Intercommunication between dynamic chemical networks plays a major role in cellular transformations. Inspired by nature, we introduce the intercommunication between two constitutional dynamic ...networks, CDNs, “S” and “T” composed, each, of four equilibrated supramolecular constituents AA′, AB′, BA′, and BB′, and of CC′, CD′, DC′, and DD′, respectively. Each of the constituents is conjugated to a Mg2+-ion-dependent DNAzyme unit that acts as a reporter element for the concentration of the respective constituent via the catalyzed cleavage of the fluorophore/quencher-functionalized substrate associated with the respective DNAzyme reporter. Also, constituents BB′ (in CDN “S”) and CC′ (in CDN “T”) include Mg2+-ion-dependent DNAzymes acting as activator units for generating triggering signals between the networks. Subjecting CDNs “S” and “T” to the catalytically cleavable hairpin trigger Hdd′ or Haa′, respectively, yields input strands that intercommunicate the CDNs by affecting the time-dependent re-equilibration of the constituents of the counter CDN without affecting the dynamic equilibrium of the constituents of the CDN that generates the triggering strands. Treatment of CDNs “S” and “T” with hairpins Hdd′ and Haa′ (or Hba′), respectively, stimulates autonomous positive/positive or positive/negative feedback to the programmed time-dependent up-regulation or down-regulation of the equilibrated constituents in the two CDNs.
The full blossoming of quantum technologies requires the availability of easy-to-prepare materials where quantum coherences can be effectively initiated, controlled, and exploited, preferably at ...ambient conditions. Solid-state multilayers of colloidally grown quantum dots (QDs) are highly promising for this task because of the possibility of assembling networks of electronically coupled QDs through the modulation of sizes, inter-dot linkers, and distances. To usefully probe coherence in these materials, the dynamical characterization of their collective quantum mechanically coupled states is needed. Here, we explore by two-dimensional electronic spectroscopy the coherent dynamics of solid-state multilayers of electronically coupled colloidally grown CdSe QDs and complement it by detailed computations. The time evolution of a coherent superposition of states delocalized over more than one QD was captured at ambient conditions. We thus provide important evidence for inter-dot coherences in such solid-state materials, opening up new avenues for the effective application of these materials in quantum technologies.
One of the most recent developments at the forefront of nanotechnology is the attempt to exploit quantum phenomena in nanometer scale materials, exploring novel applications of quantum effects. An ...effective exploitation of quantum phenomena must necessarily pass through a deep understanding of how to generate, manipulate, and characterize coherent superposition of quantum states in the nanosystems. However, despite the lively interest in this topic, the study of coherent effects in nanomaterials still represents relatively unexplored territory. Here we report an investigation on the ultrafast coherent dynamics of colloidal CdSe quantum dots (QDs) by the mean of two-dimensional electronic spectroscopy (2DES). The time evolution of specific coherent superpositions of fine structure levels in these nanomaterials is clearly demonstrated. The obtained results represent an important step forward toward a deeper understanding of quantum properties of nanomaterials.
Display omitted
•A non-stationary coherent superposition of the ground and first excited states of LiH and its isotopomers is pumped.•The two states are of opposite polarity and are separated by a ...small energy gap.•A mass-independent early charge migration is exhibited by all three isotopomers, LiH, LiD, LiT.•The closely similar coherent dynamics of all three isotopomers persists for approximately 2 fs.
Charge migration in LiH molecule and its isotopomers LiD and LiT is examined by quantum dynamics including the non-adiabatic effects of nuclear motions. Upon excitation by an ultrafast UV pulse, mass-independent charge migration occurs between the ground and first excited Σ states. The opposite polarity of these states and a relatively small energy gap between them allow the charge to oscillate at early time of the dynamics during 2 fs after the pulse is over. When the nuclei move, a mass-dependent revival of coherence is computed with a period of 80, 107, 123 fs for LiH, LiD, and LiT, respectively.
Biological systems that are capable of performing computational operations could be of use in bioengineering and nanomedicine, and DNA and other biomolecules have already been used as active ...components in biocomputational circuits. There have also been demonstrations of DNA/RNA-enzyme-based automatons, logic control of gene expression, and RNA systems for processing of intracellular information. However, for biocomputational circuits to be useful for applications it will be necessary to develop a library of computing elements, to demonstrate the modular coupling of these elements, and to demonstrate that this approach is scalable. Here, we report the construction of a DNA-based computational platform that uses a library of catalytic nucleic acids (DNAzymes), and their substrates, for the input-guided dynamic assembly of a universal set of logic gates and a half-adder/half-subtractor system. We demonstrate multilayered gate cascades, fan-out gates and parallel logic gate operations. In response to input markers, the system can regulate the controlled expression of anti-sense molecules, or aptamers, that act as inhibitors for enzymes.
Vacuum ultraviolet (VUV) photodissociation of N2 molecules is a source of reactive N atoms in the interstellar medium. In the energy range of VUV optical excitation of N2, the N–N triple bond ...cleavage leads to three types of atoms: ground-state N(4S) and excited-state N(2P) and N(2D). The latter is the highest reactive and it is believed to be the primary participant in reactions with hydrocarbons in Titan's atmosphere. Experimental studies have observed a non-monotonic energy dependence and non-statistical character of the photodissociation of N2. This implies different dissociation pathways and final atomic products for different wavelength regions in the sunlight spectrum. We here apply ab initio quantum chemical and nonadiabatic quantum dynamical techniques to follow the path of an electronic state from the excitation of a particular singlet 1Σu+ and 1Πu vibronic level of N2 to its dissociation into different atomic products. We simulate dynamics for two isotopomers of the nitrogen molecule, 14N2 and 14N15N for which experimental data on the branching are available. Our computations capture the non-monotonic energy dependence of the photodissociation branching ratios in the energy range 108 000–116 000 cm−1. Tracing the quantum dynamics in a bunch of electronic states enables us to identify the key components that determine the efficacy of singlet to triplet population transfer and therefore predissociation lifetimes and branching ratios for different energy regions.
Photodissociation of the nitrogen molecule in the vacuum ultraviolet (VUV) is a major source of reactive nitrogen atoms in the upper atmosphere of Earth and throughout the solar system. Recent ...experimental studies have revealed strong energy dependence of the VUV photodissociation branching ratios to the N(4S3/2)+N(2DJ) and N(4S3/2)+N(2PJ) product channels, the primary dissociation pathways in the 108,000–116,000 cm−1 energy region. This produces N(2DJ) and N(2PJ) excited atoms that differ significantly in their chemical reactivity. The branching ratios oscillate with increase in the VUV excitation energy. We use high-level ab initio quantum chemistry to compute the potential curves of 17 electronic excited states and their nonadiabatic and spin–orbit couplings. The dynamics follow the sequential evolution from the optically excited but bound 1Σu+ singlets. Spin–orbit coupling enables transfer to the dissociative triplet and quintet states. We compute the photodissociation yields through the dense manifold of electronic states leading to both exit channels. The dynamical simulations accurately capture the branching oscillations and enable a detailed look into the photodissociation mechanism. The major contribution to the dissociation is through the two lowest 3Πu states. However, for both isotopomers, at about 110,000 cm−1 there is an abnormally low dissociation rate into the N(4S3/2)+N(2PJ) channel that enables comparable participation of triplet 3Σu− and quintet 5Πu electronic states. This leads to the first peak in the branching ratio. At higher energies, trapping of the population in the 33Πu bound triplet state occurs. This favors dissociation to the lower-energy N(4S3/2)+N(2DJ) channel and results in the observed second switch in branching ratios.
Following a single photon VUV absorption, the N2 molecule dissociates into distinct channels leading to N atoms of different reactivities. The optically accessible singlets are bound, and ...dissociation occurs through spin–orbit induced transfer to the triplets. There is a forest of coupled electronic states, and we here aim to trace a path along the nonadiabatic couplings toward a particular exit channel. To achieve this, we apply a time-reversed quantum dynamical approach that corresponds to a dissociation running back. It begins with an atom–atom relative motion in a particular product channel. Starting with a Gaussian wave packet at the dissociation region of N2 and propagating it backward in time, one can see the population transferring among the triplets due to a strong nonadiabatic interaction between these states. Simultaneously, the optically active singlets get populated because of spin–orbit coupling to the triplets. Thus, backward propagation traces the nonradiative association of nitrogen atoms.
Nature performs complex information processing circuits, such the programmed transformations of versatile stem cells into targeted functional cells. Man-made molecular circuits are, however, unable ...to mimic such sophisticated biomachineries. To reach these goals, it is essential to construct programmable modular components that can be triggered by environmental stimuli to perform different logic circuits. We report on the unprecedented design of artificial pH-programmable DNA logic arrays, constructed by modular libraries of Mg2+- and UO2 2+-dependent DNAzyme subunits and their substrates. By the appropriate modular design of the DNA computation units, pH-programmable logic arrays of various complexities are realized, and the arrays can be erased, reused, and/or reprogrammed. Such systems may be implemented in the near future for nanomedical applications by pH-controlled regulation of cellular functions or may be used to control biotransformations stimulated by bacteria.
PDF
