1,721,115 research outputs found
Photochemically driven molecular devices and machines
No full textThe development of civilization has always been strictly related to the design and construction of devices – from wheel to jet engine – capable of facilitating man movement and travelling. Nowadays the miniaturization race leads scientists to investigate the possibility of designing and constructing machines and motors at the nanometer scale, that is, at the molecular level. Research on supramolecular chemistry has shown that molecules are convenient nanometer-scale building blocks that can be used, in a bottom-up approach, to construct ultra-miniaturized devices and machines. Chemists are in an ideal position to develop such a molecular approach to functional nanostructures because they are able to design, synthesize, investigate and operate with molecules.
Much of the inspiration to construct molecular devices and machines comes from the outstanding progress of molecular biology that has begun to reveal the secrets of the natural nanomachines which constitute the material base of life. Surely, the supramolecular architectures of the biological world are themselves the premier, proven examples of the feasibility and utility of nanotechnology, and constitute a sound rationale for attempting the realization of artificial molecular devices. The bottom-up construction of machines as complex as those present in Nature is a prohibitive task. Therefore chemists have tried (i) to construct much simpler systems, without mimicking the complexity of the biological structures, (ii) to understand the principles and processes at the basis of their operation, and (iii) to investigate the challenging problems posed by interfacing artificial molecular machines with the macroscopic world, particularly as far as energy supply and information exchange are concerned
Applied photochemistry: when light meets molecules
No full textThis monograph features what happens when light meets molecules. This edited volume contains contributions from an international array of contributors, and it is divided into sections representing a selection of carefully focussed and connected photochemistry topics: energy, technology, medicine, environmental sciences, and art. In each section one or more chapters illustrates relevant aspects of each field, such as artificial photosynthesis and solar energy conversion (energy), light emitting devices and photochromic dyes (technology), and photodynamic therapy and solar filters (medicine). Aimed at students of all levels and researchers active in photochemistry
Luminescent sensors based on quantum dot-molecule conjugates
Full text linkSemiconductor quantum dots (QDs) are inorganic nanoparticles that exhibit unique size-dependent
optical and electronic properties; in particular, they are strongly luminescent. Their surface can be
chemically modified, by either covalent or non-covalent approaches, in order to interface them with
molecular units endowed with specific physical and chemical properties. Photoinduced electron- and
energy-transfer processes between quantum dots and attached molecular species offer versatile
strategies to modulate the photophysical properties of these nanoassemblies in response to a chemical
stimulation. Hence, QD–molecule conjugates are appealing platforms for developing luminescent
sensors according to a modular design. In this review we discuss the principles underlying the rational
construction of this kind of multicomponent species, and we illustrate selected examples of luminescent
QD-based sensors taken from the recent literature
Molecular Machines and Motors - Recent Advances and Perspectives
No full textUntil now, despite the amazing progress in the synthesis of complex molecular
and supramolecular structures, nobody has succeeded in constructing a chemical
system as sophisticated as a microbe or the spore of a mold. Nevertheless, in recent
years a number of fascinating molecular-level machines and motors have been
assembled, using natural building blocks such as DNA, and have been investigated
by means of state-of-the-art techniques.
The cutting-edge advances in this research field are nicely pictured in the
chapters of the present volume. They come from world’s leading laboratories
engaged in the development of molecular machines and are authored by some of
the most respected scientists in the field. This volume shows, on the one hand, the
level of ingenuity and technical capability reached in the construction of artificial
nanomachines roughly two decades after their inception. On the other hand, it
conveys the excitement about the enormous opportunities as well as the challenges
this research area presents, as the interest of researchers is shifting from ensemble to
single-molecule measurements and from homogeneous to heterogeneous environments.
Indeed, as Feynman said in his previously mentioned talk “when we have
some control of the arrangement of things on a molecular scale, we will get an
enormously greater range of possible properties that substances can have.” Although
the answer to the “when” question is not easy to find, there is no doubt that
artificial molecular machines and motors will lead to a wide variety of applications
which we cannot even envisage today
Photo- and Redox-Driven Artificial Molecular Motors
Full text linkDirected motion at the nanoscale is a central attribute of life, and chemically driven motor proteins are nature's choice to accomplish it. Motivated and inspired by such bionanodevices, in the past few decades chemists have developed artificial prototypes of molecular motors, namely, multicomponent synthetic species that exhibit directionally controlled, stimuli-induced movements of their parts. In this context, photonic and redox stimuli represent highly appealing modes of activation, particularly from a technological viewpoint. Here we describe the evolution of the field of photo- and redox-driven artificial molecular motors, and we provide a comprehensive review of the work published in the past 5 years. After an analysis of the general principles that govern controlled and directed movement at the molecular scale, we describe the fundamental photochemical and redox processes that can enable its realization. The main classes of light- and redox-driven molecular motors are illustrated, with a particular focus on recent designs, and a thorough description of the functions performed by these kinds of devices according to literature reports is presented. Limitations, challenges, and future perspectives of the field are critically discussed
Light‐Driven Molecular Machines
No full textIn the last 40 years, the opinion of most researchers has moved from considering artificial molecular machines as simple laboratory curiosities to viewing them as valuable tools to impart novel functionalities and properties to advanced materials and multicomponent systems. In this chapter, we present an overview of the progress on the design and realization of light-activated molecular machines and on their different applications. This research field has always been in close relationship with the study of photoswitchable and photochromic compounds. Indeed, it can be confidently said that at the heart of any light-activated nanomachine, a photoswitchable moiety is at work.
After a brief description of the basic type of photoinduced processes that light-activated nanomachines exploit for their operation, a concise description of the main classes of nanomachines is presented. The chapter follows with examples in which the nanoscale motion of the machine is translated in an advanced functionality. These include switchable catalysts, linear and rotary transporters of small molecular cargos, and supramolecular pumps. Furthermore, examples in which the collective operation of an assembly of molecular machines is harnessed to perform tasks at the microscale and macroscale in hard and soft materials are also reviewed. In particular, functionalized surfaces, metal–organic frameworks, polymers, and self-assembled nanostructures are described wherein the nanoscale movement of embedded molecular machines is amplified, allowing the realization of muscle-like actuators, microfluidic devices, and polymeric materials for light energy transduction and storage
Pompe molecolari azionate dalla luce
Full text linkLA REALIZZAZIONE DI MOTORI MOLECOLARI ARTIFICIALI IN GRADO DI CONVERTIRE ENERGIA IN LAVORO MECCANICO
È UNA SFIDA AFFASCINANTE DELLA NANOTECNOLOGIA E NECESSITA DI SISTEMI CHIMICI IN GRADO DI FUNZIONARE LONTANO
DALL’EQUILIBRIO. QUESTO ARTICOLO DESCRIVE LA PROGETTAZIONE E LA COSTRUZIONE DI UN SEMPLICE SISTEMA
SUPRAMOLECOLARE NEL QUALE L’IRRADIAZIONE LUMINOSA PROMUOVE IL TRANSITO DIREZIONALE DI UN MACROCICLO
LUNGO UN ASSE MOLECOLARE NON SIMMETRICO, PONENDO LE BASI PER LO SVILUPPO DI POMPE MOLECOLARI ARTIFICIAL
The eternal youth of azobenzene: New photoactive molecular and supramolecular devices
No full textThe development of multicomponent chemical systems that can perform predetermined functions
under external control – i.e., molecular devices – is a challenging task in chemistry and a fascinating objective
in the frame of a bottom-up approach to nanostructures. Photochromic units undergo profound changes
in their chemical and/or electronic structure upon light excitation, and are highly interesting for the construction
of photocontrollable molecular devices, machines and materials. The E–Z photoisomerization of
azobenzene – owing to its high efficiency, excellent reversibility and significant physico-chemical differences
between the two forms – is a highly useful reaction in this regard. Azobenzene photoisomerization has been
known for almost 80 years and has been exploited to implement light-induced functionalities with a large
variety of compounds, biomolecules, nanosystems and materials. Here we present some of our recent investigations
highlighting how this outstanding photochrome can be utilized to develop (supra)molecular systems
with valuable light-induced functionalities
Direct synthetic routes to functionalised crown ethers
Full text linkCrown ethers are macrocyclic hosts that can complex a wide range of inorganic and organic cations as well as neutral guest species. Their widespread utilization in several areas of fundamental and applied chemistry strongly relies on strategies for their functionalisation, in order to obtain compounds that could carry out multiple functions and could be incorporated in sophisticated systems. Although functionalised crown ethers are normally synthesised by templated macrocyclisation using appropriately substituted starting materials, the direct addition of functional groups onto a pre-formed macrocyclic framework is a valuable yet underexplored alternative. Here we review the methodologies for the direct functionalisation of aliphatic and aromatic crown ethers sporadically reported in the literature over a period of four decades. The general approach for the introduction of moieties on aliphatic crown ethers involves a radical mediated cross dehydrogenative coupling initiated either by photochemical or thermal/chemical activation, while aromatic crown ethers are commonly derivatised via electrophilic aromatic substitution. Direct functionalization routes can reduce synthetic effort, allow the later modification of crown ether-based architectures, and disclose new ways to exploit these versatile macrocycles in contemporary supramolecular science and technology
Light-driven directed proton transport across the liposomal membrane
No full textWe have developed a simple artificial photoresponsive
ion-gating device by inserting molecular switches in
the membrane of liposomes. A controlled and directed proton
transport across the bilayer membrane can lower the internal pH of
the liposomes from neutral to around 4 under combined light and
chemical stimulation
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