Nonclassical Crystallization Research Articles

Nonclassical Crystallization of an Al2O3 Film by Positively Charged Secondary Nanoparticles during Aerosol Deposition

Thin film growth through nonclassical crystallization with charged nanoparticles as building blocks has been studied in chemical vapor deposition and physical vapor deposition. A similar mechanism might be applied to aerosol deposition (AD), with which the mechanism for the evolution of dense ceramic films at room temperature has not been clearly understood. Aerosol particles fracture into fragments of secondary nanoparticles during AD. In this work, secondary particles passing between the two parallel biased and grounded electrodes were captured by the transmission electron microscopy (TEM) grid membrane on each electrode, and it was revealed that they were mainly positively charged. Neutral secondary nanoparticles, not deflected by the electric field, produced a porous film on the silicon substrate, whereas charged secondary nanoparticles produced a dense film. The positive charge of the secondary nanoparticles appeared to enhance the plastic deformation required for the evolution of dense films during AD, which was supported by ab initio calculations.

Quantitative analysis of chiral transitions and its implication for non-classical crystallization in isotactic polypropylene

Molecular dynamics simulations were used to quantify chiral transitions in an isolated isotactic polypropylene (iPP) chain on a nucleating agent substrate during the early stages of ordering. The effects of temperature, dihedral rigidity, and epitaxy of a single iPP chain placed on α-iPP, β-iPP, and TPDT surfaces were investigated. Using the adaptive biasing force (ABF) method, potentials of mean force (PMF) were computed for iPP segments to explain the selective stabilization of helical segments on various epitaxies. Whereas, chiral selection of helices from the extended-coil conformations was found to be more efficient, the selection of helices from coiled segments was poor. For α-iPP and β-iPP substrates, the stability of the extended-coils and formation of helices from extended-coils were positively correlated with each other. In contrast, a negatively correlation was found for the TPDT substrate, showing that a helix existed as a competitive conformation with the extended-coils when selective stabilization was absent. These observations support the validity of multi-stage nucleation routes during polymer crystallization, Further, they show that selective stabilization of helices by an epitaxy plays a vital role in the dynamics of multi-stage nucleation.

Mesocrystal morphology regulation by “alkali metals ion switch”: Re-examining zeolite nonclassical crystallization in seed-induced process

HypothesisIt is a Holy Grail to realize the goal-oriented synthesis of zeotype crystals via direct thermodynamic/kinetic control of crystallization in the simplest inorganic system. Especially, the most commonly used counter cations (i.e., Na+ and K+) are in turn believed to play merely the role of balancing charges and stabilizing frameworks, which make the simple ion-based morphology/porosity control remain big challenges. ExperimentsWe re-examined the role of Na+ and K+ to fine-tune the classical/nonclassical crystallization process in a seed-induced system with the simplest composition (Si/Al sources, inorganic alkali, and H2O), and proposed an “ion switch” strategy. By analyzing the multiple growth curves, tracking the precursor evolution, and observing epitaxial crystallization behavior, a distinctive “ion switch”-worked nonclassical mechanism was uncovered. FindingsBy the “ion switch” strategy, ZSM-5 mesocrystals were fine-regulated with diverse architecture from single crystal to nanocrystallite assembly and intracrystal mesopore-enriched crystal. Such simple ions-controlled crystallization was achieved through microstructure heterogeneity of zeolitic building-blocks triggered by different counterions and their corresponding assembly behavior from oriented attachment to random deposition. Furthermore, this protocol can be extended to a wider H2O/SiO2 range, mixed Na+/K+ systems, and other alkali metal ions from Li+ to Cs+, and ZSM-5 mesocrystals with extended morphologies can be obtained.

Unravelling an amine-regulated crystallization crossover to prove single/multicore effects on the biomedical and environmental catalytic activity of magnetic iron oxide colloids

Elucidation of reaction mechanisms in forming nanostructures is relevant to obtain robust and affordable protocols that can lead to materials with enhanced properties and good reproducibility. Here, the formation of magnetic iron oxide monocrystalline nanoflowers in polyol solvents using N-methyldiethanolamine (NMDEA) as co-solvent has been shown to occur through a non-classical crystallization pathway. This pathway involves intermediate mesocrystals that, in addition, can be transformed into large single colloidal nanocrystals. Interestingly, the crossover of a non-classical crystallization pathway to a classical crystallization pathway can be induced by merely changing the NMDEA concentration. The key is the stability of a green rust-like intermediate complex that modulates the nucleation rate and growth of magnetite nanocrystals. The crossover separates two crystallization domains (classical and non-classical) and three basic configurations (mesocrystals, large and small colloidal nanocrystals). The above finding facilitated the synthesis of magnetic materials with different configurations to suit various engineering applications. Consequently, the effect of the single and multicore configurations of magnetic iron oxide on the biomedical (magnetic hyperthermia and enzyme immobilization) and catalytic activity (Fenton-like reactions and photo-Fenton-like processes driven by visible light irradiation) has been experimentally demonstrated.

Non-classical Crystallization of Bulk Crystals in Solution and of Thin Films in the Gas Phase by Chemical Vapor Deposition

Non-classical Crystallization of Bulk Crystals in Solution and of Thin Films in the Gas Phase by Chemical Vapor Deposition

Effect of a new modified polyamidoamine dendrimer biomimetic system on the mineralization of type I collagen fibrils: an in vitro study

We evaluate the effects of the new Dentine matrix protein 1 (DMP-1) biomimetic system composed of phosphorylated polyamidoamine dendrimer (PAMAM-PO3H2) and carboxylated polyamidoamine dendrimer (PAMAM-COOH) on the mineralization of type I collagen fibrils. PAMAM-PO3H2 and PAMAM-COOH were observed to have the ability to induce internal and external mineralization of type I collagen fibrils in vitro through non-classical mineralization crystallization pathway, which has become a hopeful biomimetic system of biomimetic remineralization and demineralization of dentin type I collagen fibrils and has great potential in inducing biomimetic remineralization of demineralized dentin.

Boron isotope fractionation during the formation of amorphous calcium carbonates and their transformation to Mg-calcite and aragonite

The non-classical crystallization pathway of carbonate minerals proceeds through the initial formation of an amorphous precursor phase and commonly takes place during biomineralization. Although the isotopic composition of marine calcifiers is often used to reconstruct paleo-environmental conditions, the impact of the crystallization pathway followed by these organisms on the isotope composition of their skeletons has rarely been quantified. This study presents the first examination of B partitioning and isotope fractionation during CaCO3 formation via an amorphous calcium carbonate phase, which provides new insights into the incorporation of B into marine calcite and aragonite that form via this route. Boron concentrations and isotope compositions of the fluids and the formed solids were characterized during the course of experiments that lasted two years and were performed at 25 °C under controlled pH conditions. The results suggest that during Mg-ACC formation, B distribution coefficients are 1.5–4 orders of magnitude higher than those reported earlier in the literature for calcite and aragonite. Additionally, B isotope fractionation during Mg-ACC formation is strongly affected by the continuous exchange of solutes between the nanoporous solid phase and the bulk fluid. The isotope composition of the transient amorphous phase is not inherited in the crystalline carbonate mineral phase that ultimately forms, because crystallization proceeds via a continuous dissolution/re-precipitation process and/or chemical/isotope exchange between the solid surface and the fluid. Interestingly, the isotope fractionation between the fluid and the final crystalline products is different from those achieved in earlier studies where mineral growth proceeded via the standard mechanism of ion-by-ion addition of solutes to advancing steps. The B isotope fractionations measured in this study are in good agreement with results of equilibrium first principle calculations for calcite and aragonite (Balan et al., 2018) except in the case of calcite formed at pH = 8.9, suggesting that changes in aqueous speciation (i.e. increase of NaB(OH)4° and CO32− concentrations) may be responsible for slight changes of the calcite BO4 environment and isotope composition. It is expected that this study will help to better decipher the mechanisms controlling B isotope fractionation during the non-classical growth of calcium carbonates involving the formation of transient amorphous precursors.

Advances of Nonclassical Crystallization toward Self-Purification of Precious Metal Nanoparticle Mixtures

In this work, we use particle-mediated crystallization to separate mixtures of precious metal nanoparticles of different size and shape.

Superhydrous hematite and goethite: A potential water reservoir in the red dust of Mars?

Abstract Water can be stored in nominally anhydrous minerals as substitutional hydroxyl, generating vast but commonly unrecognized H2O reservoirs in ostensibly dry regimes. Researchers have long known that hematite (α-Fe2O3) can accommodate small concentrations of hydroxyl through the substitution of Fe3+ by 3H+. Our study of natural hematite has demonstrated the occurrence of “hydrohematite” phases that are 10–20 mol% deficient in Fe and accordingly contain 3.6–7.8 mol% structural water. Intergrown with natural hydrohematite samples were superhydrous goethite-like phases exhibiting an Fe deficiency of 10–20 mol% relative to end-member goethite (α-FeOOH). We synthesized hydrohematite in alkaline solutions (pH 9–12) at low temperatures (T < 200 °C) using fresh ferrihydrite as the transient precursor, and we observed a nonclassical crystallization pathway involving vacancy inoculation by Fe as nanocrystals evolved. The high level of incorporation of H2O in iron (hydr)oxides dramatically alters their behaviors as catalysts and pigments, and the presence of hydrohematite in rocks may rule out high-T diagenesis. We propose that hydrohematite is common in low-T occurrences of Fe oxide on Earth, and by extension it may inventory large quantities of water in apparently arid planetary environments, such as the surface of Mars.

Wettability of Magnetite Nanoparticles Guides Growth from Stabilized Amorphous Ferrihydrite.

Crystal formation via amorphous precursors is a long-sought-after gateway to engineer nanoparticles with well-controlled size and morphology. Biomineralizing organisms, like magnetotactic bacteria, follow such a nonclassical crystallization pathway to produce magnetite nanoparticles with sophistication unmatched by synthetic efforts at ambient conditions. Here, using in situ small-angle X-ray scattering, we demonstrate how the addition of poly(arginine) in the synthetic formation of magnetite nanoparticles induces a biomineralization-reminiscent pathway. The addition of poly(arginine) stabilizes an amorphous ferrihydrite precursor, shifting the magnetite formation pathway from thermodynamic to kinetic control. Altering the energetic landscape of magnetite formation by catalyzing the pH-dependent precursor attachment, we tune magnetite nanoparticle size continuously, exceeding sizes observed in magnetotactic bacteria. This mechanistic shift we uncover here further allows for crystal morphology control by adjusting the pH-dependent interfacial interaction between liquidlike ferrihydrite and nascent magnetite nanoparticles, establishing a new strategy to control nanoparticle morphology. Synthesizing compact single crystals at wetting conditions and unique semicontinuous single-crystalline nanoparticles at dewetting conditions in combination with an improved control over magnetite crystallite size, we demonstrate the versatility of bio-inspired, kinetically controlled nanoparticle formation pathways.

Formation and Evolution of Nanoscale Calcium Phosphate Precursors under Biomimetic Conditions

Simulated body fluids (SBFs) that mimic human blood plasma are widely used media for in vitro studies in an extensive array of research fields, from biomineralization to surface and corrosion sciences. We show that these solutions undergo dynamic nanoscopic conformational rearrangements on the timescale of minutes to hours, even though they are commonly considered stable or metastable. In particular, we find and characterize nanoscale inhomogeneities made of calcium phosphate (CaP) aggregates that emerge from homogeneous SBFs within a few hours and evolve into prenucleation species (PNS) that act as precursors in CaP crystallization processes. These ionic clusters consist of ∼2 nm large spherical building units that can aggregate into suprastructures with sizes of over 200 nm. We show that the residence times of phosphate ions in the PNS depend critically on the total PNS surface. These findings are particularly relevant for understanding nonclassical crystallization phenomena, in which PNS are assumed to act as building blocks for the final crystal structure.

Investigation of ultrasonication and/or mechanical stirring on the reactive crystallization of calcium carbonate at lower temperature and higher supersaturation condition

Calcium carbonate (CaCO3, CC) distributes diversely among the abiotic and biogenic minerals/biominerals. It has six phases (three anhydrous crystalline, two hydrates and one amorphous). Phase selectivity of the synthetic CC is of considerable interest and determines its physicochemical properties and destinated applications.In the present study the reactive crystallization process of CC has been subjected to the treatment of different disturbances, i.e., mechanical stirring (ms), ultrasonication (us), and composed ms + us at lower temperature (0 ± 1℃) and higher supersaturation condition (initial concentration of Ca2+ is 0.1 M), in comparison with the quiescent condition. In order to gain insight on the role of these disturbances in controlling the crystallization process, nature, crystal habits of precipitated CC and their consecutive phase transformation, samples were collected at different time intervals (30 s, 1 min, 5 min, 10 min, 20 min, 45 min and 60 min) for investigation. Results reveals that these disturbing ways play a significant role on the CC crystallization process and can stabilize the amorphous calcium carbonate (ACC) phase for prolonged periods of time (1–60 min) in aqueous solution, which will be a powerful way for large-scale fabrication of pure ACC nanoparticles (about 100 nm) without addition of any chemicals. Longer disturbing time tends to transform the pure and spherical ACC nanoparticles competitively into spherical vaterite particles and rhombohedral calcite particles through the self-assembly of nanoparticles aggregation or Ostwald ripening mechanism, respectively. The investigation also suggested that the reactive crystallization of CC with the three disturbances undergoes a non-classical crystallization pathway to crystallize CC particles, in comparison with the quiescent reference condition. To the best of our knowledge, the report on reactive crystallization of CC crystallites as a function of different disturbances is first of its kind in the literature.

The Ambiguous Functions of the Precursors That Enable Nonclassical Modes of Olanzapine Nucleation and Growth

One of the most consequential assumptions of the classical theories of crystal nucleation and growth is the Szilard postulate, which states that molecules from a supersaturated phase join a nucleus or a growing crystal individually. In the last 20 years, observations in complex biological, geological, and engineered environments have brought to light violations of the Szilard rule, whereby molecules assemble into ordered or disordered precursors that then host and promote nucleation or contribute to fast crystal growth. Nonclassical crystallization has risen to a default mode presumed to operate in the majority of the inspected crystallizing systems. In some cases, the existence of precursors in the growth media is admitted as proof for their role in nucleation and growth. With the example of olanzapine, a marketed drug for schizophrenia and bipolar disorder, we demonstrate that molecular assemblies in the solution selectively participate in crystal nucleation and growth. In aqueous and organic solutions, olanzapine assembles into both mesoscopic solute-rich clusters and dimers. The clusters facilitate nucleation of crystals and crystal form transformations. During growth, however, the clusters land on the crystal surface and transform into defects, but do not support step growth. The dimers are present at low concentrations in the supersaturated solution, yet the crystals grow by the association of dimers, and not of the majority monomers. The observations with olanzapine emphasize that detailed studies of the crystal and solution structures and the dynamics of molecular association may empower classical and nonclassical models that advance the understanding of natural crystallization, and support the design and manufacture of promising functional materials.

A new perspective of inorganic crystallization: Non-classical nucleation and growth

<p indent=0mm>Inorganic crystals surround us and play important roles in our daily life. They form integral parts of our body (e.g., bones), make up all the ground we stand on (ours and any other rocky planet consist of crystals), as well as show significant necessity for industrial processes and technologies (from table salt over concrete to biomedical nanoparticles). Accordingly, the formation mechanisms and properties of crystals have been extensively studied over the past decades. While there are longstanding theories on both the birth of crystals (nucleation) and their subsequent evolution (growth, recrystallization, and/or transformation), a vast amount of evidence suggests that the classical view on crystallization is over-simplified. In addition to the monomer-by-monomer (i.e., atoms, ions, or molecules) addition described in the classical theories, the particle attachment has been recognized as one of the most important pathways to inorganic crystallization. These particles range from the ion pairs to well-crystallized nanoparticles, such as amorphous precursors, magic-size clusters, nanocrystals, etc. The complexity of both the free-energy landscapes and reaction kinetics leads to diverse crystallization pathways. While experimental observations clearly demonstrate the non-classical crystallization pathways, many fundamental aspects remain unknown—Particularly the interaction of solution structure, interfacial forces, and particle motion. Thus, a predictive description linking molecular details to ensemble behavior is lacking. As such description develops, long-term interpretations of inorganic crystal formation should be revisited, which is important to broaden the scope of research across various disciplines such as geological events, biomineralization mechanisms, environmental remediation, and the development of environmentally functional materials. Based on several exemplary spotlights, the current state of the art in non-classical nucleation has been firstly illustrated in our review. Specifically, two non-classical nucleation pathways (i.e., the prenucleation clusters (PNCs) and aggregation pathway) in the current crystal research field are summarized. According to the PNCs pathway, PNCs were considered as the stable solute species with chainlike structural that are precursors to nucleation. Once system reaches the equilibrium ion activity product, the change in the chemistry of linkages within PNCs causes PNCs aggregation, as a consequence of nucleus formation. Another non-classical view (aggregation pathway) pointed that the fine crystalline nuclei first form in solution and then aggregate into a larger and more stable nucleus. Besides, the non-classical oriented attachment (OA) and random attachment (RA) growth pathways are also elucidated. OA and RA growth are similar in involving the self-assembly of primary nanocrystals. However, their main difference is the orientation of the crystal lattice at the grain boundary. For RA growth pathway, there is no particular preference for the attachment whereas for the OA growth, there is a common crystallographic alignment of the attachment to occur, which is allowing for continuous crystallographic planes. Finally, the implications and perspective of non-classical crystallization research are proposed. The aim of this review is to guide the readers through the complex world of crystallizing systems, highlighting a new perspective on non-classical crystallization of inorganic materials, which drives a true renaissance in the field and provides completely new perspectives on the underlying crystallization mechanisms. Additionally, through a mechanism-based understanding, we believed that non-classical crystallization processes can be used to produce innovative structures that retain the dimensional properties of their nanoscale building blocks and create materials with enhanced or novel physical and chemical properties.

Citrate Stabilizes Hydroxylapatite Precursors: Implications for Bone Mineralization.

Mineralization of hydroxylapatite (HAp), the main inorganic phase in bone, follows nonclassical crystallization routes involving metastable precursors and is strongly influenced by organic macromolecules. However, the effect of small organic molecules such as citrate on the formation of HAp is not well constrained. Using potentiometric titration experiments and titration calorimetry, in combination with a multianalytical approach, we show that citrate stabilizes prenucleation species as well as a liquid-like calcium phosphate precursor formed before any solid phase nucleates in the system. The stabilization of a liquid-like precursor phase could facilitate infiltration into the cavities of the collagen fibrils during bone mineralization, explaining the enhancement of collagen-mediated mineralization by citrate reported in previous studies. Hence, citrate can influence bone mineralization way before any solid phase (amorphous or crystalline) is formed. We also show that HAp formation after amorphous calcium phosphate (ACP) in the absence and presence of citrate results in nanoplates of about 5–12 nm thick, elongated along the c axis. Such nanoplates are made up of HAp nanocrystallites with a preferred c axis orientation and with interspersed ACP. The nanoplatelet morphology, size, and preferred crystallographic orientation, remarkably similar to those of bone HAp nanocrystals, appear to be an intrinsic feature of HAp formed from an amorphous precursor. Our results challenge current models for HAp mineralization in bone and the role of citrate, offering new clues to help answer the long-standing question as to why natural evolution favored HAp as the mineral phase in bone.

Facile synthesis of ZSM-5 mesocrystal via novel pathway of crystallization: Fast precipitation, deconstruction and reorganization

Mesocrystal zeolite with well-defined morphology owns mesoporous channels and single crystal characteristics, which could promote diffusion efficiency, stability and catalytic activity. Thus, we performed the controllable synthesis of ZSM-5 mesocrystal without special additives and complex methods. Selected area electron diffraction (SAED) and fast Fourier transform (FFT) showed diffraction spots regardless of crystallization time, which indicated the well oriented feature of synthesized ZSM-5 zeolites. The crystallization process was further investigated. The oriented particle attachment (OPA) effectively guided the synthesis process of mesocrystals, which followed the nonclassical crystallization mechanism. The crystallinity curve exhibited valley-like shape, which manifested that the crystallization pathway went through three stages: fast precipitation, deconstruction and reorganization. The plausible formation mechanism was proposed, which might be useful for the fabrication of ZSM-5 mesocrystal. The prepared zeolites showed superior catalytic performance in aldol condensation reaction between benzaldehyde and 2-hydroxyacetophenone, obtaining 93% of the conversion. The fast precipitation gave rise to perfect oriented feature. Then, the synthesized zeolites deconstructed due to OH − ions, the lighter bule indicated imperfect crystallized crystal due to the damage of OH − ions. Finally, the reorganization happened due to further ripening of deconstructed nanoparticles. The planar graph embedded in the circle demonstrated the structure of inter domain. •ZSM-5 mesocrystal with tunable Si/Al ratio was synthesized without special additives and complex methods. •The synthesis of ZSM-5 mesocrystal underwent unusual crystallization pathway: fast precipitation, deconstruction and reorganization. •ZSM-5 mesocrystal showed excellent catalytic performance in the Claisen‐Schmidt condensation reaction.

Observation of New Dynamics of Transitions among Intermediate Species in Crystal Evolution and Its Role in a Generic Model of Crystallization

The mass and phase transitions among intermediate species are unique dynamics in nonclassical crystallization that are under investigation. In this research, we used a pulsed laser to initiate crystallization in its early stages and observed the crystal evolution through transitions and interactions among the intermediate species. The crystal evolution was induced and observed in situ simultaneously by the same electron beam in a transmission electron microscope without a liquid cell environment, thereby eliminating the complexity introduced by the additional nucleation in the precursor solution. The observed mass diffusion among species in an anti-Ostwald ripening way indicated that crystallization systems were composed of intermediate species in various phases. We found that these intermediate species were not like rigid building blocks but kept changing in size and phase and evolving in multistage transitions. Considering the observations, we propose a generic model by extending the classical nucleation theories to describe the dynamics of intermediate transitions and all possible crystal evolution pathways, discovered or not.

Two-Step Deposition of Silicon Oxide Films Using the Gas Phase Generation of Nanoparticles in the Chemical Vapor Deposition Process

Non-classical crystallization, in which charged nanoparticles (NPs) are the building blocks of film growth, has been extensively studied in chemical vapor deposition (CVD). Here, the deposition behavior of silicon oxide films by the two-step growth process, where NPs are generated in the gas phase at high temperature and deposited as films at low temperature, was studied in the CVD process. Although we supplied SiH4, H2, and N2, the deposited film turned out to be silicon oxide, which is attributed to relatively poor vacuum. Also, silicon oxide NPs were captured on transmission electron microscopy (TEM) carbon membranes of a copper grid for 10 s under various conditions. When the quartz tube with a conical nozzle was used, the size of nanoparticles increased drastically with increasing processing time (or delay time) and porous films with a rough surface were deposited. When the quartz tube without a nozzle was used, however, the size did not increase much with increasing processing time and dense films with a smooth surface were deposited. These results suggest that the size of nanoparticles is an important parameter for the deposition of dense films for two-step growth at low temperatures.

Effect of Pressure on the Film Deposition during RF Magnetron Sputtering Considering Charged Nanoparticles

Non-classical crystallization, in which charged nanoparticles (NPs) are the building blocks of film growth, has been extensively studied in chemical vapor deposition (CVD). Recently, a similar mechanism of film growth has been reported during radio frequency (RF) sputtering with a Ti target and DC magnetron sputtering using an Ag target. In this study, the effect of pressure on the generation of Ti NPs and on the film deposition was studied during RF sputtering with a Ti target. Ti NPs were captured on transmission electron microscopy (TEM) membranes with the electric biases of −30, 0, and +50 V under 20 and 80 mTorr. The number densities of the Ti NPs were 134, 103, and 21 per 100 × 100 nm2, respectively, with the biases of −30, 0, and +50 V under 20 mTorr and were 196, 98, and 0 per 100 × 100 nm2, respectively, with the biases of −30, 0, and +50 V under 80 mTorr, which was analyzed by TEM. The growth rate of Ti films deposited on Si substrates was insensitive to the substrate bias under 20 mTorr but was sensitive under 80 mTorr, with the thicknesses of 132, 133, 97, and 29 nm, respectively, after being deposited for 15 min with the substrate biases of −30, −10, 0, and +50 V. This sensitive dependence of the film growth rate on the substrate bias under 80 mTorr is in agreement with the sensitive dependence of the number density of Ti NPs on the substrate bias under 80 mTorr.

Stabilization of Calcium Oxalate Precursors during the Pre- and Post-Nucleation Stages with Poly(acrylic acid).

In this work, calcium oxalate (CaOx) precursors were stabilized by poly(acrylic acid) (PAA) as an additive under in vitro crystallization assays involving the formation of pre-nucleation clusters of CaOx via a non-classical crystallization (NCC) pathway. The in vitro crystallization of CaOx was carried out in the presence of 10, 50 and 100 mg/L PAA by using automatic calcium potentiometric titration experiments at a constant pH of 6.7 at 20 °C. The results confirmed the successful stabilization of amorphous calcium oxalate II and III (ACOII and ACO III) nanoparticles formed after PNC in the presence of PAA and suggest the participation and stabilization of polymer-induced liquid-precursor (PILP) in the presence of PAA. We demonstrated that PAA stabilizes CaOx precursors with size in the range of 20–400 nm. PAA additive plays a key role in the in vitro crystallization of CaOx stabilizing multi-ion complexes in the pre-nucleation stage, thereby delaying the nucleation of ACO nanoparticles. Indeed, PAA additive favors the formation of more hydrated and soluble phase of ACO nanoparticles that are bound by electrostatic interactions to carboxylic acid groups of PAA during the post-nucleation stage. These findings may help to a better understanding of the pathological mineralization resulting in urolithiasis in mammals.