Cesium Methylammonium Lead Iodide (Csx MA1-x PbI3 ) Nanocrystals with Wide Range Cation Composition Tuning and Enhanced Thermal Stability of the Perovskite Phase.

Cesium methylammonium lead iodide (Csx MA1-x PbI3 ) nanocrystals were obtained with a wide range of A-site Cs-MA compositions by post-synthetic, room temperature cation exchange between CsPbI3 nanocrystals and MAPbI3 nanocrystals. The alloyed Csx MA1-x PbI3 nanocrystals retain their photoactive perovskite phase with incorporated Cs content, x, as high as 0.74 and the expected composition-tunable photoluminescence (PL). Excess methylammonium oleate from the reaction mixture in the MAPbI3 nanocrystal dispersions was necessary to obtain fast Cs-MA cation exchange. The phase transformation and degradation kinetics of films of Csx MA1-x PbI3 nanocrystals were measured and modeled using an Avrami expression. The transformation kinetics were significantly slower than those of the parent CsPbI3 and MAPbI3 nanocrystals, with Avrami rate constants, k, at least an order of magnitude smaller. These results affirm that A-site cation alloying is a promising strategy for stabilizing iodide-based perovskites.

Nanoparticle Brushes: Macromolecular Ligands for Materials Synthesis.

ConspectusColloidal nanoparticles have unique attributes that can be used to synthesize materials with exotic properties, but leveraging these properties requires fine control over the particles' interactions with one another and their surrounding environment. Small molecules adsorbed on a nanoparticle's surface have traditionally served as ligands to govern these interactions, providing a means of ensuring colloidal stability and dictating the particles' assembly behavior. Alternatively, nanoscience is increasingly interested in instead using macromolecular ligands that form well-defined polymer brushes, as these brushes provide a much more tailorable surface ligand with significantly greater versatility in both composition and ligand size. While initial research in this area is promising, synthesizing macromolecules that can appropriately form brush architectures remains a barrier to their more widespread use and limits understanding of the fundamental chemical and physical principles that influence brush-grafted particles' ability to form functional materials. Therefore, enhancing the capabilities of polymer-grafted nanoparticles as tools for materials synthesis requires a multidisciplinary effort, with specific focus on both developing new synthetic routes to polymer-brush-coated nanoparticles and investigating the structure-property relationships the brush enables.In this Account, we describe our recent work in developing polymer brush coatings for nanoparticles, which we use to modulate particle behavior on demand, select specific nanoscopic architectures to form, and bolster traditional bulk polymers to form stronger materials by design. Distinguished by the polymer type and capabilities, three classes of nanoparticles are discussed here: nanocomposite tectons (NCTs), which use synthetic polymers end-functionalized with supramolecular recognition groups capable of directing their assembly; programmable atom equivalents (PAEs) containing brushes of synthetic DNA that employ Watson-Crick base pairing to encode particle binding interactions; and cross-linkable nanoparticles (XNPs) that can both stabilize nanoparticles in solution and polymer matrices and subsequently form multivalent cross-links to strengthen polymer composites. We describe the formation of these brushes through "grafting-from" and "grafting-to" strategies and illustrate aspects that are important for future advancement. We also examine the new capabilities brushes provide, looking closely at dynamic polymer processes that provide control over the assembly state of particles. Finally, we provide a brief overview of the technological applications of nanoparticles with polymer brushes, focusing on the integration of nanoparticles into traditional materials and the processing of nanoparticles into bulk solids.

Functinal and aesthetic outcome of reconstruction of large oro-facial defects involving the lip after tumor resection.

BACKGROUND: Squamous cell carcinoma of the head and neck is a challenging disease to both surgeons and radiation oncologists due to proximity of many important anatomical structures. Surgery could be curative as these cancers usually metastasize very late by blood stream. AIM OF THE WORK: This work addresses the oncologic, functional and aesthetic factors affecting reconstruction of large orofacial defects involving the lip following tumor resection. PATIENTS AND METHODS: The study reviews the surgical outcome of one hundred and twelve patients with invasive tumors at, or extending to, the lip(s), treated at the Mansoura University-Surgical Oncology Department, from January 2000 to January 2005. Tumor stage were T2 (43), T3 (56) and T4 (13). Nodal state was N0 in 80, N1 in 29 and N2 in three cases. AJCC stage grouping was II (T2N0) in 33 patients, stage III (T3N0 or T1-3N1) in 64 cases and stage IV (T4 due to bone erosion or N2) in 15 cases. The technique used for lip reconstruction was: Unilateral or bilateral myocutaneous depressor anguli oris flap (MCDAOF) for isolated lip defect (n=63). Bilateral myocutaneous depressor anguli oris (MCDAOF) plus local cervical rotational flap chin defects (n=3). Pectoralis major myocutaneous pedicled flap for cheek defects involving the lip together with a tongue flap for mucosal reconstruction (n=35). Sternocleidomastoid clavicular myo-osseous flap for concomitant mandibular defects (n=12). RESULTS: Aesthetic and functional results are evaluated regarding appearance, oral incompetence, disabling microstomia and eating difficulties. Depressor anguli oris reconstruction allowed functioning static and dynamic oral function in all cases in contrast to the Pectorails major flap. There were 18 cases of oral incompetence (46.1%), nine cases of speech difficulty (23%) and five patients with poor cosmetic appearance within the second group. Total flap loss was not encountered, Partial flap loss affected thirteen depressor anguli oris flaps (21.3%) and six pectoral flaps (15.3%).

Locally advanced cheek carcinoma; radical surgery and reconstruction of though and through defects.

BACKGROUND: Squamous cell carcinoma of the cheek is a locoregionally aggressive tumor. Radical resection may be curative in cases of large tumor without distant metastases. We reviewed forty eight consecutive cases of Sq.c.c. of the oral cavity to evaluate the feasibility and efficacy of the reconstructive method. PATIENTS AND METHODS: Forty eight cases of invasive Sq.c.c. affecting the cheek performed in Mansoura University, Surgical Oncology Department. From November 2001 to October 2004 were included. Twenty cafes presented primarily, and 28 were relapsing after previous surgery or radiotherapy. Tumors of T3 and T4 size were included. Radical excision with adequate safety margin followed by reconstruction was done in the same setting using: A- Double layered pectoralis major flap (n=30). B- Pectoralis major flap for external surface and tongue flap for mucosal lining (n=10). C- Pectoralis major flap plus free Latissmus dorsi flap (n=3). D- Latissmus dorsi flap plus tongue flap (n=5). RESULTS: Nine cases (18.7%) had local and distant relapse after a median follow up period of 36 months. However, total flap loss was not encountered. There were partial loss of three tongue flaps, seven pectoralis flaps corrected with debridement and reapproximation. Two patients had oral incompetence. Orocutaneous salivary fistula persistent more than three weeks occurred in eight patients. Functional outcome in terms of oral competence, sensibility, chewing movements was satisfactory in all but three cases. IN CONCLUSION: Radical resection of extensive cheek carcinoma and reconstruction using pedicled flaps is an effective, economic and reliable method for oncologic and functional purposes.