VNREDSat-1 is the first Vietnamese satellite enabling the survey of environmental parameters, such as vegetation and water coverages or surface water quality at medium spatial resolution (from 2.5 to 10 m depending on the considered channel). The New AstroSat Optical Modular Instrument (NAOMI) sensor on board VNREDSat-1 has the required spectral bands to assess the suspended particulate matter (SPM) concentration. Because recent studies have shown that the remote sensing reflectance, Rrs(λ), at the blue (450–520 nm), green (530–600 nm), and red (620–690 nm) spectral bands can be assessed using NAOMI with good accuracy, the present study is dedicated to the development and validation of an algorithm (hereafter referred to as V1SPM) to assess SPM from Rrs(λ) over inland and coastal waters of Vietnam. For that purpose, an in-situ data set of hyper-spectral Rrs(λ) and SPM (from 0.47 to 240.14 g·m−3) measurements collected at 205 coastal and inland stations has been gathered. Among the different approaches, including four historical algorithms, the polynomial algorithms involving the red-to-green reflectance ratio presents the best performance on the validation data set (mean absolute percent difference (MAPD) of 18.7%). Compared to the use of a single spectral band, the band ratio reduces the scatter around the polynomial fit, as well as the impact of imperfect atmospheric corrections. Due to the lack of matchup data points with VNREDSat-1, the full VNREDSat-1 processing chain (atmospheric correction (RED-NIR) and V1SPM), aiming at estimating SPM from the top-of-atmosphere signal, was applied to the Landsat-8/OLI match-up data points with relatively low to moderate SPM concentration (3.33–15.25 g·m−3), yielding a MAPD of 15.8%. An illustration of the use of this VNREDSat-1 processing chain during a flooding event occurring in Vietnam is provided.

We report a quantitative analysis of conductance in tunneling junctions based on π-conjugated oligophenyleneimine (OPI) wires incorporated with thieno[2,3-b]thiophene (TT23) or thieno[3,2-b]thiophene (TT32) units grown layer-by-layer on Au substrates by click chemistry. Reflection–adsorption infrared spectroscopy, ellipsometry, and X-ray photoelectron spectroscopy were used to monitor the stepwise growth. The electronic structure of the conjugated wires was studied with ultraviolet photoemission spectroscopy (UPS). The current–voltage curves (I–V) of the molecular wires, linear π-conjugated TT32-OPI-n and nonlinear π-conjugated TT23-OPI-n where n = 3–5, were measured with conducting probe atomic force microscopy (CP-AFM), in which the molecular layer bound to an ultrasmooth gold substrate was in a contact with a gold-coated AFM tip. By systematically measuring the low-bias junction resistance as a function of aromatic rings (3–5), we obtained the structure-dependent tunneling attenuation factors (β) of 2.6 and 3.1 nm–1 for the linear π-conjugated TT32-OPI-n and nonlinear π-conjugated TT23-OPI-n junctions. The high-bias I–V characteristic for these junctions was analyzed quantitatively with a previously validated single-level model (SLM) to extract key junction metrics, the energy offset barrier εh and the electronic coupling, Γ. The I–V simulation of these junctions using εh estimated from UPS matches well with the experimental I–V characteristic, which provides strong evidence for the validity of the SLM tool. Importantly, we find that the conductance in the linear π-conjugated TT32-OPI-n junction is much greater (100-fold) than in the nonlinear π-conjugated TT23-OPI-n junction; the much larger conductance for the linear π-conjugated TT32-OPI-n junction is primarily due to a 10-fold increase in Γ and not to any significant change in εh. Overall, the results provide insights into molecular structure–conductance relationships as well as a basis for rational design of molecular electronic devices.

The paper demonstrates the effect of the chemical conformation of the −COOH group on the transport characteristic including conductance, rectification, and length effect in molecular junctions (MJs) formed by self-assembled monolayers of carboxylic-terminated thiol molecules. For an alkyl chain shorter than C11, the transport mechanism was attributed to a direct off-resonant tunneling of a hole carrier, located at the Au–S interface, whereas a hopping mechanism was assigned to the alkyl chain longer than the C11 chain located at the −COOH group. The hopping mechanism may be operated by electron transport associated with the breaking of the −OH bonding likely driven by a voltage. Importantly, at the C11 alkyl chain, we observed that the transport carrier operating in MJs could change from a hole carrier into an electron carrier. The result strongly proves that the chemical conformation should be considered in analyzing molecular electronics and provides a basis for the rational design of molecular electronic devices.

VNREDSat-1 is the first Vietnamese satellite allowing the survey of environmental parameters such as vegetation and water coverages, or surface water quality at medium spatial resolution (from 2.5 to 10 meters depending on the considered channel). The NAOMI sensor on board VNREDSat-1 has the required spectral bands to assess the suspended particulate matter concentration, SPM. Because recent studies have shown that the remote sensing reflectance, Rrs(), at the blue (450 – 520 nm), green (530 – 600 nm), and red (620 – 690 nm) spectral bands can be assessed from NAOMI with a good accuracy, the present study is dedicated to the development and validation of an algorithm (hereafter referred to as V1SPM) to assess SPM from Rrs() over inland and coastal waters of Vietnam. For that purpose, an in situ data set of hyper-spectral Rrs() and SPM (from 0.47 to 240.14 g.m-3) measurements collected at 205 coastal and inland stations has been gathered. Among the different approaches, including 4 historical algorithms, the polynomial algorithms involving the red-to-green reflectance ratio presents the best performance on the validation data set (MAPD of 18,7%). Compared to the use of a single spectral band, the band ratio allows to reduce the scatter around the polynomial fit as well as the impact of imperfect atmospheric corrections. Due to the lack of matchup data points with VNREDSat-1, the full VNREDSat-1 processing chain (RED-NIR and V1SPM) aiming at estimate SPM from the top-of-atmosphere signal has been applied to the Landsat-8/OLI match-up data points with relatively low to moderate SPM concentration (3.33-15.25 g.m-3) showing a MAPD of 15,8%. An illustration of the use of this VNREDSat-1 processing chain during a flooding event occurring in Vietnam is provided.