The impact of thickness-related grain boundary migration on hole concentration and mobility of p-type transparent conducting CuI films.

CuI films present promising optoelectronic properties for transparent conductors. However, the high hole concentration in CuI films hinders the controllable modulation of hole mobility, limiting their application in low-dimensional thin-film transistors. In this study, CuI films were prepared through a Cu film iodination method at room temperature, and a systematic investigation was conducted on the modulation of hole concentration and mobility with varying film thickness. The films exhibited a zinc blende structure (γ-phase) with increasing grain size as the thickness increased. The transmittance and optical bandgap of the films decreased with increasing thickness. The correlation of vacancy concentration with changing film thickness was analyzed through photoluminescence spectroscopy, revealing the influence of grain boundary migration on vacancy formation. The reduction in film thickness diminishes the migration of CuI grain boundaries, consequently reducing the probability of Cu vacancy and I vacancy formation, resulting in diminished hole concentration and enhanced hole mobility and film conductivity. The film with a thickness of 20 nm demonstrated optimal performance, with a transmittance of 90%, hole concentration of 4.09 × 1017 cm-3, hole mobility of 506.50 cm2 V-1 s-1, and conductivity of 33.19 S cm-1. This work deepens the understanding of hole transport such as hole concentration and mobility modulation in CuI films, highlighting the importance of controlling grain boundary migration during the film growth process.

Machine learning-augmented surface-enhanced spectroscopy toward next-generation molecular diagnostics.

The world today is witnessing the significant role and huge demand for molecular detection and screening in healthcare and medical diagnosis, especially during the outbreak of COVID-19. Surface-enhanced spectroscopy techniques, including Surface-Enhanced Raman Scattering (SERS) and Infrared Absorption (SEIRA), provide lattice and molecular vibrational fingerprint information which is directly linked to the molecular constituents, chemical bonds, and configuration. These properties make them an unambiguous, nondestructive, and label-free toolkit for molecular diagnostics and screening. However, new issues in molecular diagnostics, such as increasing molecular species, faster spread of viruses, and higher requirements for detection accuracy and sensitivity, have brought great challenges to detection technology. Advancements in artificial intelligence and machine learning (ML) techniques show promising potential in empowering SERS and SEIRA with rapid analysis and automatic data processing to jointly tackle the challenge. This review introduces the combination of ML and SERS/SEIRA by investigating how ML algorithms can be beneficial to SERS/SEIRA, discussing the general process of combining ML and SEIRA/SERS, highlighting the molecular diagnostics and screening applications based on ML-combined SEIRA/SERS, and providing perspectives on the future development of ML-integrated SEIRA/SERS. In general, this review offers comprehensive knowledge about the recent advances and the future outlook regarding ML-integrated SEIRA/SERS for molecular diagnostics and screening.

MOF/Polymer-Integrated Multi-Hotspot Mid-Infrared Nanoantennas for Sensitive Detection of CO2 Gas.

Metal-organic frameworks (MOFs) have been extensively used for gas sorption, storage and separation owing to ultrahigh porosity, exceptional thermal stability, and wide structural diversity. However, when it comes to ultra-low concentration gas detection, technical bottlenecks of MOFs appear due to the poor adsorption capacity at ppm-/ppb-level concentration and the limited sensitivity for signal transduction. Here, we present hybrid MOF-polymer physi-chemisorption mechanisms integrated with infrared (IR) nanoantennas for highly selective and ultrasensitive CO2 detection. To improve the adsorption capacity for trace amounts of gas molecules, MOFs are decorated with amino groups to introduce the chemisorption while maintaining the structural integrity for physisorption. Additionally, leveraging all major optimization methods, a multi-hotspot strategy is proposed to improve the sensitivity of nanoantennas by enhancing the near field and engineering the radiative and absorptive loss. As a benefit, we demonstrate the competitive advantages of our strategy against the state-of-the-art miniaturized IR CO2 sensors, including low detection limit, high sensitivity (0.18%/ppm), excellent reversibility (variation within 2%), and high selectivity (against C2H5OH, CH3OH, N2). This work provides valuable insights into the integration of advanced porous materials and nanophotonic devices, which can be further adopted in ultra-low concentration gas monitoring in industry and environmental applications.

Effect of Post-Deposition Annealing on the Structural Evolution and Optoelectronic Properties of In2O3:H Thin Films.

An infrared transparent conductive material is a solution to realize the shielding function of infrared windows against electromagnetic waves, by combining the two characteristics of high transmission and conductivity in infrared wavelengths. Indium-hydroxide-doped (In2O3:H) thin films were prepared by atomic layer deposition method, which can achieve high IR transmission by reducing the carrier concentration on the basis of ensuring the electrical properties. On this basis, the effect of the post-deposition annealing process on the microstructure evolution and optoelectronic properties of In2O3:H thin films was investigated in this paper. It is demonstrated that the carrier mobility after annealing is up to 90 cm2/(V·s), and the transmittance at the 4 µm is about 70%, meanwhile, the carrier concentration after annealing in air atmosphere is reduced to 1019 cm-3, with a transmission rate of up to 83% at 4 µm. The simulations visualize the shielding performance of the annealed In2O3:H thin film against radar electromagnetic waves. It provides a guideline for fabricating lightweight, thin, and multi-functional shielding infrared transparent materials in the key fields of spacecraft and high precision electronics.

Visible and infrared optical modulation of PSLC smart films doped with ATO nanoparticles.

In recent years, smart windows have been gradually applied and developed in the fields of environmental protection, energy management, smart camouflage and display. With the continuous upgrading of market demand, smart windows with both visible and infrared band modulation functions are the future development trends. However, the optical modulation of smart windows is usually limited in the visible light band (380-780 nm). In this paper, we report a novel smart window by doping antimony doped tin oxide (ATO) nanoparticles (NPs) into polymer stabilized liquid crystal (PSLC) films. These films have the widest waveband modulation function among those reported so far, covering the visible and infrared regions (380-5500 nm). The transmittance of the as-prepared smart films can be changed reversibly from highly transparent (78.5%) state to a strong light scattering (10%) state in the visible region. In addition, due to the localized surface plasmon resonance of ATO NPs, up to 80.7% of the infrared invisible light can be effectively shielded. The significance of this research is to provide theoretical and technical support for the broadband optical modulation of novel smart windows.

Correction: Nano-graphene oxide-UCNP-Ce6 covalently constructed nanocomposites for NIR-mediated bioimaging and PTT/PDT combinatorial therapy.

Correction for 'Nano-graphene oxide-UCNP-Ce6 covalently constructed nanocomposites for NIR-mediated bioimaging and PTT/PDT combinatorial therapy' by Arif Gulzar et al., Dalton Trans., 2018, 47, 3931-3939.

Redox-responsive UCNPs-DPA conjugated NGO-PEG-BPEI-DOX for imaging-guided PTT and chemotherapy for cancer treatment.

The disulfide bond (-S-S-) is an enormously valuable functional group in a variety of chemical and biological agents that display effective reactivity or biological activities (e.g., antitumor activities). The disulfide bonds prevalent in proteins are somewhat oxidizing in the extracellular space; however, such disulfide bonds can rarely be found inside cells because of disulfide cleavage reactions facilitated by abundant free cellular thiols, including glutathione (GSH), which is the most important common thiol-containing small molecule. Interestingly, intracellular GSH concentrations are considerably higher in cancer cells than in analogous normal cells; this feature may prove to be significant in the development of anticancer drug delivery systems (DDS). Moreover, upconversion nanoparticles (UCNPs) have been extensively investigated in multimodal imaging, photodynamic therapy (PDT) and photothermal therapy. UCNPs exploit near-infrared excitation instead of ultraviolet excitation and possess exclusive properties, which include greatly increased penetration depth in biological samples and reductions in background autofluorescence, photobleaching and photodamage to biological specimens. These fascinating optical features of UCNPs may broaden their prospects in the fields of imaging and therapy. Graphene has emerged as a flat monolayer of carbon atoms that are tightly embedded in a two-dimensional (2D) honeycomb lattice. Widespread research has been carried out on graphene in recent years owing to its exclusive shape and size, as well as innumerable fascinating physical and chemical properties. Owing to their high optical absorption in the near-infrared (NIR) region, graphene and GO have been extensively employed for photothermal therapy (PTT). In this study, we attempted to merge the properties of these compounds by conjugating UCNPs and NGO-PEG-BPEI-DOX into a single platform for chemotherapy and photothermal therapy.

Nano-graphene oxide-UCNP-Ce6 covalently constructed nanocomposites for NIR-mediated bioimaging and PTT/PDT combinatorial therapy.

NIR light-induced imaging-guided cancer therapy is an encouraging route in the cancer theranostic field. Herein, we describe a novel nanoscale proposal, which is established by covalently implanting core-shell structured upconversion nanoparticles (UCNPs) with nanographene oxide (NGO) by a process utilizing polyethylene glycol (PEG), and consequently loading Chlorin e6 (Ce6) onto the surface of NGO. The acquired NGO-UCNP-Ce6 (NUC) nanocomposites can not only be employed as upconversion luminescence (UCL) imaging probes of cells and whole-body animals with high contrast for diagnosis, but also can generate reactive oxygen species (ROS) under 808 nm light excitation for photodynamic therapy (PDT); over and above, they can swiftly and proficiently translate the 808 nm photon into thermal energy for photothermal therapy (PTT). An extraordinarily enhanced and synchronized therapeutic effect paralleled to the individual PTT or PDT is achieved, rendering extraordinary therapeutic effectiveness for cancer treatment. Consequently, profiting from this inimitable multifunctional nanohybrid, the NUCs synthesized here are encouraging as a cohesive theranostic probe for impending UCL imaging-guided combinatorial PDT/PTT.

A novel core-shell structured upconversion nanorod as a multimodal bioimaging and photothermal ablation agent for cancer theranostics.

A multifunctional core-shell nanocomposite based on noble metal plasmons coated with upconversion material has emerged as a promising cancer theranostics nanoplatform that integrates properties such as multimodal imaging, photothermal effects, good biocompatibility, and efficient therapy. However, a reasonable combination of plasmons and upconversion materials, as well as increased penetration depth, has always challenged the anti-cancer efficiency. Here, a unique kind of fluorescent thermal-magnetic resonance core-shell upconversion nanostructure has been designed and fabricated to simultaneously achieve photothermal therapy (PTT) and multimodal imaging. Gold nanorods (GNRs) are used as the plasmon cores and NaGdF4 with rare-earth Yb3+/Er3+ ions co-doping are used as the upconversion luminescence (UCL) shells, merging into upconversion nanorods (UCNRs) of GNRs@NaGdF4:Yb3+,Er3+. An NaGdF4 shell synthesized by a hydrothermal method can substitute for the cetyltrimethylammonium bromide (CTAB) on the surface of GNRs, which offers the benefits of reducing toxicity and increasing biocompatibility. More significantly, the red and green emission of Yb3+/Er3+ couples convert near-infrared (NIR) into visible light, appropriately overlapping with absorbance of GNRs, which improves the photothermal conversion efficiency. Meanwhile, we designed small and low-aspect-ratio GNR cores for the absorption of UCNRs in vivo. Verification with evidence from in vivo and in vitro assays shows that these core-shell UCNRs exhibit a talented potential application in multimodal bioimaging and PTT.

Multimodal imaging and photothermal therapy were simultaneously achieved in the core-shell UCNR structure by using single near-infrared light.

Core-shell nanostructures consisting of plasmonic materials and lanthanide-doped upconversion nanoparticles (UCNPs) show promising applications in theranostics including bio-imaging, diagnosis and therapy. However, some challenges still remain in the synthetic control because of the non-coordination between energy transfer and photothermal therapy (PTT). Herein, we developed a novel type of thermal-fluorescent core-shell hybrid nanocomposite incorporating rare-earth Yb3+ and Er3+ ion doped GdOF as the shell and gold nanorods (GNRs) as the core, creating upconversion nanorods (UCNRs) of GNRs@GdOF:Yb3+,Er3+. In order to facilitate the absorption or excretion of UCNRs in vivo, we designed gold nanorods with lower aspect ratios by reducing the amount of CTAB in the growth solution. More importantly, under 980 nm near-infrared (NIR) light irradiation, the green and red emissions of GdOF:Yb3+,Er3+ generally overlap with the visible absorbance of GNRs; by altering the contents of Yb3+ and Er3+ ions appropriately, the localized surface plasmon resonance (LSPR) absorption of low aspect ratio GNRs under 980 nm NIR laser excitation can be enhanced for improving the PTT efficiency. Furthermore, in vitro and in vivo assays reveal that the composite has excellent bio-compatibility and cancer therapy efficiency. This multi-functional nanocomposite, which possesses upconversion luminescence and photothermal and biocompatibility properties, shows strong potential for application in bio-imaging and photothermal anti-cancer therapy.

Upconversion processes: versatile biological applications and biosafety.

Lanthanide-doped photon upconverting nanomaterials are evolving as a new class of imaging contrast agents, offering highly promising prospects in the area of biomedical applications. Owing to their ability to convert long-wavelength near-infrared excitation radiation into shorter-wavelength emissions, these nanomaterials are well suited to yield properties of low imaging background, large anti-Stokes shift, along with high optical penetration depth of NIR light for deep tissue optical imaging or light-activated drug release and therapy. Such materials have potential for significant advantages in analytical applications compared to molecular fluorophores and quantum dots. The use of IR radiation as an excitation source diminishes autofluorescence and scattering of excitation radiation, which leads to a reduction of background in optical experiments. The upconverting nanocrystals show exceptional photostability and are constituted of materials that are not significantly toxic to biological organisms. Excitation at long wavelengths also minimizes damage to biological materials. In this detailed review, various mechanisms operating for the upconversion process, and methods that are utilized to synthesize and decorate upconverting nanoparticles are investigated to elucidate by what means absorption and emission can be tuned. Up-to-date reports concerning cellular internalization, biodistribution, excretion, cytotoxicity and in vivo toxic effects of UCNPs are discussed. Specifically, studies which assessed the relationship between the chemical and physical properties of UCNPs and their biodistribution, excretion, and toxic effects are reviewed in detail. Finally, we also deliberate the challenges of guaranteeing the biosafety of UCNPs in vivo.

Lanthanide-doped bismuth oxobromide nanosheets for self-activated photodynamic therapy.

Low tissue penetration depth of the excited light and complicated synthetic procedures greatly hinder the clinical application of photodynamic therapy (PDT). Here we present a facile and mass production route to fabricate Yb3+/Tm3+ co-doped BiOBr nanosheets. In contrast to the complicated combination of photosensitizers (PSs) with up-conversion nanoparticles (UCNPs), which generates a PDT effect by a fluorescence resonance energy transfer process from UCNPs to PSs upon near-infrared light excitation, this as-synthesized material can be self-activated by deep-penetrating 980 nm laser light to produce a large amount of reactive oxygen species, giving rise to a high PDT efficiency which has been proven by in vitro and in vivo therapeutic assays. Surface modification of the BiOBr:Yb,Tm nanosheets with polyethylene glycol endows the system with improved biocompatibility. Through the combination of inherent fluorescence and CT imaging properties, an imaging-monitored therapeutic system has been realized. The system overcomes the problems of low tissue penetration depth, complicated structure-induced low efficiency, and potential safety concerns. Our finding presents the first demonstration of a self-activated nanoplatform for targeted and noninvasive deep-cancer therapy.

Bioapplications of graphene constructed functional nanomaterials.

Graphene has distinctive mechanical, electronic, and optical properties, which researchers have applied to develop innovative electronic materials including transparent conductors and ultrafast transistors. Lately, the understanding of various chemical properties of graphene has expedited its application in high-performance devices that generate and store energy. Graphene is now increasing its terrain outside electronic and chemical applications toward biomedical areas such as precise bio sensing through graphene-quenched fluorescence, graphene-enhanced cell differentiation and growth, and graphene-assisted laser desorption/ionization for mass spectrometry. In this Account, we evaluate recent efforts to apply graphene and graphene oxides (GO) to biomedical research and a few different approaches to prepare graphene materials designed for biomedical applications and a brief perspective on their future applications. Because of its outstanding aqueous processability, amphiphilicity, surface functionalizability, surface enhanced Raman scattering (SERS), and fluorescence quenching ability, GO chemically exfoliated from oxidized graphite is considered a promising material for biological applications. In addition, the hydrophobicity and flexibility of large-area graphene synthesized by chemical vapor deposition (CVD) allow this material to play an important role in cell growth and differentiation. Graphene is considered to be an encouraging and smart candidate for numerous biomedical applications such as NIR-responsive cancer therapy and fluorescence bio-imaging and drug delivery. To that end, suitable preparation and unique approaches to utilize graphene-based materials such as graphene oxides (GOs), reduced graphene oxides (rGOs), and graphene quantum dots (GQDs) in biology and medical science are gaining growing interest.