Achieving efficient adsorption and desorption processes by controllably tuning the properties of adsorbents at different technical stages is extremely attractive.However,it is difficult for traditional adsorbents to r...Achieving efficient adsorption and desorption processes by controllably tuning the properties of adsorbents at different technical stages is extremely attractive.However,it is difficult for traditional adsorbents to reach the target because of their fixed active sites.Herein,we report on the fabrication of a smart adsorbent,which was achieved by introducing photoresponsive azobenzene derivatives with cis/trans isomers to Ce-doped mesoporous silica.These photoresponsive groups serve as “molecular switches”by sheltering and exposing active sites,leading to efficient adsorption and desorption.Ce is also doped to provide additional active sites in order to enhance the adsorption performance.The results show that the cis isomers effectively shelter the active sites,leading to the selective adsorption of methylene blue(MB)over brilliant blue(BB),while the trans isomers completely expose the active sites,resulting in the convenient release of the adsorbates.Both selective adsorption and efficient desorption can be realized controllably by these smart adsorbents through photostimulation.Moreover,the performance of the obtained materials is well maintained after five cycles.展开更多
Some hymecromone derivatives containing chiral 1,1'-bi-2-naphthyl moiety were synthesized and their photodimerizations were investigated. It was found that fluorescence intensity and optical rotation of the new ch...Some hymecromone derivatives containing chiral 1,1'-bi-2-naphthyl moiety were synthesized and their photodimerizations were investigated. It was found that fluorescence intensity and optical rotation of the new chiral hymecromone derivatives could be regulated by light. This property has potential significance for developing a new type of dual-mode molecular switch.展开更多
Structural and electronic properties of a bistable redox-responsive molecular switch based on dibenzo[1,2]dithiine (PSBH) were studied using the DFT-B3LYP/6-31G* method. The results confirmed that the electrical co...Structural and electronic properties of a bistable redox-responsive molecular switch based on dibenzo[1,2]dithiine (PSBH) were studied using the DFT-B3LYP/6-31G* method. The results confirmed that the electrical conductivity of the closed form of considered molecular switch is higher than that of the open form. NBO electric charges on heavy atoms of biphenyl unit revealed that the positive charge on sulfur atoms reinforced, which caused the collapse of disulfide bond.展开更多
DNA is an attractive biomaterial for constructing nanomachines and nanomaterials owing to their self-recognition and self-assembly properties.In addition to the well-known double helical structures,DNA molecules can a...DNA is an attractive biomaterial for constructing nanomachines and nanomaterials owing to their self-recognition and self-assembly properties.In addition to the well-known double helical structures,DNA molecules can also form a variety of unusual structures like hairpins,triplexes and quadruplexes.These unusual DNAs sometimes have advantages over double helical DNAs in constructing nanomachines such as enhanced thermodynamic stability and higher sensitivity to external stimuli,which made them as promising motifs in recenttwo decades.Regardless of how complicated DNA-based nanomachines are,the fundamental concept in these nanomachines is based on a proper design and usage of DNA molecular switch.Among the reported DNA molecular switches,pH-controlled systems show great potentials in drug delivery and cellular pH sensing.Up to now,most of the reported pH-controlled molecular switches used i-motif or triplex DNAs.However,owing to the relatively long sequence requirement for the formation of i-motif and triplex DNAs,an invading DNA strand needs to be added to activate the molecular switch,and thus DNA wastes will be generated into the system and a full structural conversion will usually take a relatively long time of minutes to hours.To overcome the disadvantages of DNA waste generation and slow kinetics,molecular switches using smaller-size,thermodynamically stable and pH-sensible unusual DNA structures will have the advantages of easier manipulation and faster kinetics.Recently,we discovered a new type of unusual DNA structure called the minidumbbell(MDB)which is formed by a single-strand 8-nucleotide sequence.The MDB is composed of two type II tetraloops in which the first and fourth loop residues form loop-closing base pairs,the second loop residues fold into the minor groove to form base-base stacking or mispairing interactions,and the third loop residues stack on their nearby loop-closing base pairs.In particular,the MDB formed by a sequence containing two CCTG repeats has a relatively low melting temperature(Tm)of^22℃at pH 7.0,whereas its Tm can be significantly increased to^46℃at pH 5.0 due to the formation of a three hydrogen bond hemiprotonated C+·C mispair in the minor groove.This MDB,when combined with its complementary sequence,shows instant and complete structural conversions when the pH switches between 5.0 and 7.0 without using an invading DNA strand,serving as a simple and efficient pH-controlled molecular switch.In order to allow the incorporation of fluorophores to the two termini of the MDB,we aim to design a thermodynamically more stable MDB structure in this study.Through a rational design by introducing hydrophobic interactions to the MDB formed by the sequence containing two CCTG repeats at pH 5.0,we obtained an MDB structure with a record-high Tm of^62℃.Furthermore,this MDB was found to exist stably in the presence of 5’and 3’-overhanging residues,revealing its capability of being attached with fluorophores or other functional groups,and thus making it potentially a versatile pH-controlled molecular switch for designing nanomachines and nanomaterials.展开更多
Saxitoxin(STX),one of the most toxic paralytic shellfish poisons discovered to date,is listed as a required item of aquatic product safety inspection worldwide.However,conventional detection methods for STX are limite...Saxitoxin(STX),one of the most toxic paralytic shellfish poisons discovered to date,is listed as a required item of aquatic product safety inspection worldwide.However,conventional detection methods for STX are limited by various issues,such as low sensitivity,complicated operations,and ethical considerations.In this study,an aptamer-triplex molecular switch(APT-TMS)and gold nanoparticle(AuNP)nanozyme were combined to develop a label-free colorimetric aptasensor for the rapid and highly sensitive de-tection of STX.An anti-STX aptamer designed with pyrimidine arms and a purine chain was fabricated to form an APT-TMS.Specific binding between the aptamer and STX triggered the opening of the switch,which causes the purine chains to adsorb onto the surface of the AuNPs and enhances the peroxidase-like activity of the AuNP nanozyme toward 3,3’,5,5’-tetramethylbenzidine.Under optimized conditions,the proposed aptasensor showed high sensitivity and selectivity for STX,with a limit of detection of 335.6 pmol L^(−1) and a linear range of 0.59-150 nmol L^(−1).Moreover,good recoveries of 82.70%-92.66%for shellfish and 88.97%-106.5%for seawater were obtained.The analysis could be completed within 1 h.The proposed design also offers a robust strategy to achieve detection of other marine toxin targets by altering the corresponding aptamers.展开更多
Based on the nonequilibrium Green function method and density functional theory calculations, we theoretically investigate the effect of chirality on the electronic transport properties of thioxanthene-based molecular...Based on the nonequilibrium Green function method and density functional theory calculations, we theoretically investigate the effect of chirality on the electronic transport properties of thioxanthene-based molecular switch. The molecule comprises the switch which can exhibit different chiralities, that is, cis-form and trans-form by ultraviolet or visible irradiation. The results clearly reveal that the switching behaviors can be realized when the molecule converts between cis-form and trans-form. ~urthermore, the on-off ratio can be modulated by the chirality of the carbon nanotube electrodes. The maximum on-off ratio can reach 109 at 0.4 V for the armchair junction, suggesting potential applications of this type of junctions in future design of functional molecular devices.展开更多
It is observed by in situ stain that LDH (1 5) ...nNAD + can probably enter the nucleopore and can be bound bound specifically with the genes that encode them. During the in vitro expression, the dilution of heart nuc...It is observed by in situ stain that LDH (1 5) ...nNAD + can probably enter the nucleopore and can be bound bound specifically with the genes that encode them. During the in vitro expression, the dilution of heart nuclear DNA fragments could enhance the expression activity of LDH/DNA and the amount of expressed LDH (1 5) is in proportion to the amount of dissociable LDH (1 5) on the LDH/DNA. With the integration of 14C Leu to the proteins, it is also observed that the addition of LDH (1 5) ...nNAD + can suppress the in vitro expression activity of LDH/DNA. AFM observation shows that the regulation sequence at the both ends of active genes may be bound with such active factors as proteins encoded by the genes which probably is the main molecular switch of gene expression and regulation we have been always searching for. Our work shows the prospective application of the combination of AFM and isotope labeling in the research of biological reaction.展开更多
Using nonequilibrium Green's function formalism combined first-principles density functional theory, we analyze the transport properties of a 4,4-dimethyl-6-(4-nitrophenyl)-2-phenyl-3,5-diaza-bicyclo[3.1.0]hex-2-en...Using nonequilibrium Green's function formalism combined first-principles density functional theory, we analyze the transport properties of a 4,4-dimethyl-6-(4-nitrophenyl)-2-phenyl-3,5-diaza-bicyclo[3.1.0]hex-2-ene molecular optical switch. The title molecule can convert between closed and open forms by visible or ultraviolet irradiation. The I-V characteristics, differential conductance, on-off ratio, electronic transmission coefficients, spatial distribution of molecular projected self-consistent Hamiltonian orbitals, HOMO-LUMO gaps, effect of electrode materials Y(111)(Y =Au, Ag and Pt) on electronic transport and different molecular geometries corresponding to the closed and open forms through the molecular device are discussed in detail. Based on the results, as soon as possible the open form translates to the closed form, and there is a switch from the ON state to the OFF state(low resistance switches to high resistance). Theoretical results show that the donor/acceptor substituent plays an important role in the electronic transport of molecular devices. The switching performance can be improved to some extent through suitable donor and acceptor substituents.展开更多
Electrical switching of a single-molecule junction provides a practical module to perform sophisticated operations in electronic devices.However,designing an all-electrically-driven molecular switch is a great challen...Electrical switching of a single-molecule junction provides a practical module to perform sophisticated operations in electronic devices.However,designing an all-electrically-driven molecular switch is a great challenge.Here,we experimentally and theoretically investigated the charge transport characteristics of isoindigo(ISO)-molecules at the single-molecule level using the scanning tunneling microscope break junction technique.We find that the single-molecule junctions of ISO-molecules display bias voltage-driven switching characteristics.These switches are realtime,reversible,and nondestructive under low-bias voltages.Experimental results show that the mechanism of the switch is not the transition from nonresonant charge transport to resonant charge transport,but it is the shift of the frontier orbital energy levels of ISO-molecules and the change of the interfacial electronic coupling with bias voltage.Our results will advance the design of high-performance bias voltage-driven molecular switches.展开更多
In this paper, we use a molecular theory to study the anomalous switching of ssDNA monolayers. Here, both ssDNA- water and water-water hydrogen bonds and their explicit coupling to the ssDNA conformations are consider...In this paper, we use a molecular theory to study the anomalous switching of ssDNA monolayers. Here, both ssDNA- water and water-water hydrogen bonds and their explicit coupling to the ssDNA conformations are considered. We find that hydrogen bonding becomes a key element in inducing the anomalous switching of ssDNA monolayers. This finding accords well with the experimental observations. Based on our theoretical model, we predict that the anomalous switching induced by water vapor will be applicable to a wide range of hydrogen bonds polymers, and ssDNA-water hydrogen bonds and water-water hydrogen bonds hybridization will lead to the hydrogen-bond network formation of 3D ssDNA monolayers.展开更多
Using a molecular theory, we investigate the temperature-dependent self-assembly of single-stranded DNA(ss DNA)tethered to a charged nanoparticle surface. Here the size, conformations, and charge properties of ss DN...Using a molecular theory, we investigate the temperature-dependent self-assembly of single-stranded DNA(ss DNA)tethered to a charged nanoparticle surface. Here the size, conformations, and charge properties of ss DNA are taken into account. The main results are as follows: i) when the temperature is lower than the critical switching temperature, the ss DNA will collapse due to the existence of electrostatic interaction between ss DNA and charged nanoparticle surface; ii)for the short ss DNA chains with the number of bases less than 10, the switching of ss DNA cannot happen, and the critical temperature does not exist; iii) when the temperature increases, the electrostatic attractive interaction between ss DNA and charged nanoparticle surface becomes weak dramatically, and ss DNA chains will stretch if the electrostatic attractive interaction is insufficient to overcome the elastic energy of ss DNA and the electrostatic repulsion energy. These findings accord well with the experimental observations. It is predicted that the switching of ss DNA will not happen if the grafting densities are too high.展开更多
The ion selectivity of nickel hexacyanoferrate thin film to alkali cations in ESIX (electrochemically switched ion exchange) processes was investigated using molecular dynamics(MD) techniques; water and cation (Na+ an...The ion selectivity of nickel hexacyanoferrate thin film to alkali cations in ESIX (electrochemically switched ion exchange) processes was investigated using molecular dynamics(MD) techniques; water and cation (Na+ and Cs+) intercalation, configuration, and dynamics in reduced nickel hexacyanoferrate structures with different cation combinations were studied and compared with the experimental results. In the simulations, water was represented by an extended simple point-charge(SPC/E) model, and all other atomic interactions were represented by a universal force field(UFF). The potential energies of various cations combination (Cs+ and Na+) in reduced i-NiHCF and 1 mol/L Cs/NaCl mixed solution were obtained. In most cases, the total potential energy of the solid is reduced when water is intercalated into the various reduced NiHCF structures. Combining the solid and the solution simulation results, it is shown that the solid composition of 3Cs+/1Na+ is the stablest structure form (NaCs3Ni4[Fe(CN)6]3) over a range of solution compositions.展开更多
Photosensitive fluorescent probes have become powerful tools in chemical biology and molecular biophysics,which are used to investigate cellular processes with high temporal and spatial resolution.Accordingly,photosen...Photosensitive fluorescent probes have become powerful tools in chemical biology and molecular biophysics,which are used to investigate cellular processes with high temporal and spatial resolution.Accordingly,photosensitive fluorescent probes,including photoactivatable,photoconvertible,and photoswitchable fluorophores,have been extensively developed during the past decade.The photoswitchable fluorophores have received much attention because they highlight cellular events clearly.This minireview summarizes recent advances of using reversibly photoswitchable fluorophores and their applications in innovative bioimaging.Photoswitchable fluorophores include photoswitchable fluorescent proteins,photoswitchable fluorescent organic molecules(dyes),and photoswitchable fluorescent nanoparticles.Several strategies have been developed to synthesize photoswitchable fluorophores,including engineering combination proteins,chemical synthesis,polymerization,and self-assembly.Here we concentrate on polymer nanoparticles with optically switchable emission properties:either fluorescence on/offor dualalternating-color fluorescence photoswitching.The essential mechanisms of fluorescence photoswitching enable different types of photoswitchable fluorophores to change emission intensity or wavelength(color)and thus validating the basis of the fluorescence on/offor dual-color photoswitching design.Generally the possible applications of any fluorophores are to label biological targets,followed by specific imaging.The newly developed photoswitchable fluorophores enable super-resolution fluorescence imaging because of their photosensitive emission.Finally,we summarize the important area regarding future research and development on photoswitchable fluorescent nanoparticles.展开更多
The dynamic response of molecular orientation, and the temperature and pulse shape dependences of the switching behavior in ferroelectric liquid crystal are described. The switching speed and the surface energy of fer...The dynamic response of molecular orientation, and the temperature and pulse shape dependences of the switching behavior in ferroelectric liquid crystal are described. The switching speed and the surface energy of ferroelectric liquid crystal are given.展开更多
基金This work was supported by the National Science Fund for Excellent Young Scholars(21722606)the National Natural Science Foundation of China(21676138,21878149,21808110,and 21576137)+1 种基金the China Postdoctoral Science Foundation(2018M632295)the Six Talent Plan(2016XCL031).
文摘Achieving efficient adsorption and desorption processes by controllably tuning the properties of adsorbents at different technical stages is extremely attractive.However,it is difficult for traditional adsorbents to reach the target because of their fixed active sites.Herein,we report on the fabrication of a smart adsorbent,which was achieved by introducing photoresponsive azobenzene derivatives with cis/trans isomers to Ce-doped mesoporous silica.These photoresponsive groups serve as “molecular switches”by sheltering and exposing active sites,leading to efficient adsorption and desorption.Ce is also doped to provide additional active sites in order to enhance the adsorption performance.The results show that the cis isomers effectively shelter the active sites,leading to the selective adsorption of methylene blue(MB)over brilliant blue(BB),while the trans isomers completely expose the active sites,resulting in the convenient release of the adsorbates.Both selective adsorption and efficient desorption can be realized controllably by these smart adsorbents through photostimulation.Moreover,the performance of the obtained materials is well maintained after five cycles.
文摘Some hymecromone derivatives containing chiral 1,1'-bi-2-naphthyl moiety were synthesized and their photodimerizations were investigated. It was found that fluorescence intensity and optical rotation of the new chiral hymecromone derivatives could be regulated by light. This property has potential significance for developing a new type of dual-mode molecular switch.
基金Supported by the Young Researchers Club of Islamic Azad University, Shahrood Branch
文摘Structural and electronic properties of a bistable redox-responsive molecular switch based on dibenzo[1,2]dithiine (PSBH) were studied using the DFT-B3LYP/6-31G* method. The results confirmed that the electrical conductivity of the closed form of considered molecular switch is higher than that of the open form. NBO electric charges on heavy atoms of biphenyl unit revealed that the positive charge on sulfur atoms reinforced, which caused the collapse of disulfide bond.
基金supported by General Research Fund ( CUHK14302915) from the Research Grants Council of the Hong Kong Special Administrative RegionDirect Grant ( 4053270) from the Faculty of Science of The Chinese University of Hong Kong
文摘DNA is an attractive biomaterial for constructing nanomachines and nanomaterials owing to their self-recognition and self-assembly properties.In addition to the well-known double helical structures,DNA molecules can also form a variety of unusual structures like hairpins,triplexes and quadruplexes.These unusual DNAs sometimes have advantages over double helical DNAs in constructing nanomachines such as enhanced thermodynamic stability and higher sensitivity to external stimuli,which made them as promising motifs in recenttwo decades.Regardless of how complicated DNA-based nanomachines are,the fundamental concept in these nanomachines is based on a proper design and usage of DNA molecular switch.Among the reported DNA molecular switches,pH-controlled systems show great potentials in drug delivery and cellular pH sensing.Up to now,most of the reported pH-controlled molecular switches used i-motif or triplex DNAs.However,owing to the relatively long sequence requirement for the formation of i-motif and triplex DNAs,an invading DNA strand needs to be added to activate the molecular switch,and thus DNA wastes will be generated into the system and a full structural conversion will usually take a relatively long time of minutes to hours.To overcome the disadvantages of DNA waste generation and slow kinetics,molecular switches using smaller-size,thermodynamically stable and pH-sensible unusual DNA structures will have the advantages of easier manipulation and faster kinetics.Recently,we discovered a new type of unusual DNA structure called the minidumbbell(MDB)which is formed by a single-strand 8-nucleotide sequence.The MDB is composed of two type II tetraloops in which the first and fourth loop residues form loop-closing base pairs,the second loop residues fold into the minor groove to form base-base stacking or mispairing interactions,and the third loop residues stack on their nearby loop-closing base pairs.In particular,the MDB formed by a sequence containing two CCTG repeats has a relatively low melting temperature(Tm)of^22℃at pH 7.0,whereas its Tm can be significantly increased to^46℃at pH 5.0 due to the formation of a three hydrogen bond hemiprotonated C+·C mispair in the minor groove.This MDB,when combined with its complementary sequence,shows instant and complete structural conversions when the pH switches between 5.0 and 7.0 without using an invading DNA strand,serving as a simple and efficient pH-controlled molecular switch.In order to allow the incorporation of fluorophores to the two termini of the MDB,we aim to design a thermodynamically more stable MDB structure in this study.Through a rational design by introducing hydrophobic interactions to the MDB formed by the sequence containing two CCTG repeats at pH 5.0,we obtained an MDB structure with a record-high Tm of^62℃.Furthermore,this MDB was found to exist stably in the presence of 5’and 3’-overhanging residues,revealing its capability of being attached with fluorophores or other functional groups,and thus making it potentially a versatile pH-controlled molecular switch for designing nanomachines and nanomaterials.
基金funded by the National Natural Science Foundation of China(No.31801620).
文摘Saxitoxin(STX),one of the most toxic paralytic shellfish poisons discovered to date,is listed as a required item of aquatic product safety inspection worldwide.However,conventional detection methods for STX are limited by various issues,such as low sensitivity,complicated operations,and ethical considerations.In this study,an aptamer-triplex molecular switch(APT-TMS)and gold nanoparticle(AuNP)nanozyme were combined to develop a label-free colorimetric aptasensor for the rapid and highly sensitive de-tection of STX.An anti-STX aptamer designed with pyrimidine arms and a purine chain was fabricated to form an APT-TMS.Specific binding between the aptamer and STX triggered the opening of the switch,which causes the purine chains to adsorb onto the surface of the AuNPs and enhances the peroxidase-like activity of the AuNP nanozyme toward 3,3’,5,5’-tetramethylbenzidine.Under optimized conditions,the proposed aptasensor showed high sensitivity and selectivity for STX,with a limit of detection of 335.6 pmol L^(−1) and a linear range of 0.59-150 nmol L^(−1).Moreover,good recoveries of 82.70%-92.66%for shellfish and 88.97%-106.5%for seawater were obtained.The analysis could be completed within 1 h.The proposed design also offers a robust strategy to achieve detection of other marine toxin targets by altering the corresponding aptamers.
基金Supported by the National Natural Science Foundation of China under Grant No 11004156the Natural Science Foundation of Shaanxi Province under Grant No 2014JM1025+2 种基金the Science and Technology Star Project of Shaanxi Province under Grant No2016KJXX-38the Special Foundation of Key Academic Subjects Development of Shaanxi Province under Grant No 2008-169the Xi'an Polytechnic University Young Scholar Supporting Plan under Grant No 2013-06
文摘Based on the nonequilibrium Green function method and density functional theory calculations, we theoretically investigate the effect of chirality on the electronic transport properties of thioxanthene-based molecular switch. The molecule comprises the switch which can exhibit different chiralities, that is, cis-form and trans-form by ultraviolet or visible irradiation. The results clearly reveal that the switching behaviors can be realized when the molecule converts between cis-form and trans-form. ~urthermore, the on-off ratio can be modulated by the chirality of the carbon nanotube electrodes. The maximum on-off ratio can reach 109 at 0.4 V for the armchair junction, suggesting potential applications of this type of junctions in future design of functional molecular devices.
文摘It is observed by in situ stain that LDH (1 5) ...nNAD + can probably enter the nucleopore and can be bound bound specifically with the genes that encode them. During the in vitro expression, the dilution of heart nuclear DNA fragments could enhance the expression activity of LDH/DNA and the amount of expressed LDH (1 5) is in proportion to the amount of dissociable LDH (1 5) on the LDH/DNA. With the integration of 14C Leu to the proteins, it is also observed that the addition of LDH (1 5) ...nNAD + can suppress the in vitro expression activity of LDH/DNA. AFM observation shows that the regulation sequence at the both ends of active genes may be bound with such active factors as proteins encoded by the genes which probably is the main molecular switch of gene expression and regulation we have been always searching for. Our work shows the prospective application of the combination of AFM and isotope labeling in the research of biological reaction.
基金Supported by the Damghan University,the Ferdowsi University of Mashhad and the Islamic Azad University of Shahrood
文摘Using nonequilibrium Green's function formalism combined first-principles density functional theory, we analyze the transport properties of a 4,4-dimethyl-6-(4-nitrophenyl)-2-phenyl-3,5-diaza-bicyclo[3.1.0]hex-2-ene molecular optical switch. The title molecule can convert between closed and open forms by visible or ultraviolet irradiation. The I-V characteristics, differential conductance, on-off ratio, electronic transmission coefficients, spatial distribution of molecular projected self-consistent Hamiltonian orbitals, HOMO-LUMO gaps, effect of electrode materials Y(111)(Y =Au, Ag and Pt) on electronic transport and different molecular geometries corresponding to the closed and open forms through the molecular device are discussed in detail. Based on the results, as soon as possible the open form translates to the closed form, and there is a switch from the ON state to the OFF state(low resistance switches to high resistance). Theoretical results show that the donor/acceptor substituent plays an important role in the electronic transport of molecular devices. The switching performance can be improved to some extent through suitable donor and acceptor substituents.
基金supported by the National Natural Science Foundation of China(grant nos.21875279,22075080,and 52273176)the Shanghai Municipal Science and Technology Major Project(grant no.2018SHZDZX03)the Fundamental Research Funds for the Central Universities,and East China University of Science and Technology.
文摘Electrical switching of a single-molecule junction provides a practical module to perform sophisticated operations in electronic devices.However,designing an all-electrically-driven molecular switch is a great challenge.Here,we experimentally and theoretically investigated the charge transport characteristics of isoindigo(ISO)-molecules at the single-molecule level using the scanning tunneling microscope break junction technique.We find that the single-molecule junctions of ISO-molecules display bias voltage-driven switching characteristics.These switches are realtime,reversible,and nondestructive under low-bias voltages.Experimental results show that the mechanism of the switch is not the transition from nonresonant charge transport to resonant charge transport,but it is the shift of the frontier orbital energy levels of ISO-molecules and the change of the interfacial electronic coupling with bias voltage.Our results will advance the design of high-performance bias voltage-driven molecular switches.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21264016,11464047,and 21364016)the National Basic Research Program of China(Grant No.2012CB821500)the Natural Science Foundation of Xinjiang Uygur Autonomous Region,China(Grant No.2013211A053)
文摘In this paper, we use a molecular theory to study the anomalous switching of ssDNA monolayers. Here, both ssDNA- water and water-water hydrogen bonds and their explicit coupling to the ssDNA conformations are considered. We find that hydrogen bonding becomes a key element in inducing the anomalous switching of ssDNA monolayers. This finding accords well with the experimental observations. Based on our theoretical model, we predict that the anomalous switching induced by water vapor will be applicable to a wide range of hydrogen bonds polymers, and ssDNA-water hydrogen bonds and water-water hydrogen bonds hybridization will lead to the hydrogen-bond network formation of 3D ssDNA monolayers.
基金This research was supported by the National Natural Science Foundation of China(Grant No.50073018)the authors are also thankful to the support from the Key Laboratory of Supramolecular Structure and Materials in Jilin University.
基金Project supported by the Joint Funds of Xinjiang Natural Science Foundation,China(Grant No.2015211C298)
文摘Using a molecular theory, we investigate the temperature-dependent self-assembly of single-stranded DNA(ss DNA)tethered to a charged nanoparticle surface. Here the size, conformations, and charge properties of ss DNA are taken into account. The main results are as follows: i) when the temperature is lower than the critical switching temperature, the ss DNA will collapse due to the existence of electrostatic interaction between ss DNA and charged nanoparticle surface; ii)for the short ss DNA chains with the number of bases less than 10, the switching of ss DNA cannot happen, and the critical temperature does not exist; iii) when the temperature increases, the electrostatic attractive interaction between ss DNA and charged nanoparticle surface becomes weak dramatically, and ss DNA chains will stretch if the electrostatic attractive interaction is insufficient to overcome the elastic energy of ss DNA and the electrostatic repulsion energy. These findings accord well with the experimental observations. It is predicted that the switching of ss DNA will not happen if the grafting densities are too high.
基金Project (20006011) supported by the National Natural Science Foundation of China Project (20021017) by the Natural Science Foundation of Shanxi Province Project (2004-24) by the Scholarship Council Foundation of Shanxi Province
文摘The ion selectivity of nickel hexacyanoferrate thin film to alkali cations in ESIX (electrochemically switched ion exchange) processes was investigated using molecular dynamics(MD) techniques; water and cation (Na+ and Cs+) intercalation, configuration, and dynamics in reduced nickel hexacyanoferrate structures with different cation combinations were studied and compared with the experimental results. In the simulations, water was represented by an extended simple point-charge(SPC/E) model, and all other atomic interactions were represented by a universal force field(UFF). The potential energies of various cations combination (Cs+ and Na+) in reduced i-NiHCF and 1 mol/L Cs/NaCl mixed solution were obtained. In most cases, the total potential energy of the solid is reduced when water is intercalated into the various reduced NiHCF structures. Combining the solid and the solution simulation results, it is shown that the solid composition of 3Cs+/1Na+ is the stablest structure form (NaCs3Ni4[Fe(CN)6]3) over a range of solution compositions.
基金This work was supported in part by the Fundamental Research Funds for the Central Universities(HUST2010MS101),the NSFC(20874025)the Program for New Century Excellent Talents(NCET-07-00273)+1 种基金National Key Basic Research Program of China(2007CB310500)the National Science Foundation(NSF)Chemistry Division(CHE-0805547).
文摘Photosensitive fluorescent probes have become powerful tools in chemical biology and molecular biophysics,which are used to investigate cellular processes with high temporal and spatial resolution.Accordingly,photosensitive fluorescent probes,including photoactivatable,photoconvertible,and photoswitchable fluorophores,have been extensively developed during the past decade.The photoswitchable fluorophores have received much attention because they highlight cellular events clearly.This minireview summarizes recent advances of using reversibly photoswitchable fluorophores and their applications in innovative bioimaging.Photoswitchable fluorophores include photoswitchable fluorescent proteins,photoswitchable fluorescent organic molecules(dyes),and photoswitchable fluorescent nanoparticles.Several strategies have been developed to synthesize photoswitchable fluorophores,including engineering combination proteins,chemical synthesis,polymerization,and self-assembly.Here we concentrate on polymer nanoparticles with optically switchable emission properties:either fluorescence on/offor dualalternating-color fluorescence photoswitching.The essential mechanisms of fluorescence photoswitching enable different types of photoswitchable fluorophores to change emission intensity or wavelength(color)and thus validating the basis of the fluorescence on/offor dual-color photoswitching design.Generally the possible applications of any fluorophores are to label biological targets,followed by specific imaging.The newly developed photoswitchable fluorophores enable super-resolution fluorescence imaging because of their photosensitive emission.Finally,we summarize the important area regarding future research and development on photoswitchable fluorescent nanoparticles.
文摘The dynamic response of molecular orientation, and the temperature and pulse shape dependences of the switching behavior in ferroelectric liquid crystal are described. The switching speed and the surface energy of ferroelectric liquid crystal are given.