P-type electrical contacts for 2D transition-metal dichalcogenides.

Digital logic circuits are based on complementary pairs of n- and p-type field effect transistors (FETs) via complementary metal oxide semiconductor technology. In three-dimensional (3D) or bulk semiconductors, substitutional doping of acceptor or donor impurities is used to achieve p- and n-type FETs. However, the controllable p-type doping of low-dimensional semiconductors such as two-dimensional (2D) transition-metal dichalcogenides (TMDs) has proved to be challenging. Although it is possible to achieve high-quality, low-resistance n-type van der Waals (vdW) contacts on 2D TMDs1-5, obtaining p-type devices by evaporating high-work-function metals onto 2D TMDs has not been realized so far. Here we report high-performance p-type devices on single- and few-layered molybdenum disulfide and tungsten diselenide based on industry-compatible electron beam evaporation of high-work-function metals such as palladium and platinum. Using atomic resolution imaging and spectroscopy, we demonstrate near-ideal vdW interfaces without chemical interactions between the 2D TMDs and 3D metals. Electronic transport measurements reveal that the Fermi level is unpinned and p-type FETs based on vdW contacts exhibit low contact resistance of 3.3 kΩ µm, high mobility values of approximately 190 cm2 V-1 s-1 at room temperature, saturation currents in excess of 10-5 A µm-1 and an on/off ratio of 107. We also demonstrate an ultra-thin photovoltaic cell based on n- and p-type vdW contacts with an open circuit voltage of 0.6 V and a power conversion efficiency of 0.82%.

Flat-surface-assisted and self-regulated oxidation resistance of Cu(111).

Oxidation can deteriorate the properties of copper that are critical for its use, particularly in the semiconductor industry and electro-optics applications1-7. This has prompted numerous studies exploring copper oxidation and possible passivation strategies8. In situ observations have, for example, shown that oxidation involves stepped surfaces: Cu2O growth occurs on flat surfaces as a result of Cu adatoms detaching from steps and diffusing across terraces9-11. But even though this mechanism explains why single-crystalline copper is more resistant to oxidation than polycrystalline copper, the fact that flat copper surfaces can be free of oxidation has not been explored further. Here we report the fabrication of copper thin films that are semi-permanently oxidation resistant because they consist of flat surfaces with only occasional mono-atomic steps. First-principles calculations confirm that mono-atomic step edges are as impervious to oxygen as flat surfaces and that surface adsorption of O atoms is suppressed once an oxygen face-centred cubic (fcc) surface site coverage of 50% has been reached. These combined effects explain the exceptional oxidation resistance of ultraflat Cu surfaces.

Van der Waals contacts between three-dimensional metals and two-dimensional semiconductors.

As the dimensions of the semiconducting channels in field-effect transistors decrease, the contact resistance of the metal-semiconductor interface at the source and drain electrodes increases, dominating the performance of devices1-3. Two-dimensional (2D) transition-metal dichalcogenides such as molybdenum disulfide (MoS2) have been demonstrated to be excellent semiconductors for ultrathin field-effect transistors4,5. However, unusually high contact resistance has been observed across the interface between the metal and the 2D transition-metal dichalcogenide3,5-9. Recent studies have shown that van der Waals contacts formed by transferred graphene10,11 and metals12 on few-layered transition-metal dichalcogenides produce good contact properties. However, van der Waals contacts between a three-dimensional metal and a monolayer 2D transition-metal dichalcogenide have yet to be demonstrated. Here we report the realization of ultraclean van der Waals contacts between 10-nanometre-thick indium metal capped with 100-nanometre-thick gold electrodes and monolayer MoS2. Using scanning transmission electron microscopy imaging, we show that the indium and gold layers form a solid solution after annealing at 200 degrees Celsius and that the interface between the gold-capped indium and the MoS2 is atomically sharp with no detectable chemical interaction between the metal and the 2D transition-metal dichalcogenide, suggesting van-der-Waals-type bonding between the gold-capped indium and monolayer MoS2. The contact resistance of the indium/gold electrodes is 3,000 ± 300 ohm micrometres for monolayer MoS2 and 800 ± 200 ohm micrometres for few-layered MoS2. These values are among the lowest observed for three-dimensional metal electrodes evaporated onto MoS2, enabling high-performance field-effect transistors with a mobility of 167 ± 20 square centimetres per volt per second. We also demonstrate a low contact resistance of 220 ± 50 ohm micrometres on ultrathin niobium disulfide (NbS2) and near-ideal band offsets, indicative of defect-free interfaces, in tungsten disulfide (WS2) and tungsten diselenide (WSe2) contacted with indium alloy. Our work provides a simple method of making ultraclean van der Waals contacts using standard laboratory technology on monolayer 2D semiconductors.

Pharmaceutical and Immunological Evaluation of Cholera Toxin A1 Subunit as an Adjuvant of Hepatitis B Vaccine Microneedles.

PURPOSE: For successful delivery of a solid vaccine formulation into the skin using microneedles, the solubility of an adjuvant should be considered because the decrease in the dissolution rate by the addition of adjuvant decreases the delivery efficiency of the vaccine. METHODS: In this study, cholera toxin A subunit 1 (CTA1) was examined as an adjuvant to Hepatitis B vaccine (HBV) microneedles because of its good water solubility, improved safety, and positive effect as shown in intramuscular administration of a liquid vaccine. RESULTS: All solid formulations with CTA 1 dissolved in in vivo mouse skin within 30 min, and they were successfully delivered into the skin. In experiments with mice, the addition of CTA1 led to improved IgG immune response compared to the use of an aluminum hydroxide-based formulation and intramuscular administration of HBV. In addition, CTA1 induced CD8 + T cell response as much as in which the aluminum hydroxide-based formulation induced. CONCLUSIONS: CTA1 is an adjuvant that satisfies both the delivery efficiency and the immunological characteristics required for vaccine microneedles. CTA1 will be used as a potential adjuvant through vaccine microneedles.

Probing One-Dimensional Oxygen Vacancy Channels Driven by Cation-Anion Double Ordering in Perovskites.

Visualizing the oxygen vacancy distributions is highly desirable for understanding the atomistic oxygen diffusion mechanisms in perovskites. In particular, the direct observation of the one-dimensional oxygen vacancy channels has not yet been achieved in perovskites with dual ion (i.e., cation and anion) ordering. Here, we perform atomic-resolution imaging of the one-dimensional oxygen vacancy channels and their structural dynamics in a NdBaCo2O5.5 double perovskite oxide. An in situ heating transmission electron microscopy investigation reveals the disordering of oxygen vacancy channels by local rearrangement of oxygen vacancies at the specific temperature. A density functional theory calculation suggests that the possible pathway of oxygen vacancy migration is a multistep route via Co-O and Nd-Ov (oxygen vacancy) sites. These findings could provide robust guidance for understanding the static and dynamic behaviors of oxygen vacancies in perovskite oxides.

Monolithic Interface Contact Engineering to Boost Optoelectronic Performances of 2D Semiconductor Photovoltaic Heterojunctions.

In optoelectronic devices based on two-dimensional (2D) semiconductor heterojunctions, the efficient charge transport of photogenerated carriers across the interface is a critical factor to determine the device performances. Here, we report an unexplored approach to boost the optoelectronic device performances of the WSe2-MoS2 p-n heterojunctions via the monolithic-oxidation-induced doping and resultant modulation of the interface band alignment. In the proposed device, the atomically thin WOx layer, which is directly formed by layer-by-layer oxidation of WSe2, is used as a charge transport layer for promoting hole extraction. The use of the ultrathin oxide layer significantly enhanced the photoresponsivity of the WSe2-MoS2 p-n junction devices, and the power conversion efficiency increased from 0.7 to 5.0%, maintaining the response time. The enhanced characteristics can be understood by the formation of the low Schottky barrier and favorable interface band alignment, as confirmed by band alignment analyses and first-principle calculations. Our work suggests a new route to achieve interface contact engineering in the heterostructures toward realizing high-performance 2D optoelectronics.

Order-of-Magnitude, Broadband-Enhanced Light Emission from Quantum Dots Assembled in Multiscale Phase-Separated Block Copolymers.

Achieving high emission efficiency in solid-state quantum dots (QDs) is an essential requirement for high-performance QD optoelectronics. However, most QD films suffer from insufficient excitation and light extraction efficiencies, along with nonradiative energy transfer between closely adjacent QDs. Herein, we suggest a highly effective strategy to enhance the photoluminescence (PL) of QD composite films through an assembly of QDs and poly(styrene-b-4-vinylpyridine)) (PS-b-P4VP) block copolymer (BCP). A BCP matrix casted under controlled humidity provides multiscale phase-separation features based on (1) submicrometer-scale spinodal decomposition between polymer-rich and water-rich phases and (2) sub-10 nm-scale microphase separation between polymer blocks. The BCP-QD composite containing bicontinuous random pores achieves significant enhancement of both light absorption and extraction efficiencies via effective random light scattering. Moreover, the microphase-separated morphology substantially reduces the Förster resonance energy transfer efficiency from 53% (pure QD film) to 22% (BCP-QD composite), collectively achieving an unprecedented 21-fold enhanced PL over a broad spectral range.

Premedication with dexmedetomidine to reduce emergence agitation: a randomized controlled trial.

BACKGROUND: Nasal bone fracture is the most common type of facial fracture, and the high incidence of severe emergence agitation occurring after closed reduction of the nasal bone fracture can be challenging to manage. The purpose of this trial was to evaluate whether pre-operative administration of dexmedetomidine is effective in reducing the incidence and severity of emergence agitation in adults undergoing closed reduction of nasal bone fractures. METHODS: In this randomized controlled trial, 90 patients who were scheduled to undergo closed reduction of a nasal bone fracture were prospectively included and were randomly assigned to either the control group (n = 45; 0.9% saline infusion) or the dexmedetomidine group (n = 45; 1 µ/kg over 10 min, pre-operatively). The primary endpoint was Aono's four-point scale scores after anesthesia. The recovery time and numeric rating scale score were assessed as secondary endpoints. RESULTS: Aono's four-point scale scores were lower in the dexmedetomidine group than in the control group (median: 1 [1] vs. 1 [1, 2], 95% confidence interval of difference: 0.01 to 0.02, P = 0.02). The number, severity, and duration of agitation episodes were significantly lower in the dexmedetomidine group than in the control group. Furthermore, the number of patients exhibiting intraoperative movement was lower in the dexmedetomidine group. CONCLUSIONS: Pre-operative administration of dexmedetomidine demonstrated several significant benefits, such as a lower incidence of emergence agitation, reduced agitation severity, and a shorter duration of agitation. Additionally, we observed more stable maintenance of intraoperative anesthesia with less movement during the surgery. TRIAL REGISTRATION: Identifier: KCT0000585 (registration date: 12-19- 2012).

Ethnic considerations in the upper lip bite test: the reliability and validity of the upper lip bite test in predicting difficult laryngoscopy in Koreans.

BACKGROUND: Several methods have been used to predict difficult tracheal intubation. Among recently suggested methods, the upper lip bite test (ULBT) could serve as a good predictor. Soft tissue and skeletal hard tissue profiles are affected by many factors including ethnicity. We aimed to assess the clinical utility of the ULBT in Koreans while considering ethnic differences. METHODS: Three-hundred-forty-four Korean patients undergoing general anesthesia with orotracheal intubation were included. Preoperatively, we recorded the patient's Modified Mallampati (MMT) classification, ULBT ratings, and the Cormack-Lehane grade. RESULTS: The area under the receiver operating characteristic (ROC) curve (AUC) was lower for the ULBT than the MMT (95% confidence interval: 0.0697-0.191, p < 0.0001). The ULBT showed high accuracy (73.83%) and specificity (98.04%). On the other hand, the ULBT showed significantly lower sensitivity (4.49%). Only nine of 344 Korean patients could not bite their upper lip; among them, only three presented a difficult laryngoscopic view. CONCLUSIONS: One factor related to the low sensitivity is the low incidence of a grade III ULBT in Koreans. In Asians, the scarcity of a grade III ULBT is explainable as a result of anteriorly displaced temporomandibular joints and redundant lip soft tissues. Despite its high specificity, the low sensitivity and AUC of the ULBT mean that the test results should be interpreted cautiously in Koreans. Ethnic differences should be considered when evaluating parameters related to soft tissues such as the ULBT. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT01908218, Date of registration JUL 2013.

Oncological outcomes after partial vs radical nephrectomy in renal cell carcinomas of ≤7 cm with presumed renal sinus fat invasion on preoperative imaging.

OBJECTIVES: To compare oncological outcomes of partial nephrectomy (PN) and radical nephrectomy (RN) for renal tumours of ≤7 cm in which preoperative imaging reveals potential renal sinus fat invasion (cT3a), as RN is preferred for these tumours due to concerns about high tumour stage. PATIENTS AND METHODS: Among 1137 nephrectomies performed for renal tumours of ≤7 cm from January 2005 to August 2012, 401 solitary cT3a renal cell carcinomas (RCCs) without metastases were analysed. Classification as cT3a included only renal sinus fat invasion, as there were no tumours with suspected perinephric fat invasion. Multivariate models were used to evaluate predictors of recurrence-free survival (RFS) and cancer-specific survival (CSS). RESULTS: There were 34 RCCs (8.5%) with unexpected perinephric fat invasion, but only 77 RCCs (19.2%) were staged as pT3a. During the median follow-up of 43.0 months, recurrence occurred in seven (6.7%) PN cases and 25 (8.4%) RN cases. Six recurred PN cases had positive surgical margins (PSMs). The two cohorts showed equal oncological outcomes for 5-year RFS and CSS. Multivariate analyses showed PSM, pathological T stage, sarcomatoid dedifferentiation, and type of surgery as significant predictors of recurrence. Older age, pathological T stage, and sarcomatoid dedifferentiation were significant predictors of cancer-specific mortality. CONCLUSIONS: Renal tumours of ≤7 cm with presumed renal sinus fat invasion were mostly pT1. PN conferred equivalent oncological outcomes to RN. If clear surgical margins can be obtained, PN should be considered for these tumours, as patients may benefit from renal function preservation.

Analgesic efficacy of preemptive pregabalin administration in arthroscopic shoulder surgery: a randomized controlled trial.

PURPOSE: The purpose of the current study was to evaluate the effects of pregabalin administration as an adjunct to fentanyl-based intravenous patient-controlled analgesia on opioid consumption and postoperative pain following arthroscopic shoulder surgery. METHODS: In this randomized controlled trial, 60 adult patients undergoing arthroscopic shoulder surgery were randomly assigned to receive either pregabalin 150 mg (Pregabalin group, n = 30) or placebo (Control group, n = 30) one hour before anesthetic induction. The primary outcome was the cumulative amount of fentanyl consumption during 48 hr postoperatively. Secondary outcomes were pain intensity, the number of rescue analgesics administered, and adverse effects related to the analgesic regimen, which were serially assessed during 48 hr postoperatively. RESULTS: The cumulative fentanyl consumption during 48 hr postoperatively was significantly lower in the Pregabalin group than in the Control group ([1,126.0 (283.6) µg vs 1,641.4 (320.3) µg, respectively; mean difference, 515.4 µg; 95% confidence interval [CI], 359.0 to 671.8; P = < 0.001). Numeric rating scores for pain (0 to 10) were significantly lower in the Pregabalin group at six hours (mean difference, 2.9; 95% CI, 1.8 to 4.0), 24 hr (mean difference, 2.9; 95% CI, 1.9 to 3.8), and 48 hr (mean difference, 1.5; 95% CI, 0.6 to 2.3). The incidence of adverse effects related to the analgesic regimens, including nausea, sedation, and dizziness, were similar between the two groups. CONCLUSION: A preoperative dose of pregabalin 150 mg administered before arthroscopic shoulder surgery resulted in significant analgesic efficacy for 48 hr in terms of opioid-sparing effect and improved pain intensity scores without influencing complications. This trial was registered at: http://cris.nih.go.kr , number CT0000578.

Boltzmann Switching MoS2 Metal-Semiconductor Field-Effect Transistors Enabled by Monolithic-Oxide-Gapped Metal Gates at the Schottky-Mott Limit.

A gate stack that facilitates a high-quality interface and tight electrostatic control is crucial for realizing high-performance and low-power field-effect transistors (FETs). However, when constructing conventional metal-oxide-semiconductor structures with two-dimensional (2D) transition metal dichalcogenide channels, achieving these requirements becomes challenging due to inherent difficulties in obtaining high-quality gate dielectrics through native oxidation or film deposition. Here, a gate-dielectric-less device architecture of van der Waals Schottky gated metal-semiconductor FETs (vdW-SG MESFETs) using a molybdenum disulfide (MoS2) channel and surface-oxidized metal gates such as nickel and copper is reported. Benefiting from the strong SG coupling, these MESFETs operate at remarkably low gate voltages, <0.5 V. Notably, they also exhibit Boltzmann-limited switching behavior featured by a subthreshold swing of ≈60 mV dec-1 and negligible hysteresis. These ideal FET characteristics are attributed to the formation of a Fermi-level (EF) pinning-free gate stack at the Schottky-Mott limit. Furthermore, authors experimentally and theoretically confirm that EF depinning can be achieved by suppressing both metal-induced and disorder-induced gap states at the interface between the monolithic-oxide-gapped metal gate and the MoS2 channel. This work paves a new route for designing high-performance and energy-efficient 2D electronics.

Physicochemical characteristics of lignin-g-PMMA/PLA blend via atom transfer radical polymerization depending on the structural difference of organosolv lignin.

Lignin has different structural characteristics depending on the extraction conditions. In this study, three types of ethanol organosolv lignin (EOL) were produced under different extraction conditions involving the reaction temperature (140, 160, 180 °C), sulfuric acid concentration (0.5, 1, 1.5 %), and ethanol concentration (40, 60, 80 %) to compare the difference in properties when mixed with polylactic acid (PLA) matrix after atom transfer radical polymerization (ATRP). ATRP of EOL was conducted to improve its compatibility with PLA using methyl methacrylate (MMA) as a monomer. The molecular weight of each EOL increased significantly, and the glass transition temperature (Tg) decreased from approximately 150 to 110 °C. The EOL-g-PMMA copolymer exhibited a melting point (Tm), whereas EOL did not, implying that the thermoplasticity increased. The EOL-g-PMMA/PLA blend and film were prepared with 10 % of the copolymer in the PLA matrix. The tensile strength and strain of the blend were higher than those of unmodified organosolv lignin as the compatibility increased, and the UV transmittance was lower than that of neat PLA because of the UV protecting properties of EOL moiety.

Fabrication of transparent cellulose nanofibril composite film with smooth surface and ultraviolet blocking ability using hydrophilic lignin.

Ecofriendly multifunctional films with only biomass-based components have gathered significant interest from researchers as next-generation materials. Following this trend, a TEMPO-oxidized cellulose nanofibril (TOCNF) film containing hydrophilic lignin (CL) was fabricated. To produce the lignin, peracetic acid oxidation was carried out, leading to the introduction of carboxyl groups into the lignin structure. By adding hydrophilic lignin, various characteristics (e.g., surface smoothness, UV protection, antimicrobial activity, and barrier properties) of the TOCNF film were enhanced. In particular, the shrinkage of CNF was successfully prevented by the addition of CL, which is attributed to the lower surface roughness (Ra) from 18.93 nm to 4.99 nm. As a result, the smooth surface of the TOCNF/CL film was shown compared to neat TOCNF film and TOCNF/Kraft lignin composite film. In addition, the TOCNF/CL film showed a superior UV blocking ability of 99.9 % with high transparency of 78.4 %, which is higher than that of CNF-lignin composite films in other research. Also, water vapor transmission rate was reduced after adding CL to TOCNF film. Consequently, the developed TOCNF/CL film can be potentially utilized in various applications, such as food packaging.

Effect of chemically modified lignin addition on the physicochemical properties of PCL nanofibers.

In this study, a chemically modified lignin additive was successfully prepared to improve the physicochemical properties of biodegradable polycaprolactone (PCL)-based nanofibers. The molecular weight and surface functional group characteristics of lignin were effectively controlled through a solvent fractionation process using ethanol. Then, PCL-g-lignin was successfully synthesized by using ethanol-fractionated lignin as a platform for the PCL grafting process. Finally, PCL/PCL-g-lignin composite nanofibers were simply prepared by adding PCL-g-lignin to the PCL doping solution and performing a solution blow spinning process. The addition of PCL-g-lignin could dramatically improve the physical and chemical properties of PCL nanofibers, and in particular, the tensile strength (0.28 MPa) increased by approximately 280 % compared to the conventional PCL. In addition, the lignin moiety present in PCL-g-lignin was able to impart UV blocking properties to PCL nanofibers, and as a result, it was possible to effectively suppress the photolysis phenomenon that occurred rapidly in existing PCL nanofibers. Therefore, PCL-g-lignin may be widely used not only as a reinforcing agent of existing biodegradable nanofibers but also as a functional additive for UV protection.

Biodegradation behavior of acetylated lignin added polylactic acid under thermophilic composting conditions.

Acetylated lignin (AL) can improve compatibility with commercial plastic polymers compared to existing lignin and can be used as an effective additive for eco-friendly biocomposites. For this reason, AL can be effectively incorporated into polylactic acid (PLA)-based biocomposites, but its biodegradation properties have not been investigated. In this study, biodegradation experiments were performed under mesophilic and thermophilic conditions to determine the effect of AL addition on the biodegradation characteristics of PLA-based biocomposites. As a result, the PLA-based biocomposite showed a faster biodegradation rate in a thermophilic composting environment, which is higher than the glass transition temperature of PLA, compared to a mesophilic environment. 16S rDNA sequencing results showed that differences in microbial communities depending on mesophilic and thermophilic environments strongly affected the biodegradation rate of lignin/PLA biocomposites. Importantly, the addition of AL can effectively delay the thermophilic biodegradation of PLA biocomposites. As a result of tracking the changes in physicochemical properties according to the biodegradation period in a thermophilic composting environment, the main biodegradation mechanism of AL/PLA biocomposite hydrolysis. It proceeded with cleavage of the PLA molecular chain, preferential biodegradation of the amorphous region, and additional biodegradation of the crystalline region. Above all, adding AL can be proposed as an effective additive because it can minimize the decline in the mechanical properties of PLA and delay the biodegradation rate more effectively compared to existing kraft lignin (KL).

Enhancement of elongation at break and UV-protective properties of poly(lactic acid) film with cationic ring opening polymerized (CROP)-lignin.

In this study, the intrinsic brittleness of poly(lactic acid) (PLA) was overcome by chemical modification using ethyl acetate-extracted lignin (EL) via cationic ring-opening polymerization (CROP). The CROP was conducted to promote homopolymerization under starvation of the initiator (oxyrane). This method resulted in the formation of lignin-based polyether (LPE). LPE exhibited enhanced interfacial compatibility with nonpolar and hydrophobic PLA owing to the fewer hydrophilic hydroxyl groups and a long polyether chain. In addition, because of the UV-protecting and radical-scavenging abilities of lignin, LPE/PLA exhibited multifunctional properties, resulting in improved chemical properties compared with the neat PLA film. Notably, one of the LPE/PLA films (EL_MCF) exhibited excellent elongation at break of 297.7 % and toughness of 39.92 MJ/m3. Furthermore, the EL_MCF film showed superior UV-protective properties of 99.52 % in UVA and 88.95 % in UVB ranges, both significantly higher than those of the PLA film, without sacrificing significant transparency in 515 nm. In addition, the radical scavenging activity improved after adding LPE to the PLA film. These results suggest that LPEs can be used as plasticizing additives in LPE/PLA composite films, offering improved physicochemical properties.

Heterosynaptic MoS2 Memtransistors Emulating Biological Neuromodulation for Energy-Efficient Neuromorphic Electronics.

Heterosynaptic neuromodulation is a key enabler for energy-efficient and high-level biological neural processing. However, such manifold synaptic modulation cannot be emulated using conventional memristors and synaptic transistors. Thus, reported herein is a three-terminal heterosynaptic memtransistor using an intentional-defect-generated molybdenum disulfide channel. Particularly, the defect-mediated space-charge-limited conduction in the ultrathin channel results in memristive switching characteristics between the source and drain terminals, which are further modulated using a gate terminal according to the gate-tuned filling of trap states. The device acts as an artificial synapse controlled by sub-femtojoule impulses from both the source and gate terminals, consuming lower energy than its biological counterpart. In particular, electrostatic gate modulation, corresponding to biological neuromodulation, additionally regulates the dynamic range and tuning rate of the synaptic weight, independent of the programming (source) impulses. Notably, this heterosynaptic modulation not only improves the learning accuracy and efficiency but also reduces energy consumption in the pattern recognition. Thus, the study presents a new route leading toward the realization of highly networked and energy-efficient neuromorphic electronics.

Coherent consolidation of trillions of nucleations for mono-atom step-level flat surfaces.

Constructing a mono-atom step-level ultra-flat material surface is challenging, especially for thin films, because it is prohibitively difficult for trillions of clusters to coherently merge. Even though a rough metal surface, as well as the scattering of carriers at grain boundaries, limits electron transport and obscures their intrinsic properties, the importance of the flat surface has not been emphasised sufficiently. In this study, we describe in detail the initial growth of copper thin films required for mono-atom step-level flat surfaces (MSFSs). Deposition using atomic sputtering epitaxy leads to the coherent merging of trillions of islands into a coplanar layer, eventually forming an MSFS, for which the key factor is suggested to be the individual deposition of single atoms. Theoretical calculations support that single sputtered atoms ensure the formation of highly aligned nanodroplets and help them to merge into a coplanar layer. The realisation of the ultra-flat surfaces is expected to greatly assist efforts to improve quantum behaviour by increasing the coherency of electrons.

Eco-friendly alkaline lignin/cellulose nanofiber drying system for efficient redispersion behavior.

Although nanocellulose is an eco-friendly, high-performance raw material provided by nature, the agglomeration of nanocellulose that occurs during the drying process is the biggest obstacle to its advanced materialization and commercialization. In this study, a facile and simple nanocellulose drying system was designed using lignin, which is self-assembled together with cellulose in natural wood, as an eco-friendly additive. The addition of lignin not only minimized aggregation during the drying and dehydration process of nanocellulose but also ensured excellent redispersion kinetics and stability. In addition, the added lignin could be removed through a simple washing process. Through FTIR, XRD, TGA, tensile and swelling tests, it was confirmed that the addition of lignin enabled the reversible restitution of the nanocellulose physicochemical properties to the level of pristine never-dried nanocellulose in drying, redispersion, and polymer processing processes.