Solvent Response Research Articles

Assessing long-range contributions to the charge asymmetry of ion adsorption at the air-water interface.

Anions generally associate more favorably with the air–water interface than cations. In addition to solute size and polarizability, the intrinsic structure of the unperturbed interface has been discussed as an important contributor to this bias. Here we assess quantitatively the role that intrinsic charge asymmetry of water's surface plays in ion adsorption, using computer simulations to compare model solutes of various size and charge. In doing so, we also evaluate the degree to which linear response theory for solvent polarization is a reasonable approach for comparing the thermodynamics of bulk and interfacial ion solvation. Consistent with previous works on bulk ion solvation, we find that the average electrostatic potential at the center of a neutral, sub-nanometer solute at the air–water interface depends sensitively on its radius, and that this potential changes quite nonlinearly as the solute's charge is introduced. The nonlinear response closely resembles that of the bulk. As a result, the net nonlinearity of ion adsorption is weaker than in bulk, but still substantial, comparable to the apparent magnitude of macroscopically nonlocal contributions from the undisturbed interface. For the simple-point-charge model of water we study, these results argue distinctly against rationalizing ion adsorption in terms of surface potentials inherent to molecular structure of the liquid's boundary.

Dielectric relaxation of deep eutectic solvent + water mixtures: structural implications and application to microwave heating.

We studied the dielectric response of deep eutectic solvents (DESs) composed of choline chloride (ChCl) and such hydrogen bond donors (HBDs) as glycerol (glyceline) and urea (reline) mixed with water at T = 298.15 K and frequencies varying from 0.05 to 89 GHz. The dielectric loss data were used to calculate normalized heating rates for these systems upon electromagnetic irradiation at operating frequencies of domestic (ν = 2.45 GHz) and industrial (ν = 900 MHz) microwave ovens. We show that due to slow dynamics and substantial Ohmic-loss contributions DES/water mixtures constitute promising solvents for microwave synthesis. Their dielectric spectra can be best fit by a superposition of relaxation processes assigned to the reorientation of dipolar DES components and water molecules. Static permittivities were found to smoothly decrease from the value of neat water (78.4) to 22.8 for glyceline and 41.2 for reline. The analysis of the obtained relaxation amplitudes suggests that the studied systems can be viewed as mixtures of individual choline, HBD and water dipoles without pronounced dipole-dipole correlations and negligible ChCl ion pairs. However, rotational motions of the dipoles are partly synchronized, leading to the slow-down of 22 water molecules for glyceline and 9.2 for reline at infinite dilution. At vanishing DES concentration ChCl-HBD interactions appear to be negligible. Relaxation times as a function of viscosity show a break point at the ChCl : HBD : H2O ratio equal to 1 : 2 : 4. This supports the suggestion of a structural transition from homogeneous electrolyte solution to a micro-heterogeneous mixture already discussed in the literature.

Insights into microwave heating response and thermal decomposition behavior of deep eutectic solvents

The development of microwave (MW) assisted processes involving the use of deep eutectic solvents (DESs) is a fast-expanding research topic. However, there is a lack of information about the heating behavior of DESs under MW irradiation. In this work, a family of DESs composed by choline chloride and two types of hydrogen bond donors (carboxylic acids or polyols) was prepared and its MW heating response and thermal heating behavior were investigated as well as compared to that of the single components. The MW absorption properties were explored using different MW applied power at fixed MW irradiation times. The thermal behavior and the analysis of the evolved gases during the DESs thermal decomposition were assessed by TG-FTIR analysis. A strong interaction of DESs with MWs was found in all cases. Polyol-based DESs showed the highest MW response, ChCl-glycerol being the best MW absorbing system. The thermal heating behavior revealed that a decomposition process of entire DES occurred rather than a sum of evaporation steps of their single components. This decomposition can be ascribed to a synergy effect of heating and H-bond acidity strength in DESs network. Different thermal decomposition pathways for all DESs were thus proposed. All studied DESs showed thermal decomposition behavior and MW absorption properties more similar to ionic liquids (ILs) than molecular solvents. These unique properties make DESs suitable green solvents for the development of MW assisted chemical processes.

Preparation and properties of hydrophobic filter paper and cotton fabric with reversible solvent response

The preparation of hydrophobic surfaces has been extensively studied, but the reversible responsive hydrophobic surface has received less attention. In this paper, poly(styrene-random-methyl methacrylate-random-acrylic acid) (P(St-r-MMA-r-AA)) was prepared by conventional free radical polymerization, and the filter paper and cotton fabric were immersed in P(St-r-MMA-r-AA) methanol solution to construct a hydrophobic surface. The hydrophobic property, chemical composition and surface morphology of the hydrophobic filter paper and cotton fabric surface were characterized by contact angle, Gibbs free energy, infrared spectroscopy and scanning electron microscopy. The optimum conditions for constructing hydrophobic filter paper and cotton fabric surface were investigated. When the surfaces of hydrophobic filter paper and cotton fabric were treated with methanol, tetrahydrofuran and deionized water respectively, the semihydrophobic-hydrophobic-hydrophilic reversible transformation could be achieved. After ten cycles of experiments, the contact angles under the three solvent stimulations had no significant change, and the hydrophobic properties of the hydrophobic cotton fabric were superior to that of hydrophobic filter paper. The Gibbs free energy calculation of the hydrophobic surface indicated that the change in surface hydrophobic property was due to the inversion between the hydrophobic PS segment, the PMMA segment, and the hydrophilic PAA segment.

Temperature-Dependent Ultrafast Solvation Response and Solute Diffusion in Acetamide-Urea Deep Eutectic Solvent.

In the present paper, we have studied the temperature dependence of translational diffusion and solvation dynamics of a dissolved dipolar dye in the nonionic acetamide-urea deep eutectic solvent (DES), to characterize the viscosity coupling of the measured relaxation times and verify the dynamical heterogeneity aspect of this medium. Three different time-resolved experimental techniques have been employed for this purpose: fluorescence correlation spectroscopy, transient absorption (TA) spectroscopy, and optical Kerr effect (OKE) spectroscopy. The first method provides the proof that the translational diffusion time of a solute in acetamide-urea DES [fCH3CONH2 + (1 - f)CO(NH2)2, f = 0.6] exhibits a fractional viscosity dependence, with exponent 0.758, which, when compared with the viscosity-diffusion relationship for the same solute in common molecular solvents, suggests moderate deviation from the Stokes-Einstein relation. Stokes shift dynamics of a solvatochromic dye, 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran in this DES, followed via femtosecond TA measurements, have been found to be triexponential in nature and dominated by a ∼100 fs component. The other two components, which contribute to a total dynamic Stokes shift magnitude of ∼2500 cm-1, are characterized by time constants in the ∼5 and ∼50 ps regimes. Subsequent comparison with the femtosecond OKE measurements suggests that the relatively slower picosecond solvation components originate from the rapid reorientation of the solvent molecules, while the subpicosecond solvation response arises from the participation of the collective low-frequency solvent modes (such as intermolecular vibrations and librations). We find that the rotational diffusion lifetimes also exhibit fractional power dependence on medium viscosity and thus deviate from the Stokes-Einstein-Debye pprediction. All of these results therefore suggest that the nonionic acetamide-urea DES is a moderately heterogeneous medium.

Pressure-dependent electronic structure calculations using integral equation-based solvation models

Recent methodological progress in quantum-chemical calculations using the “embedded cluster reference interaction site model” (EC-RISM) integral equation theory is reviewed in the context of applying it as a solvation model for calculating pressure-dependent thermodynamic and spectroscopic properties of molecules immersed in water. The methodology is based on self-consistent calculations of electronic and solvation structure around dissolved molecules where pressure enters the equations via an appropriately chosen solvent response function and the pure solvent density. Besides specification of a dispersion-repulsion force field for solute-solvent interactions, the EC-RISM approach derives the electrostatic interaction contributions directly from the wave function. We further develop and apply the method to a variety of benchmark cases for which computational or experimental reference data are either available in the literature or are generated specifically for this purpose in this work. Starting with an enhancement to predict hydration free energies at non-ambient pressures, which is the basis for pressure-dependent molecular population estimation, we demonstrate the performance on the calculation of the autoionization constant of water. Spectroscopic problems are addressed by studying the biologically relevant small osmolyte TMAO (trimethylamine N-oxide). Pressure-dependent NMR shifts are predicted and compared to experiments taking into account proper computational referencing methods that extend earlier work. The experimentally observed IR blue-shifts of certain vibrational bands of TMAO as well as of the cyanide anion are reproduced by novel methodology that allows for weighing equilibrium and non-equilibrium solvent relaxation effects. Taken together, the model systems investigated allow for an assessment of the reliability of the EC-RISM approach for studying pressure-dependent biophysical processes.

Non-linearity in dipolar solvation dynamics in water-ethanol mixture: Composition dependence of free energy landscape.

Liquid mixtures of water and amphiphilic solutes exhibit a string of yet unexplained anomalies in the low cosolvent (or solute) concentration regime. Among such solutions, mixtures of water and ethanol stand out for their distinctive role in biology. We study, in this binary mixture, the composition dependent difference between the nonequilibrium and the equilibrium solvent responses to a dipolar probe indole in the low-to-intermediate concentration regime. The usually employed linear response formalism seems to break down at low ethanol concentration. The nonequilibrium solvent response is particularly different from that of the equilibrium solvent response in the concentration (xEtOH) between 0.07 and 0.12. We introduce an order parameter in terms of the changing local composition at the nearest neighbor separation. This order parameter captures the anomalies faithfully. The anomalies are seen to arise from a competition between hydrophilic and hydrophobic interactions and are most prominent at the small-to-intermediate length scale. We attempt to rationalize the results in terms of a composition dependent free energy length scale.

Ultra-Strong and Fast Response Gel by Solvent Exchange and Its Shape Memory Applications

Solvent response gels were synthesized by copolymerization of hydrophobic butyl methacrylate (BMA) and hydrophilic methacrylic acid (MAA) with cross-linker N,N′-methylenebis(acrylamide) (BIS) in a ...

Comparative Photophysical Study of Differently Substituted Cinnamaldehyde-Based Chalcones: From Intramolecular Charge Transfer to Fluorogenic Solvent Selectivity.

We synthesized three cinnamaldehyde-based chalcone derivatives, (2E,4E)-1-(2-hydroxyphenyl)-5-phenylpenta-2,4-dien-1-one (HPD), (2E,4E)-5-(4-(dimethylamino)phenyl)-1-phenylpenta-2,4-dien-1-one (DPPD), and (2E,4E)-5-(4-(dimethylamino)phenyl)-1-(2-hydroxyphenyl)penta-2,4-dien-1-one (DPHPD). The molecule HPD was totally nonfluorescent. Exclusion of a phenolic -OH moiety from HPD along with the introduction of a dimethylamino moiety in DPPD resulted in excellent excited-state charge-transfer properties in the solution phase. Interestingly, introduction of phenolic -OH and dimethylamino moieties in DPHPD resulted in solvent selectivity in the excited state. DPHDP behaved as a strong fluorophore only in carbonyl- or thiocarbonyl-containing solvents, such as dimethylsulfoxide (DMSO), dimethylformamide (DMF) and dimethylacetamide (DMAC) and showed a prominent red color under UV light. However, no emission was observed in similar carbonylated solvents, such as acetone or formamide, or in viscous medium, such as glycerol. The difference in solvent response was probed by various spectroscopic techniques and analyzed using the crystal structure of the three chalcones along with theoretical calculations. The practical utility of DPHPD was explored by detecting the percentage of water in DMSO solvent.

Solvent dependent relaxation dynamics in lithium ion battery electrolytes: Coupling to medium friction

Solution heterogeneity and dynamics of the industrially relevant electrolyte system, [9.795{xEC + (1 − x)PC} + 0.869LiClO4] with x representing mole fraction, were explored at different loadings of ethylene carbonate (EC) via temperature dependent measurements of time-resolved spectral response and physico-chemical properties. This system was chosen because polarity differed considerably on replacing propylene carbonate (PC) by EC but the solution viscosity remained nearly the same, allowing to investigate the polarity impact on solution inhomogeneity and solute dynamics. Coumarin 153 (C153) and trans‑2‑[4‑(dimethylamino)styryl]‑benzothiazole (trans-DMASBT) were used as fluorescent probes which differ widely in their excited state lifetimes. Driven by the potential for applications of these electrolyte systems in the energy sector, we have investigated them at an optimal composition with (PC + EC)/LiClO4 mole ratio of ~11.3, where direct current (DC) conductivity reaches at the maximum. Signatures of spatio-temporal heterogeneity were detected in steady state fluorescence and time-resolved anisotropy measurements with DMASBT (lifetime ~100–200 ps) but not with C153, suggesting a timescale over which the inhomogeneity density distributions persist in these electrolyte systems. Subsequent Stokes shift dynamics measurements using C153 captured a dynamic shift of ~700–900 cm−1 with an estimated missing portion of ~50%, and biphasic solvation response characterized by sub-100 ps and nanosecond components. Time-resolved fluorescence anisotropy measurements reflect partial viscosity decoupling for the short lifetime probe and bimodal frictional response in these electrolyte systems.

Mechanistic Insights into the Growth of Anisotropic Nanostructures Inside Reverse Micelles: A Solvation Perspective.

Reverse micelles (RMs) as soft templates have been successfully used in tailoring the structural characteristics (size and morphology) of nanomaterials that in turn have been used in various applications. In this work, we have focused on the local perturbations in the different interior domains of the cetyltrimethylammonium bromide-reverse micelle-based soft template en route to nanorod formation by monitoring the solvation response of coumarin-based solvatochromic probes (C343 and C153). We have observed an appreciable retardation of the solvent coordinate during the initial phases of nanorod growth, which we have attributed to the reorientational motion of the water molecules lodged in the interfacial region. Moreover, these rigid nanostructures leave their imprints on the soft interfacial layer as was observed from the direct correlation in the solvation response of RM-containing nanostructures and respective surfactant aggregates in supernatant solution. Supporting data from time-resolved anisotropy studies further reinforced our conclusions from the solvation experiments. Our study proves that the hydration dynamics can be a promising tool in tracking the heterogeneous growth evolution of nanostructure formation in RMs since solvent reorganization provides insights into the intrinsic, molecular-level features of the micellar assemblies.

Effect of hydrogen bond on solvation dynamics of coumarin153 in cyclohexane-phenol solvent mixtures by time-resolved optical Kerr fluorescence.

Time-resolved optical Kerr fluorescence system was used to investigate time-resolved red-shift of coumarin 153 in different solvent mixtures. The mixtures included four mole fractions of phenol-cyclohexane solvents (0, 0.013, 0.08, and 0.3), and anisole-cyclohexane solvents with the mole fraction of 0.3. The measured time-resolved fluorescence showed that, in the solvent mixtures containing phenol, the time-dependent frequency shift accelerated with the increase in the mole fraction of phenol-cyclohexane mixtures. However, the time-dependent red-shift in the fluorescence was not observed in the anisole-cyclohexane mixture, the solvent polarity could not influence the spectral Stokes shift compared with phenol. The results indicated that coumarin 153 formed an excited hydrogen bond with phenol, and the excited hydrogen bond was strengthened with an increase in the mole fraction of phenol. And, these processes also suggested that the increase in the phenol ratio improves a large number of hydrogen bond formed between phenol and carbonyl group of coumarin 153, the charge distribution will be faster towards lower the free energy of the system due to the stronger dipole moment. Therefore, the corresponding solvation response in phenol-cyclohexane mixtures with higher mole fractions decays very rapidly.

Dispersive wave and four-wave mixing generation in noninstantaneous nonlinear fiber solitons.

This paper presents a detailed analysis regarding the generation of a dispersive wave (DW) and four-wave mixing in the noninstantaneous, nonlinear response of solvents using a commercial photonic crystal fiber filled with carbon disulfide (CS2) where the beam is pumped in the anomalous dispersion domain. The main finding is the fact that the output spectrum changes from coherent DW to incoherent modulation instabilities just by changing from constant to variable nonlinear parameters. This study can be extended to other solvents including ethanol, methanol, and butanol.

Ice formation and solvent nanoconfinement in protein crystals.

Ice formation within protein crystals is a major obstacle to the cryocrystallographic study of protein structure, and has limited studies of how the structural ensemble of a protein evolves with temperature in the biophysically interesting range from ∼260 K to the protein-solvent glass transition near 200 K. Using protein crystals with solvent cavities as large as ∼70 Å, time-resolved X-ray diffraction was used to study the response of protein and internal solvent during rapid cooling. Solvent nanoconfinement suppresses freezing temperatures and ice-nucleation rates so that ice-free, low-mosaicity diffraction data can be reliably collected down to 200 K without the use of cryoprotectants. Hexagonal ice (Ih) forms in external solvent, but internal crystal solvent forms stacking-disordered ice (Isd) with a near-random stacking of cubic and hexagonal planes. Analysis of powder diffraction from internal ice and single-crystal diffraction from the host protein structure shows that the maximum crystallizable solvent fraction decreases with decreasing crystal solvent-cavity size, and that an ∼6 Å thick layer of solvent adjacent to the protein surface cannot crystallize. These results establish protein crystals as excellent model systems for the study of nanoconfined solvent. By combining fast cooling, intense X-ray beams and fast X-ray detectors, complete structural data sets for high-value targets, including membrane proteins and large complexes, may be collected at ∼220-240 K that have much lower mosaicities and comparable B factors, and that may allow more confident identification of ligand binding than in current cryocrystallographic practice.

Dynamical and Environmental Effects on the Optical Properties of an Heteroleptic Ru(II)–Polypyridine Complex: A Multilevel Approach Combining Accurate Ground and Excited State QM-Derived Force Fields, MD and TD-DFT

An integrated multilevel approach is here built by combining classical molecular dynamic (MD) simulations, time-dependent density functional theory (TD-DFT) calculations, and solvation dynamics linear response (LR) analysis, and successively employed to investigate the optical properties and solvation structure of a prototypical heteroleptic Ru(II)-polypyridyl complex, widely employed in dye sensitized solar cells. The MD simulations are performed with an accurately parametrized intramolecular force field (FF), specifically derived from the quantum chemical (DFT) description of the molecule, both for its singlet and triplet ground states. Solvent effects, in ethanol (EtOH) and dimethyl sulfoxide (DMSO), are taken into account at different levels of approximation, going from a totally implicit description (polarizable continuum) to an hybrid explicit/implicit scheme. Our results show that the developed FFs were able to accurately describe and preserve the octahedral coordination of the Ru(II) center along the MD trajectories, yielding an accurate picture of the solute dynamics. Noticeably, the dynamical effects and the inclusion of an explicit microsolvation shell were found to be crucial to get a good agreement with the experimental absorption spectrum in EtOH, in both shape and positions of the main bands. The significant experimental blue-shift of the two low-energy bands in DMSO, that is not reproduced by the simulated thermal-averaged spectra, is, instead, attributed to deprotonation phenomena of the carboxylic groups, induced by the strong nucleophilic character of the solvent. Finally, analysis of the solvent response shows that the structural changes in the first solvation shell, following the metal-ligand to ligand charge transfer excitation, cause, in the protic medium the breakdown of the linear response approximation, which, on the contrary, holds for DMSO.

Rotation and translation dynamics of coumarin 153 in choline chloride-based deep eutectic solvents.

The equilibrium and dynamic solvation responses of coumarin 153 (C153) in a range of deep eutectic solvents (DESs) based on choline chloride with either urea (molar ratio 1:2, ChCl:U), glycerol (1:2, ChCl:G), ethylene glycol (1:2, ChCl:E), or malonic acid (1:1, ChCl:Mal) were investigated using both steady-state and time-resolved fluorescence emission spectroscopy at room temperature (298 K). From steady-state fluorescence data, "red-edge effects" were observed in all the DESs studied, attributed to spatial heterogeneity of the DES matrix. Time-resolved Stokes shifts were used to quantify dynamic solvation with the solvation response function in DES found to be a biexponential function of time, which were used to obtain average solvation times (⟨τ s ⟩) which are generally faster in DES than in ionic liquids of comparable viscosity. Average solvation times showed a partial correlation with viscosity between different DESs. The choline chloride-glycerol DES showed deviation from the viscosity trend observed in the other DES for both dynamic and steady-state results. Rotational reorientation times obtained from dynamic anisotropy (r(t)) measured for these DESs showed a partial correlation with viscosity between different DESs. Determination of the DES rotational coupling with C153 showed more "slip"-like behavior than the previously reported ionic liquids and dipolar solvents.

Calculating Optical Rotatory Dispersion Spectra in Solution Using a Smooth Dielectric Model.

The calculation of specific rotation of molecules in solution is probed at the coupled cluster (CC) level utilizing a continuum dielectric model based on a definition of the dielectric permittivity as a smooth function of electron density. Solvation effects are captured through polarization of Hartree-Fock (HF) molecular orbitals before subsequent calculations with the coupled cluster singles and doubles (CCSD) method. For the challenging ( S)-methyloxirane molecule, CCSD specific rotations yield an incorrect sign for the rotation in water, and the continuum model is unable to predict the wide variations in the optical rotatory dispersion (ORD) curves seen for nonpolar solvents of similar dielectric constant. In two molecules, (1 S,4 S)-norbornenone and ( S)-2-chloropropionitrile, specific rotations computed with CCSD in conjunction with implicit solvent fail to provide solvent shifts of the correct order of magnitude, indicating that the solvent response is a major contribution to the overall solvation effect.

Femtosecond photoexcitation dynamics inside a quantum solvent

The observation of chemical reactions on the time scale of the motion of electrons and nuclei has been made possible by lasers with ever shortened pulse lengths. Superfluid helium represents a special solvent that permits the synthesis of novel classes of molecules that have eluded dynamical studies so far. However, photoexcitation inside this quantum solvent triggers a pronounced response of the solvation shell, which is not well understood. Here, we present a mechanistic description of the solvent response to photoexcitation of indium (In) dopant atoms inside helium nanodroplets (HeN), obtained from femtosecond pump–probe spectroscopy and time-dependent density functional theory simulations. For the In–HeN system, part of the excited state electronic energy leads to expansion of the solvation shell within 600 fs, initiating a collective shell oscillation with a period of about 30 ps. These coupled electronic and nuclear dynamics will be superimposed on intrinsic photoinduced processes of molecular systems inside helium droplets.

Peptide and Protein Structure Prediction with a Simplified Continuum Solvent Model.

A continuum solvent model based on screened Coulomb potentials has been simplified and parametrized to sample native-like structures in replica-exchange simulations of each of six different peptides and miniproteins. Low-energy, native, and non-native structures were used to iteratively refine 11 parameter values. The centroid of the largest cluster of structures sampled in simulations initiated from an extended conformation represents the predicted structure. The main-chain rms deviation of this prediction from the experimental structure was 0.47 Å for the 12-residue Trp-zip2, 0.86 Å for the 14-residue MBH12, 2.53 Å for the 17-residue U(1-17)T9D, 2.03 Å for the 20-residue BS1, 1.08 Å for the 20-residue Trp-cage, and 3.64 Å for the 35-residue villin headpiece subdomain HP35. The centroid of the sixth largest cluster sampled for HP35 deviated by 0.91 Å. The CHARMM22/CMAP force field was used, with an additional ψ torsion term for residues other than glycine and proline. Six parameters govern the dielectric response of the continuum solvent, and four values of surface tension approximate nonpolar effects. An atom's self-energy and interaction energies are screened independently, each depending on whether the atom is part of a charged group, a neutral hydrogen-bonding main-chain group, or any other neutral group. The parameters inferred result in strong main-chain hydrogen bonds, consistent with the view that protein folding is dominated by the formation of these bonds. (1,2) Conformations of MBH12 and BS1 were excluded from the energy-function refinement, suggesting the parameters, referred to as SCP18, are transferable. An efficient estimate of solvent-accessible surface area is also described.

Solvatochromism based on structural color: Smart polymer composites for sensing and security

We report a convenient and scalable strategy to achieve large-area transparent photonic crystal (TPC) films that can be fully reversibly switched between an initial transparent state and a structurally-colored state. This photonic material is based on an ordered colloidal crystal structure of polymer core-shell particles with an engineered refractive index balance of the core and the shell components. Highly transparent viscoelastic quasi-solid films are created that can be spatially UV-cross-linked, giving invisible encrypted photonic patterns with different solvent response compared to non-cross-linked regions, which appear after immersion in solvent media, thus demonstrating clear and fully reversible/switchable solvatochromic properties. Our intuitive simulation models demonstrate how the emergence of structural color occurs due to increasing refractive-index contrast, whereas wavelength shifting originates from commensurate solvent swelling of the shell medium. In addition to the very clear revelation of optical patterns (large fractional changes in reflectance, from transparency to a resonant reflectivity of ~10%), these materials and thin-film generation methods are inherently scalable, robust and versatile. The demonstrated stimuli-responsive photonic films may thus give rise to new practicable applications in the fields of environmental sensing and product security.