Facile preparation of highly luminescent CdTe quantum dots within hyperbranched poly(amidoamine)s and their application in bio-imaging

A new strategy for facile preparation of highly luminescent CdTe quantum dots (QDs) within amine-terminated hyperbranched poly(amidoamine)s (HPAMAM) was proposed in this paper. CdTe precursors were first prepared by adding NaHTe to aqueous Cd²⁺ chelated by 3-mercaptopropionic sodium (MPA-Na), and then HPAMAM was introduced to stabilize the CdTe precursors. After microwave irradiation, highly fluorescent and stable CdTe QDs stabilized by MPA-Na and HPAMAM were obtained. The CdTe QDs showed a high quantum yield (QY) up to 58%. By preparing CdTe QDs within HPAMAM, the biocompatibility properties of HPAMAM and the optical, electrical properties of CdTe QDs can be combined, endowing the CdTe QDs with biocompatibility. The resulting CdTe QDs can be directly used in biomedical fields, and their potential application in bio-imaging was investigated.     

In situ preparation of Au or Ag nanoparticles in the presence of hyperbranched poly(amidoamine)s with hydrophobic end‐groups as nanoreactors and reductants

Hyperbranched poly(amidoamine)s with methyl ester terminals (HPAMAM‐COOCH₃) were used as nanoreactors and reductants to prepare gold or silver nanoparticles (Au NPs or Ag NPs). HPAMAM‐COOCH₃ could bind AuCl₄ ⁻ (or Ag⁺) and then reduce AuCl₄ ⁻ (or Ag⁺) into Au NPs (or Ag NPs) through their internal amines, while the external methyl ester groups prevented the aggregation of polymers. The formation of Au NPs or Ag NPs was verified using transmission electron microscopy (TEM), ultraviolet‐visible spectroscopy (UV‐Vis), X‐Ray powder diffraction (XRD), Fourier‐transform infrared spectroscopy (FT‐IR), and thermogravimetric analysis (TGA), confirming the formation of Au NPs or Ag NPs with small particle size and low size distribution.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

A new two‐phase route to cadmium sulfide quantum dots using amphiphilic hyperbranched polymers as unimolecular nanoreactors

A new two‐phase route was developed to prepare monodisperse cadmium sulfide (CdS) quantum dots (QDs) with a narrow size distribution. In a two‐phase system, chloroform and water were used as separate solvents for palmitoyl chloride functionalized hyperbranched polyamidoamine (HPAMAM‐PC) and cadmium acetate/sodium sulfide, respectively. The amphiphilic HPAMAM‐PC, with a hydrophilic dendritic core and hydrophobic arms, formed stable unimolecular micelles in chloroform and was used to encapsulate aqueous Cd²⁺ ions. After the reaction with S²⁻ ions from the aqueous phase, monodisperse and uniform‐sized CdS QDs stabilized by HPAMAM‐PC unimolecular micelles were obtained. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci 120:991–997, 2011     

Upgrading the adhesion properties of a fast‐curing epoxy using hydrophilic/hydrophobic hyperbranched poly(amidoamine)s

A homologous series of hyperbranched polymers (HBPs) was prepared following a well‐defined method and their formation in a polymeric form bearing different extents of branching with amine functional groups at the terminals was verified using different techniques such as Fourier Transform Infrared, ¹H Nuclear Magnetic Resonance, Differential Scanning Calorimetry, and Gel Permeation Chromatography. Toughening of a commercially available fast cure epoxy was aimed through reactive blending with the formed HBPs that exhibit variation in polarity and branching according to the relevant synthesis strategy employed for each polymer. The mechanical properties (impact resistance, pull‐off adhesion, and bending) of the resulting coating films pertaining to each epoxy formulation after adhering to metal substrates revealed obvious progress in their performance with respect to a control sample that was hardened exclusively in absence of any HBP. The results were explained on the light of the ability of this class of materials to impose flexibility and dilute the intensive crosslink density associated frequently with the rapid curing of epoxy systems. The extent of gained enhancement for each formulation was accounted for by the molecular architecture of the HBPs, their degrees of branching, polarity, and relative reactive contents of primary amino groups in each case. In addition, the influence of these parameters on a proper wetting over the substrate and morphology of the films in each case was also studied using scanning electron microscopy. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Synthesis and crystal structure of bis(morpholino dithiocarbamato) Cd(II) complex and its use as precursor for CdS quantum dots using different capping agents

ABSTRACT

Cadmium(II) morpholine dithiocarbamate complex [Cd(morphdtc)₂] was synthesized and characterized by single crystal X-ray crystallography. The molecular structure of the complex showed Cd(II) ion in a distorted 4?+?2 octahedral geometry, in which the two morpholine dithiocarbamates act as bidentate chelating and the central Cd ion bond the sulfur atoms of adjacent morpholine acting as bridging ligands to form centrosymmetric five coordinate dimeric molecules. The Cd(II) complex was thermolysed at 180°C to prepare CdS nanoparticles using three different capping agents. The pXRD patterns revealed a mixture of hexagonal and cubic crystalline phases of CdS nanocrystals. TEM images revealed semi-spherical and spherical nanoparticles, with the size range of 4.50–5.70?nm for OLM-CdS, 3.33–5.96?nm for HDA-CdS, and 3.00–5.83?nm for ODA-CdS. The particle size distribution of the CdS nanocrystallite is within the range 1.06?nm (SD?±?0.73) for OLM-CdS, 0.68?nm, (SD?±0.73) for HDA-CdS and 1.18?nm, (SD?±?0.60) for ODA-CdS. The lattice fringes showed that the particles are almost in the same environment with the interplanar of 0.32?nm for OLM-CdS, 0.34?nm for HDA-CdS, and 0.32?nm ODA-CdS. The band gaps energy were confirmed to be 1.59?eV for OLM-CdS, 1.65?eV for HDA-CdS, and 1.62?eV for ODA-CdS nanoparticles, respectively.     

Utilization of hydrophilic/hydrophobic hyperbranched poly(amidoamine)s as additives for melamine urea formaldehyde adhesives

Hyperbranched poly(amidoamine)s (PAMAMs), exhibiting various levels of hydrophilicity, were used as modifiers for melamine urea formaldehyde (MUF) adhesives. The modification was achieved either with or at expense of sodium hydroxide during the last pH adjustment. Their apparent co‐condensability was expected from the measured gel times and further proved using Fourier transform infrared (FTIR) spectroscopy as well as ¹³C nuclear magnetic resonance (¹³C NMR). Utilization of these structures as modifiers for MUF, which are frequently used in particleboards production, resulted in manifold advantages. Considering the economic point of view, their use is more practical and cheaper with respect to dendritic structures. Additionally, their application in finite quantities as final additives, either immediately before the final use or at the last stage of preparation, yielded considerable upgrading of the dry internal bond (IB) strength of the produced particleboards. The improvement was extended to the resistivity to hydrolytic degradation as revealed by the wet IB strength and thickness swelling. The results were explained on the light of an extensive investigation on the resins using thermomechanical analysis (TMA) while taking into account the relevant hydrophilicity and degree of branching of each hyperbranched structure. POLYM. COMPOS., 36:2255–2264, 2015. © 2014 Society of Plastics Engineers     

UV curing behavior of methacrylated hyperbranched poly(amine‐ester)s

Methacrylated hyperbranched poly(amine ester)s as oligomers in radiation curing resins have a lower viscosity and a higher cure speed. Their viscosity was reduced sharply when an amount of a monomer was added or the temperature was increased. Their polymerization rate and final conversion of the double bond differ with the variation of the chemical structure of the end group, molar mass, and monomer content. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 51–57, 2001     

Self-healing interfaces of poly(methyl methacrylate) reinforced with carbon fibers decorated with carbon quantum dots

Fiber-polymer matrix interfacial debonding is often observed when mechanical loads are applied to fiber reinforced polymer composites. These defects usually end-up leading to a catastrophic fracture of the composites. In this work, carbon quantum dots (CDs) were incorporated on the surface of carbon fibers (CF), and poly(methyl methacrylate) (PMMA) composites with these modified fibers were able to restore their original properties after been previously damaged. To this end, CDs were synthesized and used to decorate the surface of CF. These decorated CF were then incorporated into PMMA by using a high intensity mixer. The prepared composites were submitted to dynamic mechanical, three-point bending and self-healing tests. Fluorescent CDs with diameters of 10 nm and functional groups, such as amine and carboxylic groups were successfully synthesized by the microwave pyrolysis method. The deposition of CDs on the surface of CF was evaluated and quantified by UV–vis spectroscopy and 1.2 wt.% of CDs on CF was determined. Composites with different surface treatments (including the presence of CD) did not show significant differences in strength, stiffness and damping, suggesting that the surface treatments on CF did not lead to major changes in the degree of interfacial interaction. Self-healing tests showed that damaged composites with CD decorated CF were able to restore their original properties, while no self-healing effect was noted in composites with no CD on CF. The observed self-healing behavior between PMMA and CF decorated with CD is due to the interactions between chemical groups on the surface of the CD and PMMA. Thus, damages related to fiber-matrix interfacial detachments can be repaired through reversible interactions based on CD.     

Synthesis and application of hyperbranched poly(urethane‐urea) finishing agent with amino groups

The isocyanate‐terminated linear polyurethane prepolymer (LPPU) was successfully synthesized via step‐by‐step polymerization, with isophorone disocyanate (IPDI) and polytetramethylene ether glycol (PTMG, M_n = 2000 g/mol) used as raw materials, dibutyltin dilaurate (DBTDL) as the catalyst, 1,4‐butanediol (BDO) as the chain extender and anhydrous ethanol (EtOH) as the blocking agent. Then the hyperbranched poly (urethane‐urea) (HBPU) containing amino groups was synthesized by grafting LPPU on amino‐terminated hyperbranched polymers (NH₂‐HBP). The molecular structure of LPPU and HBPU were characterized by means of FT‐IR and ¹H‐NMR. It was founded that LPPU and HBPU were successfully synthesized as anticipated. The thermal stability and crystalline morphology of LPPU and HBPU were characterized and analyzed by TG and XRD. Additionally, it was also found that, after addition of 10% HBPU, the water absorption rate, water vapor transmission rate, and water vapor permeability increased markedly by 162.02%, 400.00%, 260.00%, respectively. The tensile strength of membrane decreased by 24.57% and the elongation at break increased by 26.92%. Compared with the leather finished by commercial PU finishing agent, the leather finished by HBPU presented better properties. The water vapor permeability of the leather finished by increased by 13.0%, and the dry‐ and wet‐rub resistances and the physical and mechanical performances were excellent. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44139.     

In situ preparation of fluorescent CdTe quantum dots with small thiols and hyperbranched polymers as co-stabilizers

A new strategy for in situ preparation of highly fluorescent CdTe quantum dots (QDs) with 3-mercaptopropionic acid (MPA) and hyperbranched poly(amidoamine)s (HPAMAM) as co-stabilizers was proposed in this paper. MPA and HPAMAM were added in turn to coordinate Cd²⁺. After adding NaHTe and further microwave irradiation, fluorescent CdTe QDs stabilized by MPA and HPAMAM were obtained. Such a strategy avoids the aftertreatment of thiol-stabilized QDs in their bioapplication and provides an opportunity for direct biomedical use of QDs due to the existence of biocompatible HPAMAM. The resulting CdTe QDs combine the mechanical, biocompatibility properties of HPAMAM and the optical, electrical properties of CdTe QDs together.     

Transparent,fluorescent, and mechanical enhanced elastomeric composites formed with poly (styrene‐butadiene‐styrene) and SiO2‐hybridized CdTe quantum dots

Transparent poly(styrene‐butadiene‐styrene) (SBS)‐quantum dots (QDs) composites (SBS/CdTe QDs) that simultaneously possess strong photoluminescence (PL) and enhanced mechanical properties are presented for the first time based on the facile blending of SiO₂‐hybridized CdTe QDs with SBS. UV–vis spectrum and fluorescence measurement show that SBS/CdTe QDs composites exhibit good optical properties. The results of transmission electron microscopy show good dispersion of CdTe QDs in the SBS matrix. The results of dynamic mechanical thermal analysis indicate that the micro‐phase separated structure of the SBS is exist in the composites, and the presence of CdTe QDs can lead to an decrease of glass transition temperatures of polybutadiene (PB) and polystyrene(PS) domains. In addition, mechanical tests reveal that the addition of CdTe QDs is a useful approach to improve the mechanical properties of SBS. Meanwhile, the fluorescent photographs taken under ultraviolet light prove that SBS/CdTe QDs composites possess strong PL. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Antiplatelet adhesion behavior of hyperbranched poly(l-lactide)s containing glutamic acid terminal groups

The surface properties and antiplatelet adhesion behavior of terminally functionalized hyperbranched poly(l -lactide)s (HB PLLAn-Glu, n = 5, 10, 20) were examined. Contact angle changes and X-ray photoelectron spectroscopic measurements indicated that the hydrated glutamic acid units in HB PLLAn-Glu films migrated to the surface during immersing in water and unique microdomains were observed from the HB PLLA10-Glu film after water immersion. HB PLLA10-Glu and HB PLLA5-Glu prevented platelet adhesion, but HB PLLA20-Glu showed the typical platelet adhesion response for a hydrophobic surface. Both the high hydrophilicity and microdomain formation of HB PLLAn-Glu contributed to the efficient antiplatelet adhesion behavior. The glutamic acid-terminated HB PLLA10-Glu films were more effective at preventing platelet adhesion than the 2-methoxyethoxy-terminated HB PLLA10 films. This study is the first example of platelet adhesion properties being controlled by the terminal functional groups and branching density of hyperbranched polymers. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46910.     

Structurally modified electrospun poly(methyl methacrylate) nanofibers as advanced host matrices for PbS quantum dots

The present work deals with the studies of the host matrix nature of pure and structurally modified surface roughened and coaxial hollow electrospun poly(methyl methacrylate) (PMMA) nanofibers to lead sulphide (PbS) quantum dots. The various structural and molecular analyses conducted on these samples proved the advancements and structural modifications made in the properties of pure PMMA nanofibers by electrospinning and selective dissolution. The successful incorporation of the quantum dots to pure and structurally modified PMMA nanofibers and hence the host matrix nature of these nanofibers is proved by different spectral analyses of the samples. The coaxial hollow PMMA nanofibers are found to be the best host matrix among these PMMA nanofibers as proved by the optical studies of the samples. Photoluminescence analyses of the samples showed the influence of these quantum dots on the optical properties of PMMA nanofibers. It is observed here that, the quantum dots enhance the intensity of coaxial hollow PMMA nanofibers to about four times than its virgin form. The pure and structurally modified PMMA nanofibers incorporated with PbS quantum dots are proved to be efficient for the degradation of methylene blue dye where coaxial hollow PMMA nanofibers incorporated with PbS quantum dots is the best.     

Effects of hyperbranched poly(amido‐amine)s structures on synthesis of Ag particles

The synthesis of Ag particles stabilized poly (N,N′‐methylene bisacrylamide N‐aminoethyl piperazine) (MBA‐AEPZ) and poly(N,N′‐dodecyl diacrylamide N‐aminoethyl piperazine) (MDA‐AEPZ) was reported. The effects of hyperbranched polymer structures and hyperbranched polymer concentrations were studied on the size and size distribution of Ag particles, which were determined from the UV plasmon absorption band and transmission electronmicroscopic analyses. The data show that slight change (10.3 and 9.7 nm) and large change on particle size (3.9 and ～ 200 nm) were observed with increase in concentrations of poly(MBA‐AEPZ) and poly(MDA‐AEPZ) at the same M:D, respectively. The difference is explained in terms of a mechanism of structure‐dependent stabilization. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Multi-scale ordering of self-assembled InAs/GaAs(001) quantum dots

Ordering phenomena related to the self-assembly of InAs quantum dots (QD) grown on GaAs(001) substrates are experimentally investigated on different length scales. On the shortest length-scale studied here, we examine the QD morphology and observe two types of QD shapes, i.e., pyramids and domes. Pyramids are elongated along the [1–10] directions and are bounded by {137} facets, while domes have a multi-facetted shape. By changing the growth rates, we are able to control the size and size homogeneity of freestanding QDs. QDs grown by using low growth rate are characterized by larger sizes and a narrower size distribution. The homogeneity of buried QDs is measured by photoluminescence spectroscopy and can be improved by low temperature overgrowth. The overgrowth induces the formation of nanostructures on the surface. The fabrication of self-assembled nanoholes, which are used as a template to induce short-range positioning of QDs, is also investigated. The growth of closely spaced QDs (QD molecules) containing 2–6 QDs per QD molecule is discussed. Finally, the long-range positioning of self-assembled QDs, which can be achieved by the growth on patterned substrates, is demonstrated. Lateral QD replication observed during growth of three-dimensional QD crystals is reported.     

Synthesis and properties of novel hyperbranched polyimides end‐capped with metallophthalocyanines

A fluorinated hyperbranched polyimide (HBPI) is synthesized by using a triamine monomer, 1,3,5‐tris(2‐trifluoromethyl‐4‐aminophenoxy)benzene (TFAPOB) (B₃), as a “core” molecule, 4,4′‐oxydiphthalic anhydride (ODPA) as a A₂ monomer, and 4‐aminophthalonitrile as an end‐capping reagent. After that, a series of novel fluorinated hyperbranched polyimides end‐capped with metallophthalocyanines were prepared by the reactions of dicyanophenyl end‐capped hyperbranched polyimide with excessive amounts of 1,2‐dicyanobenzene and the corresponding metal salt in quinoline. The resulting polyimides containing metallophthalocyanine unites shows optical absorption in the visible region. The absorption bands of the polymers in chloroform solution are in the range of 665–701 nm. These polyimides show glass transition temperatures between 216 and 225°C, and the 5 wt % weight loss temperature of the polymers varied from 440 to 543°C under nitrogen. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Cellular distribution and cytotoxicity of graphene quantum dots with different functional groups

Graphene quantum dots (GQDs) have been developed as promising optical probes for bioimaging due to their excellent photoluminescent properties. Additionally, the fluorescence spectrum and quantum yield of GQDs are highly dependent on the surface functional groups on the carbon sheets. However, the distribution and cytotoxicity of GQDs functionalized with different chemical groups have not been specifically investigated. Herein, the cytotoxicity of three kinds of GQDs with different modified groups (NH₂, COOH, and CO-N (CH₃)₂, respectively) in human A549 lung carcinoma cells and human neural glioma C6 cells was investigated using thiazoyl blue colorimetric (MTT) assay and trypan blue assay. The cellular apoptosis or necrosis was then evaluated by flow cytometry analysis. It was demonstrated that the three modified GQDs showed good biocompatibility even when the concentration reached 200 μg/mL. The Raman spectra of cells treated with GQDs with different functional groups also showed no distinct changes, affording molecular level evidence for the biocompatibility of the three kinds of GQDs. The cellular distribution of the three modified GQDs was observed using a fluorescence microscope. The data revealed that GQDs randomly dispersed in the cytoplasm but not diffused into nucleus. Therefore, GQDs with different functional groups have low cytotoxicity and excellent biocompatibility regardless of chemical modification, offering good prospects for bioimaging and other biomedical applications.     

Polymerization of ethyl acrylate using hyperbranched polyglycerol with multi‐RAFT groups as chain transfer agent

Surfacing hydroxyl groups of hyperbranched polyglycerol (PG) were transformed into trithiocarbonates (TTC), an efficient multi radical addition‐fragmentation transfer (RAFT) agent, to mediate the polymerization of ethyl acrylate (EA) under controllable conditions, and PG with multiarm PEA was obtained. In this system, PG was a part of Z groups, and trithiolcarbonates were bonded directly to the PG, whereas the growing PEA macroradical was detached. The molecular weight and the molecular weight distribution of the products were in the range of 1.05–3.24 × 10⁴ g/mol and 1.28–1.42, respectively, when the concentration ratio of EA to PG‐TTC was 39.8. The number of the PEA arms was about 16. It was found that the measured molecular weights of the products were deviated from the theoretical value, and the molecular weight distribution was broadened with the conversion due to the termination between the leaving macroradicals. The final and the intermediate products were characterized by NMR in detail. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2203–2209, 2006     

Novel synthesis and solution properties of hyperbranched poly(ethyl methacrylate)s by quasi‐living radical copolymerization using photofunctional inimer

Hyperbranched poly(ethyl methacrylate)s (PEMA) were prepared by quasi‐living radical copolymerization of 2‐(N,N‐diethylaminodithiocarbamoyl)‐ethyl methacrylate (inimer: DTEM) with ethyl methacrylate (EMA) under UV irradiation. DTEM monomers play an important role in this copolymerization system as inimers capable of initiating living radical polymerization of the vinyl group. Two monomers (DTEM and EMA) showed almost equal reactivity toward both propagating species, and the copolymer composition was the same as the comonomer feed. This result means that both the branching and chain length of the hyperbranched molecules can be controlled statistically by the feed monomer ratios. The compact nature of the hyperbranched macromolecules is demonstrated by comparison of their solution properties with the linear analogues. Copyright © 2004 Society of Chemical Industry     

Cationic water‐soluble poly(p‐phenylene vinylene) for fluorescence sensors and electrostatic self‐assembly nanocomposites with quantum dots

Novel phthalocyanine amide polymers (Pc) based on 1,8-naphthalenediamine (Ar) as an aromatic amine and 1,4-diaminobutane (Al) as an aliphatic amine, were synthesized to improve the limited stabilization modes of conventional phthalocyanines. The metal-free phthalocyanines polymers (MF-Pc) were moderately soluble in DMSO only while the metalized forms (Cu&Ni-Pc) were completely insoluble. The structure of the samples was confirmed using Fourier transform infrared (FTIR), ultraviolet–visible spectrometry (UV–vis) and nuclear magnetic resonance (NMR). Additionally, the thermal stability and glass transition temperatures (T_g) were investigated by thermal gravimetric analyzer (TGA) and differential scanning calorimeter (DSC), respectively. The intercalation of the metal-free phthalocyanines, based on the aliphatic amine (MF-PcAl) and aromatic amine (MF-PcAr), into laponite from DMSO solution, was proved by X-ray diffraction (XRD). The basal space of laponite increased from 1.2 to 1.36 nm upon intercalation of MF-PcAl and extended more to 1.91 nm on using MF-PcAr as intercalant while the quaternized forms of MF-Pcs behaved likewise and could not widen the basal space of laponite to more than 1.43 nm which was attributed to the random distribution of the positive charges over the Pc chains which imposed confined arrangement inside the basal space and consequently narrower space than the attained one in the case of nonquaternized phthalocyanines. The plasticized PVC composites based on laponite treated with either MF-PcAl or MF-PcAr exhibited improved resistance to the UV radiation as revealed by the retention of the tensile strength and elongation at rupture after exposure to UV radiation for different time intervals. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008