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Preparation of all-cellulose composites with optical transparency using the banana pseudostem as a raw material
摘要： Biopolymers are intended to substitute the petroleum-based polymers and all-cellulose composite has emerged as a green alternative, especially if it can be prepared through a method consuming less energy and fewer chemicals. Here, a novel approach to obtain a nanocomposite film made of cellulose fibrils imbibed into a nanocellulose matrix is described. Banana pseudostem was used as raw material and characterized along with the resulting materials using scanning electron microscopy, optical microscopy and Raman spectroscopy, while the cellulose/nanocellulose film was studied through X-ray diffraction, UV–Vis-NIR spectroscopy and laser scanning microscopy. Results indicate that cellulose (fibrils) and nanocellulose (platelets), extracted from banana pseudostem were successfully purified using hydrolysis at a relatively low amount of chemicals. Transparent films made of a fibrils/nanoplatelets blend were prepared by the solution casting method, exhibiting a transmittance of & 83–88% and a crystallinity index of & 70, hence demonstrating the feasibility of this novel method to obtain cellulose/nanocellulose free-standing films.
关键词： Nanocomposites,Cellulose nanoplatelets,Cellulose/nanocellulose films,Agricultural waste,Inner pseudostem
更新于2025-11-21 11:08:12
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Ultra-small colloidal heavy-metal-free nanoplatelets for efficient hydrogen generation
摘要： Metal chalcogenide semiconducting nanoplatelets exhibit a broad absorption spectrum, as well as thickness-dependent optical and electronic properties. As such, they may be used as building blocks in a variety of optoelectronic devices. The direct synthesis of heavy-metal-free ultra-small sized nanoplatelets is still challenging, due to the inherent limits in existing synthetic approaches. Here, we report an efficient template-assisted cation-exchange route to synthesize heavy metal free metal chalcogenide nanoplatelets that are optically active in the near infrared. The SnSe nanoplatelets, whose lateral dimension is 6-10 nm, exhibit a quantum yield of 20%. The nanoplatelets are applied as light absorbers in a photoelectrochemical (PEC) system for hydrogen generation, leading to a saturated photocurrent density of 7.4 mA/cm2, which is a record for PEC devices using heavy metal-free colloidal quantum dots or nanoplatelets under identical measurement conditions. Our results indicate that quasi-zero-dimensional SnSe nanoplatelets hold great potential as efficient light absorbers for emerging optoelectronic technologies.
关键词： nanoplatelets,cation exchange,optoelectronic technologies,SnSe,hydrogen generation
更新于2025-11-19 16:51:07
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Electrical Permittivity and Conductivity of a Graphene Nanoplatelet Contact in the Microwave Range
摘要： This paper investigates the electrical properties in the microwave range of a contact made by graphene nanoplatelets. The final goal is that of estimating the range of values for the equivalent electrical complex permittivity of a contact obtained by integrating low-cost graphene in the form of nanoplatelets (GNPs) into a high-frequency electrical circuit. To this end, a microstrip-like circuit is designed and realized, where the graphene nanoplatelets are self-assembled into a gap between two copper electrodes. An experimental characterization is carried out, both to study the structural properties of the nanomaterials and of the realized devices, and to measure the electromagnetic scattering parameters in the microwave range by means of a microstrip technique. A full-wave electromagnetic model is also derived and used to investigate the relationship between the measured quantities and the physical and geometrical parameters. The combined use of the experimental and simulation results allows for retrieving the values of the equivalent complex permittivity. The equivalent electrical conductivity values are found to be well below the values expected for isolated graphene nanoplatelets. The real part of the electrical relative permittivity attains values comparable to those obtained with GNP nanocomposites.
关键词： nanocomposite,permittivity,scattering parameters,graphene nanoplatelets
更新于2025-09-23 15:23:52
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Sheath-Core Fiber Strain Sensors Driven by In-Situ Crack and Elastic Effects in Graphite Nanoplate Composites
摘要： The flexible and stretchable electronics, e.g., graphite nanoplatelets (GNPs) based nanocomposite devices, have attracted great interest due to their potential application in healthcare, robotics, and mechatronics technology. However, the deficient sensors with manipulation of low sensitivity, sluggish responsivity, sophisticated fabrication process and poor repeatability notoriously limit their industrial applications. To enhance the spontaneous sensitivity, flexibility and wearability in GNPs based strain sensors, in this report, the synergistic crack and elastic effects engineering is employed and in turn significantly enhances the sensitivity with the gauge factor of 20 at the strain of 30% and the stability in our developed sheath-core fiber (SCF) strain sensors. Upon reliable devices integration, it is demonstrated that the developed SCF strain sensor could detect the movement of human joint effectively with generating a resistance change rate ΔR/R0 up to 600%. Furthermore, a controlling devices system based on SCF strain sensor has been manufactured in circuit level to realize the real-time control of a robot hand, such as copying gestures and playing piano.
关键词： Graphite nanoplatelets (GNPs),Robotic mechatronics,Sheath–core structure,Strain sensors,Crack and elastic effects
更新于2025-09-23 15:23:52
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Achieving high yield of graphene nanoplatelets in poloxamer-assisted ultrasonication of graphite in water
摘要： The role of surfactant (Pluronic? F 127) concentration on the yield and morphological characteristics of graphene nanoplatelets (GNPs) produced from the sonication of aqueous graphene suspensions is investigated in this work. By employing a wide surfactant concentration range (0.1–15 wt%) and sonication power densities up to 420 W L?1 we identify two graphene exfoliation regimes: the first occurs at low sonication power densities (<340 W L?1) and produces GNPs with sizes 200–300 nm, aspect ratios between 70 and 100, and concentrations up 1 mg mL?1. In that regime, the surfactant concentration has no effect on the exfoliation results. In the second exfoliation regime (>340 W L?1), surfactant concentrations greater than 10 wt% produce dramatic increases in GNP yields, namely up to 3.0 mg mL?1, and overall larger GNPs (350–500 nm) with smaller aspect ratios (5–60). We attribute these changes to the onset of a more energy intensive mechanism, termed cleavage. Cleavage involves the separation of graphite clusters in sub-bulk multi-layered graphene entities, as opposed to exfoliation, which involves the separation of individual or few-layer GNPs. Choosing an exfoliation regime by tuning simple process parameters enables control over the yield, size and morphology of the produced GNPs.
关键词： Poloxamer,Graphite exfoliation,Surfactant-assisted exfoliation,Ultrasonication,Graphene nanoplatelets
更新于2025-09-23 15:22:29
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Tellurium Precursor for Nanocrystal Synthesis: Tris(dimethylamino)phosphine Telluride
摘要： Preparations of CdTe quantum platelets, magic-size (CdTe)13 nanoclusters, and CdTe quantum wires are described using (Me2N)3PTe (with (Me2N)3P) as a Te precursor. The (Me2N)3PTe/(Me2N)3P precursor mixture is shown to be more reactive than mixtures of trialkylphosphine tellurides and the corresponding trialkylphosphines, R3PTe/R3P, which are commonly employed in nanocrystal syntheses. For syntheses conducted in primary amine solvents, (Me2N)3PTe and (Me2N)3P undergo a transamination reaction, affording (Me2N)x(RHN)3?xPTe and (Me2N)x(RHN)3?xP (R = n-octyl or oleyl). The transaminated (Me2N)x(RHN)3?xPTe derivatives are shown to be the likely Te precursors under those conditions. The enhanced reactivities of the tris(amino)phosphine tellurides are ascribed to increased nucleophilicity due to the amino-N lone pairs.
关键词： tris(dimethylamino)phosphine telluride,tellurium precursor,CdTe quantum wires,nanocrystal synthesis,CdTe nanoplatelets,(CdTe)13
更新于2025-09-23 15:21:21
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CdSe/CdMnS Nanoplatelets with Bilayer Core and Magnetically Doped Shell Exhibit Switchable Excitonic Circular Polarization: Implications for Lasers and Light-Emitting Diodes
摘要： We utilized time-resolved photoluminescence (TRPL) spectroscopy to study the excitonic circular polarization (PX) from CdSe/CdMnS core/shell nanoplatelets (NPLs) with a bilayer core. This allows an extensive study of the emission dynamics as a function of magnetic ?eld, temperature, doping concentration, and excitation wavelength. In the presence of an external magnetic ?eld, pulsed excitation below the shell gap results in near-zero excitonic circular polarization PX at all time delays. In contrast, pulsed excitation with photon energy larger than the shell gap results in a rapid (100 ps) buildup of the excitonic circular polarization which subsequently remains constant at a level of up to 40%. We propose a model to describe the dynamics which takes into account the exchange interaction between carrier and magnetic ion (Mn) spins. The studied system exhibits a fast switchable excitonic circular polarization, implying possible applications in lasers and light emitting diodes.
关键词： spd exchange interaction,quasi-2D,time-resolved photoluminescence,nanoplatelets,magneto-optical switch
更新于2025-09-23 15:21:01
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Luminescence Line Broadening of CdSe Nanoplatelets and Quantum Dots for Application in w-LEDs
摘要： Nanoplatelets (NPLs) of CdSe are an emerging class of luminescent materials, combining tunable and narrow emission bands with high quantum yields. This is promising for application in white light LEDs (w-LEDs) and displays. The origin of the narrow spectral width of exciton emission in core NPL compared to core-shell NPL and quantum dot (QD) emission is not fully understood. Here we investigate and compare temperature dependent emission spectra of core and core-shell CdSe NPLs and QDs. A wide temperature range, 4 to 423 K, is chosen to gain insight in contributions from homogeneous and inhomogeneous broadening and also to extend measurements into a temperature regime that is relevant for operating conditions in w-LEDs (T~423 K). The results show that temperature induced homogeneous broadening does not strongly vary between the various CdSe nanostructures (ΔEhom≈60-80 meV at 423 K) indicating that electron-phonon coupling strengths are similar. Only for the smallest QDs stronger coupling is observed. The origin of the narrow bandwidth reported at 300 K for core CdSe NPLs is attributed to a very narrow inhomogeneous linewidth. At 423 K the spectral width of NPL exciton emission is still superior to that of QDs. A comparison with traditional w-LED phosphors is made to outline advantages (tunability, narrow bandwidth, high efficiency) and disadvantages (color shift, stability issues) of NPLs for application in w-LEDs.
关键词： w-LEDs,Quantum Dots,Temperature dependent emission spectra,CdSe Nanoplatelets,Luminescence
更新于2025-09-23 15:21:01
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Hybrid Nanostructures of 2D CdSe Nanoplatelets for High-Performance Photodetector Using Charge Transfer Process
摘要： Two-dimensional (2D) semiconductor colloidal nanoplatelets (NPLs) have shown great potential as light-harvesting materials due to their advanced optical properties. Here, we have designed hybrid nanostructures of 2D CdSe nanoplatelets with phenothiazine (PTZ) for high-performance photodetector with varying thickness of CdSe NPLs by controlling charge transfer process. Significant photoluminescence quenching and the shortening of the average decay time of CdSe NPLs in presence of PTZ reveal the charge transfer process. Transient absorption (TA) spectroscopic analysis reveals the hot carrier cooling dynamics varies with changing the thickness of monolayers (ML) of CdSe NPLs. Furthermore, the slow exciton recombination of CdSe NPLs in presence of PTZ indicates the efficient charge separation. The optimized CdSe NPLs-PTZ hybrid exhibits a significant enhancement of photocurrent (~4.7×103 fold photo-to-dark current ratio) as compared to pure 3 ML CdSe NPLs (~10 fold) at the applied voltage of 1.5V. The measured external quantum efficiency, maximum detectivity and response time for the optimized hybrid are found to be ~40%, 4×1011 Jones and 107 milliseconds, with the responsivity value of 160 mA/W. These highly efficient measured parameters clearly suggest that CdSe NPLs-PTZ hybrid systems are promising alternate for ultrasensitive photodetector.
关键词： 2D colloidal nanoplatelets,photodetectors,hole transfer,hybrids,photocurrent
更新于2025-09-23 15:19:57
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Synthesis of electrospun nanofibrous structures with controlled optical and electrical properties
摘要： In this study, the optical and electrical influences of 2D graphene flakes in electrospun polycaprolactone (PCL) fibers were observed. Graphene nanoplatelets were added in different concentrations into the PCL solution, and then, using the electrospinning technique, fibers were built from that solution. Three samples were prepared with different graphene concentrations of 0% w/w, 0.5% w/w, and 2.0% w/w. From all three samples, fibers were prepared and tests were conducted for the identification of the properties of fibers. An optical spectroscopy test was performed to identify the optical behavior of the fibers. Scanning electron microscopy tests were conducted for the morphological characterization of the fibers. For the comparison of the electrical conductivity of the three samples, electrical tests were also conducted. In addition, Raman spectroscopy was conducted to characterize the graphene and PCL. This study shows that using graphene can change the properties of fibers, for example, as the graphene content increases, the fiber diameter also increases. Also, by varying the 2D graphene concentration, both electrical and optical properties can be tuned; this can be utilized in the synthesis of nanosensing surfaces and structures.
关键词： polycaprolactone,graphene nanoplatelets,optical properties,electrical properties,electrospun nanofibrous structures
更新于2025-09-23 15:19:57