Search Results (37)

Cryopreservation is a critical strategy for the long-term conservation of plant germplasm, particularly for clonally propagated crops, endangered species, and plants producing recalcitrant seeds. Hydrogel-based encapsulation systems can improve survival during ultra-low-temperature storage by providing mechanical protection, moderating dehydration, and regulating cryoprotectant uptake. Although calcium–alginate beads remain the traditional matrix for encapsulation–dehydration and encapsulation–vitrification, recent advances in biomaterials science have enabled the development of composite polysaccharide blends, protein-based matrices, synthetic polymer networks, macroporous cryogels, and functionalized hybrid hydrogels incorporating surfactants, antioxidants, or nanomaterials. These engineered systems provide improved control over water state, pore architecture, diffusion kinetics, and thermal behavior, thereby reducing cryoinjury and enhancing post-thaw recovery across diverse plant explants. This review synthesizes current knowledge on hydrogel platforms used in plant cryopreservation, with emphasis on how physicochemical properties influence dehydration dynamics, cryoprotectant transport, vitrification stability, and rewarming responses. Performance across major explant types is assessed, key limitations in existing materials and protocols are identified, and design principles for next-generation hydrogel systems are outlined. Future progress will depend on material standardization, integration with automated cryopreservation workflows, and the development of responsive hydrogel matrices capable of mitigating cryogenic stresses. Full article

Composite materials are increasingly required to operate in cryogenic environments, including liquid hydrogen and oxygen storage, deep-space structures, and polar infrastructures, where long-term strength, toughness, and reliability are essential. This review provides a unique contribution by systematically integrating recent advances in understanding cryogenic behaviour into a unified multi-scale framework. This framework synthesises four critical and interconnected aspects: constituent response, composite performance, enhancement mechanisms, and modelling strategies. At the constituent level, fibres retain stiffness, polymer matrices stiffen but embrittle, and nanoparticles offer tunable thermal and mechanical functions, which collectively define the system-level performance where thermal expansion mismatch, matrix embrittlement, and interfacial degradation dominate failure. The review further details toughening strategies achieved through nano-addition, hybrid fibre architectures, and thin-ply laminates. Modelling strategies, from molecular dynamics to multiscale finite element analysis, are discussed as predictive tools that link these scales, supported by the critical need for in situ experimental validation. The primary objective of this synthesis is to establish a coherent perspective that bridges fundamental material behaviour to structural reliability. Despite these advances, remaining challenges include consistent property characterisation at low temperature, physics-informed interface and damage models, and standardised testing protocols. Future progress will depend on integrated frameworks linking high-fidelity data, cross-scale modelling, and validation to enable safe deployment of next-generation cryogenic composites. Full article

We present an experimental apparatus to investigate electron transport and thermalization in cryogenic para-hydrogen crystal matrices. This paper describes the techniques used to grow and characterize the cryogenic para-hydrogen crystals, the optical system employed to photoextract electrons, and the charge collection system used to study the behavior of electrons within the solid matrix. By probing the fundamental charge transport and energy loss processes in a quantum solid, such as para-hydrogen, this study paves the way for future precision experiments that leverage the unique properties of cryogenic crystal matrices. Full article

The efficient separation and removal of carbon dioxide (${CO}_2$) from its mixtures is an important technological challenge to limit effects resulting from the increase of the carbon dioxide concentration in the atmosphere. Membrane technology is an environmentally friendly approach, highly scalable and less energy-consuming than conventional methods such as adsorption, absorption and cryogenic separation. Hybrid membrane materials incorporating inorganic filler nanostructures in polymer matrices having polyethylene glycol (PEG) as a plasticized additive are promising membrane materials given the presence of ${CO}_2$-philic polar functional groups of PEGs and the structural refinements on the blend matrix consequent to the filler distribution. In this review, literature information on hybrid polymer/PEG membranes are critically reviewed to discuss how filler dispersion in the blend matrix gives rise to enhanced ${CO}_2$ separation performances with respect to those obtained with traditional mixed matrix membranes where filler nanostructures are dispersed in the neat polymer. The discussion will be focused on the correlation between the ${CO}_2$ transport properties, membrane structural properties and defect resulting from the polymer-filler incompatibility. It is shown that hybrid polymer/PEG membranes with dispersed filler nanostructures simultaneously offer improved ${CO}_2$ separation performances and enhanced mechanical properties compared with nanocomposite ones where filler particles are dispersed in the neat polymer matrix. PEG addition enhances the filler-matrix compatibility, delays filler aggregation and limits the formation of filler-matrix interface defects. Full article

Barium monofluoride (BaF) is a polar molecule of interest in measurements of the electron electric dipole moment. For this purpose, efforts are underway to investigate this molecule embedded within cryogenic matrices, e.g., in solid Ne. For a theoretical understanding of the electronic structure of such an embedded molecule, the need arises for efficient methods which are accurate but also able to handle a number of atoms which surround the molecule. The calculation for gas-phase BaF can be reduced to involve only outer electrons by representing the inner core of Ba with a pseudopotential, while carrying out a non-relativistic calculation with an appropriate basis set. Thus, the method is effectively at a scalar-relativistic level. In this work, we demonstrate to which extent this can be achieved using coupled-cluster methods to deal with electron correlation. As a test case, the SrF($X^2{\Sigma }^{+}\to B^2{\Sigma }^{+}$) transition is investigated, and excellent accuracy is obtained with the EOM-CC3 method. For the BaF($X^2{\Sigma }^{+}\to {A^{\prime }}^2\Delta$, $X^2{\Sigma }^{+}\to A^2\Pi$, $X^2{\Sigma }^{+}\to B^2{\Sigma }^{+}$) transitions, various coupled-cluster approaches are compared with very good agreement for EOM-CC3 with experimentally derived spectroscopic parameters, at the level of tens of ${\mathrm{cm}}^{-1}$. An exception is the excitation to the ${A^{\prime }}^2\Delta$ state, for which the energy is overestimated by $230{\mathrm{cm}}^{-1}$. The poor convergence behavior for this particular state is demonstrated by providing results from calculations with basis sets of n = 3, 4, 5)-zeta quality. The calculated excitation energy for the $B^2{\Sigma }^{+}$ state agrees better with a deperturbation analysis than with the effective spectroscopic value, with a difference of $120{\mathrm{cm}}^{-1}$. Full article

The structures and bonding of selected neutral M(CO)₆ complexes (M = Sc, Y, La, Lu, Ac and U) have been studied by density functional theory calculations. The calculations revealed the preference for C_2v symmetry and low-spin electronic state for most of these complexes. The relative stability of the low-symmetry species increases gradually with the size of the metal atom. While the characteristic O_h hexa-coordinated structure is favored in the high-spin electronic state of the smaller metals, for heavier metals, important advantages of the C_2v vs. O_h structures include larger charge transfer interactions in terms of transferred electrons as well as better steric conditions. Our joint experimental–theoretical analysis detected and confirmed the O_h structure of the Sc(CO)₆ complex in cryogenic CO/Ar matrices. Full article

The reactive open-shell species play a very important role in the radiation-induced molecular evolution occurring in the cold areas of space and presumably leading to the formation of biologically relevant molecules. This review presents an insight into the mechanism of such processes coming from matrix isolation studies with a main focus on the experimental and theoretical studies performed in the author’s laboratory during the past decade. The radicals and radical cations produced from astrochemically relevant molecules were characterized by Fourier transform infrared (FTIR) and electron paramagnetic resonance (EPR) spectroscopy. Small organic radicals containing C, O, and N atoms are considered in view of their possible role in the formation of complex organic molecules (COMs) in space, and a comparison with earlier results is given. In addition, the radical–molecule complexes generated from isolated intermolecular complexes in matrices are discussed in connection with their model significance as the building blocks for COMs formed under the conditions of extremely restricted molecular mobility at cryogenic temperatures. Full article

Research of microstructure and permeability evolution of coal following LN₂ treatment elucidate the process of cryogenic fracturing due to environmentally friendly behavior in comparison with conventional hydraulic fracturing. The evolution of the 2D microstructure of bituminous coal before and after LN₂ treatment was examined using a high-resolution camera. The image processing was implemented using functions from the OpenCV Python library that are sequentially applied to digital images of original coal samples. The images were converted into binary pixel matrices to identify cracks and to evaluate the number of cracks, crack density, total crack area, and average crack length. Results were visualized using Seaborn and Matplotlib Python libraries. There were calculations of total crack area (TCA), total number of cracks (TNC), crack density (CD), the average length of cracks (Q2), first (Q1) and third (Q3) quartiles in fracture length statistics. Our findings demonstrate a progressive increase in the Total Crack Area (δTCA) with longer freezing times and an increased number of freezing–thawing cycles. In contrast, the change in crack density (δCD) was generally unaffected by freezing time alone but exhibited a significant increase after several freezing–thawing cycles. Among the freezing times investigated, the highest crack density (CD) value of 300 m⁻¹ was achieved in FT60, while the lowest CD value of 31.25 m⁻¹ was observed in FT90 after liquid nitrogen (LN2) treatment. Additionally, the FTC4 process resulted in a 50% augmentation in the number of cracks, whereas the FTC5 process tripled the number of small cracks. Full article

Recent joint mass spectrometric and IR photodissociation studies have provided proof on the existence of octa-coordinated ionic lanthanide-carbonyl complexes under those extreme gaseous conditions. In contrast, in older literature concerning cryogenic studies of neutral Ln(CO)_x species, the highest coordination was assigned to hexa-coordinated Ln(CO)₆ molecules. The present study aims to clarify the above controversy using matrix isolation spectroscopy and DFT calculations. In order to ensure the maximum possible coordination, the Ln(CO)_x complexes were synthesized in neat CO cryogenic matrices at 10 K and were investigated by infrared and UV-visible spectroscopy. The formed complexes were identified on the basis of the characteristic CO stretching frequencies of the ground-state molecules predicted by DFT calculations. Our joint experimental–theoretical analysis confirmed the preference of octa-coordinated Ln(CO)₈ complexes in cryogenic neat CO matrices. Full article

6-Bromopyridine-2-carbaldehyde (abbreviated as BPCA) is used both as a building block in supramolecular chemistry and as a ligand for transition metal catalysts and luminescent complexes. In this study, the structure and vibrational spectra of BPCA were investigated in both the room temperature neat crystalline phase and for the compound isolated in cryogenic Ar, Kr and Xe matrices. The experimental studies were complemented by quantum chemical DFT(B3LYP)/6-311++G(d,p) calculations. For the crystalline compound, infrared and Raman spectra were obtained and interpreted. Comparison of the obtained infrared spectrum of the crystal with those obtained for the isolated molecules of BPCA in the studied cryomatrices helped to conclude that the intermolecular interactions in the crystal do not significantly perturb the intramolecular vibrational potential. Structural analysis further supports the existence of weak coupling between the intermolecular interactions and the structure of the constituting molecular units in crystalline state. The intermolecular interactions in the BPCA crystal were also evaluated by means of Hirshfeld analysis, which revealed that the most important interactions are weak and of the H^…N, H^…O, H^…H, H^…Br and Br^…Br types. The conformer of BPCA present in the crystal was found to correspond to the most stable form of the isolated molecule (trans), which bears stabilizing C–H^…O=C and C(=O)H^…N interactions. This conformer was shown to be the single conformer present in the as-deposited cryogenic matrices prepared from the room temperature gaseous compound. Broadband UV irradiation of matrix-isolated BPCA (λ ≥ 235 nm) resulted in the conversion of the trans conformer into the higher-energy cis conformer, where repulsive C–H^…H–C(=O) and C=O_LP^…_LPN (where LP designates a lone electron pair) interactions are present, and decarbonylation of the compound with formation of 2-bromopyridine (plus CO). The decarbonylation reaction was found to be more efficient in the more polarizable Xe matrix, indicating stabilization of the radicals initially formed upon breaking of the C–C(HO) and C–H (aldehyde) bonds in this medium, and testifying the occurrence of the decarbonylation reaction with involvement of radical species. TD-DFT calculations were used to access the nature of the excited states associated with the observed UV-induced reactions. As a whole, this study provides fundamental data to understand the physicochemical behavior of the compound, bridging the properties of the isolated molecule to those of the neat crystalline com-pound. Such information is of fundamental importance for the understanding of the role of BPCA in supramolecular chemistry and to potentiate its applications in synthesis and as a ligand for transition metal catalysts and luminescent complexes. Full article

Monomers of meta-fluorophenol (mFP) were trapped from the gas phase into cryogenic argon and nitrogen matrices. The estimated relative energies of the two conformers are very close, and in the gas phase they have nearly equal populations. Due to the similarity of their structures (they only differ in the orientation of the OH group), the two conformers have also similar predicted vibrational signatures, which makes the vibrational characterization of the individual rotamers challenging. In the present work, it has been established that in an argon matrix only the most stable trans conformer of mFP exists (the OH group pointing away from the fluorine atom). On the other hand, the IR spectrum of mFP in a nitrogen matrix testifies to the simultaneous presence in this matrix of both the trans conformer and of the higher-energy cis conformer (the OH group pointing toward the fluorine atom), which is stabilized by interaction with the matrix gas host. We found that the exposition of the cryogenic N₂ matrix to the Globar source of the infrared spectrometer affects the conformational populations. By collecting experimental spectra, either in the full mid-infrared range or only in the range below 2200 cm⁻¹, we were able to reliably distinguish two sets of experimental bands originating from individual conformers. A comparison of the two sets of experimental bands with computed infrared spectra of the conformers allowed, for the first time, the unequivocal vibrational identification of each of them. The joint implementation of computational vibrational spectroscopy and matrix-isolation infrared spectroscopy proved to be a very accurate method of structural analysis. Some mechanistic insights into conformational isomerism (the quantum tunneling of hydrogen atom and vibrationally-induced conformational transformations) have been addressed. Finally, we also subjected matrix-isolated mFP to irradiations with UV light, and the phototransformations observed in these experiments are also described. Full article

In this work, prereactive complexes, reaction products, and conformational preferences derived from the photochemical reaction between CS₂ and ClF were analyzed following the codeposition of the reactants trapped in argon matrices at cryogenic temperatures. After codeposition of CS₂ and ClF diluted in Ar, the formation of van der Waals complexes is observed. When the mixture is subsequently irradiated by means of broad-band UV-visible light (225 ≤ λ ≤ 800 nm), fluorothiocarbonylsulfenyl chloride (FC(S)SCl) and chlorothiocarbonylsulfenyl fluoride (ClC(S)SF) are produced. These species exist as two stable planar anti- and syn-conformers (anti- and syn- of the C=S double bond with respect to the S–Cl or S–F single bond, respectively). For both novel molecules, anti-FC(S)SCl and anti-ClC(S)SF are the lowest-energy computed rotamers. As expected due to the photochemical activity of these species, additional reaction products due to alternative or subsequent photochannels are formed during this process. Full article

Two different mid-infrared (mid-IR) solid-state crystalline laser active media of Cr${}^{2+}$, Fe${}^{2+}$:Zn${}_{1-\mathrm{x}}$Mn${}_{\mathrm{x}}$Se and Cr${}^{2+}$, Fe${}^{2+}$:Zn${}_{1-\mathrm{x}}$Mg${}_{\mathrm{x}}$Se with similar amounts of manganese or magnesium ions of x ≈ 0.3 were investigated at cryogenic temperatures for three different excitation wavelengths: Q-switched Er:YLF laser at the wavelength of 1.73 $\mathsf{\mu }$m, Q-switched Er:YAG laser at 2.94 $\mathsf{\mu }$m, and the gain-switched Fe:ZnSe laser operated at a liquid nitrogen temperature of 78 K at ∼4.05 $\mathsf{\mu }$m. The temperature dependence of spectral and laser characteristics was measured. Depending on the excitation wavelength and the selected output coupler, both laser systems were able to generate radiation by Cr${}^{2+}$ or by Fe${}^{2+}$ ions under direct excitation or indirectly by the Cr${}^{2+}$→ Fe${}^{2+}$ energy transfer mechanism. Laser generation of Fe${}^{2+}$ ions in Cr${}^{2+}$, Fe${}^{2+}$:Zn${}_{1-\mathrm{x}}$Mn${}_{\mathrm{x}}$Se and Cr${}^{2+}$, Fe${}^{2+}$:Zn${}_{1-\mathrm{x}}$Mg${}_{\mathrm{x}}$Se (x ≈ 0.3) crystals at the wavelengths of ∼4.4 and ∼4.8 $\mathsf{\mu }$m at a temperature of 78 K was achieved, respectively. The excitation of Fe${}^{2+}$ ions in both samples by direct 2.94 $\mathsf{\mu }$m as well as ∼4.05 $\mathsf{\mu }$m radiation or indirectly via the Cr${}^{2+}$→ Fe${}^{2+}$ ions’ energy transfer-based mechanism by 1.73 $\mathsf{\mu }$m radiation was demonstrated. Based on the obtained results, the possibility of developing novel coherent laser systems in mid-IR regions (∼2.3–2.5 and ∼4.4–4.9 $\mathsf{\mu }$m) based on A${}^{\mathrm{II}}$B${}^{\mathrm{VI}}$ matrices was presented. Full article

In this paper, the photochemistry of glyoxal–hydroxylamine (Gly–HA) complexes is studied using FTIR matrix isolation spectroscopy and ab initio calculations. The irradiation of the Gly–HA complexes with the filtered output of a mercury lamp (λ > 370 nm) leads to their photoconversion to hydroxyketene–hydroxylamine complexes and the formation of hydroxy(hydroxyamino)acetaldehyde with a hemiaminal structure. The first product is the result of a double hydrogen exchange reaction between the aldehyde group of Gly and the amino or hydroxyl group of HA. The second product is formed as a result of the addition of the nitrogen atom of HA to the carbon atom of one aldehyde group of Gly, followed by the migration of the hydrogen atom from the amino group of hydroxylamine to the oxygen atom of the carbonyl group of glyoxal. The identification of the products is confirmed by deuterium substitution and by MP2 calculations of the structures and vibrational spectra of the identified species. Full article

We present an experimental and theoretical investigation of the spectroscopy of dilute alkali atoms in a solid matrix of inert gases at cryogenic temperatures, specifically Rubidium atoms in a solid Argon or Neon matrix, and related aspects of the interaction energies between the alkali atoms and the atoms of the solid matrix. The system considered is relevant for matrix isolation spectroscopy, and it is at the basis of a recently proposed detector of cosmological axions, exploiting magnetic-type transitions between Zeeman sublevels of alkali atoms in a magnetic field, tuned to the axion mass, assumed in the meV range. Axions are one of the supposed constituents of the dark matter (DM) of the Universe. This kind of spectroscopy could be also relevant for the experimental search of new physics beyond the Standard Model, in particular the search of violations of time-reversal or parity-charge-conjugation (CP) symmetry. In order to efficiently resolve the axion-induced transition in alkali-doped solid matrices, it is necessary to reduce as much as possible the spectral linewidth of the electronic transitions involved. The theoretical investigation presented in this paper aims to estimate the order of magnitude of the inhomogeneous contribution to the linewidth due to the alkali–matrix interactions (Coulomb/exchange and dispersion), and to compare the theoretical results with our experimental measurements of spectra of dilute Rubidium atoms in Argon and Neon solid matrix. The comparison of the expected or measured spectral linewidths will be important for selecting the most appropriate combination of alkali atoms and matrix inert elements to be used in the proposed axion detection scheme. It is finally suggested that dilute Lithium atoms diffused in a cold parahydrogen solid matrix could be, overall, a good system upon which the proposed detector could be based. Full article