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Open AccessArticle

Multi-Mode Lanthanide-Doped Ratiometric Luminescent Nanothermometer for Near-Infrared Imaging within Biological Windows

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Nanomaterials 2023, 13(1), 219; https://doi.org/10.3390/nano13010219 - 03 Jan 2023

Viewed by 840

Abstract

Owing to its high reliability and accuracy, the ratiometric luminescent thermometer can provide non-contact and fast temperature measurements. In particular, the nanomaterials doped with lanthanide ions can achieve multi-mode luminescence and temperature measurement by modifying the type of doped ions and excitation light [...] Read more.

Owing to its high reliability and accuracy, the ratiometric luminescent thermometer can provide non-contact and fast temperature measurements. In particular, the nanomaterials doped with lanthanide ions can achieve multi-mode luminescence and temperature measurement by modifying the type of doped ions and excitation light source. The better penetration of the near-infrared (NIR) photons can assist bio-imaging and replace thermal vision cameras for photothermal imaging. In this work, we prepared core–shell cubic phase nanomaterials doped with lanthanide ions, with Ba₂LuF₇ doped with Er³⁺/Yb³⁺/Nd³⁺ as the core and Ba₂LaF₇ as the coating shell. The nanoparticles were designed according to the passivation layer to reduce the surface energy loss and enhance the emission intensity. Green upconversion luminescence can be observed under both 980 nm and 808 nm excitation. A single and strong emission band can be obtained under 980 nm excitation, while abundant and weak emission bands appear under 808 nm excitation. Meanwhile, multi-mode ratiometric optical thermometers were achieved by selecting different emission peaks in the NIR window under 808 nm excitation for non-contact temperature measurement at different tissue depths. The results suggest that our core–shell NIR nanoparticles can be used to assist bio-imaging and record temperature for biomedicine. Full article

(This article belongs to the Special Issue Advanced Nanocomposites for Photonics and Optoelectronics and Mechanics)

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Open AccessArticle

Carbon Nanodots as Electron Transport Materials in Organic Light Emitting Diodes and Solar Cells

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Georgios Chatzigiannakis

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Konstantina-Kalliopi Armadorou

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Leonidas C. Palilis

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Alexander Chroneos

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Evangelos K. Evangelou

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Spiros Gardelis

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Abd. Rashid bin Mohd Yusoff

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Athanassios G. Coutsolelos

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Konstantinos Aidinis

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Maria Vasilopoulou

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Anastasia Soultati

Nanomaterials 2023, 13(1), 169; https://doi.org/10.3390/nano13010169 - 30 Dec 2022

Viewed by 905

Abstract

Charge injection and transport interlayers play a crucial role in many classes of optoelectronics, including organic and perovskite ones. Here, we demonstrate the beneficial role of carbon nanodots, both pristine and nitrogen-functionalized, as electron transport materials in organic light emitting diodes (OLEDs) and [...] Read more.

Charge injection and transport interlayers play a crucial role in many classes of optoelectronics, including organic and perovskite ones. Here, we demonstrate the beneficial role of carbon nanodots, both pristine and nitrogen-functionalized, as electron transport materials in organic light emitting diodes (OLEDs) and organic solar cells (OSCs). Pristine (referred to as C-dots) and nitrogen-functionalized (referred to as NC-dots) carbon dots are systematically studied regarding their properties by using cyclic voltammetry, Fourier-transform infrared (FTIR) and UV–Vis absorption spectroscopy in order to reveal their energetic alignment and possible interaction with the organic semiconductor’s emissive layer. Atomic force microscopy unravels the ultra-thin nature of the interlayers. They are next applied as interlayers between an Al metal cathode and a conventional green-yellow copolymer—in particular, (poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-{2,1′,3}-thiadiazole)], F8BT)—used as an emissive layer in fluorescent OLEDs. Electrical measurements indicate that both the C-dot- and NC-dot-based OLED devices present significant improvements in their current and luminescent characteristics, mainly due to a decrease in electron injection barrier. Both C-dots and NC-dots are also used as cathode interfacial layers in OSCs with an inverted architecture. An increase of nearly 10% in power conversion efficiency (PCE) for the devices using the C-dots and NC-dots compared to the reference one is achieved. The application of low-cost solution-processed materials in OLEDs and OSCs may contribute to their wide implementation in large-area applications. Full article

(This article belongs to the Special Issue Advanced Nanocomposites for Photonics and Optoelectronics and Mechanics)

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Open AccessArticle

Modulation of Casimir Force between Graphene-Covered Hyperbolic Materials

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Nanomaterials 2022, 12(13), 2168; https://doi.org/10.3390/nano12132168 - 23 Jun 2022

Viewed by 982

Abstract

A flexible method for modulating the Casimir force is proposed by combining graphene and hyperbolic materials (HMs). The proposed structure employs two candidates other than graphene. One is hexagonal boron nitride (hBN), a natural HM. The other is porous silicon carbide (SiC), which [...] Read more.

A flexible method for modulating the Casimir force is proposed by combining graphene and hyperbolic materials (HMs). The proposed structure employs two candidates other than graphene. One is hexagonal boron nitride (hBN), a natural HM. The other is porous silicon carbide (SiC), which can be treated as an artificial HM by the effective medium theory. The Casimir force between graphene-covered hBN (porous SiC) bulks is presented at zero temperature. The results show that covering HM with graphene increases the Casimir force monotonically. Furthermore, the force can be modulated by varying the Fermi level, especially at large separation distances. The reflection coefficients are thoroughly investigated, and the enhancement is attributed to the interaction of surface plasmons (SPs) supported by graphene and hyperbolic phonon polaritons (HPhPs) supported by HMs. Moreover, the Casimir force can be controlled by the filling factor of porous SiC. The Casimir force can thus be modulated flexibly by designing desired artificial HMs and tuning the Fermi level. The proposed models have promising applications in practical detection and technological fields. Full article

(This article belongs to the Special Issue Advanced Nanocomposites for Photonics and Optoelectronics and Mechanics)

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Open AccessArticle

Enhancement of Casimir Friction between Graphene-Covered Topological Insulator

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Nanomaterials 2022, 12(7), 1148; https://doi.org/10.3390/nano12071148 - 30 Mar 2022

Cited by 1 | Viewed by 1012

Abstract

Casimir friction is theoretically studied between graphene-covered undoped bismuth selenide (Bi₂Se₃) in detail. In the graphene/Bi₂Se₃ composite structure, the coupling of the hyperbolic phonon polaritons supported by Bi₂Se₃ with the surface plasmons supported [...] Read more.

Casimir friction is theoretically studied between graphene-covered undoped bismuth selenide (Bi₂Se₃) in detail. In the graphene/Bi₂Se₃ composite structure, the coupling of the hyperbolic phonon polaritons supported by Bi₂Se₃ with the surface plasmons supported by graphene can lead to the hybrid surface plasmon–phonon polaritons (SPPPs). Compared with that between undoped Bi₂Se₃, Casimir friction can be enhanced by more than one order of magnitude due to the contribution of SPPPs. It is found that the chemical potential that can be used to modulate the optical characteristic of SPPPs plays an important role in Casimir friction. In addition, the Casimir friction between doped Bi₂Se₃ is also studied. The friction coefficient between doped Bi₂Se₃ can even be larger than that between graphene-covered undoped Bi₂Se₃ for suitable chemical potential due to the contribution of unusual electron surface states. The results obtained in this work are not only beneficial to the study of Casimir frictions but also extend the research ranges of topological insulators. Full article

(This article belongs to the Special Issue Advanced Nanocomposites for Photonics and Optoelectronics and Mechanics)

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Open AccessArticle

Magnetic Field Sensing Based on Whispering Gallery Mode with Nanostructured Magnetic Fluid-Infiltrated Photonic Crystal Fiber

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Nanomaterials 2022, 12(5), 862; https://doi.org/10.3390/nano12050862 - 03 Mar 2022

Cited by 12 | Viewed by 1848

Abstract

A kind of novel and compact magnetic field sensor has been proposed and investigated experimentally. The proposed sensor consists of a tapered single mode fiber coupled with a nanostructured magnetic fluid-infiltrated photonic crystal fiber, which is easy to be fabricated. The response of [...] Read more.

A kind of novel and compact magnetic field sensor has been proposed and investigated experimentally. The proposed sensor consists of a tapered single mode fiber coupled with a nanostructured magnetic fluid-infiltrated photonic crystal fiber, which is easy to be fabricated. The response of magnetic fluid to magnetic field is used to measure the intensity of magnetic field via whispering gallery mode. The magnetic field-dependent shift in resonance wavelength is observed. The maximum magnetic field intensity sensitivity is 53 pm/mT. The sensor sensitivity is inversely proportional to the thickness of the photonic crystal fiber cladding. Full article

(This article belongs to the Special Issue Advanced Nanocomposites for Photonics and Optoelectronics and Mechanics)

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Open AccessEditor’s ChoiceArticle

Superfluorescence of Sub-Band States in C-Plane In_0.1Ga_0.9N/GaN Multiple-QWs

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Nanomaterials 2022, 12(3), 327; https://doi.org/10.3390/nano12030327 - 20 Jan 2022

Viewed by 865

Abstract

Superfluorescence is a collective emission from quantum coherent emitters due to quantum fluctuations. This is characterized by the existence of the delay time (

τ_{D})

for the emitters coupling and phase-synchronizing to each other spontaneously. Here we report the observation of [...] Read more.

Superfluorescence is a collective emission from quantum coherent emitters due to quantum fluctuations. This is characterized by the existence of the delay time (

τ_{D})

for the emitters coupling and phase-synchronizing to each other spontaneously. Here we report the observation of superfluorescence in c-plane In_0.1Ga_0.9N/GaN multiple-quantum wells by time-integrated and time-resolved photoluminescence spectroscopy under higher excitation fluences of the 267 nm laser and at room temperature, showing a characteristic

τ_{D}

from 79 ps to 62 ps and the ultrafast radiative decay (7.5 ps) after a burst of photons. Time-resolved traces present a small quantum oscillation from coupled In_0.1Ga_0.9N/GaN multiple-quantum wells. The superfluorescence is attributed to the radiative recombination of coherent emitters distributing on strongly localized subband states, E_e₁→E_hh₁ or E_e₁→E_lh₁ in 3nm width multiple-quantum wells. Our work paves the way for deepening the understanding of the emission mechanism in the In_0.1Ga_0.9N/GaN quantum well at a higher injected carrier density. Full article

(This article belongs to the Special Issue Advanced Nanocomposites for Photonics and Optoelectronics and Mechanics)

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Review

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Open AccessReview

Recent Progress in Contact Engineering of Field-Effect Transistor Based on Two-Dimensional Materials

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Nanomaterials 2022, 12(21), 3845; https://doi.org/10.3390/nano12213845 - 31 Oct 2022

Viewed by 1087

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Two-dimensional (2D) semiconductors have been considered as promising candidates to fabricate ultimately scaled field-effect transistors (FETs), due to the atomically thin thickness and high carrier mobility. However, the performance of FETs based on 2D semiconductors has been limited by extrinsic factors, including high [...] Read more.

Two-dimensional (2D) semiconductors have been considered as promising candidates to fabricate ultimately scaled field-effect transistors (FETs), due to the atomically thin thickness and high carrier mobility. However, the performance of FETs based on 2D semiconductors has been limited by extrinsic factors, including high contact resistance, strong interfacial scattering, and unintentional doping. Among these challenges, contact resistance is a dominant issue, and important progress has been made in recent years. In this review, the Schottky–Mott model is introduced to show the ideal Schottky barrier, and we further discuss the contribution of the Fermi-level pinning effect to the high contact resistance in 2D semiconductor devices. In 2D FETs, Fermi-level pinning is attributed to the high-energy metal deposition process, which would damage the lattice of atomically thin 2D semiconductors and induce the pinning of the metal Fermi level. Then, two contact structures and the strategies to fabricate low-contact-resistance short-channel 2D FETs are introduced. Finally, our review provides practical guidelines for the realization of high-performance 2D-semiconductors-based FETs with low contact resistance and discusses the outlook of this field. Full article

(This article belongs to the Special Issue Advanced Nanocomposites for Photonics and Optoelectronics and Mechanics)

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Open AccessReview

Evolution Application of Two-Dimensional MoS₂-Based Field-Effect Transistors

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Chunlan Wang

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Yongle Song

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Hao Huang

Nanomaterials 2022, 12(18), 3233; https://doi.org/10.3390/nano12183233 - 18 Sep 2022

Viewed by 1378

Abstract

High-performance and low-power field-effect transistors (FETs) are the basis of integrated circuit fields, which undoubtedly require researchers to find better film channel layer materials and improve device structure technology. MoS₂ has recently shown a special two-dimensional (2D) structure and superior photoelectric performance, [...] Read more.

High-performance and low-power field-effect transistors (FETs) are the basis of integrated circuit fields, which undoubtedly require researchers to find better film channel layer materials and improve device structure technology. MoS₂ has recently shown a special two-dimensional (2D) structure and superior photoelectric performance, and it has shown new potential for next-generation electronics. However, the natural atomic layer thickness and large specific surface area of MoS₂ make the contact interface and dielectric interface have a great influence on the performance of MoS₂ FET. Thus, we focus on its main performance improvement strategies, including optimizing the contact behavior, regulating the conductive channel, and rationalizing the dielectric layer. On this basis, we summarize the applications of 2D MoS₂ FETs in key and emerging fields, specifically involving logic, RF circuits, optoelectronic devices, biosensors, piezoelectric devices, and synaptic transistors. As a whole, we discuss the state-of-the-art, key merits, and limitations of each of these 2D MoS₂-based FET systems, and prospects in the future. Full article

(This article belongs to the Special Issue Advanced Nanocomposites for Photonics and Optoelectronics and Mechanics)

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Open AccessReview

Perovskite Quantum Dots for Emerging Displays: Recent Progress and Perspectives

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Nanomaterials 2022, 12(13), 2243; https://doi.org/10.3390/nano12132243 - 29 Jun 2022

Cited by 9 | Viewed by 2637

Abstract

The excellent luminescence properties of perovskite quantum dots (PQDs), including wide excitation wavelength range, adjustable emission wavelength, narrow full width at half maximum (FWHM), and high photoluminescence quantum yield (PLQY), highly match the application requirements in emerging displays. Starting from the fundamental structure [...] Read more.

The excellent luminescence properties of perovskite quantum dots (PQDs), including wide excitation wavelength range, adjustable emission wavelength, narrow full width at half maximum (FWHM), and high photoluminescence quantum yield (PLQY), highly match the application requirements in emerging displays. Starting from the fundamental structure and the related optical properties, this paper first introduces the existing synthesis approaches of PQDs that have been and will potentially be used for display devices, and then summarizes the stability improving approaches with high retention of PQDs’ optical performance. Based on the above, the recent research progress of PQDs in displays is further elaborated. For photoluminescent display applications, the PQDs can be embedded in the backlighting device or color filter for liquid crystal displays (LCD), or they may function as the color conversion layer for blue organic light-emitting diodes (OLED) and blue micro-scale light-emitting diodes (μLED). In terms of next-generation electroluminescent displays, notable progress in perovskite quantum-dot light emitting diodes (PeQLED) has been achieved within the past decade, especially the maximum external quantum efficiency (EQE). To conclude, the key directions for future PQD development are summarized for promising prospects and widespread applications in display fields. Full article

(This article belongs to the Special Issue Advanced Nanocomposites for Photonics and Optoelectronics and Mechanics)

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