Reduction reactions at the interface between CdS quantum dot and Z-type ligands driven by electron injection in the electroluminescent processes.

The efficient and stable electroluminescence of quantum dots (QDs) is of great importance in their applications in new display technologies. The short service life of blue QDs, however, hinders their development and commercialization. Different mechanisms have been proposed for the destabilization of QDs in electroluminescent processes. Based on real-time time-dependent density functional theory studies on the QD models covered by Z-type ligands (XAc2, X = Cd, Zn, Mg), the structural evolution is simulated to reveal the mechanism of the reduction reactions induced by electron injection. Our simulations reproduce the experimental observations that the reduction reactions occur at the QD-ligand interface, and the reduced Cd atom is almost in a zero valence state. However, different sites are predicted for the reactions in which the surface metal atom of the QD instead of the metal atom in the ligands is reduced. As a result, one of the arms of the chelate ligand leaves the QD, which tends to cause damage to its electroluminescent performance. Our findings contribute to a mechanistic understanding of the reduction reactions that occurred at the QD-ligand interface.

Synthesis and biological evaluation of novel aromatic amide derivatives as potential BCR-ABL inhibitors.

BCR-ABL1 kinase is a key driver of the pathophysiology of chronic myeloid leukemia (CML). Current treatments need to broaden the chemical diversity of BCR-ABL1 kinase inhibitors to overcome drug resistance. We designed and synthesized a series of aromatic amide derivatives based on several generations of BCR-ABL1 kinase inhibitors. Biological studies showed that compared with Imatinib, these compounds showed significant proliferation inhibitory activities of HL-60 and K562 in cell activity assay. Compounds 4g and 4j exhibited significant anti-tumor activity against the K562 cells with IC50 values of 6.03 ± 0.49 µM and 5.66 ± 2.06 µM respectively. Compounds 4g and 4j, as potential BCR-ABL1 inhibitors, inhibit the phosphorylation of ABL1 and CRKL in a dose-dependent manner. Therefore, compounds 4g and 4j can be used as a starting point for further optimization.

Shell effects on the dielectric properties of core-shell quantum dots.

The dielectric properties in semiconductor quantum dots are crucial for exciton formation, migration, and recombination. Different from 3D bulk materials, the dielectric response is, however, ambiguous for the small-sized 0D dots in which the effect of outer atoms on the inner atoms is usually described qualitatively. Based on the first-principles calculated electron density, the polarizability of the core-shell CdSe@ZnS wurtzite quantum dots is decomposed into the distributional contributions among which the dipole polarizability of the core is proposed to measure the shell effect on the dielectric properties of core-shell quantum dots. The shell thickness dependence on the shell effect is then studied, which is significant for the outermost shell but decays rapidly in the additional shells. Moreover, this model gives explicit physical origins of the core dipole polarizability in the core-shell QDs, which is determined by the intra-shell polarization and inter-core-shell charge transfer. Our study proposes a new approach for studying the dielectric properties of core-shell quantum dots, which is effective and extendable for other low-dimensional structures.

Adult Bone Marrow-Derived Mesenchymal Stem Cells Seeded on Tissue-Engineered Cardiac Patch Contribute to Myocardial Scar Remodeling and Enhance Revascularization in a Rabbit Model of Chronic Myocardial Infarction.

BACKGROUND: Although the transplantation of tissue-engineered cardiac patches with adult bone marrow-derived mesenchymal stem cells (MSCs) can enhance cardiac function after acute or chronic myocardial infarction (MI), the recovery mechanism remains controversial. This experiment aimed to investigate the outcome measurements of MSCs within a tissue-engineered cardiac patch in a rabbit chronic MI model. METHODS: This experiment was divided into four groups: left anterior descending artery (LAD) sham-operation group (N = 7), sham-transplantation (control, N = 7), non-seeded patch group (N = 7), and MSCs-seeded patch group (N = 6). PKH26 and 5-Bromo-2'-deoxyuridine (BrdU) labeled MSCs-seeded or non-seeded patches were transplanted onto chronically infarct rabbit hearts. Cardiac function was evaluated by cardiac hemodynamics. H&E staining was performed to count the number of vessels in the infarcted area. Masson staining was used to observe cardiac fiber formation and to measure scar thickness. RESULTS: Four weeks after transplantation, a remarkable improvement in cardiac functionality could be distinctly observed, which was most significant in the MSCs-seeded patch group. Moreover, labeled cells were detected in the myocardial scar, with most of them differentiated into myofibroblasts, some into smooth muscle cells, and only a few into cardiomyocytes in the MSCs-seeded patch group. We also observed significant revascularization in the infarct area implanted in either MSCs-seeded or non-seeded patches. In addition, there were significantly greater numbers of microvessels in the MSCs-seeded patch group than in the non-seeded patch group.

An integrative gene expression signature analysis identifies CMS4 KRAS-mutated colorectal cancers sensitive to combined MEK and SRC targeted therapy.

BACKGROUND: Over half of colorectal cancers (CRCs) are hard-wired to RAS/RAF/MEK/ERK pathway oncogenic signaling. However, the promise of targeted therapeutic inhibitors, has been tempered by disappointing clinical activity, likely due to complex resistance mechanisms that are not well understood. This study aims to investigate MEK inhibitor-associated resistance signaling and identify subpopulation(s) of CRC patients who may be sensitive to biomarker-driven drug combination(s). METHODS: We classified 2250 primary and metastatic human CRC tumors by consensus molecular subtypes (CMS). For each tumor, we generated multiple gene expression signature scores measuring MEK pathway activation, MEKi "bypass" resistance, SRC activation, dasatinib sensitivity, EMT, PC1, Hu-Lgr5-ISC, Hu-EphB2-ISC, Hu-Late TA, Hu-Proliferation, and WNT activity. We carried out correlation, survival and other bioinformatic analyses. Validation analyses were performed in two independent publicly available CRC tumor datasets (n = 585 and n = 677) and a CRC cell line dataset (n = 154). RESULTS: Here we report a central role of SRC in mediating "bypass"-resistance to MEK inhibition (MEKi), primarily in cancer stem cells (CSCs). Our integrated and comprehensive gene expression signature analyses in 2250 CRC tumors reveal that MEKi-resistance is strikingly-correlated with SRC activation (Spearman P < 10-320), which is similarly associated with EMT (epithelial to mesenchymal transition), regional metastasis and disease recurrence with poor prognosis. Deeper analysis shows that both MEKi-resistance and SRC activation are preferentially associated with a mesenchymal CSC phenotype. This association is validated in additional independent CRC tumor and cell lines datasets. The CMS classification analysis demonstrates the strikingly-distinct associations of CMS1-4 subtypes with the MEKi-resistance and SRC activation. Importantly, MEKi + SRCi sensitivities are predicted to occur predominantly in the KRAS mutant, mesenchymal CSC-like CMS4 CRCs. CONCLUSIONS: Large human tumor gene expression datasets representing CRC heterogeneity can provide deep biological insights heretofore not possible with cell line models, suggesting novel repurposed drug combinations. We identified SRC as a common targetable node--an Achilles' heel--in MEKi-targeted therapy-associated resistance in mesenchymal stem-like CRCs, which may help development of a biomarker-driven drug combination (MEKi + SRCi) to treat problematic subpopulations of CRC.

Effect of Mn doping on the electron injection in CdSe/TiO2 quantum dot sensitized solar cells.

Promotion in power conversion efficiency is an appealing task for quantum dot-sensitized solar cells that have emerged as promising materials for the utilization of clean and sustainable energy. Doping of Mn atoms into quantum dots (QD) has been proven to be one of the effective approaches, although the origin of such a promotion remains controversial. While several procedures are involved in the power conversion process, electron injection from the QD to the semiconductor oxide substrate is focused on in this work using first-principles calculations. Based on the Marcus theory, the electron injection rates are evaluated for the quantum dot-sensitized solar cell models in which the pure and Mn-doped core-shell CdSe clusters are deposited on a semiconductor titanium dioxide substrate. Enhanced rates are obtained for the Mn-doped structure, which is in qualitative agreement with the experiments. A large number of dominant injection channels and strong QD-substrate coupling are responsible for the Mn-induced rate enhancement, which could be achieved by manipulating the band structure mapping between the QD and the semiconductor oxide. By addressing the role of an Mn dopant in the electron injection process, strategies for the promotion of electron injection rates are proposed for the design of quantum dot-sensitized solar cells.

Luteoloside prevents lipopolysaccharide-induced osteolysis and suppresses RANKL-induced osteoclastogenesis through attenuating RANKL signaling cascades.

Bone destruction or osteolysis marked by excessive osteoclastic bone resorption is a very common medical condition. Identification of agents that can effectively suppress excessive osteoclast formation and function is crucial for prevention and treatment of osteolytic conditions such as periprosthetic joint infection and periprosthetic loosening. Luteoloside, a flavonoid, is a natural bioactive compound with anti-inflammation and anti-tumor properties. However, the effect of Luteoloside on inflammation-induced osteolysis is unknown. Here, we found that Luteoloside exhibited a strong inhibitory effect on lipopolysaccharide (LPS)-induced osteolysis in vivo. In addition, Luteoloside suppressed RANKL-induced osteoclast differentiation and abrogated bone resorption in a dose-dependent manner. Further, we found that the anti-osteoclastic and anti-resorptive actions of Luteoloside are mediated via blocking NFATc1 activity and the attenuation of RANKL-mediated Ca2+ signaling as well as NF-κB and MAPK pathways. Taken together, this study shows that Luteoloside may be a potential therapeutic agent for osteolytic bone diseases associated with abnormal osteoclast formation and function in inflammatory conditions.

Theoretical characterization on the size-dependent electron and hole trapping activity of chloride-passivated CdSe nanoclusters.

Ligand passivation is often used to suppress the surface trap states of semiconductor quantum dots (QDs) for their continuous photoluminescence output. The suppression process is related to the electrophilic/nucleophilic activity of surface atoms that varies with the structure and size of QD and the electron donating/accepting nature of ligand. Based on first-principles-based descriptors and cluster models, the electrophilic/nucleophilic activities of bare and chloride-coated CdSe clusters were studied to reveal the suppression mechanism of Cl-passivated QDs and compared to experimental observations. The surface atoms of bare clusters have higher activity than inner atoms and their activity decreases with cluster size. In the ligand-coated clusters, the Cd atom remains as the electrophilic site, while the nucleophilic site of Se atoms is replaced by Cl atoms. The activities of Cd and Cl atoms in the coated clusters are, however, remarkably weaker than those in bare clusters. Cluster size, dangling atoms, ligand coverage, electronegativity of ligand atoms, and solvent (water) were found to have considerable influence on the activity of surface atoms. The suppression of surface trap states in Cl-passivated QDs was attributed to the reduction of electrophilic/nucleophilic activity of Cd/Se/Cl atoms. Both saturation to under-coordinated surface atoms and proper selection for the electron donating/accepting strength of ligands are crucial for eliminating the charge carrier traps. Our calculations predicted a similar suppressing effect of chloride ligands with experiments and provided a simple but effective approach to assess the charge carrier trapping behaviors of semiconductor QDs.

Coupled-cluster method for open-shell heavy-element systems with spin-orbit coupling.

The coupled-cluster approach with spin-orbit coupling (SOC) included in post-self-consistent field treatment (SOC-CC) using relativistic effective core potentials is extended to spatially non-degenerate open-shell systems in this work. The unrestricted Hartree-Fock determinant corresponding to the scalar relativistic Hamiltonian is employed as the reference and the open-shell SOC-CC approach is implemented at the CC singles and doubles (CCSD) level as well as at the CCSD level augmented by a perturbative treatment of triple excitations (CCSD(T)). Due to the breaking of time-reversal symmetry and spatial symmetry, this open-shell SOC-CC approach is rather expensive compared with the closed-shell SOC-CC approach. The open-shell SOC-CC approach is applied to some open-shell atoms and diatomic molecules with s1, p3, σ1, or π2 configuration. Our results indicate that rather accurate results can be achieved with the open-shell SOC-CCSD(T) approach for these systems. Dissociation energies for some closed-shell molecules containing heavy IIIA or VIIA atoms are also calculated using the closed-shell SOC-CC approach, where energies of the IIIA or VIIA atoms are obtained from those of the closed-shell ions and experimental ionization potentials or electron affinities. SOC-CCSD(T) approach affords reliable dissociation energies for these molecules. Furthermore, scalar-relativistic CCSD(T) approach with the same strategy can also provide reasonable dissociation energies for the 5th row IIIA or VIIA molecules, while the error becomes pronounced for the 6th row elements.

Eriodictyol Inhibits RANKL-Induced Osteoclast Formation and Function Via Inhibition of NFATc1 Activity.

Receptor activator of nuclear factor kappa-B ligand (RANKL) induces differentiation and function of osteoclasts through triggering multiple signaling cascades, including NF-κB, MAPK, and Ca(2+) -dependent signals, which induce and activate critical transcription factor NFATc1. Targeting these signaling cascades may serve as an effective therapy against osteoclast-related diseases. Here, by screening a panel of natural plant extracts with known anti-inflammatory, anti-tumor, or anti-oxidant properties for possible anti-osteoclastogenic activities we identified Eriodictyol. This flavanone potently suppressed RANKL-induced osteoclastogenesis and bone resorption in a dose-dependent manner without detectable cytotoxicity, suppressing RANKL-induced NF-κB, MAPK, and Ca(2+) signaling pathways. Eriodictyol also strongly inhibited RANKL-induction of c-Fos levels (a critical component of AP-1 transcription factor required by osteoclasts) and subsequent activation of NFATc1, concomitant with reduced expression of osteoclast specific genes including cathepsin K (Ctsk), V-ATPase-d2 subunit, and tartrate resistant acid phosphatase (TRAcP/Acp5). Taken together, these data provide evidence that Eriodictyol could be useful for the prevention and treatment of osteolytic disorders associated with abnormally increased osteoclast formation and function. J. Cell. Physiol. 231: 1983-1993, 2016. © 2016 Wiley Periodicals, Inc.

Surface Structure of Hydroxyapatite from Simulated Annealing Molecular Dynamics Simulations.

The surface structure of hydroxyapatite (HAP) is crucial for its bioactivity. Using a molecular dynamics simulated annealing method, we studied the structure and its variation with annealing temperature of the HAP (100) surface. In contrast to the commonly used HAP surface model, which is sliced from HAP crystal and then relaxed at 0 K with first-principles or force-field calculations, a new surface structure with gradual changes from ordered inside to disordered on the surface was revealed. The disordering is dependent on the annealing temperature, Tmax. When Tmax increases up to the melting point, which was usually adopted in experiments, the disordering increases, as reflected by its radial distribution functions, structural factors, and atomic coordination numbers. The disordering of annealed structures does not show significant changes when Tmax is above the melting point. The thickness of disordered layers is about 10 Å. The surface energy of the annealed structures at high temperature is significantly less than that of the crystal structure relaxed at room temperature. A three-layer model of interior, middle, and surface was then proposed to describe the surface structure of HAP. The interior layer retains the atomic configurations in crystal. The middle layer has its atoms moved and its groups rotated about their original locations. In the surface layer, the atomic arrangements are totally different from those in crystal. In particular for the hydroxyl groups, they move outward and cover the Ca(2+) ions, leaving holes occupied by the phosphate groups. Our study suggested a new model with disordered surface structures for studying the interaction of HAP-based biomaterials with other molecules.

Spin-orbit coupling with approximate equation-of-motion coupled-cluster method for ionization potential and electron attachment.

Various approximate approaches to calculate cluster amplitudes in equation-of-motion coupled-cluster (EOM-CC) approaches for ionization potentials (IP) and electron affinities (EA) with spin-orbit coupling (SOC) included in post self-consistent field (SCF) calculations are proposed to reduce computational effort. Our results indicate that EOM-CC based on cluster amplitudes from the approximate method CCSD-1, where the singles equation is the same as that in CCSD and the doubles amplitudes are approximated with MP2, is able to provide reasonable IPs and EAs when SOC is not present compared with CCSD results. It is an economical approach for calculating IPs and EAs and is not as sensitive to strong correlation as CC2. When SOC is included, the approximate method CCSD-3, where the same singles equation as that in SOC-CCSD is used and the doubles equation of scalar-relativistic CCSD is employed, gives rise to IPs and EAs that are in closest agreement with those of CCSD. However, SO splitting with EOM-CC from CC2 generally agrees best with that with CCSD, while that of CCSD-1 and CCSD-3 is less accurate. This indicates that a balanced treatment of SOC effects on both single and double excitation amplitudes is required to achieve reliable SO splitting.

Core-shell interaction and its impact on the optical absorption of pure and doped core-shell CdSe/ZnSe nanoclusters.

The structural, electronic, and optical properties of core-shell nanoclusters, (CdSe)(x)@(CdSe)(y) and their Zn-substituted complexes of x = 2-4 and y = 16-28, were studied with density functional theory calculations. The substitution was applied in the cores, the shells, and/or the whole clusters. All these clusters are characterized by their core-shell structures in which the core-shell interaction was found different from those in core or in shell, as reflected by their bondlengths, volumes, and binding energies. Moreover, the core and shell combine together to compose a new cluster with electronic and optical properties different from those of separated individuals, as reflected by their HOMO-LUMO gaps and optical absorptions. With the substitution of Cd by Zn, the structural, electronic, and optical properties of clusters change regularly. The binding energy increases with Zn content, attributed to the strong Zn-Se bonding. For the same core/shell, the structure with a CdSe shell/core has a narrower gap than that with a ZnSe shell/core. The optical absorption spectra also change accordingly with Zn substitution. The peaks blueshift with increasing Zn concentration, accompanying with shape variations in case large number of Cd atoms are substituted. Our calculations reveal the core-shell interaction and its influence on the electronic and optical properties of the core-shell clusters, suggesting a composition-structure-property relationship for the design of core-shell CdSe and ZnSe nanoclusters.

Polarization response of clathrate hydrates capsulated with guest molecules.

Clathrate hydrates are characterized by their water cages encapsulating various guest atoms or molecules. The polarization effect of these guest-cage complexes was studied with combined density functional theory and finite-field calculations. An addition rule was noted for these systems whose total polarizability is approximately equal to the polarizability sum of the guest and the cage. However, their distributional polarizability computed with Hirshfeld partitioning scheme indicates that the guest-cage interaction has considerable influence on their polarization response. The polarization of encapsulated guest is reduced while the polarization of water cage is enhanced. The counteraction of these two opposite effects leads to the almost unchanged total polarizability. Further analysis reveals that the reduced polarizability of encapsulated guest results from the shielding effect of water cage against the external field and the enhanced polarizability of water cage from the enhanced bonding of hydrogen bonds among water molecules. Although the charge transfer through the hydrogen bonds is rather small in the water cage, the polarization response of clathrate hydrates is sensitive to the changes of hydrogen bonding strength. The guest encapsulation strengthens the hydrogen bonding network and leads to enhanced polarizability.

Highly Cost-Effective Nitrogen-Doped Porous Coconut Shell-Based CO2 Sorbent Synthesized by Combining Ammoxidation with KOH Activation.

The objective of this research is to develop a cost-effective carbonaceous CO2 sorbent. Highly nanoporous N-doped carbons were synthesized with coconut shell by combining ammoxidation with KOH activation. The resultant carbons have characteristics of highly developed porosities and large nitrogen loadings. The prepared carbons exhibit high CO2 adsorption capacities of 3.44-4.26 and 4.77-6.52 mmol/g at 25 and 0 °C under atmospheric pressure, respectively. Specifically, the sample NC-650-1 prepared under very mild conditions (650 °C and KOH/precursor ratio of 1) shows the CO2 uptake 4.26 mmol/g at 25 °C, which is among the best of the known nitrogen-doped porous carbons. The high CO2 capture capacity of the sorbent can be attributed to its high microporosity and nitrogen content. In addition, the CO2/N2 selectivity of the sorbent is as high as 29, higher than that of many reported CO2 sorbents. Finally, this N-doped carbon exhibits CO2 heats of adsorption as high as 42 kJ/mol. The multiple advantages of these cost-effective coconut shell-based carbons demonstrate that they are excellent candidates for CO2 capture.

Optical absorption of warped nanographenes tuned by five- and seven-membered carbon rings.

The introduction of multiple carbon rings is one of the common ways for graphene modification. Starting from warped C80H30 nanographene, which consists of a number of six- and seven-membered carbon rings (C6 and C7) centering at a five-membered carbon ring (C5), we explored the structure and property variations of its derivatives in which their C7 rings were gradually replaced with C6 rings. With reducing number of C7 rings, their curved boundary with the C6 rings becomes flat until a bowl-like structure is formed when all the C7 rings disappear. The optical absorption spectra vary accordingly. Both the α-bands and the maximum absorption bands in the visible region are related to the number and location of the C7 rings. Further analysis of the excited states of the C80H30 derivatives, as well as on the designed model systems, revealed that the C7 rings affect the electron excitations in two ways. In addition to their participation in electronic transitions, they control the composition of molecular orbitals that are involved in the excitations. The highest occupied molecular orbitals are mainly contributed by atoms on the C6 and C7 rings, while the lowest unoccupied molecular orbitals by atoms on the C5 and C6 rings. Our study sheds some light on how the multiple carbon rings affect the optical absorption of nanographenes and provides information for the preparation of nanographenes with tunable structural and optical properties.

A study of optical absorption of cysteine-capped CdSe nanoclusters using first-principles calculations.

Understanding the size-dependent structures and properties of ligand-capped nanoclusters in solvent is of particular interest for the design, synthesis and application of II-VI colloidal QDs. Using DFT and TDDFT calculations, we studied the structure and optical property evolution of the cysteine-capped (CdSe)N clusters of N = 1-10, 13, 16 and 19 in gas, toluene, water and alkaline aqueous solution, and made a comparison with their corresponding bare clusters. The cysteine binds with (CdSe)Nvia several patterns depending on the medium they exist in, affecting the cluster structures and in consequence their optical absorption. In general, the absorption bands of (CdSe)N blueshift when cysteine is added, and the shift varies with the interaction strength between the cluster and the ligand, and the dielectric constant of the solvent. However, bare clusters retain their size sensitivity, in particular the redshift trend with increasing cluster size, and some similarity was noted for the optical absorption of the bare and ligated clusters regardless of the gas or solvent media. Population analysis reveals that the excitations are mainly from orbitals distributing on the (CdSe)N part, while the ligand is negligibly involved in the excitations. This is an important feature for the II-VI QDs as biosensors with which the information of biomolecules is detected from the size dependent optical absorption or emission of the QDs other than the biomolecules.

Berberine Sulfate Attenuates Osteoclast Differentiation through RANKL Induced NF-κB and NFAT Pathways.

Osteoporosis, a metabolic bone disease, is characterized by an excessive formation and activation of osteoclasts. Anti-catabolic treatment using natural compounds has been proposed as a potential therapeutic strategy against the osteoclast related osteolytic diseases. In this study, the activity of berberine sulfate (an orally available form of berberine) on osteoclast differentiation and its underlying molecular mechanisms of action were investigated. Using bone marrow macrophages (BMMs) derived osteoclast culture system, we showed that berberine sulfate at the dose of 0.25, 0.5 and 1 µM significantly inhibited the formation of osteoclasts. Notably, berberine sulfate at these doses did not affect the BMM viability. In addition, we observed that berberine sulfate inhibited the expression of osteoclast marker genes, including cathepsin K (Ctsk), nuclear factor of activated T cells cytoplasmic 1 (NFATc1), tartrate resistant acid phosphatase (TRAcP, Acp5) and Vacuolar-type H+-ATPase V0 subunit D2 (V-ATPase d2). Luciferase reporter gene assay and Western blot analysis further revealed that berberine sulfate inhibits receptor for activation of nuclear factor ligand (RANKL)-induced NF-κB and NFAT activity. Taken together, our results suggest that berberine sulfate is a natural compound potentially useful for the treatment of osteoporosis.

Natural Germacrane Sesquiterpenes Inhibit Osteoclast Formation, Bone Resorption, RANKL-Induced NF-κB Activation, and IκBα Degradation.

Osteolytic bone diseases are commonly presented with enhanced osteoclast formation and bone resorption. Sesquiterpene lactone natural compounds have been found to possess anti-inflammatory and immune-modulation effects. Here, we identified three germacrane sesquiterpenes using computer-based virtual screening for the structural similarity with sesquiterpene lactone, parthenolide. We showed that natural germacrane sesquiterpene compounds A, B, and C inhibit osteoclast formation and bone resorption in a dose-dependent manner, with relative potency compound A > compound C > compound B based on their equimolar concentrations. Mechanistic studies by Luciferase reporter gene assay and Western blot analysis showed that germacrane sesquiterpene compound A inhibits RANKL-induced activation of NF-κB and IκBα degradation. This study reveals that natural germacrane sesquiterpene compounds are inhibitors for osteoclast formation and bone resorption, and provides evidence that naturally-occurring compounds might be beneficial as alternative medicine for the prevention and treatment of osteolysis.

Mechanistic study of the role of primary amines in precursor conversions to semiconductor nanocrystals at low temperature.

Primary alkyl amines (RNH2) have been empirically used to engineer various colloidal semiconductor nanocrystals (NCs). Here, we present a general mechanism in which the amine acts as a hydrogen/proton donor in the precursor conversion to nanocrystals at low temperature, which was assisted by the presence of a secondary phosphine. Our findings introduce the strategy of using a secondary phosphine together with a primary amine as new routes to prepare high-quality NCs at low reaction temperatures but with high particle yields and reproducibility and thus, potentially, low production costs.