1,720,995 research outputs found
Energy consumption in chemical fuel-driven self-assembly
Full text linkNature extensively exploits high-energy transient self-assembly structures that are able to perform work through a dissipative
process. Often, self-assembly relies on the use of molecules as fuel that is consumed to drive thermodynamically unfavourable
reactions away from equilibrium. Implementing this kind of non-equilibrium self-assembly process in synthetic systems is
bound to profoundly impact the fields of chemistry, materials science and synthetic biology, leading to innovative dissipative
structures able to convert and store chemical energy. Yet, despite increasing efforts, the basic principles underlying chemical
fuel-driven dissipative self-assembly are often overlooked, generating confusion around the meaning and definition of scientific
terms, which does not favour progress in the field. The scope of this Perspective is to bring closer together current experimental
approaches and conceptual frameworks. From our analysis it also emerges that chemically fuelled dissipative processes
may have played a crucial role in evolutionary processes
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
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
Light-powered autonomous and directional molecular motion of a dissipative self-assembling system
Full text linkBiomolecular motors convert energy into directed motion and operate away from thermal equilibrium. The development of
dynamic chemical systems that exploit dissipative (non-equilibrium) processes is a challenge in supramolecular chemistry
and a premise for the realization of artificial nanoscale motors. Here, we report the relative unidirectional transit of a nonsymmetric
molecular axle through a macrocycle powered solely by light. The molecular machine rectifies Brownian
fluctuations by energy and information ratchet mechanisms and can repeat its working cycle under photostationary
conditions. The system epitomizes the conceptual and practical elements forming the basis of autonomous light-powered
directed motion with a minimalist molecular design
Nuclear Magnetic Resonance Reveals Molecular Species in Carbon Nanodot Samples Disclosing Flaws
Full text linkCarbon nanodots are currently one of the hot topics in the nanomaterials world, due to their accessible synthesis and promising features. However, the purification of these materials is still a critical aspect, especially for syntheses involving molecular precursors. Indeed, the presence of unreacted species or small organic molecules formed during solvothermal treatments can affect the properties of the synthesized nanomaterials. To illustrate the extreme importance of this issue, we present two case studies in which insufficient purification results in misleading conclusions regarding the chiral and fluorescent properties of the investigated materials. Key to identify molecular species is the use of nuclear magnetic resonance, which proves to be an effective tool. Our work highlights the need to include nuclear magnetic resonance as a standard characterization technique for carbon‐based nanomaterials, to minimize the risk of observing properties that arise from molecular species, rather than the target carbon nanodots
Light-powered, artificial molecular pumps: a minimalistic approach
Full text linkThe realization of artificial molecular motors capable of converting energy into mechanical work is a fascinating challenge of nanotechnology and requires reactive systems that can operate away from chemical equilibrium. This article describes the design and construction of a simple, supramolecular ensemble in which light irradiation causes the directional transit of a macrocycle along a nonsymmetric molecular axle, thus forming the basis for the development of artificial molecular pumps
Analysis of kinetic asymmetry in a multi-cycle reaction network establishes the principles for autonomous compartmentalized molecular ratchets
Full text linkKinetic asymmetry is a key parameter describing non-equilibrium systems: it indicates the directionality of a reaction network under steady-state conditions. So far, kinetic asymmetry has been evaluated only in networks featuring a single cycle. Here, we have investigated kinetic asymmetry in a multi-cycle system using a combined theoretical and numerical approach. First, we report the general expression of kinetic asymmetry for multi-cycle networks. Then, we specify it for a recently reported electrochemically controlled network comprising diffusion steps, which we used as a model system to reveal how key parameters influence directionality. In contrast with the current understanding, we establish that spatial separation—including compartmentalization—can enable autonomous energy ratchet mechanisms, with directionality dictated by thermodynamic features. Kinetic simulations confirm analytical findings and illustrate the interplay between diffusion, chemical, and electrochemical processes. The treatment is general, as it can be applied to other multi-cycle networks, facilitating the realization of endergonic processes across domains
Photochemically controlled molecular machines with sequential logic operation
No full textA molecular machine is an assembly of molecular components (i.e., a supramolecular structure) designed to perform specific mechanical movements in response to external stimuli. Biomolecular machines are essential for living organisms and are proven examples of the feasibility and utility of nanotechnology. Artificial molecular machines have been built in the laboratory and their use for smart materials and devices is the subject of much investigation. Here we discuss molecular machines based on rotaxane-like species, whose operation depends both on the type and sequencing of stimuli. These systems have the potential to store information and when carefully designed, the interplay of thermodynamic and kinetic features of supramolecular assemblies can yield sequential behavior. The investigation of ‘intelligent’ molecules capable of recognizing a specific input code can introduce new concepts to the field of chemistry and stimulate research in the bottom-up construction of nanodevices
Optical processes in carbon nanocolloids
No full textIn recent years, carbon dots, graphene quantum dots, and other carbon nanocolloids have attracted a mounting interest as readily available, non-toxic, and tailorable carbon-based nanomaterials. One of the most fascinating features of carbon nanocolloids is their luminescence, the origin of which remains a source of dispute. The lack of understanding of the optical properties of carbon nanocolloids hampers their use in technological, environmental, and biomedical processes. Here, we review the current knowledge of excited states in carbon nanocolloids and related properties, inviting researchers to embrace the complexity of carbon nanocolloids. We point to the fundamental problems associated with their structure, photophysics, and photochemistry and highlight multiple directions of current and future research of this exciting class of nanomaterials.Fil: Ragazzon, Giulio. Università degli Studi di Trieste; ItaliaFil: Cadranel, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; ArgentinaFil: Ushakova, Elena V.. City University of Hong Kong; ChinaFil: Wang, Yichun. University of Michigan; Estados UnidosFil: Guldi, Dirk. Universitat Erlangen-Nuremberg; AlemaniaFil: Rogach, Andrey L.. City University of Hong Kong; ChinaFil: Kotov, Nicholas A.. University of Michigan; Estados UnidosFil: Prato, Maurizio. Università degli Studi di Trieste; Itali
Transfer of Axial Chirality to the Nanoscale Endows Carbon Nanodots with Circularly Polarized Luminescence
Full text linkWe report the synthesis, purification and characterization of chiral carbon nanodots starting from atropoisomeric precursors. The obtained atropoisomeric carbon nanodots are soluble in organic solvents and have good thermal stability, which are desirable features for technological applications. The synthetic protocol is robust, as it supports a number of variations in terms of molecular doping agents. Remarkably, the combination of axially chiral precursors and 1,4‐benzoquinone as doping agent results in green‐emissive carbon dots displaying circularly polarized luminescence. Dissymmetry factors of |3.5|×10(−4) are obtained in solution, without the need of any additional element of chirality. Introducing axial chirality expands the strategies available to tailor the properties of carbon nanodots, paving the way for carbon nanoparticles that combine good processability in organic solvents with engineered advanced chiroptical properties
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