We present a study on InAs/InGaAs QDs nanostructures grown by molecular beam epitaxy on InGaAs metamorphic buffers, that are designed so as to determine the strain of QD and, then, to shift the luminescence emission t...We present a study on InAs/InGaAs QDs nanostructures grown by molecular beam epitaxy on InGaAs metamorphic buffers, that are designed so as to determine the strain of QD and, then, to shift the luminescence emission towards the 1.5 μm region （QD strain engineering）. Moreover, we embed the QDs in InAIAs or GaAs barriers in addition to the InGaAs confining layers, in order to increase the activation energy for confined carrier thermal escape; thus, we reduce the thermal quenching of the photoluminescence, which prevents room temperature emission in the long wavelength range. We study the dependence of QD properties, such as emission energy and activation energy, on barrier thickness and height and we discuss how it is possible to compensate for the barrier-induced QD emission blue-shift taking advantage of QD strain engineering. Furthermore, the combination of enhanced barriers and QD strain engineering in such metamorphic QD nanostmctures allowed us to obtain room temperature emission up to 1.46μm, thus proving how this is a valuable approach in the auest for 1.55 um room temperature emission from ODs grown on GaAs substrates.展开更多
In this work, we demonstrated a simple and efficacious two-step method for the synthesis of Ag@Au core-shell nanoparticles （Ag@AuNPs） and the Ag/Au hollow nanocages （Ag/AuNCs） with Ag nanoparticles （AgNPs） as se...In this work, we demonstrated a simple and efficacious two-step method for the synthesis of Ag@Au core-shell nanoparticles （Ag@AuNPs） and the Ag/Au hollow nanocages （Ag/AuNCs） with Ag nanoparticles （AgNPs） as seeds by adjusting pH, and the preparation of hybrid Ag@AuNPs- or Ag/AuNCs-graphene oxide nanocomposites （Ag@AuNPs-GO or Ag/AuNCs-GO） based on the self-assembly. It was noticed from the elec- trostatic assembly experiment that the loading amount of Ag/AuNCs on GO nanosheet was more than that of Ag@AuNPs. The as-synthesized hybrid materials were characterized by transmission electron microscopy, atomic force microscopy, ξ-potential, high-angle annular dark- field scanning transmission electron microscopy, thermo- gravimetric analyzer and X-ray diffraction. Catalytic activities of Ag@AuNPs, Ag/AuNCs and Ag/AuNCs-GO nanostructures were investigated in the reduction of 4-, 3-or 2-nitrophenol to 4-, 3- or 2-aminophenol, and on the basis of comparative kinetic studies the following trend was obtained for the related catalytic activity： Ag/AuNCs- GO 〉 Ag/AuNCs 〉 Ag@AuNPs. These observations were attributed to the simultaneous effects of surface area available for catalytic reaction and composition of the hybrid nanostructures.展开更多
The assembly of nanocrystals into ordered structures called supercrystals or superstructures has become a pivotal frontier owing to numerous useful applications such as correlating the arrangements of atoms in macrosc...The assembly of nanocrystals into ordered structures called supercrystals or superstructures has become a pivotal frontier owing to numerous useful applications such as correlating the arrangements of atoms in macroscopic crystals and tuning the collective properties to meet the demands of various applications. In this article, recent progress in the preparation of three-dimensional superlattices of nanocrystals is outlined, with a particular emphasis on the driving forces and evolutionary routes beyond orderly assembly. First, the leading or repulsive forces that internally and externally govern the formation of three-dimensional supercrystals are systematically identified and discussed with respect to their origins and functions in three-dimensional self-organization. Then a synoptic introduction of commonly applied means of nanocrystal self-assembly based on growth scenarios such as droplet evaporation and a liquid/liquid interface is presented with specific cases and detailed analyses. Finally, the existing challenges and prospects for this field are briefly highlighted.展开更多
Peptoids(or poly-N-substituted glycines)are a promising class of bioinspired sequence-defined polymers due to their highly efficient synthesis,high chemical stability,enzyme hydrolysis resistance,and biocompatibility....Peptoids(or poly-N-substituted glycines)are a promising class of bioinspired sequence-defined polymers due to their highly efficient synthesis,high chemical stability,enzyme hydrolysis resistance,and biocompatibility.By tuning the side chain chemistry of peptoids,it allows for precise control over sequences and achieving a large side-chain diversity.Due to these unique features,in the last several years,many amphiphilic peptoids were designed as highly tunable building blocks for the preparation of biomimetic nanomaterials with well-defined hierarchical structures and desired functionalities.Herein,we provide an overview of the recent achievements in this area by dividing them into the following three aspects.First,mica-and silica-templated peptoid selfassembly are summarized.The presence of inorganic substrates provides the guarantee of investigating their selfassembly mechanisms and interactions between peptoids and substrates using nanoscale characterization techniques,particularly in situ atomic force microscopy(AFM)and AFMbased dynamic force spectroscopy(AFM-DFS).Second,solution-phase self-assembly of peptoids into nanotubes and nanosheets is presented,as well as their self-repair properties.Third,the applications of peptoid-based nanomaterials are outlined,including the construction of catalytic nanomaterials as a template and cytosolic delivery as cargoes.展开更多
Block copolymers can yield a diverse array of nanostructures.Their assembly structures are influenced by their inherent structures,and the wide variety of structures that can be prepared especially becomes apparent wh...Block copolymers can yield a diverse array of nanostructures.Their assembly structures are influenced by their inherent structures,and the wide variety of structures that can be prepared especially becomes apparent when one considers the number of routes available to prepare block copolymer assemblies.Some examples include self-assembly,directed assembly,coupling,as well as hierarchical assembly,which can yield assemblies having even higher structural order.These assembly routes can also be complemented by processing techniques such as selective crosslinking and etching,the former technique leading to permanent structures,the latter towards sculpted and the combination of the two towards permanent sculpted structures.The combination of these pathways provides extremely versatile routes towards an exciting variety of architectures.This review will attempt to highlight destinations reached by LIU Guojun and coworkers following these pathways.展开更多
Numerous peptides derived from naturally occurring proteins or de novo designed have been found to self-assemble into various nanostructures.These well-defined nanostructures have shown great potential for a variety o...Numerous peptides derived from naturally occurring proteins or de novo designed have been found to self-assemble into various nanostructures.These well-defined nanostructures have shown great potential for a variety of biomedical and biotechnological applications.In particular,surfactant-like peptides(SLPs)have distinctive advantages in their length,aggregating ability,and water solubility.In this article,we report recent advances in the mechanistic understanding of the self-assembly principles of SLPs and in their applications,most of which have been made in our laboratory.Hydrogen bonding between peptide backbones,hydrophobic interaction between hydrophobic side chains,and electrostatic repulsion between charged head groups all have roles in mediating the self-assembly of SLPs;the final self-assembled nanostructures are therefore dependent on their interplay.SLPs have shown diverse applications ranging from membrane protein stabilization and antimicrobial/anticancer agents to nanofabrication and biomineralization.Future advances in the self-assembly of SLPs will hinge on their large-scale production,the design of new functional SLPs with targeted properties,and the exploitation of new or improved applications.展开更多
Prior studies using single and binary adsorbates indicate that nanografting impacts the reaction pathways and local structure of self-assembled monolayers （SAMs）. This work explores the influence of nanografting in ...Prior studies using single and binary adsorbates indicate that nanografting impacts the reaction pathways and local structure of self-assembled monolayers （SAMs）. This work explores the influence of nanografting in the case of ternary SAMs. Using atomic force microscopy （AFM） as both a nanografting and imaging tool, the local structures of two ternary SAMs, SC14：SSC10CHO：SC2COOH and SC18：SSC10CHO：SC2COOH, formed under natural growth and nanografting were imaged and compared. The results indicate that nanografting impacts the degree of phase segregation and the domain height in ternary SAMs. In addition to the previously known effect of altering self-assembly pathways, this study reveals an additional impact for these ternary systems： By shaving over the previous trajectory （grafted region）, nanografting could start exchange reactions and lateral movement of surface-bound thiols, which leads to new and somewhat unanticipated local structures.展开更多
基金The work has been partially supported by the "SANDiE" Networkof Excellence of EU(contract no. NMP4-CT-2004-500101).
文摘We present a study on InAs/InGaAs QDs nanostructures grown by molecular beam epitaxy on InGaAs metamorphic buffers, that are designed so as to determine the strain of QD and, then, to shift the luminescence emission towards the 1.5 μm region （QD strain engineering）. Moreover, we embed the QDs in InAIAs or GaAs barriers in addition to the InGaAs confining layers, in order to increase the activation energy for confined carrier thermal escape; thus, we reduce the thermal quenching of the photoluminescence, which prevents room temperature emission in the long wavelength range. We study the dependence of QD properties, such as emission energy and activation energy, on barrier thickness and height and we discuss how it is possible to compensate for the barrier-induced QD emission blue-shift taking advantage of QD strain engineering. Furthermore, the combination of enhanced barriers and QD strain engineering in such metamorphic QD nanostmctures allowed us to obtain room temperature emission up to 1.46μm, thus proving how this is a valuable approach in the auest for 1.55 um room temperature emission from ODs grown on GaAs substrates.
基金Acknowledgments This work was supported by the National Nalural Science Foundation of China （21 105042）, the Science Foundation of China Postdoctor （2014M560572）, the Natural Science Foundation of Shandong Province IZR2015BM024）, and Tai-Shan Scholar Research Fund of Shandong Province. The sludy was partially supported by grant NIH IR01DA037838 to Drs. Li and Nair.
文摘In this work, we demonstrated a simple and efficacious two-step method for the synthesis of Ag@Au core-shell nanoparticles （Ag@AuNPs） and the Ag/Au hollow nanocages （Ag/AuNCs） with Ag nanoparticles （AgNPs） as seeds by adjusting pH, and the preparation of hybrid Ag@AuNPs- or Ag/AuNCs-graphene oxide nanocomposites （Ag@AuNPs-GO or Ag/AuNCs-GO） based on the self-assembly. It was noticed from the elec- trostatic assembly experiment that the loading amount of Ag/AuNCs on GO nanosheet was more than that of Ag@AuNPs. The as-synthesized hybrid materials were characterized by transmission electron microscopy, atomic force microscopy, ξ-potential, high-angle annular dark- field scanning transmission electron microscopy, thermo- gravimetric analyzer and X-ray diffraction. Catalytic activities of Ag@AuNPs, Ag/AuNCs and Ag/AuNCs-GO nanostructures were investigated in the reduction of 4-, 3-or 2-nitrophenol to 4-, 3- or 2-aminophenol, and on the basis of comparative kinetic studies the following trend was obtained for the related catalytic activity： Ag/AuNCs- GO 〉 Ag/AuNCs 〉 Ag@AuNPs. These observations were attributed to the simultaneous effects of surface area available for catalytic reaction and composition of the hybrid nanostructures.
基金This work was partially supported DOE STFR program and CEI grant 68195. C. W. thanks ＂Dissertation Fellowship Award＂ supported by the State University of New York at Binghamton C. S. is partially supported by the Provost＇s Summer Doctoral Fellowship and J. Z. acknowledges grants （the National Natural Science Foundation of China （Nos. 21471160 and 14CX05037A）） and TaiShan Scholar Foundation.
文摘The assembly of nanocrystals into ordered structures called supercrystals or superstructures has become a pivotal frontier owing to numerous useful applications such as correlating the arrangements of atoms in macroscopic crystals and tuning the collective properties to meet the demands of various applications. In this article, recent progress in the preparation of three-dimensional superlattices of nanocrystals is outlined, with a particular emphasis on the driving forces and evolutionary routes beyond orderly assembly. First, the leading or repulsive forces that internally and externally govern the formation of three-dimensional supercrystals are systematically identified and discussed with respect to their origins and functions in three-dimensional self-organization. Then a synoptic introduction of commonly applied means of nanocrystal self-assembly based on growth scenarios such as droplet evaporation and a liquid/liquid interface is presented with specific cases and detailed analyses. Finally, the existing challenges and prospects for this field are briefly highlighted.
基金supported by the Startup Research Fund of Dongguan University of Technology(KCYKYQD2017015)the US Department of Energy,Office of Science,Office of Basic Energy Sciences,as part of the Energy Frontier Research Centers program:CSSAS—The Center for the Science of Synthesis Across Scales(DESC0019288)。
文摘Peptoids(or poly-N-substituted glycines)are a promising class of bioinspired sequence-defined polymers due to their highly efficient synthesis,high chemical stability,enzyme hydrolysis resistance,and biocompatibility.By tuning the side chain chemistry of peptoids,it allows for precise control over sequences and achieving a large side-chain diversity.Due to these unique features,in the last several years,many amphiphilic peptoids were designed as highly tunable building blocks for the preparation of biomimetic nanomaterials with well-defined hierarchical structures and desired functionalities.Herein,we provide an overview of the recent achievements in this area by dividing them into the following three aspects.First,mica-and silica-templated peptoid selfassembly are summarized.The presence of inorganic substrates provides the guarantee of investigating their selfassembly mechanisms and interactions between peptoids and substrates using nanoscale characterization techniques,particularly in situ atomic force microscopy(AFM)and AFMbased dynamic force spectroscopy(AFM-DFS).Second,solution-phase self-assembly of peptoids into nanotubes and nanosheets is presented,as well as their self-repair properties.Third,the applications of peptoid-based nanomaterials are outlined,including the construction of catalytic nanomaterials as a template and cytosolic delivery as cargoes.
基金Guojun Liu wishes to thank NSERC of Canada for a Tier 1 Canada Research Chair and for funding
文摘Block copolymers can yield a diverse array of nanostructures.Their assembly structures are influenced by their inherent structures,and the wide variety of structures that can be prepared especially becomes apparent when one considers the number of routes available to prepare block copolymer assemblies.Some examples include self-assembly,directed assembly,coupling,as well as hierarchical assembly,which can yield assemblies having even higher structural order.These assembly routes can also be complemented by processing techniques such as selective crosslinking and etching,the former technique leading to permanent structures,the latter towards sculpted and the combination of the two towards permanent sculpted structures.The combination of these pathways provides extremely versatile routes towards an exciting variety of architectures.This review will attempt to highlight destinations reached by LIU Guojun and coworkers following these pathways.
基金supported by the National Natural Science Foundation of China(21373270,21033005)the Natural Science Foundation of Shandong Province(JQ201105).the support of the Program for New Century Excellent Talents in University(NCET-11-0735)
文摘Numerous peptides derived from naturally occurring proteins or de novo designed have been found to self-assemble into various nanostructures.These well-defined nanostructures have shown great potential for a variety of biomedical and biotechnological applications.In particular,surfactant-like peptides(SLPs)have distinctive advantages in their length,aggregating ability,and water solubility.In this article,we report recent advances in the mechanistic understanding of the self-assembly principles of SLPs and in their applications,most of which have been made in our laboratory.Hydrogen bonding between peptide backbones,hydrophobic interaction between hydrophobic side chains,and electrostatic repulsion between charged head groups all have roles in mediating the self-assembly of SLPs;the final self-assembled nanostructures are therefore dependent on their interplay.SLPs have shown diverse applications ranging from membrane protein stabilization and antimicrobial/anticancer agents to nanofabrication and biomineralization.Future advances in the self-assembly of SLPs will hinge on their large-scale production,the design of new functional SLPs with targeted properties,and the exploitation of new or improved applications.
文摘Prior studies using single and binary adsorbates indicate that nanografting impacts the reaction pathways and local structure of self-assembled monolayers （SAMs）. This work explores the influence of nanografting in the case of ternary SAMs. Using atomic force microscopy （AFM） as both a nanografting and imaging tool, the local structures of two ternary SAMs, SC14：SSC10CHO：SC2COOH and SC18：SSC10CHO：SC2COOH, formed under natural growth and nanografting were imaged and compared. The results indicate that nanografting impacts the degree of phase segregation and the domain height in ternary SAMs. In addition to the previously known effect of altering self-assembly pathways, this study reveals an additional impact for these ternary systems： By shaving over the previous trajectory （grafted region）, nanografting could start exchange reactions and lateral movement of surface-bound thiols, which leads to new and somewhat unanticipated local structures.
