Falcon algorithm to show marked imaging resolution enhancement, compared with wide-field images, which provide a new protocol for biomedical imaging.
2020, 78(2): 140-146
doi: 10.6023/A19100372
Abstract:
Two thermally activated delayed fluorescence (TADF) materials TBP-DmCz and TBP-TmCz were successfully synthesized using 1, 3, 5-tribenzoylbenzene (TBP) as electron-acceptor, 1, 8-dimethylcarbazole (DmCz) and 1, 3, 6, 8-tetra-methylcarbazole (TmCz) as electron-donor, respectively. Thermal gravimetric analysis show that the thermal decomposition temperatures (Td) are 479℃ for TBP-DmCz and 484℃ for TBP-TmCz and no glass transition was found for both materials during the differential scanning calorimetry investigations. The highest occupied molecular orbitals (HOMO) are confined on the carbazole unit, while the lowest unoccupied molecular orbitals (LUMO) are located on the 1, 3, 5-tribenzoylbenzene unit, and there is almost no overlap between HOMO and LUMO, which is the typical molecular orbital character of TADF materials. Meanwhile, TBP-DmCz and TBP-TmCz possess degenerated HOMO and LUMO, which would promote the radiative transitions as the transitions could take place from all degenerated LUMOs to HOMOs. The HOMO level of TBP-TmCz is obviously higher than that of TBP-DmCz due to increasing the number of methyl groups at the electron-donor carbazole, and the LUMO levels of TBP-DmCz and TBP-TmCz only show a small difference because these materials have the same electron-acceptor 1, 3, 5-tribenzoylbenzene. In toluene solution, these materials have very similar absorption spectra and exhibit absorption bands assigned to intramolecular charge-transfer transition. The spectral peaks are located at 488 nm for TBP-DmCz and 502 nm for TBP-TmCz, respectively, in toluene solution at room temperature. According to the fluorescence and phosphorescence spectra of these materials in 1, 3-bis(N-carbazolyl)benzene (mCP) film at 77 K, the energy gaps between the lowest singlet and triplet (ΔEST) of TBP-DmCz and TBP-TmCz are calculated to be 0.05 and 0.01 eV, respectively. The fluorescence decay behaviors at different temperatures (100, 200 and 300 K) proved that emissions of TBP-DmCz and TBP-TmCz contain TADF component. The electroluminescence devices with TBP-DmCz and TBP-TmCz as the emitters show high efficiency and low efficiency roll-off. The maximum external quantum efficiencies of devices based on TBP-DmCz and TBP-TmCz are 13.6% and 18.3%, respectively.
Two thermally activated delayed fluorescence (TADF) materials TBP-DmCz and TBP-TmCz were successfully synthesized using 1, 3, 5-tribenzoylbenzene (TBP) as electron-acceptor, 1, 8-dimethylcarbazole (DmCz) and 1, 3, 6, 8-tetra-methylcarbazole (TmCz) as electron-donor, respectively. Thermal gravimetric analysis show that the thermal decomposition temperatures (Td) are 479℃ for TBP-DmCz and 484℃ for TBP-TmCz and no glass transition was found for both materials during the differential scanning calorimetry investigations. The highest occupied molecular orbitals (HOMO) are confined on the carbazole unit, while the lowest unoccupied molecular orbitals (LUMO) are located on the 1, 3, 5-tribenzoylbenzene unit, and there is almost no overlap between HOMO and LUMO, which is the typical molecular orbital character of TADF materials. Meanwhile, TBP-DmCz and TBP-TmCz possess degenerated HOMO and LUMO, which would promote the radiative transitions as the transitions could take place from all degenerated LUMOs to HOMOs. The HOMO level of TBP-TmCz is obviously higher than that of TBP-DmCz due to increasing the number of methyl groups at the electron-donor carbazole, and the LUMO levels of TBP-DmCz and TBP-TmCz only show a small difference because these materials have the same electron-acceptor 1, 3, 5-tribenzoylbenzene. In toluene solution, these materials have very similar absorption spectra and exhibit absorption bands assigned to intramolecular charge-transfer transition. The spectral peaks are located at 488 nm for TBP-DmCz and 502 nm for TBP-TmCz, respectively, in toluene solution at room temperature. According to the fluorescence and phosphorescence spectra of these materials in 1, 3-bis(N-carbazolyl)benzene (mCP) film at 77 K, the energy gaps between the lowest singlet and triplet (ΔEST) of TBP-DmCz and TBP-TmCz are calculated to be 0.05 and 0.01 eV, respectively. The fluorescence decay behaviors at different temperatures (100, 200 and 300 K) proved that emissions of TBP-DmCz and TBP-TmCz contain TADF component. The electroluminescence devices with TBP-DmCz and TBP-TmCz as the emitters show high efficiency and low efficiency roll-off. The maximum external quantum efficiencies of devices based on TBP-DmCz and TBP-TmCz are 13.6% and 18.3%, respectively.
2020, 78(2): 147-154
doi: 10.6023/A19090338
Abstract:
Metal organic frameworks (MOFs) have unique advantages in adsorption and preconcentration of heavy metal ions due to their structure and composition characteristics, which make them show great potential in optical sensing of heavy metal ions. However, their applications in the field of electrochemical sensing is greatly limited because of their poor conductivity. In this work, a functionalized MOF composite, thermally reduced graphene oxide-Au nanoparticles-zeolitic imidazolate skeleton material (RGO-Au-ZIF-8), was fabricated. It exhibits much improved electrochemical properties compared with the pristine MOF. A novel electrochemical sensing platform was constructed based on it, and simultaneous detection of lead ions (Pb2+) and copper ions (Cu2+) in aqueous solution was realized. Specifically, the Au-ZIF-8 was prepared by adding polyvinylpyrrolidone (PVP)-stabilized Au nanoparticles (AuNPs) to the reaction solution of ZIF-8. The modification of AuNPs effectively improved the conductivity of the material. After compounding with RGO, the RGO-Au-ZIF-8 composite was prepared. The RGO was used as scaffold for the Au-ZIF-8 in the composite to increase the effective surface area of electrode and improve conductivity. The morphology and structure of the prepared materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-visible absorption spectroscopy (UV-Vis). The electrochemical properties of the modified electrodes were characterized by various electrochemical techniques. The experimental parameters, such as pH value of working solution, accumulation potential, accumulation time and composition ratio of Au-ZIF-8 to RGO were optimized. Under the optimized conditions, simultaneous and sensitive detection of Pb2+ and Cu2+ on the prepared electrochemical sensor was realized with the detection limits of 2.6×10-9 and 7.8×10-9 mol·L-1 for Pb2+ and Cu2+, respectively (S/N=3). The interference test showed that the electrochemical sensor has good selectivity for the detection of Pb2+ and Cu2+, and further electrochemical studies revealed that the designed sensor has excellent reproducibility and good stability. The result of recovery test indicated that the prepared electrochemical sensor has great potential in Pb2+ and Cu2+ detection in real water samples. This work provides a new platform for simultaneous, rapid and sensitive detection of heavy metal ions, and greatly expands the electrochemical applications of MOF materials.
Metal organic frameworks (MOFs) have unique advantages in adsorption and preconcentration of heavy metal ions due to their structure and composition characteristics, which make them show great potential in optical sensing of heavy metal ions. However, their applications in the field of electrochemical sensing is greatly limited because of their poor conductivity. In this work, a functionalized MOF composite, thermally reduced graphene oxide-Au nanoparticles-zeolitic imidazolate skeleton material (RGO-Au-ZIF-8), was fabricated. It exhibits much improved electrochemical properties compared with the pristine MOF. A novel electrochemical sensing platform was constructed based on it, and simultaneous detection of lead ions (Pb2+) and copper ions (Cu2+) in aqueous solution was realized. Specifically, the Au-ZIF-8 was prepared by adding polyvinylpyrrolidone (PVP)-stabilized Au nanoparticles (AuNPs) to the reaction solution of ZIF-8. The modification of AuNPs effectively improved the conductivity of the material. After compounding with RGO, the RGO-Au-ZIF-8 composite was prepared. The RGO was used as scaffold for the Au-ZIF-8 in the composite to increase the effective surface area of electrode and improve conductivity. The morphology and structure of the prepared materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-visible absorption spectroscopy (UV-Vis). The electrochemical properties of the modified electrodes were characterized by various electrochemical techniques. The experimental parameters, such as pH value of working solution, accumulation potential, accumulation time and composition ratio of Au-ZIF-8 to RGO were optimized. Under the optimized conditions, simultaneous and sensitive detection of Pb2+ and Cu2+ on the prepared electrochemical sensor was realized with the detection limits of 2.6×10-9 and 7.8×10-9 mol·L-1 for Pb2+ and Cu2+, respectively (S/N=3). The interference test showed that the electrochemical sensor has good selectivity for the detection of Pb2+ and Cu2+, and further electrochemical studies revealed that the designed sensor has excellent reproducibility and good stability. The result of recovery test indicated that the prepared electrochemical sensor has great potential in Pb2+ and Cu2+ detection in real water samples. This work provides a new platform for simultaneous, rapid and sensitive detection of heavy metal ions, and greatly expands the electrochemical applications of MOF materials.
2020, 78(2): 155-160
doi: 10.6023/A19100364
Abstract:
Anionic surfactants play a key role in many industrial fields such as drug delivery, detergent, oil displacement and food processing because of their unique amphiphilic properties. The structure of surfactant in oil-water system has a great influence on the interfacial behavior. It is of great significance to study the structure and interfacial properties of surfactants. In this paper, the all-atomic molecular dynamics method was used to study the aggregation behavior of nonylphenol-substituted series of alkyl sulfonate surfactants (Cn-NPAS) at the decane/water interface. The effects of different sulfoalkyl chain lengths on the interfacial properties of nonylphenol-substituted alkyl sulfonate surfactants were investigated by analyzing the interface thickness, interface formation energy, interfacial tension, the radial distribution function and coordination number. Simulation results have shown that the interfacial thickness increases at first and then decreases as the length of sulfoalkyl chain increases. The same trend was found in the results of the interface formation energy (IFE). The absolute value of IFE follows the order of C12-NPAS > C14-NPAS > C10-NPAS > C16-NPAS > C8-NPAS, indicating that the C12-NPAS is the most stable system in terms of energy which should be attribute to the stronger aggregation ability. Moreover, it is observed that the trend of interfacial tension is in agreement with that of interface formation energy and the interface thickness. Surfactant C12-NPAS induces the minimum interfacial tension. The calculation results are consistent with the experimental data. Furthermore, the radial distribution function and the coordination number of water around the surfactant headgroup were obtained for evaluating the interaction strength between the hydrophilic headgroup and water molecules. The results are well in accordance with the trend of the interface formation energy and interfacial tension. This indicates that the length of alkyl tail affect the interaction between hydrophilic headgroup and water indirectly. Simulation results suggest that the length of alkyl tail plays a dominant role in the interfacial behaviors. We expect that the results of this study could be valuable for the understanding of mechanism and the design of high performance surfactants.
Anionic surfactants play a key role in many industrial fields such as drug delivery, detergent, oil displacement and food processing because of their unique amphiphilic properties. The structure of surfactant in oil-water system has a great influence on the interfacial behavior. It is of great significance to study the structure and interfacial properties of surfactants. In this paper, the all-atomic molecular dynamics method was used to study the aggregation behavior of nonylphenol-substituted series of alkyl sulfonate surfactants (Cn-NPAS) at the decane/water interface. The effects of different sulfoalkyl chain lengths on the interfacial properties of nonylphenol-substituted alkyl sulfonate surfactants were investigated by analyzing the interface thickness, interface formation energy, interfacial tension, the radial distribution function and coordination number. Simulation results have shown that the interfacial thickness increases at first and then decreases as the length of sulfoalkyl chain increases. The same trend was found in the results of the interface formation energy (IFE). The absolute value of IFE follows the order of C12-NPAS > C14-NPAS > C10-NPAS > C16-NPAS > C8-NPAS, indicating that the C12-NPAS is the most stable system in terms of energy which should be attribute to the stronger aggregation ability. Moreover, it is observed that the trend of interfacial tension is in agreement with that of interface formation energy and the interface thickness. Surfactant C12-NPAS induces the minimum interfacial tension. The calculation results are consistent with the experimental data. Furthermore, the radial distribution function and the coordination number of water around the surfactant headgroup were obtained for evaluating the interaction strength between the hydrophilic headgroup and water molecules. The results are well in accordance with the trend of the interface formation energy and interfacial tension. This indicates that the length of alkyl tail affect the interaction between hydrophilic headgroup and water indirectly. Simulation results suggest that the length of alkyl tail plays a dominant role in the interfacial behaviors. We expect that the results of this study could be valuable for the understanding of mechanism and the design of high performance surfactants.
2020, 78(2): 161-169
doi: 10.6023/A19100378
Abstract:
In this paper, we prepared reduced graphene oxide (rGO) films by first drop-casting graphene oxide (GO)/ethanol dispersion on top of silicon nanowires array, followed by thermal reduction in 95% Ar-5% H2 (volume ratio) atmosphere. A series of rGO thin films were prepared by thermal reduction at different annealing temperatures ranging from 100℃ to 1200℃, and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, four-probe square resistance tester and scanning electron microscopy (SEM). The experimental results indicate that reduction of oxygen-containing groups, dehydrogenation of C-H groups and reconstruction of C=C skeleton occurred significantly on the GO plane. Compared with the insulating GO film, the resistance of rGO thin films decreases greatly, and the sheet resistance of rGO films shows a decreasing trend with increase of reduction temperature. Then, flexible polydimethylsiloxane (PDMS) encapsulated graphene-based devices (P-rGO-P) were fabricated by spin-coating PDMS on the surface of obtained rGO films with evaporated Au interdigital electrodes. The flexible devices maintained the integrity of the rGO films while providing self-supporting characteristics. The rGO film in the device had a clear layered structure, and a certain movable space between the upper and lower PDMS layers. This sandwich structure ensures that when the P-rGO-P flexible detector is bent and squeezed, the rGO film has sufficient buffer space, and would not be subjected to excessive stress arising from adhesion to PDMS. In short, the sandwich structure endows the originally fragile device with excellent flexibility. The P-rGO-P detector was successfully applied to detecting infrared laser irradiation, human body infrared radiation, bending motions and pressure changes. The experimental results showed that the flexible encapsulated P-rGO-P infrared detectors derived from the rGO thin films reduced at varied temperatures all had response to near-infrared (1064 nm) laser irradiation, and the maximum response reached up to 2.78 mA/W. In addition, the P-rGO-P flexible detector also demonstrated fast and sensitive response to human body infrared radiation and bending changes, and could maintain its integrity and responsiveness after repeated bending.
In this paper, we prepared reduced graphene oxide (rGO) films by first drop-casting graphene oxide (GO)/ethanol dispersion on top of silicon nanowires array, followed by thermal reduction in 95% Ar-5% H2 (volume ratio) atmosphere. A series of rGO thin films were prepared by thermal reduction at different annealing temperatures ranging from 100℃ to 1200℃, and characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, four-probe square resistance tester and scanning electron microscopy (SEM). The experimental results indicate that reduction of oxygen-containing groups, dehydrogenation of C-H groups and reconstruction of C=C skeleton occurred significantly on the GO plane. Compared with the insulating GO film, the resistance of rGO thin films decreases greatly, and the sheet resistance of rGO films shows a decreasing trend with increase of reduction temperature. Then, flexible polydimethylsiloxane (PDMS) encapsulated graphene-based devices (P-rGO-P) were fabricated by spin-coating PDMS on the surface of obtained rGO films with evaporated Au interdigital electrodes. The flexible devices maintained the integrity of the rGO films while providing self-supporting characteristics. The rGO film in the device had a clear layered structure, and a certain movable space between the upper and lower PDMS layers. This sandwich structure ensures that when the P-rGO-P flexible detector is bent and squeezed, the rGO film has sufficient buffer space, and would not be subjected to excessive stress arising from adhesion to PDMS. In short, the sandwich structure endows the originally fragile device with excellent flexibility. The P-rGO-P detector was successfully applied to detecting infrared laser irradiation, human body infrared radiation, bending motions and pressure changes. The experimental results showed that the flexible encapsulated P-rGO-P infrared detectors derived from the rGO thin films reduced at varied temperatures all had response to near-infrared (1064 nm) laser irradiation, and the maximum response reached up to 2.78 mA/W. In addition, the P-rGO-P flexible detector also demonstrated fast and sensitive response to human body infrared radiation and bending changes, and could maintain its integrity and responsiveness after repeated bending.
2020, 78(2): 170-176
doi: 10.6023/A19120445
Abstract:
Gold nanoparticles (Au NPs), smaller than 10 nm, have a high ratio of surface area to volume, and therefore have excellent catalytic activity. They are widely used in the field of catalysis. The concentration of small particle sized Au NPs synthesized by traditional wet chemical method is too low, and further enrichment is needed in order to meet the experimental requirements. However, small particle sized Au NPs are prone to aggregate during the concentration process and lose the catalytic activity. It is a challenge to concentrate the small Au NPs while keeping their catalytic activities. In this work, 500 nm silanized SiO2 particles which are covered by positive charges were used to adsorb 5 nm Au NPs through electrostatic interaction, and self-assemble to form Au NPs@SiO2 composite at room temperature. The loaded efficiency of Au NPs can reach 99.5% and the amount of Au NPs particles loaded on each SiO2 particle reached 800~1000, which greatly increased the effective concentration of Au NPs in the local area. Moreover, Au NPs enriched on the surface of SiO2 were bound by electrostatic action and uniformly distributed on the surface of SiO2 without agglomeration. The results showed that the catalytic activity of AuNPs@SiO2 was greatly enhanced by increasing the local concentration of AuNPs, and the catalytic activity was 3 times higher than that of AuNPs at the same concentration. After 5 times of reuse, the catalytic conversion efficiency remained at about 80%. The Au NPs@SiO2 composite could be preserved for one month with the same structure and catalytic activity. Moreover, by adjusting the molar ratio of SiO2 and Au NPs, the assembly density of Au NPs at SiO2 can be precisely regulated, and the catalytic activity of Au NPs@SiO2 can also be changed precisely. This work provides a simple method for preparing small sized Au NPs with high concentration and greatly improves the catalytic activity of Au NPs. The method has wide application in enriching other small sized nanoparticles.
Gold nanoparticles (Au NPs), smaller than 10 nm, have a high ratio of surface area to volume, and therefore have excellent catalytic activity. They are widely used in the field of catalysis. The concentration of small particle sized Au NPs synthesized by traditional wet chemical method is too low, and further enrichment is needed in order to meet the experimental requirements. However, small particle sized Au NPs are prone to aggregate during the concentration process and lose the catalytic activity. It is a challenge to concentrate the small Au NPs while keeping their catalytic activities. In this work, 500 nm silanized SiO2 particles which are covered by positive charges were used to adsorb 5 nm Au NPs through electrostatic interaction, and self-assemble to form Au NPs@SiO2 composite at room temperature. The loaded efficiency of Au NPs can reach 99.5% and the amount of Au NPs particles loaded on each SiO2 particle reached 800~1000, which greatly increased the effective concentration of Au NPs in the local area. Moreover, Au NPs enriched on the surface of SiO2 were bound by electrostatic action and uniformly distributed on the surface of SiO2 without agglomeration. The results showed that the catalytic activity of AuNPs@SiO2 was greatly enhanced by increasing the local concentration of AuNPs, and the catalytic activity was 3 times higher than that of AuNPs at the same concentration. After 5 times of reuse, the catalytic conversion efficiency remained at about 80%. The Au NPs@SiO2 composite could be preserved for one month with the same structure and catalytic activity. Moreover, by adjusting the molar ratio of SiO2 and Au NPs, the assembly density of Au NPs at SiO2 can be precisely regulated, and the catalytic activity of Au NPs@SiO2 can also be changed precisely. This work provides a simple method for preparing small sized Au NPs with high concentration and greatly improves the catalytic activity of Au NPs. The method has wide application in enriching other small sized nanoparticles.
