Spatially selective p-type doping for constructing lateral WS2 p-n homojunction via low-energy nitrogen ion implantation.

The construction of lateral p-n junctions is very important and challenging in two-dimensional (2D) semiconductor manufacturing process. Previous researches have demonstrated that vertical p-n junction can be prepared simply by vertical stacking of 2D materials. However, interface pollution and large area scalability are challenges that are difficult to overcome with vertical stacking technology. Constructing 2D lateral p-n homojunction is an effective strategy to address these issues. Spatially selective p-type doping of 2D semiconductors is expected to construct lateral p-n homojunction. In this work, we have developed a low-energy ion implantation system that reduces the implanted energy to 300 eV. Low-energy implantation can form a shallow implantation depth, which is more suitable for modulating the electrical and optical properties of 2D materials. Hence, we utilize low-energy ion implantation to directly dope nitrogen ions into few-layer WS2 and successfully realize a precise regulation for WS2 with its conductivity type transforming from n-type to bipolar or even p-type conduction. Furthermore, the universality of this method is demonstrated by extending it to other 2D semiconductors, including WSe2, SnS2 and MoS2. Based on this method, a lateral WS2 p-n homojunction is fabricated, which exhibits significant rectification characteristics. A photodetector based on p-n junction with photovoltaic effect is also prepared, and the open circuit voltage can reach to 0.39 V. This work provides an effective way for controllable doping of 2D semiconductors.

The HLA-DRB1*04:357 allele first identified in a Chinese transplant recipient.

HLA-DRB1*04:357 differs from HLA-DRB1*04:17:02 by two nucleotides in exon 2.

[Polymorphism of HLA-A, -B, -C, -DRB1 and -DQB1 Allele and Haplotype Frequency at High Resolution in Guangxi Zhuang Population].

OBJECTIVE: To analyze the characteristics of allelic and haplotypic polymorphisms of human leukocyte antigens at HLA-A, -B, -C, DRB1 and DQB1 loci in Guangxi Zhuang population. METHODS: Polymerase chain reaction-sequence based typing (PCR-SBT) was used to detect. The five loci (HLA-A, -B, -C, -DRB1, -DQB1) in 350 unrelated Zhuang ethnic individual from Guangxi region. Allelic and haplotypic frequencies were calculated by using Arlequin software 3.5.2.2. Phylogeny tree were constructed by using MEGA software 6.0, and SPSS software was used for principal component analysis. RESULTS: Among the five loci in the population, only HLA-A and DRB1 loci were observed as departures from Hardy-Weinberg expectations. A total of 19 HLA-A, 42 HLA-B, 22 HLA-C, 25 HLA-DRB1 and 15 HLA-DQB1 alleles were found in 350 samples. The most highest frequent alleles were A*11: 01(28.57%), B*46: 01(14.00%), C*01: 02(18.43%), DRB1*16: 02 (15.71%）and DQB1*05: 02 (35.00%) . The most common five loci haplotype was A*33: 03-C*03: 02-B*58: 01-DRB1*03: 01-DQB1*02: 01（6.86%）. The phylogenetic tree analysis showed that Guangxi Zhuang population had a relative close genetic relationship with southern Han Chinese populations. CONCLUSION: This reaserch found that the HLA-A, B, C, DRB1 and DQB1 loci are highly polymorphic in Guangxi Zhuang population.

Allelic and haplotype diversity of HLA-A, HLA-B and HLA-DRB1 gene at high resolution in the Nanning Han population.

The distribution of human leucocyte antigen (HLA) allele and haplotype varied among different ethnic populations. In this study, we investigated the allele and haplotype frequencies of HLA-A, HLA-B and HLA-DRB1 loci in the Nanning Han population who live in Guangxi province of China. We identified 26 HLA-A, 56 HLA-B and 31 HLA-DRB1 alleles in 562 Nanning individuals of Han ethnic group by sequence-based typing method. Of these, the three most common alleles in HLA-A, HLA-B and HLA-DRB1 loci, respectively, were A*11:01 (32.12%), A*02:07 (12.54%), A*24:02 (12.01%); B*46:01 (14.41%), B*15:02 (13.61%), B*40:01 (11.48%); DRB1*15:01 (14.15%), DRB1*16:02 (11.57%) and DRB1*12:02 (10.14%). With the exception of HLA-DRB1, the p values of the HLA-A and HLA-B loci showed that the HLA allelic distribution in this population was in accordance with Hardy-Weinberg expectation (p > 0.05). A total of 173 HLA~A-B~DRB1 haplotype with a frequency of >0.1% were presented and the three most common haplotype were HLA-A*33:03~B*58:01~DRB1*03:01 (6.12%), HLA-A*11:01~B*15:02~DRB1*12:02 (3.39%) and HLA-A*11:01~B*15:02~DRB1*15:01 (3.22%). The phylogenetic tree and the principal component analysis suggested that Nanning Han population had a relative close genetic relationship with Chinese Zhuang population and a relative distant genetic relationship with Northern Han Chinese. The information will be useful for anthropological studies, for HLA matching in transplantation and disease association studies in the Chinese population.

[Identification of a novel HLA allele HLA-B*46:01:18].

OBJECTIVE: To report on a novel human leukocyte antigen (HLA) allele. METHODS: Polymerase chain reaction-sequence based typing was used for routine HLA typing. For one sample, the result of B locus typing showed mismatch of one base with B*46:01:01, B*15:25:01 at locus 384. The group specific sequencing primers, which target at B*46 and B*15, were used to confirm the difference between the novel allele and the highest homologous allele. RESULTS: The sequencing results showed that the highest homologous allele to the novel allele was B*46:01:01. The two sequences only differed for position 384 within the exon 3 (384G>T), which resulted in a codon change (GGG>GGT), though the amino acid sequence of the novel allele at position 104 was still Glycine (G). Investigation of the family showed that the novel allele was inherited from the father. CONCLUSION: The novel HLA-B allele, discovered in ethnic Zhuangs from Guangxi, has been designated as HLA-B *46:01:18 by the World Health Organization (WHO) HLA Nomenclature Committee.

[Identification of A Novel HLA-B*13:92 Allele and Analysis of Its 3D Model Structure].

OBJECTIVE: To identify a novel human leukocyte antigen (HLA) allele HLA-B*13:92 and analyze 3D model of HLA molecule. METHODS: Polymerase chain reaction sequencing-based (PCR-SBT) was used in routine HLA typing, the B locus typing results of one sample was one base mismatch with B*13:01:01, B*58:01:01 at locus 189, The Group Specific Sequencing Products (GSSP) which target at B*13 and B*58 were used to confirm difference between the new allele and highest homologous allele, then the new allele was modeled by Swiss-model to its 3D structure. RESULTS: The sequencing results showed that the new allele with highest homologous allele B*13:01:01 was the difference in the second exon at position 189 C>A (codon 39 GAC>GAA), 39 Asp (D) was changed to Glu (E). The amino acid substitution at residue 39 of the HLA polypeptide was located in α-helices of antigenic peptide-biding region. CONCLUSION: This allele is a new HLA-B allele found in Chinese Guangxi Zhang population and has been designated as HLA-B*13:92 by the World Health Organization (WHO) HLA Nomenclature Committee.