Dielectric Solvent Research Articles

Ionic Conductivity and Viscosity Behavior of PMMA-based Nano-dispersed Polymer Gel Electrolytes Containing Lithium Perchlorate

Abstract: In this study, nano-dispersed polymer gel electrolytes containing polymethylmethacrylate (PMMA), lithium perchlorate (LiClO4), diethyl carbonate (DEC), dimethylacetamide (DMA), and nano-sized fumed silica (SiO2) have been synthesized and characterized. The electrolytes showed high ionic conductivity for electrolytes with higher dielectric constant solvents. The polymer enhanced the ionic conductivity of liquid electrolytes having a lower dielectric constant solvent (DEC) at all PMMA concentrations than the electrolytes containing a high dielectric constant solvent (DMA). Further, with the addition of nano-sized fumed silica, the ionic conductivity showed a small increase along with an increase in the mechanical stability of the electrolytes. The viscosity behavior of the electrolytes was also discussed, and it was correlated with the results of the ionic conductivity test. Nano-dispersed polymer gel electrolytes exhibited high ionic conductivity (10-2 S/cm). Further, the conductivity showed only a small change (by a factor, not by an order) over the 25-100°C temperature range and did not vary with time, which is desirable for their use in practical applications.

Electrolyte Design via Cation-Anion Association Regulation for High-Rate and Dendrite-Free Zinc Metal Batteries at Low Temperature.

Low-temperature zinc metal batteries (ZMBs) are highly challenged by Zn dendrite growth, especially at high current density. Here, starting from the intermolecular insights, we report a cation-anion association modulation strategy by matching different dielectric constant solvents and unveil the relationship between cation-anion association strength and Zn plating/stripping performance at low temperatures. The combination of comprehensive characterizations and theoretical calculations indicates that moderate ion association electrolytes with high ionic conductivity (12.09 mS cm-1 at -40 °C) and a stable anion-derived solid electrolyte interphase (SEI) jointly account for highly reversible and dendrite-free Zn plating/stripping behavior, resulting in high-rate and ultrastable cycle performance at low temperature. As a result, at -40 °C, Zn//Zn cells can stably cycle over 400 h at 5 mA cm-2 and 10 mAh cm-2 and Zn//Cu cells exhibit an exceptional average Coulombic efficiency (CE) of 99.91% for 1800 cycles at 1 mA cm-2 and 1 mAh cm-2. Benefiting from enhanced low-temperature Zn plating/stripping performance, Zn//PANI full cells stably operate for 12,000 cycles at 0.5A g-1 and 35,000 cycles at 5 A g-1. Impressively, at -60 °C, Zn//Cu cells still display a high average CE of 99.68% for 2000 cycles. This work underscores the crucial effect of cation-anion association regulation for high-rate and dendrite-free Zn metal anodes, deepening the understanding of intermolecular interaction insights for low-temperature electrolyte design.

Conformational Switching of a Nano-Size Urea-Bridged Zn(II)Porphyrin Dimer by External Stimuli.

For the first time, explicit stabilization of all the three conformers, viz. (cis,cis), (cis,trans) and (trans,trans), of a 'nano-sized' highly-flexible urea-bridged Zn(II)porphyrin dimer have been achieved via careful manipulations of external stimuli such as solvent dielectrics, temperature, anionic interactions, axial ligation and surface-induced stabilization. The conformers differ widely in their structures, chemical and photophysical properties and thus have vast potential applicability. X-ray structural characterizations have been reported for the (cis,cis) and (cis,trans)-conformers. While (cis,cis) conformer stabilized exclusively in dichloromethane, more polar solvents resulted in the stabilization of (cis,trans) and (trans,trans)-conformers. Low temperature promotes the stabilization of (cis,trans)-conformer while rise in temperature facilitates flipping to the (cis,cis) one. Significantly, exclusive stabilization of the (trans,trans)-isomer has been illustrated using acetate anion which facilitates H-bonding with the two amide linkages of the urea spacer. Remarkably, HOPG surface facilitates stabilization of the energetically challenging (trans,trans)-conformer via CH⋅⋅⋅π and π⋅⋅⋅π interactions with the solid surface to the porphyrinic cores. DFT calculations demonstrate that the relative stability of the conformers can be modulated upon slight external perturbations as also observed in the experiment. Several factors contributing towards the conformational landscape for the highly flexible urea-bridged porphyrin dimers have been mapped.

Absorption Intensities of Organic Molecules from Electronic Structure Calculations versus Experiments: the Effect of Solvation, Method, Basis Set, and Transition Moment Gauge.

Recently, we derived experimental oscillator strengths (OSs) from well-defined UV-visible absorption spectral peaks of 100 molecules in solution. Here, we focus on a subset of transitions with the highest reliability to further benchmark the OSs from several wave function methods and density functionals. We consider multiple basis sets, transition moment gauges (length, velocity, and mixed), and solvent corrections. Most transitions in the comparison set come from conjugated molecules and have π → π* character. We use an automated algorithm to assign computed transitions to experimental bands. OSs computed using the Tamm-Dancoff approximation (TDA), CIS, or EOM-CCSD exhibited a strong gauge dependence, which is diminished in linear response theories (TD-DFT, TD-HF, and to a smaller degree LR-CCSD). OSs calculated from TD-DFT with PCM solvent models are systematically larger than apparent OSs derived from experimental spectra. For example, fcomp from hybrid functionals and PCM have mean absolute errors that are ∼10% of n·fexp, where n is a solvent refractive index factor that arises from the energy flux of the radiation field in a dielectric (solvent). Theoretical cavity field corrections considering spherical cavities do not improve the agreement between computed and experimental data. Corrections that account for the molecular shape and the direction of transition dipole moments, or that explicitly account for the effect of solvent molecules on the local field, should be more appropriate.

(Invited) Probing Charge Carrier-Induced Changes in the Complex Dielectric Function in Carbon Nanotube Dispersions

The injection of charge carriers into pi-conjugated semiconductors, whether by electrochemical injection or chemical charge transfer, is a powerful approach to tune their electrical conductivity. Recently, the concept of dielectric catastrophe, where the charge carrier density is sufficiently large to significantly alter the intrinsic dielectric properties, has been demonstrated at high doping levels in organic semiconductor thin films. The observed increase in the dielectric constant leads to reduced coulombic interactions between charge carriers and the associated counterions, promoting enhanced free carrier generation and transport.Here, we employ a combination of steady state optical spectroscopy, quantitative 19F NMR studies, and microwave dielectric loss spectroscopy to probe charge carrier density and transport in doped single-walled carbon nanotube dispersions. We demonstrate that a similar dielectric catastrophe phenomenon can be observed even in isolated single-walled carbon nanotubes dispersed in a low dielectric constant solvent AND, perhaps more surprisingly, at carrier densities less than one carrier per nanotube. The precise details of the observed changes in complex dielectric function are dependent on the chemical structure of the charge-transfer dopant, with a near-instantaneous increase in the dielectric constant and electrical conductivity observed for low carrier densities using bulky benzyloxy-substituted icosahedral dodecaborane cluster dopants, DDBs. We attribute the observations to weak coulombic interactions between the injected charge carrier and the dopant counterion, along with the large polarizability afforded by the unique physicochemical properties of single-walled carbon nanotubes. If time permits, we will show results from recent studies where we extend this approach to the doping of other nanocarbons.

Elucidating the Impact of the Dielectric Environment on Excitons and Trions in 2D Semiconductor Electrodes

Transition metal dichalcogenides (TMDs) (MX2; M = Mo, W; X = S, Se) are a promising class of materials for photoelectrochemical solar energy conversion applications due to their optimal bandgaps and natural abundance. In this configuration, TMDs are placed onto a conductive substrate and employed as a photoelectrode. A key step in the solar energy conversion process is to photo-excite the semiconductor and dissociate the photogenerated excitons to drive a reaction of interest (e.g., H2 evolution). Because these materials are so physically thin, the excitons are sensitive to the local environment. In this work, we characterize the exciton and trion formation behavior as a function of solvent dielectric, ionic strength, and chemistry. As the dielectric constant of the solvent decreases, trion formation increases. The lower dielectric solvent causes lower Coulombic screening, increasing the probability that an exciton will encounter another electron to generate a trion. I will discuss how these findings relate to a working photoelectrochemical cell.

Unlocking 4.9 V Quasi-Solid-State Lithium Metal Battery via Solvent Screening and Interfacial Manipulation.

Parlous structure integrity of the cathode and erratic interfacial microdynamics under high potential take responsibility for the degradation of solid-state lithium metal batteries (LMBs). Here, high-voltage LMBs have been operated by modulating the polymer electrolyte intrinsic structure through an intermediate dielectric constant solvent and further inducing the gradient solid-state electrolyte interphase. Benefiting from the chemical adsorption between trimethyl phosphate (TMP) and the cathode, the gradient interphase rich in LiPFxOy and LiF is induced, thereby ensuring the structural integrity and interface compatibility of the commercial LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode even at the 4.9 V cutoff voltage. Eventually, the specific capacity of NCM811|Li full cell based on TMP-modulated polymer electrolyte increased by 27.7% from 4.5 to 4.9 V. Such a universal screening method of electrolyte solvents and its derived electrode interfacial manipulation strategy opens fresh avenues for quasi-solid-state LMBs with high specific energy.

A locally solvent-tethered polymer electrolyte for long-life lithium metal batteries

Solid polymer electrolytes exhibit enhanced Li+ conductivity when plasticized with highly dielectric solvents such as N,N-dimethylformamide (DMF). However, the application of DMF-containing electrolytes in solid-state batteries is hindered by poor cycle life caused by continuous DMF degradation at the anode surface and the resulting unstable solid-electrolyte interphase. Here we report a composite polymer electrolyte with a rationally designed Hofmann-DMF coordination complex to address this issue. DMF is engineered on Hofmann frameworks as tethered ligands to construct a locally DMF-rich interface which promotes Li+ conduction through a ligand-assisted transport mechanism. A high ionic conductivity of 6.5 × 10−4 S cm−1 is achieved at room temperature. We demonstrate that the composite electrolyte effectively reduces the free shuttling and subsequent decomposition of DMF. The locally solvent-tethered electrolyte cycles stably for over 6000 h at 0.1 mA cm−2 in Li | |Li symmetric cell. When paired with sulfurized polyacrylonitrile cathodes, the full cell exhibits a prolonged cycle life of 1000 cycles at 1 C. This work will facilitate the development of practical polymer-based electrolytes with high ionic conductivity and long cycle life.

Functional Electrolyte: Highly-Safe LIB Using Branched Carboxylic Acid Ester as Electrolyte Additive

The electrolyte in current automotive lithium-ion batteries is a mixture of ethylene carbonate (EC), which has a high dielectric constant, and ethyl methyl carbonate or dimethyl carbonate, which have a low viscosity. However, the flash point of these mixed solvents is as low as 25 °C, so safety precautions must be taken. On the other hand, if only EC or propylene carbonate with a high flash point is used, the flash point will be 120 °C or higher. However, the high dielectric constant solvent cannot wet the hydrophobic separator whose material is polyethylene and/or polypropylene. Therefore, there is a problem that the battery does not work. In 1999, we proposed a “functional electrolyte” in which a small amount of an additive with a new function is added to the electrolyte, and many additives have since been commercialized. In recent work, we focused on a low viscosity linear carboxylic acid esters, designed an electrolyte with a flash point above 120 °C that provides wettability to the separator even in an electrolyte with a high dielectric constant solvent.

Photolysis of tolfenamic acid in aqueous and organic solvents: a kinetic study.

Tolfenamic acid (TA) is a non-steroidal anti-inflammatory drug that was studied for its photodegradation in aqueous (pH 2.0-12.0) and organic solvents (acetonitrile, methanol, ethanol, 1-propanol, 1-butanol). TA follows first-order kinetics for its photodegradation, and the apparent first-order rate constants (k obs) are in the range of 0.65 (pH 12.0) to 6.94 × 10-2 (pH 3.0) min-1 in aqueous solution and 3.28 (1-butanol) to 7.69 × 10-4 (acetonitrile) min-1 in organic solvents. The rate-pH profile for TA photodegradation is an inverted V (∧) or V-top shape, indicating that the cationic form is more susceptible to acid hydrolysis than the anionic form of TA, which is less susceptible to alkaline hydrolysis. The fluorescence behavior of TA also exhibits a V-top-shaped curve, indicating maximum fluorescence intensity at pH 3.0. TA is highly stable at a pH range of 5.0-7.0, making it suitable for formulation development. In organic solvents, the photodegradation rate of TA increases with the solvent's dielectric constant and solvent acceptor number, indicating solute-solvent interactions. The values of k obs decreased with increased viscosity of the solvents due to diffusion-controlled processes. The correlation between k obs versus ionization potential and solvent density has also been established. A total of 17 photoproducts have been identified through LC-MS, of which nine have been reported for the first time. It has been confirmed through electron spin resonance (ESR) spectrometry that the excited singlet state of TA is converted into an excited triplet state through intersystem crossing, which results in an increased rate of photodegradation in acetonitrile.

Intramolecular interaction induced C-C cleavages in fructose conversion in polar aprotic solvents-origin of the formation of excess formic acid and oligomers.

Understanding the mechanism of excess formic acid formation in the dehydration of fructose to HMF would be beneficial to improve HMF selectivity and carbon efficiency. The production of formic acid from keto-D-fructose in polar aprotic solvents, such as THF, DIO, and MTHF, and MIBK solvents without a catalyst was investigated via DFT calculations. It was found that in THF, DIO and MTHF solvents, fructose tended to generate formic acid directly with the catalysis of the intramolecular hydroxyls, especially C6-OH (terminal hydroxyl), while in MIBK, the solvent molecule could react with the intermediates produced in the process, making the barrier of production of acetic acid lower than that of formic acid. Molecular dynamics simulations showed that the lower dielectric polar aprotic solvents (THF, DIO and MTHF) could not destroy the intramolecular H-bonds of hydroxyls in fructose, which could promote the keto-enol tautomerization and hydration steps, facilitating the formation of six-member-ring transition states, which reduced the ring tension and decreased the activation energy greatly, leading to the overproduction of formic acid and oligomers. ETS-NOCV analysis further indicated that the donated electrons from C-O σ-bonds on the carbon chain of fructose made the intramolecular hydroxyls more basic, which could catalyse keto-enol tautomerization with a lower energy barrier than water molecules. To obtain more target products, such as HMF, suitable reaction environments, such as a higher polar aprotic solvent with a low boiling point or restriction of the activity of hydroxyls of fructose, might be selected to destroy the intramolecular interaction and then reduce the overproduction of formic acid and the formation of oligomers.

An efficient method to establish electrostatic screening lengths of restricted primitive model electrolytes.

We present a novel, and computationally cheap, way to estimate electrostatic screening lengths from simulations of restricted primitive model (RPM) electrolytes. We demonstrate that the method is accurate by comparisons with simulated long-ranged parts of the charge density, at various Bjerrum lengths, salt concentrations and ion diameters. We find substantial underscreening in low dielectric solvent, but with an "aqueous" solvent, there is instead overscreening, the degree of which increases with ion size. Our method also offers a possible path to (future) more accurate classical density functional treatments of ionic fluids.

(Best Poster Award - 2nd Place) Energy Harvesting from CO2 Emission Exploiting an Ionic-Liquid Based Electrochemical Capacitor

Global warming is one of the most serious problems that the humanity is facing in his history.Since 1900 to nowadays, the global temperature has risen by 1 °C and, according to the scientificcommunity, the cause is related to the climate-changing emissions due to anthropogenic activities.In order to avoid an environmental disaster, 196 countries have signed the Paris agreement thataims to maintain global warming below 1.5 °C compared with pre-industrial levels.The reduction of greenhouse gas emissions is a key issue in contemporary science, and in thiscontext, the ability of certain ionic liquids (ILs) to capture carbon dioxide has attracted a lot ofinterest. The idea presented in this work is to design an electric double layer supercapacitor whichis able to harvest energy by exploiting the reaction between an ionic liquid and carbon dioxide. Inparticular, the system consists of two carbon-based electrodes and a polymeric separator soakedin ionic liquid. The use of carbon electrodes ensures a high surface area and excellent electricalconductivity while imidazole-based ionic liquid acts and as electrolyte and as capture media.The operating principle of this system is a novel mechanism which exploits the formation of avoltage drop across the device when the electrode-IL interfaces are different; the two differentinterfaces are ensured by the presence of imidazole carbamate in a part of the cell (Im − CO2reaction’s product) and just imidazole in the other part.Unfortunately the high viscosity of ionic liquids affects a lot the carrier transport and consequentlythe device’s performance too; this aspect worsens when imidazole reacts with CO2. Improved ionmobility is achieved by reducing the ion pairing through the use of high dielectric solvents capableto screen the ions’ electric field. Polar aprotic solvents tend to have large dipoles making themsuitable for the solvation of charged species.Several mixtures have been analyzed to detect the best dilution which guarantees high ionic mobilitystill maintaining a large amount of active species.A further performance improvement has been achieved through the engineering of the electrodes,namely the capacitance of the supercapacitor has been enhanced by exploiting the huge specificsurface area of the activated carbon.The results show that all the upgrades mentioned lead to an improvement of 500 times in terms ofharvested energy.Acknowledgement: This result is part of a project that has received funding from the European Research Council(ERC) under the European Union’s ERC Starting Grant Grant agreement No. 949916 Figure 1

Semitransparent Organic Photovoltaics Utilizing Intrinsic Charge Generation in Non-Fullerene Acceptors.

In organic semiconductors, a donor/acceptor heterojunction is typically required for efficient dissociation of excitons. Using transient absorption spectroscopy to study the dynamics of excited states in non-fullerene acceptors (NFAs), it is shown that NFAs can generate charges without a donor/acceptor interface. This is due to the fact that dielectric solvation provides a driving force sufficient to dissociate the excited state and form the charge-transfer (CT) state. The CT state is further dissociated into free charges at interfaces between polycrystalline regions in neat NFAs. For IEICO-4F, incorporating just 9 wt% donor polymer PTB7-Th in neat films greatly boosts charge generation, enhancing efficient exciton separation into free charges. This property is utilized to fabricate donor-dilute organic photovoltaics (OPV) delivering a power conversion efficiency of 8.3% in the case of opaque devices with a metal top-electrode and an active layer average visible transmittance (AVT) of 75%. It is shown that the intrinsic charge generation in low-bandgap NFAs contributes to the overall photocurrent generation. IEICO-4F-based OPVs with limited PTB7-Th content have high thermal resilience demonstrating little drop in performance over 700h. PTB7-Th:IEICO-4F semitransparent OPVs are leveraged to fabricate an 8-series connected semitransparent module, demonstrating light-utilization efficiency of 2.2% alongside an AVT of 63%.

Simulation of aqueous solutes using the adaptive solvent-scaling (AdSoS) scheme

The Adaptive Solvent-Scaling (AdSoS) scheme [J. Chem. Phys. 155 (2021) 094107] is an adaptive-resolution approach for performing simulations of a solute embedded in a fine-grained (FG) solvent region surrounded by a coarse-grained (CG) solvent region, with a continuous FG ↔ CG switching of the solvent resolution across a buffer layer. Instead of relying on a distinct CG solvent model, AdSoS is based on CG models defined by a dimensional scaling of the FG solvent by a factor s, accompanied by the s-dependent modulation of its mass and interaction parameters. The latter changes are designed to achieve an isomorphism between the dynamics of the FG and CG models, and to preserve the dispersive and dielectric solvation properties of the solvent with respect to a solute at FG resolution. As a result, the AdSoS scheme minimizes the thermodynamic mismatch between different regions of the adaptive-resolution system. The present article generalizes the scheme initially introduced for a pure atomic liquid in slab geometry to more practically relevant situations involving (i) a molecular dipolar solvent (e.g., water); (ii) a radial geometry (i.e., spherical rather than planar layers); and (iii) the inclusion of a solute (e.g., water molecule, dipeptide, ion, or ion pair).

The Effects of Solvent Dynamics on the Back Reaction of Solar-Thermal Energy Storage Systems.

We have investigated dynamic solvent effects on molecular solar-thermal energy storage systems using models describing the effects of frequency dependent viscosities and dielectric constants on chemical reaction rates. We have utilized the generalized Langevin model for understanding how the reactions are affected by the frequency dependent viscosities and dielectric constants. Our results show that the rate constants of the molecular solar-thermal energy storage systems depend strongly on the dielectric electric solvent properties and the frequency dependent viscosities of the solvents.

Construction diversified morphologies of NiCo2O4 via tuning dielectric solvents as battery-type electrodes for supercapacitors

The construction of effective nano-microstructures electrode has been a tireless pursuit in the energy storage field. Herein, Controllable construction of diversified morphologies NiCo2O4 nanomaterials by tuning the dielectric constant and viscosity of the mixed solvent. We employed different solvent compositions as deionized water (DI), DI:Ethanol (1:1), DI: Isopropanol (1:1), DI: Propylene glycol (1:1), DI: Butanediol (1:1). In mixed aqueous solvents with low dielectric constants of ethanol and isopropanol, metal ions diffuse well and the nanomaterials tend to construct sheet-like nanostructures whereas high viscosity of the propylene glycol and butanediol solution will slow down the rate of metal ion diffusion, which only grow uni-directionally to form rod-like nanostructures. The formed ear-shaped NiCo2O4 nanostructures in Vpropylene glycol: VH2O = 1 : 1 mixed solvent have a large specific surface area and provide more electrochemically active sites, which facilitates effectively access electrolytes and thus accelerates the redox reaction rate. The resulting NiCo2O4 nanoears exhibits favorable capacity of 251 mAh g−1 and excellent rate performance with a 73.0% capacity retention at 20 A g−1. More importantly, the asymmetric supercapacitors assembled with the preferred NiCo2O4 nanoears and active carbon (AC) reveal excellent electrochemical performance at operating potential of 1.6 V, great specific capacity (58.0 mAh g−1), energy and power density of 46.4 Wh kg−1 at 801 W kg−1 and a specific capacity retention rate of 90.7% after 5000 cycles. This work provides a new perspective for the controllable construction of new micro-nanostructure materials.

Nuclear-Electronic Orbital QM/MM Approach: Geometry Optimizations and Molecular Dynamics.

Hybrid quantum mechanical/molecular mechanical (QM/MM) methods allow simulations of chemical reactions in atomistic solvent and heterogeneous environments such as proteins. Herein, the nuclear-electronic orbital (NEO) QM/MM approach is introduced to enable the quantization of specified nuclei, typically protons, in the QM region using a method such as NEO-density functional theory (NEO-DFT). This approach includes proton delocalization, polarization, anharmonicity, and zero-point energy in geometry optimizations and dynamics. Expressions for the energies and analytical gradients associated with the NEO-QM/MM method, as well as the previously developed polarizable continuum model (NEO-PCM), are provided. Geometry optimizations of small organic molecules hydrogen bonded to water in either dielectric continuum solvent or explicit atomistic solvent illustrate that aqueous solvation can strengthen hydrogen-bonding interactions for the systems studied, as indicated by shorter intermolecular distances at the hydrogen-bond interface. We then performed a real-time direct dynamics simulation of a phenol molecule in explicit water using the NEO-QM/MM method. These developments and initial examples provide the foundation for future studies of nuclear-electronic quantum dynamics in complex chemical and biological environments.

Lateral Electron and Hole Hopping between Dyes on Mesoporous ZrO2: Unexpected Influence of Solvents with a Low Dielectric Constant

Lateral intermolecular charge transfer between photosensitizers on metal oxide substrates is important for the understanding on the overall working principles of dye-sensitized systems. Such studies usually concentrate on either hole or electron transfer separately and are conducted in solvents with a high dielectric constant (εs) that are known, however, to show a drastic decrease of the local dielectric constant close to the metal oxide surface. In the present study, both hole and electron hopping between organic donor-acceptor photosensitizers was experimentally investigated on PB6 dye-sensitized mesoporous ZrO2 films. The donor (close to the surface) and acceptor (away from surface) subunit of the PB6 dye were observed to be involved in hole and electron hopping, respectively. Hole and electron transfer kinetics were found to differ remarkably in high-εs solvents, but similar in solvents with εs < 12. This finding indicates that low-εs solvents maintain similar local dielectric constant values close to, and further away from, the semiconductor surface, which is different from the previously observed behavior of high dielectric constant solvents at a metal oxide interface.

Bimodal 1/f Noise and Anticorrelation between DNA-Water and DNA-Ion Energy Fluctuations.

The coupling between the conformational fluctuations of DNA and its surrounding environment, consisting of water and ions in solution, remains poorly understood and relatively less investigated as compared to proteins. Here, with the help of molecular dynamics simulations and statistical mechanical analyses, we explore the dynamical coupling among DNA, water, and counterions through correlations among respective energy fluctuations in both double- (ds-) and single-stranded (ss-) DNA solutions. Fluctuations in the collective DNA-water and DNA-ion interaction energies are found to be strongly anticorrelated across all the systems. The fluctuations of DNA self-energy, however, are weakly coupled to DNA-water and DNA-ion interactions in ds-DNA. An enhancement of the DNA-water coupling is observed in ss-DNA, where the system is less rigid. All the interaction energies exhibit 1/f noise in their energy power spectra with surprisingly prominent bimodality in the DNA-water and DNA-ion fluctuations. The nature of the energy spectra appears to be indifferent to the relative rigidity of the DNA. We discuss the role of the observed correlations in ion-water motions on a DNA duplex in the experimentally observed anomalous slow dielectric relaxation and solvation dynamics and in furthering our understanding of the DNA energy landscape.