Effect of manganese (Mn) doping on the optical properties of zinc sulfide (ZnS) semiconductor nanocrystals

Mohammadreza Tahriri,Elham Mohagheghpour,Mohammad Rabiee,Fathollah Moztarzadeh 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.2

In this research, we report the synthesis of ZnS nanocrystals with a size range of 1-10 nm in diameter with varying manganese (Mn) concentrations. Various samples of Zn1-x MnxS, with x = 0.0001, 0.007, 0.02, 0.03, 0.055, 0.09 and 0.13, have been prepared from a quaternary W/O microemulsion system. It is observed that by adding Mn to ZnS nanoparticles, the emission intensity changed and by using 5.5% magnesium for total Zn+2, a maximum emission were achieved. A photoluminescence (PL) study was carried out by band-to-band excitation (λex = 293 nm and 321 nm) upon ZnS : Mn, which results in two emission peaks corresponding to surface states and Mn+2 emission. Also, we observe orange emission from Mn2+ ions in the doped ZnS nanocrystals, apart from the blue emission characteristic of the ZnS defect states. The relative intensity of the orange emission compared with the blue varies with the manganese concentration in a nonmonotonic way. For analyses of the quality and quantity of this product, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDS), inductive coupled plasma (ICP), and spectrograph techniques were used.

Nanostructured Hydroxyapatite for Biomedical Applications: From Powder to Bioceramic

Eslami, Hossein,Tahriri, Mohammadreza,Moztarzadeh, Fathollah,Bader, Rizwan,Tayebi, Lobat The Korean Ceramic Society 2018 한국세라믹학회지 Vol.55 No.6

In this study, a wet chemical method was used to synthesize nanostructured hydroxyapatite for biomedical applications. Diammonium hydrogen phosphate and calcium nitrate 4-hydrate were used as starting materials with a sodium hydroxide solution as an agent for pH adjustment. Scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy, differential thermal analysis, thermal gravimetric analysis, atomic absorption spectroscopy, and ethylenediaminetetraacetic acid (EDTA) titration analysis were used to characterize the synthesized powders. Having been uniaxially pressed, the powders formed a disk-like shape. The sinterability and electrical properties of the samples were examined, and the three-point bending test allowed for the measurement of their mechanical properties. Sedimentation analysis was used to analyze the slurry ability of hydroxyapatite. As in-vitro biological properties of the samples, biocompatibility and cytotoxicity were assessed using osteoblast-like cells and the L929 cell line, respectively. Solubility was assessed by employing a simulated body fluid.

Formation of hydroxyapatite nanoneedles on the surface of a novel calcium phosphate/blood plasma proteins biocement in simulated body fluid (SBF)

Mahdi Rezvannia,Fathollah Moztarzadeh,Mohammadreza Tahriri 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.5

In this study, we report on needle-like hydroxyapatite grown on the surface of calcium phosphate/blood plasma proteins biocement in simulated body fluid (SBF). Scanning electron microscope revealed the formation of nano-sized needle-like hydroxyapatite crystals on the surface of the biocement after 7 days immersion in the simulated body fluid. X-ray diffraction analysis of the biocement structures indicated that the nanoneedle crystals were hydroxyapatite. Finally Fourier transform infra-red investigations were employed to detect the functional groups of the biocement which this technique demonstrated to be hydroxyapatite. In this study, we report on needle-like hydroxyapatite grown on the surface of calcium phosphate/blood plasma proteins biocement in simulated body fluid (SBF). Scanning electron microscope revealed the formation of nano-sized needle-like hydroxyapatite crystals on the surface of the biocement after 7 days immersion in the simulated body fluid. X-ray diffraction analysis of the biocement structures indicated that the nanoneedle crystals were hydroxyapatite. Finally Fourier transform infra-red investigations were employed to detect the functional groups of the biocement which this technique demonstrated to be hydroxyapatite.

The influence of some processing conditions on host crystal structure and phosphorescence properties of SrAl2O4:Eu2+, Dy3+ nanoparticle pigments synthesized by combustion technique

Ehsan Shafia,Masoud Bodaghi,Mohammadreza Tahriri 한국물리학회 2010 Current Applied Physics Vol.10 No.2

The spectroscopic and host phase properties of SrAl2O4:Eu2+, Dy3+ phosphors with a series of different initiating combustion temperature, urea concentration as a fuel and critical pH of precursor solution are investigated. The SrAl2O4:Eu2+, Dy3+ nanoparticle pigments were obtained by exothermic combustion process within less than 5 min. The sample that ignited at initiating combustion temperature of 600 ℃exhibits highest intensity emission peak at 517 nm in which the SrAl2O4 host phase has the maximum fraction of monoclinic SrAl2O4 phase. The excitation spectra consist of 240 and 254 nm broad peaks. The experimental results show that the optimum ratio of urea is 2.5 times higher than theoretical quantities for best emission condition of SrAl2O4:Eu2+, Dy3+ phosphor particles. The critical pH was obtained about 5.2. The crystallite size of these pigments is about 40 nm before thermal treatment and 62 nm after thermal treatment, respectively.

Preparation and characterization of absorbable hemostat crosslinked gelatin sponges for surgical applications

Maryam Kabiri,Shahriar Hojjati Emami,Mohammad Rafinia,Mohammadreza Tahriri 한국물리학회 2011 Current Applied Physics Vol.11 No.3

The aim of this study, is synthesis of an absorbable hemostat gelatin sponge crosslinked with 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC). The effects of various gelatin contents and crosslinking agent concentrations, freezing temperature on the mechanical properties, rate of biodegradation in 24 h,hemolytic ability and cell viability of sponges were investigated. The results of scanning electron microscopy (SEM) showed that freezing temperature had a significant effect on the structure and density of sponges. SEM views of the sponges demonstrated that they have pores with mean diameters of 180―280 μm. Fourier transform infrared (FTIR) spectra indicated that there is no residual of the crosslinking agent in the structure of final gelatin sponges because of C―N bonds (urea derivatives) absence. The sample with 1% gelatin and 0.05% EDC freezed at ―25 ℃ (before freeze-drying) showed more than 0.37 cm^-1 UV absorption of hemoglobin or blood clotting in half an hour. The compression modulus of the same sample was more than 150 kPa and percentage of degradation was about 28% in 24 h.

Synthesis and characterization of nanocrystalline fluorinated hydroxyapatite powder by a modified wet-chemical process

Hossein Eslami,Mehran Solati-Hashjin,Mohammadreza Tahriri 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.3

Fluorinated hydroxyapatite (FHA; fluorhydroxyapatite) powder was synthesized through a pH-cycling method by varying the sodium fluoride [NaF] concentration in a hydroxyapatite suspension as a modified wet-chemical process. The powder sample was characterized by the commonly used bulk techniques of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), F-selective electrode, atomic absorption spectroscopy (AAS) and EDTA titration analyses. SEM was used to estimate the particles size of the powder and observe the morphology and agglomeration state of the powder. The functional groups presented in the synthesized powder were ascertained by FTIR investigations. AAS and EDTA titration techniques were employed for calculation of the Ca/P molar ratio. F-selective electrode analysis also was used to measure the fluorine (F) content in the crystalline network of the synthesized powder. Finally, the FHA and other phases according to processing parameters were observed by XRD analysis Fluorinated hydroxyapatite (FHA; fluorhydroxyapatite) powder was synthesized through a pH-cycling method by varying the sodium fluoride [NaF] concentration in a hydroxyapatite suspension as a modified wet-chemical process. The powder sample was characterized by the commonly used bulk techniques of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), F-selective electrode, atomic absorption spectroscopy (AAS) and EDTA titration analyses. SEM was used to estimate the particles size of the powder and observe the morphology and agglomeration state of the powder. The functional groups presented in the synthesized powder were ascertained by FTIR investigations. AAS and EDTA titration techniques were employed for calculation of the Ca/P molar ratio. F-selective electrode analysis also was used to measure the fluorine (F) content in the crystalline network of the synthesized powder. Finally, the FHA and other phases according to processing parameters were observed by XRD analysis

A new phantom to evaluate the tissue dissolution ability of endodontic irrigants and activating devices

Khoshroo Kimia,Shah Brinda,Johnson Alexander,Baeten John,Barry Katherine,Tahriri Mohammadreza,Ibrahim Mohamed S.,Tayebi Lobat 대한치과보존학회 2020 Restorative Dentistry & Endodontics Vol.45 No.4

Objective: The aim of this study was to introduce a gelatin/bovine serum albumin (BSA) tissue standard, which provides dissolution properties identical to those of biological tissues. Further, the study evaluated whether the utilization of endodontic activating devices led to enhanced phantom dissolution rates. Materials: and Methods Bovine pulp tissue was obtained to determine a benchmark of tissue dissolution. The surface area and mass of samples were held constant while the ratio of gelatin and BSA were varied, ranging from 7.5% to 10% gelatin and 5% BSA. Each sample was placed in an individual test tube that was filled with an appropriate sodium hypochlorite solution for 1, 3, and 5 minutes, and then removed from the solution, blotted dry, and weighed again. The remaining tissue was calculated as the percent of initial tissue to determine the tissue dissolution rate. A radiopaque agent (sodium diatrizoate) and a fluorescent dye (methylene blue) were added to the phantom to allow easy quantification of phantom dissolution in a canal block model when activated using ultrasonic (EndoUltra) or sonic (EndoActivator) energy. Results: The 9% gelatin + 5% BSA phantom showed statistically equivalent dissolution to bovine pulp tissue at all time intervals. Furthermore, the EndoUltra yielded significantly more phantom dissolution in the canal block than the EndoActivator or syringe irrigation. Conclusions: Our phantom is comparable to biological tissue in terms of tissue dissolution and could be utilized for in vitro tests due to its injectability and detectability.

Effects of incorporation of 2.5 and 5 wt% TiO2 nanotubes on fracture toughness, flexural strength, and microhardness of denture base poly methyl methacrylate (PMMA)

Sahar Abdulrazzaq Naji,Marjan Behroozibakhsh,Tahereh Sadat Jafarzadeh Kashi,Hossein Eslami,Reza Masaeli,Hosseinali Mahgoli,Mohammadreza Tahriri,Mehrsima Ghavvami Lahiji,Vahid Rakhshan 대한치과보철학회 2018 The Journal of Advanced Prosthodontics Vol.10 No.2

PURPOSE. The aim of this preliminary study was to investigate, for the first time, the effects of addition of titania nanotubes (n-TiO2) to poly methyl methacrylate (PMMA) on mechanical properties of PMMA denture base. MATERIALS AND METHODS. TiO2 nanotubes were prepared using alkaline hydrothermal process. Obtained nanotubes were assessed using FESEM-EDX, XRD, and FT-IR. For 3 experiments of this study (fracture toughness, three-point bending flexural strength, and Vickers microhardness), 135 specimens were prepared according to ISO 20795-1:2013 (n of each experiment=45). For each experiment, PMMA was mixed with 0% (control), 2.5 wt%, and 5 wt% nanotubes. From each TiO2:PMMA ratio, 15 specimens were fabricated for each experiment. Effects of n-TiO2 addition on 3 mechanical properties were assessed using Pearson, ANOVA, and Tukey tests. RESULTS. SEM images of n-TiO2 exhibited the presence of elongated tubular structures. The XRD pattern of synthesized n-TiO2 represented the anatase crystal phase of TiO2. Moderate to very strong significant positive correlations were observed between the concentration of n-TiO2 and each of the 3 physicomechanical properties of PMMA (Pearson’s P value ≤.001, correlation coefficient ranging between 0.5 and 0.9). Flexural strength and hardness values of specimens modified with both 2.5 and 5 wt% n-TiO2 were significantly higher than those of control (P≤.001). Fracture toughness of samples reinforced with 5 wt% n-TiO2 (but not those of 2.5% n-TiO2) was higher than control (P=.002). CONCLUSION. Titania nanotubes were successfully introduced for the first time as a means of enhancing the hardness, flexural strength, and fracture toughness of denture base PMMA.

Advancements in craniofacial prosthesis fabrication: A narrative review of holistic treatment

Jazayeri, Hossein E.,Kang, Steve,Masri, Radi M.,Kuhn, Lauren,Fahimipour, Farahnaz,Vanevenhoven, Rabecca,Thompson, Geoffrey,Gheisarifar, Maryam,Tahriri, Mohammadreza,Tayebi, Lobat The Korean Academy of Prosthodonitics 2018 The Journal of Advanced Prosthodontics Vol.10 No.6

The treatment of craniofacial anomalies has been challenging as a result of technological shortcomings that could not provide a consistent protocol to perfectly restore patient-specific anatomy. In the past, wax-up and impression-based maneuvers were implemented to achieve this clinical end. However, with the advent of computer-aided design and computer-aided manufacturing (CAD/CAM) technology, a rapid and cost-effective workflow in prosthetic rehabilitation has taken the place of the outdated procedures. Because the use of implants is so profound in different facets of restorative dentistry, their placement for craniofacial prosthesis retention has also been widely popular and advantageous in a variety of clinical settings. This review aims to effectively describe the well-rounded and interdisciplinary practice of craniofacial prosthesis fabrication and retention by outlining fabrication, osseointegrated implant placement for prosthesis retention, a myriad of clinical examples in the craniofacial complex, and a glimpse of the future of bioengineering principles to restore bioactivity and physiology to the previously defected tissue.